Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A DEVICE FOR AIDING RE-SPIRATION
The invention relates to a device for producing a continuous positive
pressure in the respiratory passages during spontaneous respiration in
accordance with the preamble of claim 1.
Continuous positive pressures in the respiratory passages during
spontaneous respiration have been successfully employed for a matter of two
decades for coping with instable pulmonary c:onditions and for improving the
uptake of oxygen by the lungs of prematurely and newly born inFants. For
this purpose three different methods are in use. All three methods have
the feature in common that a closed respiratory tube system with a respira-
tory gas reservoir and an overpressure valve which can be 0xactly set by
hand are utili~ed, into which humidified, pre~armed, oxygen enriched fresh
respiratory gas is supplied in excess. With this respiratory gas the lungs
of the spontaneously breathing patient connected with the device are venti~
15 llated using a defined overpressure, which is as far as possible kept con- :
stant and furthermore the spent respiratory gas exhaled into the respirato-
ry tube system is let o-ff into the surroundings via an excess pressure
valve. The technical differences between the methods employed today clini-
cally only reside in the way of supplying the respiratory gas in order to
obtain the therapeutically desired overpressure in the lungs, which is held
constant as far as possible.-Together with the additional resulting clini-
cal problems, such methods will be briefly reviewed in the following.
Method No. 1
An endotracheal tube is employed, which is placed in the trachea of
the patient in order to introduce respiratory gas directly into the bron-
chial system and into the lungs and to build up and maintain the desired
overpressure therein. It is consequently possible to establish extremely
constant pressures in the lungs.
Main Problems of this method
Intubation of the patient is necessary and hose must be const~ntly
kept in the trachea as a foreign body, which may cause constant irritation,
damage to the vocal cords and to the trachea and also infections of the
bronchial system and of the lungs. Moreover the hose in the trachea means
that there has to be intermittent artificial aspiration of mucus in order
to keep the respiratory passages clear. Additionally such respirato
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represents a substan-tial resistance to flow, which has to be overcome by
the patient when inhaling and exhaling.
Method No. 2
Fresh respiratory gas is introduced into the nasopharyngeal-oral
cavity through one or two pieces of hose through the nose to establish the
desired continuous overpressure in the nasopharyngeal-oral cavity and re-
spiratory passages in communication there~lith as well in the lungs.
Main problems of the method
Uncontrolled, substantial gas leaks more particularly through the
mouth and minor leaks through the nose. These leaks may all in all be so
large that it is no longer possible to maintain a constant positive pres-
sure in the oral cavity so that for this reason the overpressure in the
lungs collapses as well or can only be kept at an uncontrolled, extreme1y
low level which rnay be inherently physiologically ineffective. In order to
overcome such gas leaks of varying size large quantities of fresh gas are
however necessary, which however can not be supplied without any substan-
tial pressure loss into the nasopharyngeal-oral cavity through the compara-
tively fine nasal hoses so that the therapeutically desired pressures in
the respiratory hose system set with a gas reservoir can not be achieved in
the oral cavity.
Method No. 3
Respiratory gas is supplied into the nasopharyngeal-oral cavity and
the respiratory passa~es connected therewith and the lungs with the aid of
a tightly fitting mask, which includes both the nose as well as the mouth.
This means that there are no mouth and nose leaks and also there is the
possibility of the supply of respiratory gas through the nose and mouth.
There would then be a satisfactory constancy of pressure.
Main problems of this method
Difficulties with leaks under the mask over the face of the newly
born, which in part can not be overcome despite using dangerously high
pressures over the face1 skull and back of the head, and complications,
such as ~or example pressurë injury to the skin and in some cases even
brain hemorrhage. A further point is that the use of a large, bulky hold-
ing fixture in the incubator is necessary. Substantial obstruction and
limitations are then involved as regards nursing care and therapy.
One object of the present invention is to provide a respirator in the
case of which leak-compensated respiration is possible without intubation
and which is particularly suitable for premature and newly born infants.
Taking as a starting point the prior art described this object is to
be achieved by a respirator which is improved in accordance with the char- ~.
