Note: Descriptions are shown in the official language in which they were submitted.
Ol~lZ
This invention relates to apparatus for
col]ecting both excess anaesthetic gas and exhalation from
a patient and for directing these waste gases out of the
operating room environment.
Modern operating rooms are equipped to supply
anaesthetic gas to a patient using apparatus which is placed
in communication with the patient's airway. Suc~ e~uipment
has designed to meet a number of desirable characteristics.
These include simplicity of design which is generally inter-
preted to mean that the equipment should have few if anymoving parts such as valves. It is also desirable that the
equipment should permit an anaesthetist attending the patient
to assist respiration instantaneously in the event that the
patient does not breathe.
A number of different approaches have been
taken to satisfy these design requirements and one of the most
successful is known as an ~Ayres T-piece". This structure has
no moving parts and simply stated supplies a continuous flow
of anaesthetic gas sufficient to permit the patient to inhale
the gas whenever required. A common and widely used modification
is known as a "Jackson-Rees modification" and this includes
tubing attached to the Ayres T-piece and leading to a bellows
which can be used by the anaesthetist to assist respiration.
Recently a further criterion has been added
to the design requirements for anaesthetic equipment. It is
now considered important to evacuate waste gases which include
a high percentage of anaesthetic gas away from the operating
room environment. There have been reports of probable toxicity
associated with chronic exposure to anaesthetic gases and
there have been well documented reports of impairment of both
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motor and intellectual faculties following acute exposure
to these gases. ~lthough conclusive evidence is not avail-
able, there has been increasing awareness of these problems
by medical practitioners generally. Consequently it has
become most desirable to reduce possible gas contamination
within the operating environment.
Gas contamination can be reduced in three
ways. Firstly, by lowering the flow of anaesthetic gases
and using a recirculating breathing system to lower the volume
of gas wasted. Secondly, by rapid and frequent change of air
in the operating room, and lastly, by local scavenging of
waste gases.
The present invention is directed to the third
approach. Because the Ayres T-piece has proved to be emenantly
satisfactory, the present approach is directed to providing
apparatus having the advantages of this structure and which
also satisfies the requirement that waste gases emanating from
the apparatus will be collected and directed out of the
operating room.
Several embodiments of the invention are pro-
vided. A first embodiment is provided for attachment to the
Jackson-Rees modification; a second embodiment can be used
simply with the Ayres T-piece; and third embodiment is complete.
All operate in similar fashion as will be explained. The
third embodiment includes a T-piece having an inlet portion,
a patient connector portion, and an outlet portion meeting at
a junction so that anaesthetic gas fed continuously to the
inlet portion is available to the patient through the connector
portion during inhalation and so that waste gases in the form
both of eXhalation through the connector portion and excess `
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anaesthetic gas leave by way of the outlet portion. An
exhaust system is coupled to the outlet portion for convey-
ing the waste gases away from the T-piece, the exhaust
system including a flexible bellows which expands during
exhalation and collapses during inhalation. The exhaust
system includes an outlet from which the waste gases leave
the exhaust system and means to occlude the exhaust system
is provided between,the bellows and the outlet. Use of the
occluding means permits pressure to be exerted by squeezing
the bellows to expand the patient's lungs if required. A
chamber is also included having an inlet port, an outlet port
adjacent the inlet port, and an air-bleed port remote from
the inlet and outlet ports. The inlet port is coupled to the
exhaust system outlet to receive the waste gases from the
exhaust system and the outlet port is adapted to be coupled
to an evacuation system which draws gases from the chamber
continuously. Consequently during exhalation waste gas~s
enter the chamber displacing air towards and out of the
; air-bleed port to prevent a build-up of positive pressure in
the chamber while the waste gases are drawn out of the chamber
through the exhaust port. Also, during inhalation the rest
of the waste gases are drawn out of the exhaust port and air
again enters the chamber through the air-bleed port to
prevent a build-up of negative pressure in the chamher.
The invention will be better understood with
reference to the following description which refers to the
drawings, in which:
Fig. 1 is a sectional side view of equipment
according to a preferred embodiment of the invention;
Fig. 2 is a perspective view showing parts in
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sect:ion and ilIustrating a second embodiment of the invention;
and
Fig. 3 is a diagrammatic view of a third
embodiment of the invention.
Reference is first made to Fig. 1 which shows
equipment designated generally by the numeral 20 for use in
supplying anaesthetic gas received from a tube 22 to a patient
24 and for controlling excess anaesthatic gas and exhalation
from the patient and directing these waste gases to an
outlet tube 26.
