Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BREATHING CIRCUITS HAVING UNCONVENTIONAL
RESPIRATORY CONDUITS AND SYSTEMS AND METHODS FOR
OPTIMIZING UTILIZATION OF FRESH GASES
PRIORITY
This application is a division of application 2,460,773 filed September 24,
2002
and claims priority of U.S. provisional patent application serial number
60/340,206,
filed December 12, 2001 and U.S. provisional patent application serial no.
60/324,554,
filed September 24, 2001.
FIELD OF THE INVENTION
This invention relates to devices for use in resuscitating and/or providing
anesthesia and/or assisted and artificial ventilation to patients, and more
particularly relates to breathing circuits with interacting mutually
adjustable length
fluid carrying members, to a multilumen breathing circuit utilizing
unconventional
(or new era) conduits, and to systems and methods for optimizing utilization
of
fresh gases (e.g. anesthetic agents and oxygen) during provision of anesthesia
and/or assisted and artificial ventilation.
BACKGROUND OF THE INVENTION
Assisted and/or artificial ventilation systems are an essential component of
modem medicine. Generally, such systems provide inspiratory fresh gases to a
patient from a source of same, such as from an anesthesia or a ventilator
machine,
and conduct expired gases away from the patient. Inspiratory gases are
conducted
through a different conduit from the expired gases and thus at least two
conduits
are required. Commonly used circuits have two limbs (e.g., two independent
tubes). The ends of the tubes in a breathing circuit are generally held in
spaced
relationship by a connector located at the patient, or distal, end of the
circuit. The
connector can place the distal (i.e., patient) ends of the tubes in a fixed
parallel
relationship, or the connector can be a Y-piece with the two tubes converging
at an
angle. Conventional respiratory tubes are corrugated and flexible to permit
movement while minimizing collapse and kinking of the tubes. Recently, the use
of axially expandable and contractible pleated ("accordion-like") tubing has
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become popular. Commonly used accordion-like or pleated tubing is known as
ULTRA-FLEX (available from King Systems Corporation, Noblesville, Indiana,
U.S.A.), FLEXITUBE or ISOFLEXT'4, in which the length can be adjusted by
axially expanding or contracting one or more pleats between a closed and open
position. Whether the pleats are in the open or closed position, the tube wall
remains corrugated to minimize the risk of kinking or collapse upon
convolution
or bending of the tubing.
RESPIRATORY CARE AND ICU TYPE NON-REBREATHING SYSTEM
In a non-rebreathing breathing system, which can be used for respiratory care
or in an intensive care unit (ICU), a one-way valve permits gases to flow to a
patient
through an inspiratory conduit, while another one-way valve causes expired gas
from
the patient to flow through an expiratory conduit and then to an exhaust
conduit.
CIRCLE CO2 ABSORPTION AND MAPLESON TYPE BREATHING
SYSTEMS
In a "circle system," a one-way valve permits gas to flow to a patient
through a first or inspiratory conduit, while another one-way valve permits
partial
recirculation of the gases by causing expired gases to flow from the patient
through a second or expiratory conduit to a "recirculation module" or
"scrubber
circuit", which generally comprises a carbon dioxide absorber to eliminate the
expired carbon dioxide resulting in "scrubbed gases". The scrubbed gases are
then
combined with the fresh gases coming from the anesthesia machine, and the
mixed
gases are referred to herein as "refreshed gases". Some or all of the
refreshed
gases can be rebreathed by the patient. Excess gases are directed to an
exhaust
conduit and/or scavenger. Thus, new fresh gases are combined with scrubbed
gases at the scrubber circuit, and are delivered as refreshed gases to the
first
conduit, while expired gases are carried by a second conduit to a "scrubber
circuit"
for re-circulation and/or exhaust.
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It is believed that in low flow anesthesia with the circle system, the
anesthetic concentration of the refreshed gases decreases progressively from
the
initial fresh gas concentration (concentration at the vaporizer) in the
process of re-
circulation. Such a decrease may be due to dilution by the expired gases
and/or
scrubbed gases, leakage, and adsorption and/or absorption by plastic, rubber
and
other materials in the system. Therefore, low flow anesthesia, including
totally
closed anesthesia using prior art circle systems, is in theory possible, but
very
limited in practice.
In Mapleson A-F type circuits, fresh gas is delivered into a common
breathing tube by a fresh gas delivery/supply tube, wherein the breathing tube
acts
to provide gases to the patient and receive expired gases therefrom.
Generally, the
diameter of the fresh gas supply tube is small thereby limiting its function
to being
a fresh gas delivery or supply conduit rather than an inspiratory tube (i.e.,
a tube
from which a patient directly inspires as in a circle system). A Mapleson D
type
circuit (the most commonly used circuit among the Mapleson circuits) does not
use valves, therefore, the flow of fresh gases required is sufficiently high
to
minimize CO2 rebreathing. During inspiration, the patient will inhale fresh
gases
from the fresh gas delivery/supply tube inlet and gases from the common
breathing tube, which may be a mixture of fresh gas and expired alveolar
gases.
High fresh gas flow will flush the breathing tube, pushing the expired
alveolar
gases out of the circuit.
THE BAIN CIRCUIT
An embodiment of a unilimb modification of the Mapleson D type circuit,
often referred to as a "Bain circuit" or "Bain," is described in U.S. Patent
3,856,051, in which the fresh gas delivery line is inserted through the wall
of the
common breathing tube near the proximal rather than near the distal end
thereof,
and the delivery tube then extends lengthwise through the common breathing
tube
so that its distal end is near the distal end of the common breathing tube.
This
creates a unilimb circuit from dual members. The fresh gas delivery line is
sealably bonded to the common breathing tube at its junction therewith.
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Another embodiment of a Mapleson D type circuit is described in U.S.
Patent 5,121,746, to Sikora, in which a flexible corrugated tube is divided by
an
internal common wall into a larger and smaller flow passage and is provided
with
a bayonet type connector at the patient end and a double friction fit
connector at
the machine end. A modification of the circuit described in this patent is
used to
form a circle circuit sold as the LimbOTM by Vital Signs, Inc. of Totowa, New
Jersey, USA.
THE UNIVERSAL F CIRCUIT
With reference to U.S. Patent No. 4,265,235, to Fukunaga, a unilimb
device of universal application for use in different types of breathing
systems is
described which provides many advantages over prior systems. The Fukunaga
device, sold as the Universal Ft by King Systems Corporation of Noblesville,
Indiana, U.S.A., utilizes a space saving co-axial, or tube within a tube,
design to
provide inspiratory gases and remove expiratory gases. Numerous advantages
flow
from this arrangement, such as a reduction in the size of the breathing
apparatus
connected to a patient. Further, the device acts as an artificial nose since
the
expired gases warm and maintain humidity of the inspired gases as the two
opposing flows are countercurrent in the unilimb device.
UNIVERSAL F2 TECHNOLOGY
With reference to U.S. Patent No. 5,778,872, to Fukunaga et al., unilimb
multi-lumen circuits are disclosed and embodiments thereof are sold as the
F2Tm
or Universal F2 by King Systems Corporation of Noblesville, Indiana, U.S.A.,
which have revolutionized artificial ventilation systems and methods of
providing
assisted ventilation and anesthesia. The F2TM system provides for safe and
ready
attachment and detachment of multilumen (e.g., co-axial) system components
from the proximal terminal. This permits more efficient placement and
utilization
of other breathing circuit components, improves system performance, and yet
reduces medical waste and costs. In general, the Universal F and the F2Tm are
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used in a circle system configuration with a carbon dioxide absorber. For more
information about the F2114 technology, one may contact King Systems
Corporation.
For further information on breathing systems, and anesthetic and assisted
5 ventilation techniques, see U.S. Patent Nos. 3,556,097, 4,007,737,
4,188,946,
4,265,235, 4,463,755, 4,232,667, 5,284,160, 5,778.872, Austrian Patent No.
93,941, British Patent 1,270,946, Dorsch, J.A., and Dorsch, S.E.,
Understanding
Anesthesia Equipment: Construction, Care And Complications Williams &
Wilkins Co., Baltimore (1974), and Andrews, J.J., "Inhaled Anesthetic Delivery
Systems," in Anesthesia, 4" Ed. Miller, Ronald, M.D., Editor, Churchill
Livingstone, Inc., N.Y. (1986).
COST EI-1- ,CTIVE ANESTHESIA SYSTEMS AND UNCONVENTIONAL
NEW ERA RESPIRATORY CONDUITS
Hospitals, medical personnel, and related entities are always looking for
ways to improve medical care. Numerous monitoring standards have been
implemented to ensure that the required medical care is being safely
administered.
For example, in the field of respiratory care and anesthesia, non-invasive and
invasive monitoring methods have become routinely used, such as alarm
monitoring systems that warn the user of obstruction and/or disconnection of
gas
flows, inspired and end-tidal gas monitoring, oxygen saturation monitoring by
pulse oximeter, arterial blood gas and mixed venous blood gas monitoring.