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ac-terizing parr of claim 1. In accordance with the invention for the sup
ply of fresh respiratory gas two nasopharyngeal hoses are employed, which
in their lumen or in the wall thereof possess one or two thin pressure
sensing hoses or ducts. The supplied fresh respiratory gas is not however,
unlike all known and described methods, held at the desired therapeutic
pressure of 5 to 10 cm HzO but at an overpressure of 25 to 30 cm H20 and
additionally is modulated by pressure oscillations. Major leaks through
the mouth are compensated for in the device in accordance with the inven-
tion by continuously monitoring the pressure in the nasopharyngeal-oral
cavity through thin sensing probes or ducts connected with the inputs of
electrical-electronic pressure measuring devices and with the aid of a
selective recognizing electronic system and an electronic regulation member
with a metering valve the supply of fresh respiratory gas is so controlled
that an increase in the mouth leal< causes a respective enhanced compensa-
tion gas flow in the nasopharyngeal-oral hoses. The pressure drop neces-
sarily occurring at a high gas flow rate however does not, as ln the known
methods, lead to a pressure drop in the oral cavity and in the lungs, and
can, since between the fresh respiratory gas feed pressure (25 to 30 cm H20~
and the therapeutically employed pressures in the nasopharyngeal-oral cavi-
ty (of 5 to 10 cm H20) there is a pressure difference of at least 20 cm H20,be compensated for by regulation of the gas supply rate without any diffi-
culty. In connection with this technique it is absolutely necessary, in
the interest of patient safety, to take care to see that no excessively
high pressures occur in the oral cavity and therefore in the lungs either,
as would be likely in the case of an abrupt decrease in the size of the gas
leaks.
A first limitation of pressure to a raised pressure level is produced
in the device in accordance with the invention owing to a feed pressura,
which is limited to 25 to 30 cm H20, of the fresh respiratory gas. A second
limitation of pressure to the therapeutic level of 5 to 10 cm H20 is per-
formed by the continuous exact measurements of pressure in the nasopharyn-
geal-oral cavity and by regulation, dependently thereon, of feed of the
fresh respiratory gas. On the occurrence of blockage of a pressure sensing
probe by nasal mucus, something which is hardly a rare occurrence, if the
pressure measuring element (which is connected with the input of the probe)
is not vented into the surroundings, the probe ~ill for a long time be
acted upon by the pressure, which obtained shortly in the nasopharyngeal-
oral cavity prior to blockage of the probe. A dangerous spurious regula
tion of the fresh respira~ory gas feed accompanied by the build up of high
pressures to a maximum of 30 cm H20 might be the result. In order to reli--
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ably prevent such spurious measurements and regulation effects, the device
in accordance with the invention uses ~resh respirator~ gas which is modu-
lated by pressure oscillations. Such oscillations are however only trans-
mitted to the Following electrical-electronic pressure measuriny element as
long as the pressure measuring probe is clear and not when it is blocked.
In this manner it is possible to use a novel electronic system to provide
for ready recognition of the blockage during processing of the signals.
Immediate activation of the automatic pneumatic probe clearing device inte-
grated in the condition can then deal with the trouble condition. If, in
some infrequent cases this should be impossible, an automatic device alarrn
system is tripped and simultaneously the fresh respiratory gas supply is
choked back to a minimum. If the measurement of pressure and regulation
means as described is designed in the form of two completely separately
operating regulation circuits with pressure probes, pressure measuring
elements and furthermore selective and con-trol-regulation electronics, it
is then possible to attain an extremely high degree of patient safety. A
problem is then only presented in connection with exhalation by the patient
into the nasopharyngeal-oral cavity with the danger that, if the mouth is
shut and the nose is stopped up, spent exhaled respiratory air will become
enriched here and will be inhaled by the patient again and again. In order
to deal with this problem a small leak into the surroundings is allowed
with the aid of a kink-proof hose placed in the oral cavity. By means of
a constant feed of fresh respiratory gas at a rate of 2 to 5 l/min it is
possible to achieve a reliable flushing of the spent exhaled respiratory
air into the surroundings.
Fur~her advantages and details of the invention will be understood
from the following detailed descriptive disclosure of one embodiment there-
of in conjunction with the accompanying drawings.
Figure 1 diagrammatically shows the individual
modules of the device in accordance
with the invention and the logic cir-
cuitry connecting them.
Figure 2 sho~s the placement aid for the naso--
pharyngeal tubes with an oral ~ube.
Figure 3 shows in perspective laterally and
from the front the novel nasopharyn-
geal oral tube for the supply of re-
spiratory gas, the pressure monitoring
means and the means for venting the
nasopharyngeal cavity. ~ ~c~ls~ ~ !