Anaesthetic gas from inlet tube 22 is received
at an inlet portion 28 of a combination T-piece and elbow 30
of a type often designated as an Ayres T-piece. This inlet
portion 28 terminates at a junction with a patient connector
portion 32 and an outlet portion 34. Excess anaesthetic gas
and exhalation from the patient 24 constitute waste gase~s
which leave the outlet portion 34 and which then enter an ex-
haust system 36. Subsequently the waste gases leave the system
36 and enter a chamber 38 before finally lea~ing through the
outlet tube 26 as will be described. Initially parts of the
exhaust system 36 will be described in detail followed by a
description of the chamber 38. Subsequently the operation of
the equipment 20 will be described in detail.
The exhaust system 36 includes a connector 40
engaged on the outlet portion 34 and having an opposite end
engaged in an elongated and ~lexible tube 42.
The tube 42 extends from the connector 40 to
a second connector 44 which in turn terminates in a rounded
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framework 46. This framework is contained within a flex-
ible bellows 48 which tends towards a collapsed position
and which is prevented from occluding the opening in the
connector 44 by the rounded framework 46. This bellows
48 will expand when the patient exhales and will collapse
as the patient inhales.
Waste gases collecting in the bellows 48
leave through a tubular portion 50 which can be used to
occlude the exhaust system 36 as will be described. The
portion 50 terminates at an opening 52 through which the
gases normally pass from the exhaust system 36 into the
chamber 38.
The chamber 38 includes a bag 54 of flimsy
filmic material. This bag extends about the bulb 48 and
connects to a coupling 56 spaced from the connector 44 by
radial elements 58.
The filmic bag 54 effectively forms an
inlet port for the chamber in that the bag collects waste
gases from the exhaust system and guides these gases by
way of the coupling 56 both to an outlet port 60 formed in
the coupling 56 and attached to the tube 26 and to a flex-
ible and corrugated tube 62 which contains the tube 42 of
the exhaust system 36. Tube 62 terminates at a sleeve
64 which is spaced from the connector 40 by radial elements
66. The tube 62 is readily flexed but exhibits resistance
to collapsing unless of course the flexing is extreme.
In use the equipment 20 shown in Fig. 1 is
connected both to the inlet tube 22 and to the outlet tube
26 which would normally extend to an evacuating or vacuum
system in an operating room. Bo~h the supply of anaesthetic
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gas through the inlet tube 22 and the vacuum source are
applied continuously whereas the movement of gases within
the equipment will be pulsatile in nature due to the
inhalation and exhalation of the patient. Assuming that the
patient is inhaling, gases entering the inlet portion 28 of
the T-piece 30 will be largely inhaled by the patient.
Upon exhalation the anaesthetic gas which continue~ to flow
into the T-piece together with the exhalation will form
waste gases which pass into the exhaust system 36. The
increased flow in this system will result in the bellows 48
expanding which serves to indicate that the patient is exhaling
normally. The waste gases will proceed from the system 36
into the bag 54 of the chamber 38. The gases will then pass
into the outer tube 62 while some of these gases are removed
through the- outlet port 60 as a result of the application
of the vacuum source to the tube 26. However the flow of
waste gases during exhalation will be such that part of the
outer tube 62 will be filled with the waste gas thereby
displacing air through an air-bleed port formed between the
radial elements 66 associated with the sleeve 64 at an end
of the chamber remote from the bag 54 and outlet port 60.
As soon as the patient begins to inhale once
more the flow of anaesthetic gas into the inlet portion 28
~ of the T-piece 30 is substantially used by the patient so
; that the flow of gases through the system 36 is substant-
ially reduced if not stopped. Consequently because the vacuum
source is applied continuously to the tube 26 the waste gases
will be removed from the chamber and air will enter by way of
the air-bleed pork. It will be evident that this air-bleed
port eliminates the possibility of either a positive pressure
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build-up during exhalation or a negative pressure build-up
duri.ng inhalation in the system. Consequently should the
vacuum become excessive the patient could continue to breathe
without severe impediment. Similarly if the supply of
anaesthetic gas should suddenly increase in flow then this
increase in flow will simply force anaesthetic gas through
the system and out of the air-bleed port without applying
significant increase in pressure to the patient. A further
possibility is that the anaesthetic gas supply would simply
stop and the vacuum source would cause a negative pressure
at the patient's lungs. This possibility is prevented by
using a relief valve (not shown).
