Tracheal or tracheostomy tube and systems for mechanical ventilation equipped therewith

The invention relates to a double-barrelled tube with a respiratory (11) and an inhaling (12) passage for the mechanically controllable respiration of a patient in which the inhaling passage connected to a respiratory gas source is fitted at the distal outlet with a nozzle directed towards the distal outlet aperture of the respiratory passage. The respiratory passage is connected at the proximal outlet with an exhalation valve (60) which can be opened and closed by means of an electrical control device. The electrical control device is connected to an electrocardiograph or a blood pressure measuring instrument so that respiration may be effected synchronously with the pulse rate using the respiratory gas fed to the inhalation passage with a retrograde flow of respiratory gas. Inhalation may take place in either the systole or the diastole.

The invention relates to a tube for introduction into the respiratory tract 
of a patient, especially orotracheal or nasotracheal tubes or tracheostomy 
tubes for controllable mechanical ventilation of a patient, with a distal 
end insertable into the respiratory tract and a proximal end provided with 
connectors and two continuous passages extending essentially from the 
proximal to the distal end of the tube, one of the two passages serving as 
a fresh passage in ventilation or breathing and the other of the two 
passages serving as an inspiration passage for additional or sole 
administration of fresh gas. 
Tracheal and tracheostomy tubes are used for artificial ventilation of a 
human being in conjunction with ventilators usually comprising an 
expiration valve and a fresh gas source. The invention therefore consists 
in an improvement on the tube with a ventilator for improving breathing 
and for reducing the residual gas remaining in the respiratory tract by 
using a tube with an improved function. 
Artificial ventilation of a human being is normally conducted at the 
natural respiratory rate. In the various methods of high-frequency 
ventilation, respiratory rates in the range of the heart rate are also 
used, without any synchronization of the ventilation phases with the heart 
action. 
The conventional ventilators known heretofore, with a controllable 
expiration valve and fresh gas supply controllable by means of an 
electrically controllable pressure-reduction valve, require one tube with 
a single passage (ventilation tube) or a tube with two passages 
(inspiration passage, expiration passage) so designed that the gas flow in 
one passage has no effect on that in the other passage; see DE 25 35 191 
A1, AT 389 818. For all practical purposes, known ventilators can be 
influenced only by damming up the fresh gas source, whereupon any alveolar 
gas residue remains in the tube in each cycle and has a disadvantageous 
effect. 
The goal of the invention is to eliminate this disadvantage of ventilators 
with double-lumen tubes. In addition, the control of ventilation is to be 
effected as a function of signals delivered by an electrocardiograph or a 
blood pressure monitor for example. 
To achieve this goal, according to the invention the tube design proposed 
in the preamble of claim 1 provides that each of the two passages has a 
distal outlet opening and the distal outlet opening of the inspiration 
passage is directed at the distal outlet opening of the ventilation 
passage. In a preferred embodiment of the tube, the inspiration passage is 
bent at approximately 180.degree. in the vicinity of the distal end of the 
tube and directed at or into the distal outlet opening of the ventilation 
passage and through the ventilation passage to the proximal end of the 
tube. Preferably, in the tube according to the invention one of the two 
passages has a cross section smaller than that of the other of the two 
passages in the tube and the passage with the cross section that is larger 
than that of the other passage serves as the ventilation passage for 
ventilation and breathing, and the passage with the cross section that is 
smaller than that of the other passage serves as the inspiration passage 
for the additional or sole supply of fresh gas. 
The tube according to the invention, which can be designed as an 
orotracheal, nasotracheal, or tracheostomy tube, has two passages so 
designed that conventional ventilation can be conducted through the 
ventilation passage (for example, intermittent positive pressure 
ventilation, or IPPV). In addition, endotracheal and endobronchial 
suctioning can be performed through this passage both with conventional 
disposable suction catheters and with a bronchoscope. The inspiration 
passage, made with a smaller cross section than that of the ventilation 
passage, is intended for additional or sole supply of fresh gas to the 
patient. Both the additional and sole gas supply through the inspiration 
passage can be provided intermittently, preferably on expiration, or 
constantly or continuously, but as a function of the fresh phase with a 
different current, also termed flux or flow. The distal end of the tube, 
which is placed in the trachea, is designed so that the inspiration 
passage narrows to form a jet and its opening or openings point or extend 
toward or into the open distal outlet end of the ventilation passage. In 
other words, the nozzle-shaped distal end of the inspiration passage 
"blows" into the outlet opening of the ventilation passage, namely in the 
expiration direction through the ventilation passage at the proximal end 
of the tube, in other words out of the trachea and hence out of the 
patient. At the proximal end of the tube, outside the trachea, both 
passages in the tube have connections (connectors) for the connecting 
lines to the fresh gas sources, valves, or other equipment being used. 