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Fresh respiratory gas passes from a commercially available high pres-
sure air-oxygen mixing unit 1 to the solenoid metering valve 2 with a per-
manently set bypass (2 to 5 l/min flushing permanent gas flow) and hence to
the low pressure regulator 3, which limits the pressure to between 25 and
30 cm H20. This regulator provides respiratory gas for the modulator 5,
which modulates the flow with oscillations in pressure (using a frequency
range of 0.1 to 100 Hz with an amplitude o~f 0.5 to 10 cm H20) prior to the
flow of the fresh gas through a commercially available respiratory gas
- humidifying and warming device 6 and via the connection hose 7 to enter the
Y piece gas manifold 8. Here two novel nasopharyngeal-oral tubes 9 are
connected using adapters 10 in order to supply the diagrammatica'l'ly illus-
trated nasopharyngeal-oral cavity 16 and the trachea 19 in communication
with i-t and then the lungs with respiratory gas at the prese'lected overpre-
ssure (5 to lO cm H20). Gas leaks 18 of varying size are indicated symboli-
cally by parallel lines.
A tube 17 (in the form of a kink-proof hose) inserted into the oral
cavity functions to provide a constant leak into the surroundings for reli-
able flushing of the spent exhaled air from the nasopharyngeal-oral cavity
16 using fresh respiratory gas supplied continuously via the regula-tor 3.
Through the thin pressure measuring probes 11 which extend through the
lumen in the nasopharyngeal-oral tubes 9 and which in each case are con-
nected via connection hoses 12 and 13 with a respective electrical-elec-
tronic pressure measuring' element 14 and 15, and by means o~ a further
following selective electronic unit 21 and an electronic regulation member
22 the metering valve 2 and the overpressure valve 4 are controlled.
Should there be a blockage of the thin pressure measuring probes, for in-
stance owing to nasal mucus, pressure signals will be detected, without any
modulation by pressure oscillation, by the pressure measuring elements 14
and 15 and may consequently be recognized by the selective electronic cir-
cuit as a blockage. This will cause an operation of the automatic pneumat--
ic clearing device 23, which via the solenoid valves 2~ and 25 causes re-
spiratory gas under pressure to be discharged for a short time into -the
connection hoses 12 and 13 and the associated pressure measuring probes 9
so that the stoppage will as a rule be dealt with. Since during such probe
clearance operation t:he valves 24 and 25 simultaneously cause a venting of
the pressure measuring elements 14 and 15 into the surroundings, after the
termination of the pneumatic clearing operation there will be, without much
delay, despite the thin measuring probes employed, an exact measurement of
the pressure.
Figure 2 shows the holding device for the nasopharyngeal tub
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for the oral tube. ~t consists of a base plate 26 of elastic material
(such as silicone or other rubber), which has openings. The openings 27
and 28 serve for the insertion and clamping retention of the nasopharyn-
geal-oral tubes 9 and -the opening 29 is for the oral tube 17. To the side
to the left and to the right there are rectangular stamped out portions 30
and 31 for the attachment of holding straps. As shown in the figure the
openings 24 and 25 are only surrounded by a narrow border of elastic mate-
rial 327 which is connected by means of a respective narrow rib 33 and 34
with the base plate 26. When securing the base plate on the upper lip of
the patient these ribs render possible a substantially pressure-free at-
tachmen-t of the nasopharyngeal tubes in a position turned through approxi-
mately 90'.
As an alternative to the device for the supply of resp-iratory gas via
nasopharyngeal tubes figure 3 shows a novel nasopharyngeal tube 35 manufac-
tured of soft synthetic resin. It is in the form of a slightly angled tubewith an oval cross section, whose lower side 36 opens onto the tongue of
the patient and whose open end 37, in which the hoses 40, 41, 42 and 43 end
approximately 1 cm from the end, in a manner protected from mucus, is in
the pharynx or point of entry into the throat of the patient. The plate 38
arranged at the front end of the nasopharyngeal-oral tube furthermore rests
on the lips of the patient where it can be secured in position by means of
attachment slots 39, for instance. The hoses fitted in the lumen of the
tube and secured in position in a gas-tight manner function to ~easure the
pressure at 40 and 41 (with a narrow lumen), for the supply of respiratory
gas 42 (with a wide lumen) and for removal 43 of air from the nasopharyn-
geal-oral cavity and consequently from the respiratory passages and the
lungs communicating therewith.
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