In the event that the anaesthetist using the
equipment finds it necessary to assist respiration due to
the patient failing to inhale, then this can be achieved
as follows. Firstly the bellows 48 is nipped at the portion
50 thereby discontinuing the flow of gases through the portion
50. This can be done irrespective of the bag 54 which exhibits
no noticable resistance to this manipulation of the bellows
48. The bellows 48 will either be in an expanded position
due to the last exhalation of the patient or will become
expanded due to the input of anaesthetic gas. Next the
anaesthetist squeezes the bellows 48 thereby forcing gases
into the patient's lungs. Upon exhalation the anaesthetist
will allo~ the gases to pass through the opening 52 and then,
while the bellows is still expanded he will again occlude
the portion 50 and force gases back into the patient's
lungs. Continuing gas flow from the anaesthesia machine
along tube 22 prevents back flow of gases down the tube so
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that the pressure applied by the anaesthetist is directed
solely to the patient's lungs. A pressure release valve
to protect against extreme pressure is sometimes included
in tube 22.
It will be evident that the equipment 20
will both meet the requirements of patient safety and prevent
significant introduction of anaesthetic gases into the
operating room. This is achieved relatively simply without
the use of expensive and troublesome valving and high
resistance, and with equipment which is readily understood
by an anaesthetist due to the use of a standard Ayres T-piece
system and parts which resemble generally those associated
with such a T-piece.
It will be evident that some of the parts
can be manufactured more efficiently using plastic moulding
techniques. For instance the connector 40, radial elements
66, and sleeve 64 could be formed as a single piece. Similarly
the radial element 58 could be integral with the coupling
56 and connector 44. However it is important to note that
20 for the purposes of this description the radial elements 66
form part of the chamber in that air-bleed ports are defined
by these elements. Similarly, passage between the bag 54
and the tube 62 is effected about the elements 58 and they
consequently form part of the chamber rather than part of
the exhaust system. This embodiment could well be supplied
without the T-piece so that existing T-pieces would be
used.
A second and less compact embodiment of the
invention is shown in Fig. 2. However this embodiment maybe
desirable in some situations.
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As seen in Fig. 2 equipment designated
generally by the numeral 68 includes a T-piece 70, which
is similar to T-piece 30 (Fig. 1) and which leads waste
gases to an exhaust system 72 including a bellows 74 having
a tubular portion 76 for occluding flow of waste gases
towards an opening at the end of the bellows. In this
embodiment the end of the bellows is attached to a chamber
78 which extends between the bellows 74 and an outlet tube
80 which leads to a source of vacuum supply.
The chamber 78 includes an inlet port 82
which consists of a tubular èlement 84 to which the bellows
is attached and which extends through a sleeve 86 before
ending where it meets a flexible tube 88. This flexible
tube terminates adjacent an outlet port 90 associated with
the outlet tube 80. Consequently the inlet port directs
waste gases into the chamber at a location adjacent the
outlet port 90.
The flexible tube 82 is surrounded by
corrugated outer tube 92 which is also flexible and which
resists radial distortion. The tube extends between a
blind end piece 94 which includes the outlet port 90 and
an outer sleeve 96 adjacent the bellows 74 and attached to
the inner sleeve 86 by radial elements 98. These elements
combine with the sleeves 86, 96 to define an air-bleed port
providing access for air into the chamber and allowing air
to be displaced from the chamber in the manner described
with reference to the embodiment shown in Fig. 1.
The tubular element 84 of the chamber 78
supports an end of a generally U-shaped bellows support
element 100. This element includes two coplanar portions
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102, 104 which permit an anaesthetist to sqeeze the bellows
adjacent these coplanar portions and to thereby occlude the
passage through which waste gases pass from the exhaust
system to the chamber. Furthermore the support element prevents
accidental occlusion of the passage by flexing or rotation
of bellows 74 at tubular portion 76.
The tubular element 84 is free to rotate in
the sleeve 86 of the chamber 78 so that in the event that
the chamber must be rotated relative to the exhaust system
this rotation can be accommodated within this structure. It
will be evident that the tube 88 must be quite flexible
otherwise when the tube 92 is deflected into a curved
position there will be a resistance as an attempt is made
to rotate the tube 88 within the tube 92 due to the
connection of the tube 88 to the rotatable element 84.
The Fig. 2 embodiment could be supplied with-
out the T-piece and Jackson-Rees modification so that this
existing equipment would be used with the other parts of
the embodiment.
A third embodiment is shown diagrammatically
in Fig. 3. In this embodiment a T-piece 106 is connected
to an exhaust system 108 which includes a bellows 110 and
a readily deformable tube 112 which can be closed by radial
pressure to occlude flow from the exhaust system 108 to
a chamber 114. This chamber has an inlet port 116, outlet
port 118 and air-bleed port 120. It will be evident that
this structure operates in a similar fashion to those
described with reference to Figs. 1 and 2 but differs in
that passage of the waste gases to the chamber is prevented
30 by a tube 112 rather by a part of the bellows 110.
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