As a result of the design according to the invention for the distal end of 
the inspiration passage, which serves to supply the fresh gas, in the 
shape of a nozzle, the gas flowing through the inspiration passage is 
deflected through 180.degree. so that it is guided from the distal end of 
the tube into the ventilation passage of the tube in the direction of its 
proximal end and flows toward the proximal end. To achieve a jet effect 
using the jet pump principle, the cross sectional area of the inspiration 
passage of the tube is reduced at the distal end up to the nozzle outlet 
opening, preferably by approximately one-half. 
When the tube according to the invention is used for the ventilation of a 
patient, as a result of a continuous supply of fresh gas through the 
smaller passage, the dead space during ventilation can be considerably 
reduced, i.e. the volume of residual gas that is not expired is reduced 
considerably. In order to improve ventilation during mechanical 
ventilation of a patient, it is even possible with the tube according to 
the invention to reduce the dead space, thus increasing carbon dioxide 
elimination by administering a continuous retrograde or expiratory 
retrograde fresh gas flow through the smaller tube passage. 
In the tubes according to the invention, with two passages of different 
sizes, the larger passage is intended to permit both unimpeded 
conventional ventilation and spontaneous breathing by the patient. In 
addition, the larger passage is intended to allow cleaning up the bronchi 
with suction catheters or with a bronchoscope. The smaller passage of the 
tube is used to supply the fresh gas. Its cross sectional area is 
therefore selected so that with each size of tube correct for the patient, 
up to five times the spontaneous fresh minute volume can be supplied with 
assumed pressures as behind commercially available flow regulators 
associated with fresh gas sources. 
For example, the following cross-sectional ratios can be given as 
guidelines: larger passage (fresh passage) to smaller passage (inspiration 
passage) to nozzle outlet opening, 8:2:1. In tubes for adults, the cross 
sectional area of the larger passage should correspond to that of a 
conventional tube with an inside diameter of 7 mm, i.e. approximately 38.5 
mm.sup.2. The smaller passage of the tube at 9.6 mm.sup.2 then corresponds 
to an inside diameter of a conventional tube with an inside diameter of 
3.5 mm. The cross-sectional area of the nozzle outlet opening of the 
smaller passage in this example is then 4.8 mm.sup.2. 
Advantageous embodiments of the tube according to the invention are shown 
in the characterizing features of subclaims 2 to 21. 
The tubes can be made with or without a cuff. The cuff can be inflatable 
(balloon) or unfold by itself (so-called "foam cuff"). When no cuff is 
provided, so-called "gills" can be used which are wafer-thin membranes or 
structures made of silicone, arranged in a circle around the shaft of the 
tube for sealing. 
The tubes themselves are made of a tissue-compatible plastic, for example 
PVC, preferably a plastic that does not change in the body even when left 
there for a long period of time and can be disposed of in an 
environmentally safe manner after use. It is also possible to use 
spiral-reinforced tubing made of rubber or silicone (according to 
Woodbridge). For optimum utilization of the cross-sectional area of the 
tube, its wall should be as thin as possible. 
To achieve a jet effect with the aid of the nozzle formed at the distal end 
of the inspiration passage as well as the deflection of the flow in the 
inspiration passage in the direction of the ventilation passage, entering 
the distal end thereof, the nozzle outlet opening of the inspiration 
passage can project slightly into the outlet opening, i.e. into the 
ventilation passage, or be arranged in front of the outlet opening of the 
ventilation passage or directly adjoining it. The arrangement of the 
outlet opening of the ventilation passage and the nozzle outlet opening of 
the inspiration passage should leave sufficient space for entrainment of 
the expired gas, but at the same time must not block the outlet opening of 
the ventilation passage so that unimpeded flow is possible during 
ventilation and a suction catheter can also be passed through the 
ventilation passage of the tube, for example. 
To achieve a Venturi effect which increases the volume of gas dram out of 
the respiratory tract, a bead (short reduction of the cross-sectional area 
up to about 25%) can be located in the (distal) inlet area of the 
ventilation passage near the patient. 