These
techniques and devices enable continuous patient monitoring, which permits the
. vigilant healthcare practitioner to more accurately adjust or
titrate the necessary
dosages of anesthetic gases or drugs, and readily detect problems due to the
pathophysiologic condition of the patient or due to those caused by medical
equipment failure or settings. There is a desire for an anesthesia system that
can
optimize the use of such expensive monitoring equipment, which for example,
could be used to decrease the waste of anesthetic gases.
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Respiratory care is commonly and increasingly provided in medicine.
Respiratory care includes, for example, artificial ventilation techniques,
such as
assisted ventilation and/or oxygen therapy. Certain devices widely used in
respiratory care include breathing circuits, filters, HME's (heat and moisture
exchangers), endotracheal tubes, laryngeal masks, laryngeal tubes, and
breathing
masks. Breathing circuits comprised of rigid pipes or flexible corrugated
tubes
made of rubber, plastic or silicon flexible tubes have been widely used all
over the
world for almost a century. In order to prevent cross contamination, "single
use"
breathing circuits are disposed of after a single use, or alternatively, more
sturdy
and more expensive reusable breathing circuit are used that can be sterilized
by
autoclave or other means. Both types of circuits are expensive to produce
and/or
use. Sterilization of the circuit requires substantial labor and processing
costs,
likewise disposing of the breathing circuit after a single use, while it is
very
effective in preventing cross contamination, also results in additional cost
to the
hospital.
US Patent 5,901,705, to Leagre, discloses a sleeve and filter for a breathing
circuit, wherein the filter and a tubular sleeve or sheath encase a breathing
circuit
during use. The filter housing has two ports, one port is for connection to a
patient
and the other to the distal end of a breathing circuit. The sleeve is
connected to the
exterior of the filter housing and is extendable in a proximal direction over
the
breathing circuit. After use, the filter and sleeve are discarded, while the
breathing
circuit is reused for multiple patients. The sleeve and filter reduces the
need for
sterilizing the circuit after each use. The sleeve is constructed of a
lightweight,
relatively inexpensive material to help minimize the costs of producing the
sleeve
member. A clear, extruded polyethylene, polypropylene or polyvinyl film having
a
thickness generally similar to a heavy-duty plastic food storage bag has been
found to perform admirably in this role as a sleeve member. The sleeve does
not
serve as a conduit for providing or exhausting respiratory gases.
US Patent 5,377,670, to Smith, discloses a casing or envelope for a
breathing circuit to reduce heat transfer between the corrugated tube and the
ambient atmosphere, thus the case or sleeve of the breathing circuit serves as
an
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insulation means. The envelope or casing is not a conduit for providing
inhaled
and receiving exhaled gases. US Patent 5,983,896, to Fukunaga, discloses a
multilumen unilimb breathing circuit that provides the advantages of
maintaining
humidity and temperature due to the counter-current effect of the gases.
While the above devices fulfill their respective, particular objectives and
requirements, the aforementioned patents and the prior art do not describe a
device
wherein at least one of the respiratory conduits is comprised of a non-
conventional
(also referred to as "new era") pipe or tube (i.e., different from a rigid-
walled tube,
pipe, corrugated tube, or pleated tube), which is both axially and radially
flexible,
but which has little or no compliance beyond a certain conduit radius and/or
volume. By radially flexible, it is meant that the diameter of the conduit can
be
substantially reduced or the conduit can be relaxed or collapsed in cross-
section in
comparison to rigid-walled conventional tubing. This is distinguished from
axially
bending the tubing without substantially altering the cross-sectional area of
the
tube at the bend as is possible with rigid-walled prior art tubing. Prior art
rigid-
walled respiratory conduits maintain patency under ambient conditions as well
as
under the pressure differentials between their interior and exterior that
occur
during use for providing inspiratory and/or receiving expiratory gases. Since
these
prior art respiratory conduits do not radially collapse under ambient
conditions
(e.g., when not in use), they require greater space for shipping and storage,
and
they require thicker walls to have sufficient rigidity to avoid collapse under
ambient and operating conditions. Thus, a greater amount of plastic is used to
produce such tubing, which increases costs, as well as the volume of the waste
produced.
In general, circuit compliance (i.e., expansion of the volume of circuit
tubing under operating pressures) is undesired as it interferes with the
accuracy
and precision of gas administration. Further, excessive compliance may lead to
insufficient gases reaching the patient's lungs.
The present inventors discovered that, so long as the respiratory conduits,
and preferably the inspiratory conduit, can maintain patency for inspiratory
and
expiratory gases, the conduits do not need to be always patent like rigid-
walled
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pipes or tubes (e.g., corrugated plastic tubes that maintain a fixed diameter
at
ambient conditions and /or which are relatively rigid or straight). The
respiratory
conduits of the present invention should, however, provide low resistance and
little compliance during use sufficient to meet the requirements for
spontaneous
and assisted ventilation. It is preferred that the inspiratory conduit permit
gas flow
at all times, and even under negative pressure, and that the expiratory line
provide
positive pressure even in spontaneous ventilation.
DEFINITIONS
To facilitate further description of the prior art and the present invention,
some terms are defined immediately below, as well as elsewhere in the
specification. As used herein, the term "artificial or assisted ventilation"
shall also
incorporate "controlled and spontaneous ventilation" in both acute and chronic
environments, including during anesthesia. Fresh gases include gases such as
oxygen and anesthetic agents such as nitrous oxide, halothane, enflurane,
isoflurane, desflurane, sevoflurane, that are generally provided by a
flowmeter and
vaporizer. The end of a conduit directed toward a patient shall be referred to
as the
distal end, and the end of a conduit facing or connected to a source of
inspiratory
gases shall be referred to as the proximal end. Likewise, fittings and
terminals or
other devices at the distal end of the breathing circuit, e.g., connecting to
or
directed at the patient airway device (i.e., endotracheal tube, laryngeal
mask,
laryngeal tube, face mask etc.), will be referred to as distal fittings and
terminals,
and fittings and terminals or other devices at the proximal end of the
breathing
circuit will be referred to as proximal fittings and terminals. So, a distal
adaptor or
connector would be located at the distal or patient end of a circuit.
It is generally understood that a proximal terminal in a multilumen unilimb
breathing circuit context is located at the machine end of the circuit and
separates
at least two independent flow paths that are in parallel closely-spaced or
apposed
relationship or that are coaxial in the circuit so that at least one flow path
can be
connected to a source of inspiratory gases while another flow path can be
connected to an exhaust port that is spaced from the inspiratory gas port. A
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proximal terminal may also comprise a rigid housing that merges two
independent
flow paths into a common flow path, for example a Y-type fitting, preferably
with
a septum. The use of a proximal fitting with a proximal terminal in a unilimb
circuit is a new concept brought about by the Universal F2 inventions, which
for
the first time made it possible to readily connect and disconnect plural tubes
to a
proximal terminal on an assisted ventilation machine via a corresponding
proximal
fitting. Unlike the proximal terminal, when a proximal fitting comprises
multiple
lumens, the proximal fitting maintains the spatial relationship of the
proximal ends
of the tubes forming a multilumen circuit. Hence a proximal fitting in a
breathing
circuit is to generally be understood as a fitting which permits ready
connection of
tubing to a proximal terminal which can provide inspiratory gases and exhaust
expiratory gases from separate spaced ports. In some embodiments of the
present
invention tubing may be directly bonded to a proximal terminal, while in other
embodiments tubing may connect to a proximal fitting that can engage a
corresponding port or ports on a proximal terminal. The proximal fitting may
include filter means, or may engage a filter which in turn connects to a
proximal
terminal.
The term conduit broadly comprises fluid carrying members without being
limited to conventionally used corrugated tubes, such as those used in
presently
available breathing and/or anesthesia circuits (i.e., a conduit has a lumen
defined
by one or more walls, has a variety of shapes and diameters, and serves the
purpose of carrying inspiratory gases to or expiratory gases from a patient).
For
example, conduits for use with the present inventions may comprise flexible
fabric
or plastic sheaths (like a film or sheet made of plastic, such as polyvinyl,
that can
have a cylindrical or tubular form when gases or fluid are contained, but
collapses
or looses the tubular form when deflated or emptied) and/or flexible tubes
that
may be smooth-walled, straight, corrugated, collapsible, and/or coiled. In
this
respect, certain embodiments of the present invention substantially depart
from the
conventional concept and design of prior art respiratory conduits. Embodiments
of
flexible conduits for carrying respiratory gases to and/or from a patient in
accordance with the present invention can be both flexible in the radial and
axial
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directions up to a maximum volume and/or radius (or maximum cross-sectional
area where the cross-sectional shape is not circular), and have a wide variety
of
cross-sectional shapes, and in so doing provide a low cost apparatus very well
suited to providing respiratory care, i.e., assisted ventilation to a patient,
which is
5 effective and practical.