The nozzle-shaped element that forms the nozzle at the distal end of the 
tube of the inspiration passage that is near the patient likewise consists 
of a tissue-compatible plastic that can be disposed of in an 
environmentally safe manner, with a harder material being used than for 
the tube itself. The nozzle or the nozzle-shaped body has a defined seat 
relative to the tube, for example by means of a snap closure; it is also 
glued or welded to the tube. 
The double-lumen tube according to the invention with a nozzle at the 
distal outlet of the inspiration passage, which blows into the ventilation 
passage from the distal end thereof, can be used to support ventilation 
with a continuous retrograde fresh gas flow or an exhalational retrograde 
fresh gas flow or for ventilation with a continuous retrograde fresh gas 
flow. Fresh gas can be air or oxygen supplied from a gas source, 
additionally equipped with a flowmeter for compressed air or oxygen. 
Mechanical ventilation in addition to the double-lumen tube inserted into 
the trachea of a patient and the fresh gas source also requires a 
controllable expiration valve connected to the proximal end, in other 
words the end of the larger passage of the tube away from the patient. The 
expiration valve, the fresh gas source, a pressure reduction valve in the 
fresh gas supply, and a tube constitute a ventilator. 
Controlled or assisted ventilation is performed in the usual manner through 
the ventilation passage, in other words the larger passage on the tube. To 
improve ventilation, i.e. to increase carbon dioxide elimination by 
reducing dead space, a continuous, preferably exhalational fresh gas flow 
can be added through the inspiration passage of the tube. Basically, air 
or oxygen can be fed continuously into the smaller passage of the tube 
using the ventilator. Then, besides the double-lumen tube, only one 
flowmeter is needed for compressed air or oxygen as fresh gas from the 
fresh gas source. 
For ventilation with a continuous retrograde gas flow, according to the 
invention an electrical control device is provided for the controllable 
expiration valve associated with the proximal outlet of the ventilation 
passage of the tube. The control device utilizes electrical signals 
delivered from the ventilator and opens the expiration valve for 
continuous retrograde gas flow during the exhalation phase, i.e. whenever 
the expiration valve is in the "open" position. 
Naturally the inspiratory oxygen concentration of the continuous or 
exhalational retrograde gas flow can also be identical with the 
respiratory oxygen concentration supplied through the ventilator or the 
fresh unit, i.e. through the fresh gas source. This is accomplished by 
connecting the flowmeter for the continuous or exhalational retrograde gas 
flow to the air/oxygen mixer of the fresh gas source or to a separate 
air/oxygen mixer with the same setting. The fresh gas for the continuous 
or exhalational retrograde gas flow can be heated and moistened in the 
same way as is done for a gas delivered by a ventilator. In particular, 
ventilation of a patient with a ventilator using the double-lumen tube 
according to the invention is possible with a continuous retrograde fresh 
gas flow. If, to support ventilation with a continuous retrograde gas 
flow, one begins at the level of a fraction of the required minute volume 
and the continuous retrograde gas flow is increased with a simultaneous 
reduction of conventional ventilation up to a multiple of the minute 
volume originally required for conventional ventilation, a point is 
eventually reached at which conventional ventilation using the fresh 
passage of the tube can be completely suspended. All of the fresh gas then 
flows through the inspiration passage of the tube into the trachea and is 
distributed, with the expiration valve closed, into the 
lungs--inspiration--or escapes with the expiration valve open together 
with the gas that flowed into the lung during the inhalation phase, 
outward through the ventilation passage of the tube--expiration. This type 
of ventilation is termed ventilation with a continuous retrograde gas 
flow. 
In its simplest from, ventilation with a continuous retrograde gas flow can 
be performed manually. Then the fresh gas source is connected to the 
smaller passage of the tube (fresh gas flow 10 l/min for example) and the 
person administering ventilation manually closes the outer opening of the 
fresh passage of the tube (inhalation phase) for 3 seconds for example and 
then releases it again (exhalation phase), for example for 3 seconds as 
well, so that a minute volume of 5 liters is obtained in this example. 
In theory, any conventional ventilator with a time-controlled expiration 
valve and fresh gas source can be used for ventilation with a continuous 
retrograde gas flow. The gas connections of the ventilator are then not 
used and the device is merely supplied with current. The inspiration 
passage of the tube is connected with the fresh gas source and the 
ventilation passage of the tube is connected through a connecting hose 
with the expiration valve. On the ventilator the inhalation/exhalation 
ratio and the respiratory rate or the inhalation and exhalation times can 
be adjusted directly. The level of the required continuous retrograde gas 
flow for efficient carbon dioxide elimination then depends on the 
respiratory rate and the inhalation/exhalation ratio. The mean airway 
pressure critical for oxygenation is adjusted by changing the 
inhalation/exhalation ratio and the PEEP valve or the PEEP function of the 
ventilator. Therefore a suitable time-controlled expiration valve is 
required. The task of a time-controlled expiration valve with positive end 
exhalation pressure function can also be supplied by an expiration valve 
that is independent of a ventilator, said valve being usable in cases when 
ventilation with a continuous retrograde fresh gas flow is conducted 
exclusively in a patient. 
The double-lumen tube according to the invention and the principle of 
ventilation with a continuous retrograde gas flow with a ventilator reduce 
the dead space when ventilating a patient in such a way that ventilation 
can be conducted at respiratory rates that are much higher than those 
conventionally employed. It is then possible according to the invention, 
by conducting ventilation with a continuous retrograde gas flow and using 
the tube designed according to the invention, to work at respiratory rates 
that correspond to the human heart rate. According to the invention 
therefore the double-lumen tube is used in a ventilator that makes it 
possible to perform ventilation with a continuous retrograde gas flow that 
is EKG--triggered and in synchronization with the pulse. 
For this purpose, according to the invention a ventilator is proposed using 
the double-lumen tube according to the invention according to claim 24. 
According to the invention the electrical control device receives the 
output signals from conventional electrocardiographs or blood pressure 
monitors to close and open the expiration valve which is available in 
conventional ventilators or as a device by itself in synchronization with 
the pulse. 
With a ventilator system equipped according to the invention, the 
inspiration phase can be synchronized with the systole. This measure is 
capable of lowering the afterload of the left ventricle, which is 
hemodynamically favorable in left ventricular heart failure (e.g. 
myocardial infarction). It is also possible to synchronize the inhalation 
phase with the diastole, and as a result the right ventricle does not have 
to eject the blood against a high vascular resistance into the pulmonary 
circulation compressed by the respiratory pressure. This measure reduces 
the load on the right ventricle which has an advantageous effect in all 
conditions involving acutely elevated pulmonary vascular resistance, e.g. 
pulmonary embolism. 
Advantageous improvements on the ventilator using the double-lumen tube 
according to the invention and an electrical control device for the 
expiration valve can be obtained from the characterizing features of 
claims 25 to 36. 
Integration of an electrocardiograph into the ventilator makes it possible, 
using the signals from the electrocardiograph, to control the expiration 
valve connected to the larger passage of the tube in such a way that 
ventilation takes place in synchronization with the pulse, using a fresh 
gas supplied through the inspiration passage of the tube, a so-called 
pulse-synchronized positive pressure ventilation. The control device for 
the expiration valve is also equipped with functions for changing the time 
relationship from inspiration to expiration (inhalation/exhalation ratio) 
and for the alternative selection of synchronization of inhalation with a 
contraction of the heart muscle (systolic inhalation) or with its 
relaxation (diastolic inhalation). 
In another embodiment of the invention, an electrically controllable valve, 
especially a pressure-reduction valve, is provided, arranged in the supply 
line from the fresh gas source to the inspiration passage of the tube, and 
the fresh gas flowing to the inspiration passage of the tube can be 
metered with its aid so that the gas flow during inhalation and gas flow 
during exhalation may be freely selected. 
During mechanical ventilation with a continuous retrograde gas flow, a 
constant fresh gas flow can be set for the sake of simplicity. 
Advantageously, however, there is the possibility of adjusting the 
magnitudes of the continuous fresh gas flow for the inhalation phase and 
for the exhalation phase separately. The electrically controllable 
pressure-reduction valve is provided for this purpose. The inhalational 
gas flow can be adjusted to the minute volume required for carbon dioxide 
elimination and the exhalational gas flow can be adjusted to the mean 
airway pressure critical for oxygenation.

FIG. 1 shows schematically a ventilator 6 with double-lumen tube 1, fresh 
gas source 5 with flowmeter 50, and a controllable pressure reduction 
valve 2 in gas supply line 80 to tube 1 and an electrically controllable 
expiration valve 60 with electrical connections 61. Tube 1 inserted into 
the trachea 3 of a patient up to carina 100 has two continuous passages 11 
and 12, of which passage 11 used as the inspiration passage has a smaller 
cross section than passage 12 used as the ventilation passage. The 
ventilator system 6 shown is suitable for controlled mechanical 
ventilation of a patient. The double-lumen tube according to FIG. 1 has an 
inflatable cuff 4 for holding and sealing in trachea 3. Inspiration 
passage 11 is connected on the inlet side, in other words proximal end 11, 
through a connector 8 and through flowmeter 50 to a fresh gas source 5. 