Unconventional or non-conventional tubular conduits refer to conduits used
in a respiratory circuit for carrying patient inspiratory and/or expiratory
gases that
are made of materials and/or have shapes not previously used in assisted
ventilation or anesthesia machines for carrying inspiratory and expiratory
gases
10 between a patient or other mammal and the machine. By carrying patient
inspiratory and/or expiratory gases, it is understood that the gases are being
provided via a conduit to a patient from a source (e.g., ventilator machine)
and
exhausted via the same and/or another conduit to an exhaust (e.g., assisted
ventilation machine). For example, a coiled inspiratory or expiratory conduit
when
used in accordance with the present invention is a non-conventional tubular
conduit. Likewise, a conduit formed of flexible, gas impermeable fabric, such
as
but not limited to extruded polyethylene, polypropylene or polyvinyl film,
that is
radially expandable to a maximum radius and volume under pressures generally
used in assisted respiration and is collapsible when the pressure inside of
same is
less than ambient pressure or the pressures generally used in assisted
respiration,
can be used as a non-conventional respiratory conduit in accordance with the
present invention. Ambient pressure refers to the pressure normally
encountered
outside of tubes, which is generally atmospheric pressure. Such conduits can
maintain patency as needed in use yet readily relax or collapse (collapsing
may
require some assistance depending on the embodiment) to smaller diameters,
lengths, and volumes, particularly when the internal pressure inside is
sufficiently
lower than the pressure outside of the conduit.
For the purposes of brevity, the term Suave Tm flexible tube is used to
describe a flexible respiratory conduit for use in carrying respiratory gases
(i.e.,
gases to be inspired and expired gases to be exhausted) between a patient and
a
ventilation machine or respiratory care device in which the conduit is
radially
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collapsible when not in use, and can expand to a maximum predetermined
diameter (or maximum cross-sectional area; maximum diameter and maximum
radius incorporate maximum cross-sectional area when the cross-sectional shape
is
not circular) and volume during use (such a conduit shall be hereinafter
referred to
in this document as a suave tube or suave conduit; no trademark rights are
waived
by use of the term suave or any other mark used herein regardless of case or
inclusion of the TM or symbol). Upon expansion to its maximum diameter
(i.e.,
maximum cross-sectional area) a suave tube exhibits substantially the same
compliance in assisted ventilation applications as conventional corrugated
tubes or
pleated tubing (i.e., ULTRA-FLEX ) conduits. Suave flexible tubes may also be
axially expanded or contracted. Suave tubes are much less expensive to
manufacture than conventional conduits having a relatively rigid diameter or
cross-sectional shape, such as those formed of corrugated tubing.
Preferred radially collapsible tubes for use in the present invention will,
when inflated at pressures encountered in providing assisted ventilation
and/or
anesthesia to humans and other mammals, have a compliance of less than about
50%, preferably less than about 20%, more preferably less than about 10 %,
even
more preferably less than about 5%, and most preferably less than about 2%.
Preferred radially collapsible tubes for use in the present invention have a
minimum cross-sectional area when fully inflated sufficient to meet the
desired
flow characteristics (hereinafter, referred to as the inflated cross-sectional
area),
and can collapse so that the collapsed cross-sectional area is preferably less
than
about 90% of the inflated cross-sectional area, more preferably less than
about
70% of the inflated cross-sectional area, even more preferably less than about
50%
of the inflated cross-sectional area, even more preferably less than about 25%
of
the inflated cross-sectional area, and most preferably less than 10% of the
inflated
cross-sectional area.
In one embodiment, the suave tubes are shipped and stored in collapsed
form, and after inflation thereof no subsequent effort may be made to collapse
them, except optionally to compress the suave tubes to a smaller volume for
disposal. In this way, manufacture, shipping and storage costs are minimized.
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Gravitational forces will cause the suave tubes to collapse to varying degrees
in
some embodiments when not pressurized sufficiently.
BREATHING CIRCUIT REQUIREMENTS
A patient requiring artificial ventilation or anesthesia may be positioned in
an awkward position and depending on the surgical site the required length of
the
circuit may vary. This is also so in patients undergoing diagnosis, e.g., MRI,
CT
scans, etc. It is therefore desirable to have a breathing circuit that is
flexible and
that the length of both the inspiratory or fresh gas delivery tube and the
expiratory
or exhaust tube can be adjusted while minimizing disconnections, obstructions,
entangling and kinking. It is also desirable to have breathing circuits that
are light
in weight. Furthermore, for cost containment, the health care providers (i.e.,
hospital, physician, ambulatory surgery center, nursing homes, etc.) require
inexpensive breathing circuits and/or inexpensive methods to provide
artificial
ventilation or anesthesia to patients in need thereof.
Breathing circuits may be classified based on how carbon dioxide is
eliminated. Carbon dioxide can be eliminated by "washout", which is dependent
on the fresh gas inflow (i.e., CO2 absorption is not required, e.g., in a
Mapleson
type circuit), or by using a CO2 absorber such as soda lime and the like,
(i.e., as in
a circle circuit). Thus, breathing circuits in anesthesia are generally
provided as
circle circuits (CO2 absorption system) or Mapleson type circuits. Because
Mapleson D type partial rebreathing systems require high fresh gas flows, the
circle system is the most widely accepted system. Breathing systems wherein
low
fresh gas flow can be utilized are advantageous because of reduced consumption
and waste of fresh gases (e.g., anesthetic gases), ecological benefits
(reduced
environmental pollution), and cost-savings. However, a major concern of low
flow techniques in anesthesia is the efficiency of fresh gas utilization and
the
unpredictability concerning the alveolar or inspired concentration of
anesthetics
provided to the patient that should be administered in sufficient dosages to
achieve
desired anesthetic endpoints (e.g., avoid awareness during surgery without
overdosing). Moreover, there is a significant discrepancy between the volatile
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anesthetic vaporizer setting concentration and the inspired concentration of
anesthetic gases. A further concern with the circle system is the interaction
of
volatile anesthetics with the carbon dioxide absorber (e.g., soda lime), which
has
been recently reported as producing toxic substances. This concern includes
the
formation of carbon monoxide and Compound A during degradation of volatile
anesthetics by soda lime. For example, CO has been found in anesthetics,
including halothane, enflurane, isoflurane and desflurane circle systems.
Moreover, in the case of sevoflurane, it is known that sevoflurane is degraded
in
the presence of soda lime to olefin and Compound A, which has been reported to
have nephrotoxic potential at clinical concentrations. Further, it is desired
to
reduce waste of expensive anesthetic and respiratory gases in circle systems
and
Mapleson type systems.
A major concern with prior unilimb breathing circuits is that the inspiratory
gas or fresh gas line not become disconnected or blocked (e.g., via kinking)
during
use. For this reason, rigidly bonding the proximal end of the inspiratory gas
line to
the fresh gas inlet fitting was stressed, while the distal end was permitted
to move
with respect to the distal end of the outer conduit (e.g., exhaust conduit),
which
could create a variable dead space. Despite the surprising discovery reported
in
U.S. Patent 5,778,872, to Fukunaga, that an appropriate dead space in a
breathing
circuit could be beneficial by yielding normocapnia without hypoxia, there is
still
a desire for a circuit that has either a minimum and/or fixed dead space
regardless
of circuit manipulation, yet is flexible and safe. Further, there is a desire
for
systems that more efficiently utilize anesthetic gases in a safe and
predictable
manner. It is also desired that the same breathing circuit be utilized in both
adult
and pediatric cases, or at least in a greater number of patients, thereby
minimizing
the need for circuits of different size. There is also a need for breathing
circuits
and systems that are simpler, lightweight, cost-effective, safer, and/or
easier to
operate and handle than prior circuits and systems.
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SUMMARY OF THE INVENTION
An embodiment of the present invention includes a breathing circuit,
wherein at least one of the respiratory conduits is a non-conventional
conduit.
Thus, in a unilimb, dual limb or a multilimb circuit, a non-conventional
conduit
may be used to carry inspiratory and/or expiratory gases between a patient or
other
mammal and a machine. For example, in an embodiment, at least one tube in the
circuit may be a collapsible or suave tube, or may be a spiral or coiled tube.
Such
circuits may be referred to as F3TM circuits or Universal F3Thl circuits (no
waiver
of trademark rights is made hereby for these or other marks used herein).
An embodiment of the present invention includes a multilumen respiratory
circuit comprising first and second conduits, wherein the proximal ends of the
first
and second conduits can each be connected to a respective inlet or outlet
fitting,
and movement of the distal end of the first conduit causes a corresponding
movement of the distal end of the second conduit. Thus, the circuit members
interact so that axial extension or contraction of one member causes a
corresponding axial extension or contraction in length of a second member.
This
latter type of circuit may also be referred to herein as an F3Tm contractible
circuit
or a Universal F3114 circuit. In an embodiment, at least one of the conduits
is a
coiled tube. In another embodiment, a coiled tube is contained within an outer
flexible tube that is axially extendable and compressible, forming a unilimb
multilumen respiratory circuit, which may also be referred to herein as an F
Coil
circuit.
In an embodiment, the outer flexible conduit may be a pleated tube or a
non-conventional conduit to provide for axial extension and contraction. In an
embodiment, an accordion-like tube (e.g., UTLRA-FLEX tube), is divided
internally by a common wall that is made of a flexible plastic or gas-
impermeable
fabric that allows simultaneous radial expansion of one lumen while causing
contraction of the other lumen(s) sharing the common flexible wall. In another
embodiment, a non-conventional conduit can be joined side by side with a
pleated
tube either by continuous or spaced attachment. Further, two or more Suave'm
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tubes can be used together to create a multi-lumen Suave" 4 tube respiratory
conduit. Such a multi-lumen SuaveTM tube respiratory conduit can be
manufactured by extruding a tube of flexible plastic in much the same way
plastic
storage bags are formed. However, rather than heat sealing radially across the
5 extruded tube to form a bag, axial seams can be heat formed in the axial
direction
to form separate gas carrying lumens.