The fresh gas is under a desired positive pressure. Ventilators with tubes 
not according to the invention are known. 
Ventilation passage 12 is connected on the output side, i.e. at proximal 
end 121, with electrically controllable expiration valve 60. 
In the vicinity of distal end of tube 1, near carina 100, inspiration 
passage 11 and exhalation passage 12 are connected together by a nozzle 17 
formed at the distal end 112 of the inspiration passage. Conical nozzle 17 
has its nozzle outlet opening 171 or nozzle mouth close to or at outlet 
opening 123 of ventilation passage 12, so that an open annular space 18 
remains between the nozzle outlet and the distal end of ventilation 
passage 12 and/or the inside wall of ventilation passage 127. With 
expiration valve 60 closed, the fresh gas, which is under pressure, fills 
the lung through inspiration passage 11 of tube 1, emerging at nozzle 17. 
With expiration valve 60 open, the fresh gas flows through nozzle 17 into 
ventilation passage 12 from the distal end and outward through ventilation 
passage 12 and expiration valve 60. During this process, the gas in the 
lung is simultaneously expelled by the vacuum prevailing in free annular 
space 18 through ventilation passage 12 and expiration valve 60. Nozzle 17 
at the distal end of inspiration passage 11 is arranged so that it is 
directed at the distal end of the ventilation passage and blows into the 
ventilation passage from the nozzle of the inspiration passage, in the 
exhalation direction. 
Between gas source 5 and inspiration passage 11 of tube 1, an electrically 
controllable pressure reduction valve 2, shown by the dashed lines, can be 
inserted which makes it possible to provide different fresh gas pressures 
for the inhalation phase and the exhalation phase. In this way, the 
exhalation process can be accelerated timewise for example. 
The additional design of ventilator system 6 according to the invention 
according to FIG. 1 for controlled mechanical ventilation consists in 
controlling expiration valve 60 as a function of a signal from an 
electrocardiograph. The system thus equipped then makes it possible to 
perform ventilation with positive pressure in synchronization with the 
heart cycle. For example, the efficiency of the failing left ventricle can 
be improved by systolic inhalation, so-called afterload reduction and 
diastolic exhalation, so-called minimization of preload reduction. 
Likewise, in situations with acute fight ventricular failure the fight 
ventricle can be relieved by diastolic inhalation and systolic exhalation. 
Depending on the therapeutic goal, electrically controllable expiration 
valve 60 and/or electrically controllable pressure-reduction valve 2 can 
be controlled by signals controlled in turn by medical instruments, as for 
example an electrocardiograph, or by a clock that replaces these devices. 
In FIGS. 2 to 6, a double-lumen tube 1, suitable for use in controlled 
mechanical ventilation with a continuous retrograde gas flow, is shown. 
Tube 1 has two through passages 11, 12 separated from one another by a 
partition 14; see FIG. 3. The through passages have different sizes, with 
the larger passage serving as a ventilation passage for unimpeded 
conventional ventilation as well as spontaneous breathing by the patient, 
and in addition must be sufficiently large in cross section to permit 
introduction of a suction catheter or bronchoscope. Smaller passage 11 
serves as the inspiration passage for supplying the fresh gas. Tube 1 is 
long enough so that regardless of the size of the tube or patient, a 
portion of the shaft of the tube projects from the patient and is suitable 
for fastening, preferably with adhesive or hook-and-loop fasteners. The 
length 1 of an average tube is 220 mm for example. In the vicinity of the 
distal end 19 of the tube, at a slight distance from the latter, an 
inflatable tube cuff is provided. Tube cuff 4 is supplied with inflating 
air through an air supply duct 42 formed in the wall of tube 10; see FIG. 
5. In the vicinity of the proximal end of tube 1, control balloon 40 is 
mounted with a connection 43 through air supply hose 41 to the output 44 
of air channel 42. At the proximal end 121 of larger passage 12, a 
suitable connecting stub 7 is provided. At the proximal outlet 11 of 
inspiration passage 11 a connecting stub 8 is likewise provided that, for 
the sake of improved handling, is connected through a supply tube 15 with 
the proximal input of the inspiration passage. At the distal end 19 of 
tube 1, inspiration passage 11 is designed to be tapered in the form of a 
nozzle, see FIGS. 3 and 4, with the nozzle channel of nozzle 17 being bent 
at 180.degree. so that nozzle outlet opening 171 points at the open distal 
end 122 of ventilation passage 12. The fresh gas flow flowing through 
inspiration passage 11, see FIG. 3, in the direction of arrow a is guided 
at the distal end of tube 19 by the design of noble 17 with a cross 
section that decreases relative to the cross section of inspiration 
passage 11 toward the outlet of the nozzle, with a simultaneous deflection 
by 180.degree. in the direction of ventilation passage 12, with 
simultaneous acceleration, and flows in the direction of arrow b, i.e. in 
the opposite direction, from the distal end of the tube into fresh passage 
12. For those cases in which the expiration valve (see FIG. 1) is closed 
at the proximal outlet of passage 12, the gas flowing in the direction of 
arrow b into the ventilation passage, after filling ventilation passage 
12, can escape through distal outlet opening 123 of ventilation passage in 
the direction of arrow c and reach the lung. When the expiration valve is 
open at the proximal outlet of ventilation passage 12, on the other hand, 
the gas flow moving in the direction of arrow b into ventilation passage 
12 from the distal end thereof entrains the exhalation gas coming from the 
lungs and clears the lungs well to remove exhalation gas and improve 
ventilation considerably, i.e. increase carbon dioxide elimination by 
reducing dead space. 
In the example shown in FIGS. 2 to 6, the design of distal end 112 of 
inspiration passage 11 with a nozzle is shown, with deflection of the flow 
channel with the aid of a nozzle-shaped piece 9 inserted into the distal 
end of the tube and inspiration passage 11. Nozzle-shaped piece 9 has a 
leg 90 abutting the wall of tube 10 internally, so that a flow channel 
continuing inspiration passage 11 is formed between partition 14 and leg 
90. Nozzle-shaped piece 9, as an extension of leg 90, is made hook-shaped 
with a shorter leg 94 guided around the distal end of the partition, 
leaving a space forming nozzle channel 17a. Nozzle channel 17a terminates 
with a flow direction that runs axially parallel to lengthwise axis X of 
the tube. The outlet opening 171 of the nozzle channel and hence of the 
inspiration passage 11 at the distal end is shown doubled outward in the 
example shown in FIG. 3, making improved outward flow in arrow direction c 
during inhalation possible. In addition, nozzle outlet opening 171 of 
inspiration passage 11 is located at the periphery of the cross section of 
ventilation passage 12 so that an outlet opening 123 that is as large as 
possible remains for ventilation passage 12. This outlet opening 123, for 
example in the example shown, can have a diameter p of 5.9 mm. Tube wall 
10 should be as thin as possible; when a suitable material is selected, 
for example PVC, it can be 1.2 mm. Outlet opening 123 must also be large 
enough to permit unimpeded introduction of a suction catheter through 
ventilation passage 12 to evacuate the respiratory tract. For this reason, 
outlet opening 123, also beveled, for example at 45.degree. relative to 
the lengthwise axis X of tube 1, in such fashion that the tip of the tube 
is tapered at one end toward distal end 19. In this manner as well outlet 
opening 123 is made larger. It is also possible, by further separation of 
distal outlet opening 123 of ventilation passage 12 and distal outlet 
opening 171 of inspiration passage 11, to increase the outlet area, with 
reference being made for example to the embodiment shown in FIG. 11, where 
outlet openings 123 and 171 contact one another only in foot area FP at 
partition 14. 
Nozzle-shaped piece 9 is mechanically engaged in the vicinity of tube wall 
10 by means of a projecting locking nose 91 that engages a recess 13 in 
the tube wall. In addition, tubular-shaped piece 9 is glued or sealed in 
the area of tube wall 10. 