Proximal and distal fittings can be bonded at the proximal and/or distal
ends of the lumens in the respiratory conduit devices of the present invention
to
facilitate operative connection to machines and patients, respectively.
10 An embodiment of the present invention includes a multilumen
respiratory
conduit comprising at least first and second flexible tubes, wherein the
proximal
ends of the first and second flexible tubes can each be connected to an inlet
or
outlet fitting, and wherein at least one of the flexible tubes is comprised of
a non-
conventional plastic tubular material (e.g., formed of a flexible fabric, such
as
15 polyvinyl). Such a respiratory conduit is capable of maintaining
respiratory
patency under the range of conditions encountered in providing respiration,
whether spontaneous or assisted ventilation (i.e., affording free passage of
inspiratory and expiratory gases), but may partially or substantially
completely
collapse when not in use. Such a tube can be shipped in collapsed or
substantially
collapsed form. The tubes forming the multilumen respiratory conduit can be
arranged side by side, have periodic connections to one another, or one can be
contained within another, and their shapes can be greatly varied. For example,
a
circular cross-sectional shape is not necessary. The distal and proximal ends
of
each tube can be formed of a more rigid material than the rest of the tube or
be
bonded to a fitting to facilitate connection to an inspiratory gas source, an
exhaust
outlet, to a carbon dioxide canister for recirculation of gases such as that
used in
an anesthesia machine, and to airway devices such as respiratory masks and
endotracheal tubes.
The present invention also involves new systems and methods of
optimizing utilization of fresh gases during artificial or assisted
ventilation,
including administering anesthesia. In an embodiment, a Mapleson D type system
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is modified and combined with a modified CO2 absorption circle system to
produce an efficient system, wherein the system is capable of optimizing the
utilization of anesthetic gases in a safe and predictable manner. By providing
undiluted fresh gases at the patient side (i.e., distal end of the circuit)
and
circulating the expired gases through a scrubber circuit having a carbon
dioxide
absorber, the system provides assurance that the patient receives more
accurate
fresh gas concentrations (i.e., close to the anesthesia machine flow meter's
oxygen
concentration and the volatile anesthetic vaporizer's concentration setting).
In
addition, recirculating the gases allows re-use of the gases after CO2
elimination,
thereby providing reliable low flow anesthesia. As a result, utilization of
fresh
gases is optimized. Furthermore, by using a unilimb multilumen breathing
circuit
wherein the dimensions of at least one of the breathing conduits can be
altered to
adjust the volume therein or by using mutually adjustable length members, the
anesthetic concentration and amount of rebreathing can be safely adjusted and
predictably optimized, and the same breathing conduit or circuit may be
utilized
universally in adult and pediatric cases.
The circuits do not need to be individually packaged, but more than one
circuit can be packaged together. An advantage of having several circuits
packed
together is that the packaging can be more compact, also reducing storage and
shipping costs, and waste. Furthermore, only one bag or box needs to be opened
instead of several plastic bags, which decreases set up time. All of the above
savings can be substantial as they help optimize operating room utilization
(e.g.,
reduced waiting time for professionals between operations due to reduced
operating room cleaning and set up time). Therefore, the present invention
enhances health care cost-effectiveness beyond device cost savings. The
circuits
and systems of the present invention are simple, compact and lightweight to
facilitate storage and shipping, use less plastic and result in less medical
waste
being generated, and are safe, practical, easy to handle, protect the
environment
and promote cost-effective artificial ventilation.
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In another embodiment of the present invention, there is provided in a
ventilation or anesthesia system with a recirculation module, a rebreathing
tube comprising a
proximal end opening operatively connected to the recirculation module for
providing expired
gases to and receiving gases from the recirculation module, a distal end
opening spaced apart
from the proximal end opening, the proximal end in fluid communication with
the distal end
opening such that the expired gases and the gases received from the
recirculation module mix
within the rebreathing tube, and a distal input for fresh gases, wherein said
distal input is
located in a distal portion of said rebreathing tube or in a distal fitting
operatively connected to
said distal portion of said rebreathing tube, wherein the length of said
rebreathing tube is
adjustable and adjustment of said length adjusts a volume of said rebreathing
tube and the
concentration of fresh gases administered to a patient or mammal connected to
said system.
In another embodiment of the present invention, there is provided use of a
rebreathing circuit for providing anesthetic and respiratory gases at low
flows to a human or
other mammal, wherein the rebreathing circuit has a distal and proximal end
and comprises a
first tube and a second tube, wherein the second tube has a distal end and a
proximal end,
wherein the proximal end of the second tube is operatively connected to a
scrubbing module
for scrubbing and recirculating at least a portion of expired gases received
thereby, and the
first tube has an output that is operatively connected to said distal end of
said circuit for
providing fresh gases to the human or other mammal via the distal end of the
circuit, wherein
the length of said second tube is adjustable and adjustment of said length
adjusts a volume of
said second tube and the concentration of fresh gases administered to a
patient or mammal
connected to said rebreathing circuit.
The present invention may be better understood by reference to the figures and
further detailed description below. For the purposes of facilitating
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understanding of the invention, in the following figures certain fitting
components
are not shown and/or certain fitting components are shown in simplified form.
For
example, struts or flanges for spacing components from one another are not be
shown, and wall thickness and relative tube diameters and lengths are not to
scale.
DESCRIPTION OF THE FIGURES
Fig. 1 is a diagram illustrating a retracted first, coiled-tube conduit
contained within a compressed second conduit, with both the proximal ends of
the
first and second conduits being attached to a common proximal fitting, wherein
a
portion of the second conduit is not shown to permit viewing of the first
conduit.
Fig. 2 is a diagram illustrating a portion of the device of Fig. 1 upon
extension.
Fig. 3 A - D illustrate the operation of a Mapleson D type system and
Circle CO2 Absorption System.
Fig. 4 A ¨ C illustrate the components and operation of a system
constructed in accordance with the present invention, with 4B&C illustrating
the
system using a coil within a tube circuit embodiment of the present invention,
in
which the outer tube is an accordion-like tube (e.g., Ultra-Flex ).
Fig. 5 A ¨ D illustrate the components and operation of systems
constructed in accordance with the present invention using the double coiled
circuit embodiment of the present invention.
Fig. 6 A-B illustrate the components and operation of the sliding inner tube
embodiment of the present invention, in which a smooth-walled conventional
inspiratory gas line is inserted through a fitting into an axially expandable
and
collapsible tube.
Fig. 7 A - B illustrate the components and operation of a dual coaxial
accordion tube embodiment of the present invention.
Fig. 8 A ¨ B illustrate the components and operation of a wavy tube or
sheath in an accordion tube embodiment of the present invention, with a
portion of
the outer tube removed to reveal the inner tube.
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Fig. 9 A ¨ B illustrate the components and operation of a common
contractile wall embodiment of the present invention, with a portion of the
outer
tube removed to reveal the inner tube.
Fig. 10 illustrates the components and operation of another version of the
embodiment of Figure 8, in which a first conduit formed of a smooth plastic
lamina, a suave tube, envelopes an inner tube or second conduit comprised of a
corrugated tube in which the outer tube is cut away to reveal the inner tube,
and an
intermediate section removed to accommodate scaling of the figure. While the
outer or first conduit can collapse when not being used, the inner conduit
maintains its diameter during respiratory care operating conditions and during
ambient and non-use conditions,
Fig. 11 illustrates the components and operation of a unilimb respiratory
conduit, in which a first flexible tube is a conventional flexible corrugated
or
pleated tube that maintains a fixed diameter at ambient conditions and over
respiratory therapy operating conditions, while the second tube is a non-
conventional plastic tube that may radially collapse when patency is not
required.
Fig. 12 illustrates the components and operation of a unilimb respiratory
conduit formed of two non-conventional tubes or conduits, e.g., suave tubes,
joined at their distal and proximal ends. One of the tubes includes a coiled
tube,
which is more radially rigid than the tube in which it is contained so as to
assist in
maintaining patency of its host tube.
Fig. 13 (a) and (b) illustrate a respiratory conduit in expanded form (a) and
compressed form (b), in which the outer or first conduit is a suave tube with
a
portion removed to reveal the inner tube, and the inner conduit is a coiled
tube
wherein the coiled tube lumen has a relatively rigid cross-sectional shape.
Fig. 14 is a graph illustrating the relationship of inspired (F1) and
delivered
(FD) isoflurane concentration during graded low fresh gas flow (FGF)
anesthesia.
Fig. 15 is a graph illustrating the relationship of inspired (F1) and end
tidal
(PET) concentration to delivered (FD) concentration with a constant vaporizer
setting of 1.2% isoflurane during low flow anesthesia (1 L/min FGF).
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Fig. 16 illustrates an exemplary dispenser for dispensing multiple
respiratory conduits, the latter being shown in block form.