For the double-lumen tube to function well, especially with good 
ventilation and gas direction, the sizes of the cross sections of the 
ventilation passage, the inspiration passage, and the nozzle outlet 
opening, individually and in relation to one another, are critical. The 
cross section of the inspiration passage must be sufficiently large to 
permit a fresh gas supply sufficient for up to five times the spontaneous 
minute ventilation to pass through at usual pressure. The cross section of 
the ventilation passage must permit unimpeded conventional ventilation or 
spontaneous breathing by the patient, and the passage of a suction 
catheter. Under these circumstances, a ratio of cross section C of the 
ventilation passage to the cross section A of the inspiration passage to 
the size B of nozzle outlet opening 171 of the inspiration passage of 
approximately 8:2:1 is provided. Cross sections A, B, C, as stated above, 
are evident from the cross sections shown in FIGS. 4 and 5 for the 
catheter according to FIG. 2. With an inside diameter of ventilation 
passage 12 corresponding to a conventional tube with an inside diameter of 
7 mm, the cross-sectional area C is approximately 38.5 mm.sup.2, 
cross-sectional area A is approximately 9.6 mm.sup.2, and nozzle outlet 
area B is approximately 4.8 mm.sup.2. Accordingly, the outside diameter r 
of tube 1 is approximately 11 mm. 
As connectors for inspiration passage 11, preferably those with integrated 
tapping stubs for monitoring airway pressure or gas composition can be 
used, possibly also for the proximal entrance of ventilation passage 12. 
In FIGS. 7 to 10, another version of a nozzle-shaped piece 9 for insertion 
into inspiration passage 11 for forming a nozzle outlet opening at the 
distal end of tube 1 is shown. The nozzle-shaped piece likewise has a long 
leg 90 for insertion into inspiration passage 11 from the distal end 19 of 
the tube, as shown in FIG. 11, while tube wall 10 is expanded outward 
corresponding to the thickness of leg 90 in order to continue inspiration 
passage 11 with the same cross section at the beginning of the 
nozzle-shaped piece. The nozzle-shaped piece also has leg 94 bent at 
90.degree., which leads to a bend in the flow channel by 180.degree. and 
ends with a bevel 95 at the outlet opening. The channel enclosed by short 
leg 94 has a cross section that tapers and narrows toward end 95, thanks 
to additional bends 94a. In connection with partition 14, the closed flow 
channel for the fresh gas in the direction of arrow a is then formed; see 
FIG. 11. To anchor nozzle-shaped piece 9 to tube 1, externally on the 
longer leg, projecting locking hook 91 and stop lug 92 with receiving 
pocket 93 for locking, see FIG. 11, are formed on tube wall 10. Depending 
on the arrangement of nozzle outlet opening 17 1 formed by nozzle-shaped 
piece 9, mounted at the tube end, according to FIG. 11, for inspiration 
passage 11, and the design of nozzle outlet opening 123 of ventilation 
passage 12, corresponding ventilation is made possible as indicated by 
arrows c and b for the fresh gas supplied through inspiration passage 11. 
FIG. 12 shows another variation on a nozzle-shaped piece 9 for forming the 
nozzle-shaped constriction at the distal end of the inspiration passage 
and nozzle outlet opening 171, inserted at the distal end 19 of tube 1. In 
this case, only a relatively short nozzle-shaped section has its long leg 
9 inserted into the expanded end of the tube into inspiration passage 11 
and glued therewith. 
To achieve a Vemuri effect, intended to increase the volume of gas 
entrained by gas flow b from the respiratory tract, near distal outlet 
opening 123 of ventilation passage 12 a bead 16a can be impressed into the 
ventilation passage for reducing the cross section by means of a notch 16 
in wall 10 of the tube. A reduction of the cross section by up to about 
25% can be achieved in this manner. 
FIG. 13 is a view of the distal end 19 of the tube in cross section, where 
H represents the cross-sectional area of ventilation passage 12 reduced by 
bead 16a. 
FIG. 15 shows a design of double-lumen tube with two pipes brought together 
to form one tube, containing the smaller inspiration passage 11 and the 
larger ventilation passage 12. The two pipes containing the passages are 
connected together by strips 20 and strips 45, 46 in the vicinity of 
inflatable tube cuff 4. In addition, the pipes forming tube 1, see the 
cross section in FIG. 16, can be permanently connected to one another by 
gluing in contact area 22. It is also possible to weld them together in 
this area by using a suitable plastic, for example by using solvents. In 
tube 1 according to FIG. 15, outlet opening 171 of the end of the 
nozzle-shaped inspiration passage that is bent to an angle of 180.degree. 
is located a short distance from the distal outlet opening 123 of 
ventilation passage 12, so that a free outward flow of the gas emerging 
from the nozzle outlet opening 171 into the lungs can take place with the 
expiration valve closed, and distal outlet opening 123 is sufficient to 
pass a suction catheter through and also, with the expiration valve open, 
the gas flow from nozzle outlet opening 171 can blow directly into outlet 
opening 123 into large ventilation passage 12. 