DETAILED DESCRIPTION OF THE INVENTION
Firm CIRCUITS ¨ CIRCUITS WITH UNCONVENTIONAL (NEW ERA)
CONDUITS
With reference to Fig. 1, an embodiment of the present invention is
illustrated, including a multilumen breathing circuit with interacting
mutually
adjustable length members. This embodiment, also referred to herein as the F-
CoilTM circuit, has optional proximal fitting 10 and an optional distal
fitting 20.
First conduit 30 is a coiled resilient tube having a proximal end 32 and a
distal end
34. Proximal end 32 of first conduit 30 is connected to proximal fitting 10
and
distal end 34 of first conduit 30 is connected to distal fitting 20. In an
alternative
embodiment, proximal fitting 10 may provide a proximal connector for tube 30.
End 32 and fitting 10.may vary in diameter, shape and spatial relationship to
provide for connection to any standard "Ffm type" proximal terminal, such as
that
described in U.S. Patent 5,778,872, to Fukunaga.
In a preferred embodiment, the second or outer tube 40 is flexible and
corrugated, and formed of a transparent (or semi-transparent) material.
Preferred
corrugated tubing includes, for example ULTRA-FLEX , which upon axial
extension from its compressed axial conformation, or vice versa, will retain
its
axial length (e.g., will not rebound; i.e., accordion-like pleated tubing).
Further,
the ULTRA-FLEX , when bent, will retain the angle of curvature to which it is
bent without substantial reduction in the tube's inner diameter. Suitable
corrugated
tubing for use in the present invention is used in the Ultra-Flex circuit,
ULTRA-
FLEX tubing from King Systems Corporation, of Noblesville, IN, U.S.A., or the
tubing used in the IsoflexTM circuit sold by Baxter Corporation of Round Lake,
IL,
USA. The tubing may be formed with integral distal and/or proximal fittings,
wherein the fittings have relatively thicker or more rigid walls than the
tubing, or
the tubing can be bonded or welded to appropriately shaped fittings as
desired.
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As should be abundantly clear to one of skill in the art from the forgoing
summary and definitions, there are many embodiments of the present invention
that are envisioned and encompassed. For example, diameters of first and
second
conduits (30, 40) may vary depending on use. Also, outer tube 40 or inner tube
30
5 may be replaced with a suave tube. It should be clear that a coiled
flexible tube
may change its overall axial configuration without altering the cross-
sectional
shape of the lumen or lumens within it.
The outer tube 40 ends in an optional distal outer fitting 20, which is
designed for ready connection to patient devices, such as an endotracheal
tube,
10 laryngeal tube, laryngeal mask or anesthesia mask.
In an embodiment, the distal end 34 of the first tube may be directly
bonded to the interior of second tube 40. Optionally, the first tube may be
directly
bonded to the interior of second tube 40 at a series of designated points
along the
length of tube 40. First tube 30 may also be wrapped around the exterior of
tube
15 40, and periodically bonded to the exterior thereof.
With reference to optional distal fitting 20, the distal end 34 of first tube
30
is shown bonded thereto. In an embodiment, distal fitting 20 is connected to
an
optional inner distal fitting to which the distal end 34 of first tube 30 may
be
connected. The length of fitting 20 may be extended and the connection point
20 between fitting 20 and the optional distal inner fitting made axially
adjustable,
wherein a predetermined dead space may be provided.
With reference to Figure 2, it can be seen that second conduit 40 has been
axially extended, which causes first conduit 30 to axially extend. The length,
diameter, number of coils per inch, and resiliency of first conduit 30 is
selected to
prevent kinking of first conduit 30 upon extension that would block flow
therethrough, yet provide for axial retraction or rebound of coil 30 upon
axial
contraction of outer tube 40, without compromising the performance of the
unilimb circuit. Preferably, the resiliency of the coil, or tendency to
recoil, should
not cause disconnection of the proximal end 32 of the inner conduit 30 from
proximal fitting 10 when the outer conduit 40 is axially extended to its
maximum
length, and likewise it should not cause the distal end 34 of inner conduit 30
to
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axially move with respect to the distal end of tube 40. Inner conduit 30 can
be
manufactured from medical grade plastic, for example, that used to provide for
respiratory gas sampling, or such as that used in intravenous fluid devices.
An axially extensible and collapsible or compressible tube (e.g, accordion-
like tubing, coiled tubing, etc.) used as the first tube (which may be an
inner or
outer tube), and wherein the second, or inner tube or adjacent tube also
expands or
compresses in a synchronized manner with the first tube is greatly desirable
because it promotes safety, as disconnections, obstructions and kinking are
diminished. This also enhances rebreathing control and provides greater
flexibility and cost effectiveness as manufacturing, storage and shipping
become
less expensive.
DOUBLE COIL CIRCUIT EMBODIMENT
With reference to Figure 5A-B, an embodiment of a new circuit is
illustrated. Two coiled tubes 60 and 62 are in parallel-coiled relationship to
form a
double coil circuit. The tubes may be bonded together at one or more external
points, one tube may be formed within the other, or one tube may be divided by
a
common wall forming two lumens. With reference to 5B, the interaction of the
members upon expansion is illustrated in an exploded view, along with their
alignment with a proximal fitting 70 and proximal terminal 80 used in a circle
system. Flow arrows demonstrate the paths of inspiratory gases from the FGF
(fresh gas flow) inlet and to the expiratory gas outlet. Tubes 60 and 62 are
connected at their distal ends to a distal fitting 72 via nipples 74.
Figures 5C-D illustrate an alternative embodiment of the double coil
illustrated in
Figures 5A-B. Coiled tubes 600 and 620 are connected to a proximal fitting
700,
which connects the respective tubes to proximal terminal 800 used in a circle
system. Note that tubes 600 and 620 are interlocked by the interaction of
their
coils, and may optionally be periodically bonded together. As the proximal and
distal openings in tubes 600 and 620 are independent, fittings can be attached
on
either the inside or outside of the walls of tubes 600 and 620. Tubes 600 and
620
are connected at their distal ends to a distal fitting 702 via nipples 704.
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SLIDING INNER TUBE CIRCUIT EMBODIMENT
With reference to Figures 6 A-B, the components and operation of an
embodiment of a circuit in accordance with the present invention is
illustrated. A
first tube 90 is slidably inserted into proximal fitting 92 via sealing
fitting 94. A
second tube 96 is connected at its proximal end to proximal fitting 92, with a
portion of tube 96 removed to reveal the first tube 90 inside. Tube 96 is
axially
compressible and extendable, and may be for example made of ULTRA-FLEX
tubing. First tube 90 is provided with a smooth walled portion to permit
sliding in
and out of fitting 92 in response to axial contraction and extension of tube
96. The
mutually axial interaction of the circuit members may be accomplished by
direct
connection of the distal end of tube 90 to the distal end of tube 96, via a
common
distal fitting, or other operative connection techniques and devices.
DUAL ACCORDION CIRCUIT EMBODIMENT
With reference to Figures 7A-B, the components and operation of an
embodiment of a circuit in accordance with the present invention is
illustrated in
schematic form. Dual coaxial accordion tubes 98 and 100 may be connected at
their proximal ends to each other or to a proximal fitting. The tubes 98 and
100
may both be ULTRA-FLEX tubing. Spacing flanges or perforated disks 102 may
be placed between the inner and outer tubes to optimize flow. The mutually
axial
interaction of the circuit members may be accomplished by direct connection of
the distal ends of the tubes to each other, via a common distal fitting, or
other
operative connection techniques and devices, for example by a spacing flange
or
disk 102 placed near or at the distal end of tube 98.
WAVY TUBE CIRCUIT EMBODIMENT
Figures 8A-B illustrate the components and operation of a wavy tube
sheath in an accordion tube circuit embodiment of the present invention in
schematic form. A relatively smooth walled tube 106 has a fixed bias to have a
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wavy contracted shape. Tube 106, of resilient material, can straighten when
extended and return to its pre-biased contracted shape. An outer tube 108 can
be
extended and contracted simultaneously with tube 106. Spacing flanges or
perforated disks may be placed between the inner and outer tubes to optimize
flow. As with other circuit embodiments, the mutually axial interaction of the
circuit members may be accomplished by direct connection of the distal end of
the
tubes to each other, via a common distal fitting, or other operative
connection
techniques and devices. Further, a variety of material can be used. For
example,
while tube 108 may be ULTRA-FLEX , tube 106 may be a fabric or plastic sheath
that can be elastic and radially flexible. Preferably, the axial resiliency
(i.e.,
tendency to recoil or contract) of the inner conduits in the circuits of the
present
invention is insufficient to dislodge the proximal end thereof from an
inspiratory
gas inlet when the circuit is fully extended. For example, in drawing 8B, the
tendency of tube 106 to rebound to its compressed or relaxed state,
illustrated in
drawing 8A, should not be sufficient to dislodge the proximal end of tube 106
from proximal fitting 110 when the fitting is held stationary and the conduits
108
and 106 extended. As noted above, tube 106 may be a fabric or plastic sheath
that
can be radially flexible. Thus, tube 106 may be a suave tube, and/or tube 108
may
be a suave tube. For example, the inner or outer tubes of a respiratory
conduit in
accordance with this embodiment of the present invention may relax or collapse
when not in use and expand to required patency on demand. Additional lumens
can be added in this and other embodiments.
HYBRID CIRCUIT EMBODIMENT
A hybrid circuit comprises conventional conduit and at least one flexible
plastic sheet (e.g., polyvinyl) that forms a wall defining two or more lumens
in the
conduit. Figures 9A-B illustrate the components and operation of hybrid
circuit
with a common contractile wall of the present invention in schematic form.
First
and second tubes 116 and 118 share a common outer wall 120 that is axially
expandable and contractible, and a common dividing wall 122 that can axially
expand and contract with the outer wall. This embodiment may be constructed of
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pleated material such as that used to form ULTRA-FLEX . Alternatively,
common dividing wall 122 may be formed of a flexible plastic sheet, which
permits the cross-sectional size of the two lumens to accommodate usage
conditions. For example, when pressure is higher in one lumen than the other,
the
wall expands into the lower-pressure lumen to make it smaller than the higher-
pressure lumen, while the former lumen becomes larger. Preferably, the wall
has a
maximum radius under respiratory care operating conditions. Additional lumens
can be included, which either share the common flexible wall, or have
diameters
that are independent of the diameters of the other lumens. This embodiment can
be
formed by cutting conventional tubing in half, and bonding a flexible plastic
sheet
in between the two halves, or by extruding elongated hemi-circular shaped
portions of plastic, and bonding a flexible plastic sheet between matching
tube
halves.
RELAXED CIRCUIT EMBODIMENTS
Fig. 10 illustrates the components and operation of another version of the
embodiment of Figure 8 in schematic form, in which a second conduit formed of
a
smooth plastic lamina, e.g., a Suave ml tube, 140 envelopes an inner tube or
first
conduit 150 comprised of a corrugated tube. While the outer or second conduit
140 can collapse when not being used, the inner conduit 150 maintains its
diameter during respiratory care operating conditions and during ambient and
non-
use conditions. This embodiment makes more explicit what is stated in regards
to
Figure 8, in that one of the tubes can be radially flexible. In a preferred
embodiment, the respiratory conduit 141 includes a proximal fitting 142 that
is
bonded to proximal ends of tubes 140 and 150. The proximal fitting facilitates
connection to a corresponding proximal terminal. A distal fitting 151 is
connected
to the distal ends of tubes 140 and 150. The distal end of tube 150 is bonded
to
flanges 152. Radial flanges 152 are not solid annular rings, but have gaps 153
to
permit flow of gases from common zone 154 into tube 140. While tube 140 may
collapse under ambient, non-use conditions, in use, tube 140 may be expanded
to
its maximum radius and volume during expiration as well as during inspiration
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(depending on whether it is used for inspiration or expiration) provided there
is a
sufficient flow rate of gases; there is no or minimal compliance at maximum
radius. Axial flanges 155 connect to radial flanges 152 and grip the distal
end of
inner tube 150. Tube 150 may be bonded to radial flanges. Axial extension of
5 radial flanges 152 and/or axial flanges 155 can provide a greater fixed
dead space.
As noted in other embodiments, the distal fitting, such as distal fitting 151,
can be
modified to provide for a sliding connection between the distal fitting main
housing and the connector to the inner conduit, wherein the dead space may be
adjusted to a desired volume.
10 Fig. 11 illustrates the components and operation of a unilimb
respiratory
conduit in schematic form, in which a first flexible tube 160 is a
conventional
flexible tube that maintains a fixed diameter at ambient conditions and over
respiratory therapy operating conditions, while the second tube 170 is a non-
conventional plastic tube that may radially collapse when patency is not
required.
15 In a preferred embodiment, tube 170 is a suave flexible tube. A new
proximal
fitting 162 is illustrated, in which a coaxial flow is diverted into two
independent
lumens 163 and 164 that have two independent non-interfering ports 165 and
166,
i.e., independent, non-interfering ports are ports that can be individually
accessed
without blocking or interfering with access to another port or requiring the
20 disconnection of one port. Distal fitting 172 has axial walls 173 and
174 to which
the distal ends of tubes 160 and 170 may be bonded. Extension of axial walls
173
and 174 permits for dead space adjustment. Connecting flange 175 has a gap 176
to provide for patency, while holding wall 174 in spaced relationship with
wall
173.
25 Fig. 12 illustrates the components and operation in schematic form
of a
unilimb respiratory conduit formed of two non-conventional tubes or conduits
180
and 190, e.g., suave tubes, joined at their distal ends by distal fitting 182
and at
their proximal ends by proximal fitting 192. Tube 190 includes a coiled tube
200,
which is more radially rigid than the tube in which it is contained so as to
assist in
maintaining patency of its host tube. Tube 200 may be used for gas sampling or
other purposes. For example, tube 190 may provide inspiratory gases. Tube 190
is
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held patent by the coiled tube 200, and tubes 180 and 190 are of fixed axial
length.
The recoiling of tube 200 causes tubes 180 and 190 to collapse axially. In an
embodiment, tube 200 includes a wire of metal or plastic that maintains
whatever
length it is extended to rather than being axially elastic as in other
embodiments.
The inner wall of tube 190 is optionally bonded at periodic intervals to tube
200 so
as to provide for even folding and extension of the fabric forming tube 190.
In an
embodiment, tube 200 is a solid wire.
Fitting 192 provides for rapid connection of the respiratory conduit to a
corresponding multilumen proximal terminal. While outlet 201 of tube 200 is
shown passing through the wall of fitting 192, fitting 192 may have an extra
lumen
for connecting tube 200 to a corresponding inlet or outlet.
The above non-limiting examples describe breathing circuits, also referred
to as multilumen unilimb respiratory conduits, which axially and/or radially
expand or contract. However, the breathing circuit does not need to expand or
contract axially. An embodiment may comprise one fixed length conduit that is
a
conventional corrugated tube or a smooth resilient tube having a pipe-like
configuration or. an ULTRA-FLEX tube, and the second conduit can be a non-
conventional conduit. Hence, the respiratory conduit can be of fixed length,
and
one or more of the tubes in it may radially expand and contract.
A breathing circuit or unilimb respiratory conduit of the present invention
can be readily connected to a respirator or ventilator, or to an anesthesia
machine
either via the proximal fitting of the respiratory conduits or via a proximal
terminal, such as the one described in US Patent 6,003,511. By matching the
proximal end of the proximal fitting to a unilimb respiratory conduit of the
present
invention to a corresponding proximal terminal, respiratory conduits in
accordance
with the present invention can be provided for quick and safe connection to a
variety of respiratory devices, including but not limited to anesthesia
machines and
ventilator machines. This can be done directly or via a filter. A breathing
circuit
of the present invention can be connected to a single filter or a multilumen
filter,
or manufactured integrally with a monolumen or multilumen filter. The proximal
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end of the filter housing can be configured for quick and safe connection to a
proximal terminal of a machine, and the distal end of the filter housing can
match
the configuration of the proximal end of the respiratory conduit.
Respiratory conduits of the present invention can also be used to ventilate
patients during transport, or be connected to a gas source (e.g., oxygen
source in
the post-anesthesia care setting, emergency room, etc.). Thus, the breathing
circuit
of the present invention is a multi-purpose breathing circuit. Instead of
utilizing a
new device, such as an expensive ambubag for transport, the same breathing
circuit of the present invention can be utilized to provide oxygenation during
transportation of a patient, for example to the PACU or other location. After
the
patient is transported for example from the operating room to the PACU, the
same
breathing circuit can be utilized to oxygenate the patient in the PACU,
without the
need to utilize an additional oxygen supply device, such as a nasal cannula or
clear
oxygen mask provided with an oxygen tube or a T piece set.
OPERATION OF MAPLESON D SYSTEMS AND CIRCLE CO2
ABSORPTION SYSTEMS
With reference to Figures 3A-D, drawing 3A illustrates a schematic
diagram of a Mapleson D system, in which the fresh gas flow ("FGF") 1 is
provided via fresh gas delivery tube 2 (shown in schematic form only) to a
distal
fitting 3. The operation of the system is better understood by reference to
the
numbered arrows and or part numbers. For example, during inspiration, gas to
lungs 4 flows simultaneously from fresh gas flow inlet 1 and bag 7 via flow
paths
a and b described in the key below Fig. 3A and by reference to part numbers
and
numbered arrows as follows: (1¨, 2¨, 3-4 4) + (7-0 6¨, 5¨, 4). During
expiration, gases flow from lungs 4 to waste gas outlet 8 via flow paths a'
and b'
as follows: 4¨, 5¨, 6¨, 7¨* 8.
Drawing 3B illustrates a Bain circuit used with a Mapleson D system. A
key feature of the Bain is that the fresh gas tube 2 is inserted in the
proximal
terminal at the proximal end of the circuit and the tube extended through
breathing
tube 5 to have its distal end 3 at the distal end of the circuit.
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Drawing 3C illustrates a circle CO2 absorption system, which has a CO2
absorber 12, check valves (i.e., unidirectional valves) 4 and 9, as well as
inspiratory conduit 5 and expiratory conduit 8 that meet at distal fitting 6.
During
inspiration, gas to lungs 7 flows simultaneously from fresh gas flow source 1
and
bag 10 via flow paths c and d in the key below Fig. 3C as follows: (1-4 2-, 3-
4-* 5-, 6-, 7) + (10-, 12-, 4-, 5-4 6-, 7). During expiration, gases flow from
lungs 7 to waste gas outlet 11 via flow paths c' and d' as follows: (1-42-*3-
)12)
+ (7-, 6-, 8-+ 9-4 10-* 11.
Drawing 3D illustrates a circle CO2 absorption system, which uses either a
Universal F or Universal F2 circuit using an F21m-type proximal terminal.
Inspiratory conduit 5 is coaxial within expiratory conduit 8 distal of the
proximal
terminal.
It is important to note that in the circle system, fresh gases are combined
with recirculated scrubbed gases near or at the CO2 absorber, and carried in a
common conduit 5 to the patient. In contrast, the Mapleson D system provides
the
fresh gases at the distal end of the circuit.
GAS CONSERVATION SYSTEM: "F3Tm COMBO SYSTEM"
With reference to Figure 4, drawing 4A illustrates an assisted ventilation
system of the present invention utilizing an embodiment of a new breathing
circuit
of the present invention. Fresh gas flow from a source 1 (e.g., an anesthesia
machine) passes via flow diverter 70 through fresh gas delivery tube 2 (shown
in
schematic form only). Flow diverter 70 is optional as it is provided for
modifying
a circle system having a fresh gas input port in the scrubber circuit
(generally near
or at the CO2 absorber). The flow diverter closes off the fresh gas input port
on top
of CO2 absorber 12 so that fresh gases can be directly fed to the distal end 3
of the
breathing conduit (i.e. FGF bypasses the scrubber module so it is not mixed
with
scrubbed gases). A seal could be used in place of the flow diverter, and the
fresh
gas source could come from a variety of locations. In this embodiment, tube 2
is,
as with a Bain, rigidly bonded to proximal fitting 50, and fresh gases are
delivered
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directly to the distal end 3 of the breathing circuit, which continuously feed
the
common inspiratory/expiratory conduit 5, also referred to as a rebreathing
tube.
However, with reference to drawing 4 C, unlike a Bain, the dimensions of
conduit
can be altered so that the tube volume and the concentration of its contents
are
5 altered so that the inspired concentration of gases can be adjusted for
each patient,
and rebreathing can be controlled. For example, tube 5 may be an ULTRA-FLEX
tube. Control can be achieved by adjusting the dimensions of tube 5, for
example
by axially adjusting the length of tube 5 (titration of tube volumes and
contents in
response to inspired and/or end-tidal gas concentration data provided by the
monitoring equipment).
Note that unlike the conventional circle system, in the new system of the
present invention the fresh gases delivered directly from the anesthesia
machine
are not mixed or diluted at the machine/scrubber circuit end. Because the
fresh gas
flow is delivered close to the patient, the inspired anesthetic concentrations
are
almost equal to the delivered concentrations. Thus, the anesthetist can rely
on the
anesthetic concentrations reported by the flow meter and the vaporizer as
indicative of the inspired concentrations. In contrast to the Mapleson D
system, in
the new system the expired gases are not all disposed of but are reused as
"refreshed gas," as expired gases pass through a scrubber module for
recirculation.
This new "F system" provides a surprising improvement in the control and
quality
of respiratory and anesthetic ventilation while avoiding waste of anesthetic
gases.
If a coiled fresh gas tube is used, upon contraction of tube 5, tube 2 coils
to
contract, as can be seen in Figure 4 C. The fresh gas tube 2 can have other
shapes
and can be arranged to be an inner or outer tube with respect to tube 5. If
tube 2 is
smooth-walled, it can slide in and out of a fitting as shown in Fig. 6.
Preferably,
the volume of tube 5 during use is adjusted to be larger than the tidal volume
(VT)
to minimize mixing of the fresh gases with the "scrubbed gases". This allows
optimal utilization of the fresh gases (anesthetic agents) as well as 02 and
CO2
rebreathing control.
In a preferred embodiment, the length of the rebreathing tube may be
variable for multiple usages. The same breathing system may be universally
used,
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in an operating room, ICU, emergency room, respiratory care ward, in adult and
pediatric cases, etc.
Drawing 4B illustrates a proximal terminal 52 in schematic form that may
be separately detached and connected to breathing conduit 5 and fresh gas tube
2.
5 An additional proximal terminal 6 is also shown in schematic form.
Terminal 6
can be an F2 type or Y adaptor. Referring back to drawing 4A, the system
components also preferably includes a reservoir bag or ventilator device 10,
waste
gas outlet 11, which may be attached to a scavenger, CO2 absorber 12, check
valves 40 and 90, inspiratory conduit 5', expiratory conduit 8', and a
proximal
10 terminal 6 that connects to proximal fitting 50.
The operation of the system is better understood by reference to the
numbered arrows and or part numbers. For example, in a preferred embodiment,
during inspiration, gas to lungs 4 flows simultaneously from fresh gas flow
source
1 and bag/ventilator 10 as follows: (1¨+ 2--+ 4) + (10¨. 5'¨+
15 3-04). During expiration, gases flow from lungs 4 to waste gas
outlet 11 as
follows: (1-32-43¨>5) + (4-6¨> 8'¨+ 90-- 10--3 11).
Thus, in a preferred embodiment, a new ventilation and anesthesia system
is provided, comprising a recirculation module, a rebreathing tube operatively
connected at its proximal end opening to the recirculation module for
providing
).0 expired gases to and receiving gases from the recirculation module,
and a distal
input for fresh gases, wherein the distal input is located in the distal
portion of the
rebreathing tube or in a distal fitting operatively connected to the distal
end of the
rebreathing tube. The recirculation module preferably includes a scrubbing
circuit,
which may include at least two unidirectional valves, an expiratory input
conduit,
?.5 CO2 absorber, exhaust vent, scrubbed gas output conduit, and squeeze
bag and/or
ventilator. In a preferred embodiment, a filter device can be detachably
connected
at the proximal end of the rebreathing conduit 5; the filter device may also
be
integrally formed with conduit 5. A preferred embodiment of this new system is
referred to as an F3TM COMBO system.
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A SYSTEM THAT OPTIMIZES UTILIZATION OF FRESH GASES THAT IS
ALSO MORE EFFICIENT AND SAFER
It is well recognized that methods of low flow anesthesia have considerable
advantages over high flow anesthesia methods because they reduce the amount of
wasted anesthetic gases, therefore, they are more economic and reduce
healthcare
costs. Moreover, such methods maintain better humidification and temperature
of
the inhaled gases. They also minimize the amount of gas released from the
system
to the environment, reducing operating room pollution, which provides a safer
working environment and in general less air pollution. However, despite
numerous advantages of low flow anesthesia techniques, the use of these
methods
and associated systems is hampered by numerous limitations that make them
unsafe. Therefore, there is a need to improve these systems and methods.
Traditionally, high fresh gas flow, defined as flow greater than five liters
per minute (FGF > 5 L/min), has been used in a conventional anesthesia circle
breathing system with CO2 absorption, and over 7 L/min in the Mapleson D
system. However, more than 90% of the newly delivered fresh gases are wasted.
One of the main reasons for high flow anesthesia practice is the fear of over-
dosing or under-anesthetizing the patient when low flow anesthesia is
provided.
With high fresh gas flows, the inspired (anesthetic) gas concentration (Fl or
F1)
can be assumed to be equivalent to the delivered gas concentration (FL) or FD
vaporizer setting concentration). Such an assumption cannot be made with low
flow anesthesia. Lowering the FGF results in a gradually increasing gradient
(difference) between the delivered gas concentration (FD) and the patient's
inspired gas (Fl), which is in part due to the increasing dilution of the
fresh gas
with the scrubbed gases within the system. For example, during low FGF of less
than 3 L/min, there are significant discrepancies (over 20%) between the
inspired
gas concentration and the delivered gas concentration. This may result in
under-
anesthetized patients. Therefore, low flow anesthesia has not been recommended
unless continuous flow adjustments are made during anesthesia and by very
careful monitoring the inspiratory and the end-tidal gas concentrations.
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EXAMPLES
The following hypotheses were tested: a) The inspired and the delivered
fresh gas concentration (FUFD) ratio is dependent on the fresh gas flow (FGF)
over time; and b) Using the F3TM COMBO system the Fi/FD ratio can be improved
at low flows.
The effects of lower FGF on patients' inspired gas concentrations were
compared to the delivered gas concentrations (i.e., anesthetic concentrations
indicated by the vaporizer's dial setting) during general anesthesia.
After obtaining institutional approval and patient consent, a total of 34
healthy (ASA class I) adult patients undergoing elective surgery were included
in
the studies. The studies were conducted using standard methods of anesthesia:
Anesthesia was induced with thiopental and endotracheal intubation was
facilitated with 1 mg/kg succinylcholine. Anesthesia was initially maintained
with
high flow (5 L/min) of 3/2 N20-02 mixture and 1.5% isoflurane as per vaporizer
setting using the standard anesthesia circle system with CO2 absorption. The
patient's lungs were mechanically ventilated using the traditional mode of
intermittent positive pressure ventilation with a tidal volume of 10 ml/kg,
ventilation frequency (10-12 breaths/min) and inspiratory/expiratory ratio
(1:2).
The above parameters were kept constant throughout the study. Fraction of
delivered (FD), inspired (Fl) and end-tidal (PET) anesthetic gas
concentrations
were continuously monitored by mass spectrometry (Medical Gas Analyzer 100;
Perkin-Elmer, Pomona, CA).
In study I, after 15 min of stabilization with high fresh gas flow (FGF > 5
L/min), FGF was changed to lower FGF, selected from 4 L/min (n=3), 3 L/min
(n=3), 2 L/min (n=3), 1 L/min (n=6) and 0.5 L/min (n=6), which was assigned
randomly, while the same vaporizer setting (1.5% isoflurane) was maintained.
Measurements of F1 and PET and FD were repeated for comparison of F1/ FD
ratios
and statistical analysis. The results of the study are summarized in Fig. 14.
The
results demonstrate that as the FGF is lowered the F1/ FD (or FUFD) ratio is
significantly decreased in a parallel way. Furthermore, the study shows that
there
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is indeed a significant discrepancy between F1 and Fp and points out the
limitations of low flow anesthesia when the conventional circle system is
utilized.
Table 1 shows data from Study II, in which 12 patients were randomly
assigned to group A, using the conventional circle system (n=6), and to group
B,
using the F3TM COMBO system during a low flow anesthesia (1 L/min) FGF.
Notice in Table 1 that the F1 concentration and the F1/ Fp concentration
ratios are
greatly improved in group B wherein the P3TM COMBO system is utilized. It also
shows that the difference between the F1 and FD are minimal and that the new
system provides a better correlation. This supports the hypothesis that low
flow
anesthesia can be safely administered by using the F3 COMBOTm system, and
over-dosing or under-dosing of anesthetics can be avoided.
With the present F3 COMBOTm system, the anesthetist will be able to better
control the inspired concentration of anesthetic gases in a more accurate and
predictable manner. Therefore, even in the absence of expensive multi-gas
monitoring equipment, a safe and reliable low flow anesthesia can be achieved.
Also, recovery from anesthesia can be accelerated at the end of surgery and
anesthesia. This can be accomplished by providing high flows of oxygen
directly
at the distal end so that the residual anesthetic in the lungs and the
breathing
circuit will be washed out very quickly. Quick recovery from anesthesia can
save
anesthesia recovery time and money. Therefore, the F3 COMBOTm circuit and/or
methods for utilizing same can conserve anesthetic gases as well as oxygen,
while
minimizing pollution and health hazards, and thus improve breathing/anesthesia
system efficiency. This will result in an overall lower health care costs,
while
optimizing patient health care.
Fig. 15 shows the changes of continuous and simultaneous monitoring of
the delivered (FD), inspired (F1) and end-tidal (FET) gas concentration during
low
flow anesthesia of 1 L/min with a constant isoflurane vaporizer setting of
1.2%
over time. Notice the significant difference between the FE, gas concentration
(i.e.,
vaporizer setting concentration) and the F1 and PET gas concentration.
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TABLE 1
Effect of diverting the FGF to the distal end of the circuit on the F1 and
F1/FD ratio during low flow isoflurane anesthesia (1 L/min) using a
conventional system versus the F3 COMBOrm system
Patient Vaporizer Group A (n=6) Group B (n=6)
No Setting Without Diverting Diverting
FGF**
(FD) Vol. % FGF* (i.e., gas (i.e., gas provided at
provided at machine patient end)
side) (F1) Vol % (F1/F0)
(F1) Vol % (F1/F0)
1 1.5 0.92 0.61 1.46 0.97
2 1.5 0.96 0.64 1.20 6.80
3 1.5 1.00 0.67 1.20 0.80
4 1.5 1.20 0.80 1.45 0.97
1.5 0.89 0.59 1.20 0.80
6 1.5 0.95 0.63 1.35 0.90
Mean 1.5 0.99 0.66 1.31 0.87
+ SD 0.0 0.11 0.08 0.13 0.08
F1: Inspired concentration; Fp: Delivered concentration (as per vaporizer
setting); FWD: Concentration ratio.
As is now clear, the present invention provides a method of providing
assisted ventilation or anesthesia wherein fresh gases are provided at low
flow, for
5 example a volume of about 1 liter per minute (flows considered low range
from
about 0.5 to less than 5 L/min, or less than 3 L/min in preferred
embodiments),
and the F1/ FD concentration ratio can be maintained at a desired level, for
example
above about 0.80 or higher, by adjusting the volume of the rebreathing tube
proximal of the fresh gas input. In a preferred embodiment, fresh gas flows
from
about 1 to about 3 L/min are used, and more preferably from about 1 to about 2
L/min.
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AN EXEMPLARY DISPENSER
The present invention permits use of smaller respiratory conduits, and
disposable components therefore. Currently, multiple circuits must be used for
a
single day's surgeries. This requires that the circuits be stored in or near
the
5 operating room. To prepare for each surgery, a new circuit is removed
from a
sterile package, and the bag is disposed of. If care is not taken in opening
the bag,
the circuit can be damaged.
Since the present invention enables less circuit components to be disposed
of, the new circuit components required for each procedure are reduced.
Further,
10 due to the ability to axially contract, and in certain embodiments
radially contract,
the components, the respiratory conduits can be made much smaller for
packaging,
storage, and transport. With reference to Figure 16, a dispenser box 200 is
illustrated. Shown in block diagram are respiratory conduits 210, optionally
sandwiched between thin protective plastic sheets 212. Preferably, the
respiratory
15 conduits 210 are not individually wrapped. In an embodiment, box 200
includes a
line of perforations 214 on its face and top to permit tearing removal or
rotating or
pivoting elevation of a portion of the box. A sealing tape 216 can be provided
over
perforations 214 to reduce the chance of accidental opening or tampering.
Boxes
of varying quantities can be provided, for example, 4,6, 8, 10, 12, 15,24 or
more
20 than 100 respiratory conduits. The box flap may close under gravity or
seal
between uses. Loading of such a dispenser box eliminates the need for sealing
individual disposal circuit components in separate bags, as well as reduces
the
time to open and remove bag contents. The dispenser box also reduces the
amount
of waste generated as less material is disposed of than when individual sealed
bags
25 are used.
In an embodiment, the respiratory conduits are essentially cylindrical in
their cross-sectional shape. Hence the dispenser box may have a thickness and
length sufficient for one respiratory conduit in its compressed form, and a
height
proportional to the number of conduits therein. The perforations for the box
flap
30 may extend the length of one side of the box, and box incrementally
opened at the
perforation to access each conduit in order.
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As can be seen by the unilimb respiratory conduit illustrated in Figures 13
(a) and (b), multilumen conduits of the present invention come in a variety of
forms, and can be compressed into relatively small volumes for shipping and
storage. Hence, a plurality of such conduits can fit nicely into the
dispensers
described above.
With further reference to Figure 13, a respiratory conduit is shown in
expanded form (a) and in compressed form (b). An outer or first conduit 220 is
a
suave tube, and the inner conduit 230 is a coiled tube wherein the coiled tube
lumen has a relatively rigid cross-sectional shape. When compressed, excess
fabric
in suave tube 220 takes on a ruffled or wrinkled appearance. The wrinkles may
be
evenly distributed by periodic attachment of tube 220 to inner tube 230.
Proximal
fitting 240 is coaxial, with the distal end of coiled tube 230 being bonded to
an
inner pipe 242 or being integral therewith, although other variations are
possible.
In an alternative embodiment, a rigid inner pipe and rigid outer pipe are
held together by rigid spacing means to form a proximal fitting to which inner
and
outer conduits can be connected. Thus, the present invention allows for
optimization of respiratory conduit manufacture that can depend upon the
machinery, parts, materials, and skills available. Inner pipe 242 can be
integrally
formed with rigid coil 230 in one step. In another step, inner pipe 242,
integrally
formed to coil 230, can be bonded to an outer pipe, such as pipe 244, with
appropriate spacing means. A suave tube can then be bonded to outer pipe 244.
A
single distal fitting 246, with an inner member 248 and an outer member 250
can
be bonded to the corresponding tubes prior to bonding of the suave tube to the
proximal fitting. The distal fitting 246 can also be constructed in a series
of steps
as it is connected to the tubes. For example, inner member 246 can be
integrally
formed to the distal end of tube 230 when the proximal end of tube 230 is
bonded
to inner pipe 242. Various combinations of construction steps are possible.
It should be clear to one of skill in the art that the F3Tm circuits described
herein are not limited to a unilimb tubing arrangements, but can also use dual
limb
arrangements in which at least one tube is a suave or coiled tube, which can
lead
to significant reduced costs in manufacturing, shipping and storage.
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Thus, exemplary embodiments and uses of the present inventions have
been described. Alternative embodiments, descriptions and terms are
contemplated. For example, the conduits in the circuit may be of different
sizes
from one another, and more than two lumens may be present. Using the present
invention, larger or smaller diameter conduits may be used, and both circle
circuit
and Mapleson type circuits may be constructed.
While exemplary embodiments of the present invention have been set forth
above, it is to be understood that the pioneer inventions disclosed herein may
be
constructed or used otherwise than as specifically described.
=