FIG. 17 shows another embodiment of double-lumen tube 1 according to the 
invention, in which the distal end of tube 1 is provided with an annular 
nozzle-shaped section that forms both the tapering nozzle outlet channel 
at the distal end for inspiration passage 11 and also outlet opening 123 
of ventilation passage 12 at the distal end. 
FIG. 19 shows view I according to FIG. 17 looking at the distal end of the 
tube with nozzle-shaped piece 9. In FIG. 18, axial lengthwise section MM 
shows in FIG. 18 the distal end area of the tube in cross section and the 
annular molded part 9, which is attached externally to tube wall 10 and 
fits over it, and internally forms a tapering annular space with a 
plurality of nozzle outlet openings 171. Inner nozzle annular wall 96 also 
forms the limit for outlet opening 123 of the ventilation passage. At a 
slight distance from distal end 19 of tube 1, once again in the vicinity 
of ventilation passage 12, a notch 16 is provided to form a bead 16a that 
reduces the cross section partially and over a short distance. 
FIG. 20 shows that the tube in the middle area, see cross section LL in 
FIG. 17, has continuous fresh passage 12 with cross section C and 
continuous inspiration passage 11 with cross section A, of a size 
sufficient to perform its functions. 
For pulse-synchronized ventilation with a continuous retrograde gas flow, 
expiration valve 60 of ventilator 6 according to FIG. 1 is controlled by 
means of a control device. For pulse-synchronized ventilation, the control 
device is connected to an electrocardiograph EKG whose EKG signal is 
received by the control device, processed electronically, and used as the 
control signal for the expiration valve. 
FIG. 21 is a block diagram of the functional layout. The control device 
forms a connection between the EKG or the blood pressure measuring device 
and the expiration valve of a ventilator and delivers the control signal 
to open or close the expiration valve. The basic system of a ventilator 
system for pulse-synchronized ventilation is shown schematically in FIG. 
22 and includes the following parts: a gas source, a double-lumen tube 
with a nozzle at the distal end of the inspiration passage, an expiration 
valve, a control device, and an electrocardiograph or blood pressure 
measuring device. The ventilator system can be equipped with conventional 
EKG units or blood pressure measuring devices as well as commercially 
available ventilators with an expiration valve, for example a Siemens 
Servo Ventilator 900C in conjunction with the electronic adaptable control 
device according to the invention and in conjunction with the double-lumen 
tube according to the invention, with a nozzle outlet at the distal end of 
the inspiration passage and permits pulse-synchronized ventilation for 
anesthesia, intensive care, and emergency medicine. 
The charts for pulse-synchronized ventilation are shown in FIG. 23. Curve I 
shows the EKG signals with the QRS complexes obtained by the EKG. The time 
duration AZ calculated from time interval AZ between two QRS complexes 
corresponds to the duration of one fresh cycle. Curve II shows the changes 
in pressure in the aorta and in the left ventricle. Curve III shows 
systolic inhalation and curve IV shows diastolic inhalation. 
In order to perform pulse-synchronized ventilation, the contraction time 
(systole) of the heart must be determined. The beginning of systole can be 
derived from the QRS complex of the electrocardiogram. There is no defined 
technical signal for the end of systole. Therefore, the following estimate 
is performed: a heart period consists of three pleases: contraction, 
relaxation, and the resting period, with each of these phases occupying 
approximately one-third of the total period between two heart beats with 
normal heart activity. The time for systole is therefore assumed to be 
one-third of the time between two heartbeats, i.e. between two successive 
QRS complexes. In order to obtain a defined synchronization, the ratio 
between inhalation and exhalation can be vaned. During systolic 
ventilation, the beginning of inhalation is determined from the QRS 
complex of the EKG signal. The duration of systole is determined from the 
pulse frequency, which in turn is determined by the interval of the 
respective previous QRS complex, and from the adjusted 
inhalation/exhalation ratio. At the end of systole, a switch is made to 
exhalation and a new QRS signal is awaited to start a new inhalation. 
In diastolic inhalation, exhalation is started with a QRS complex in the 
EKG signal. The moment of beginning of inhalation is determined from the 
pulse frequency, which is determined from two previous ORS complexes, as 
well as from the I/E ratio. When this point is reached, a switch is made 
to inhalation. Then the next QRS complex is awaited again. In systolic 
ventilation, therefore, the beginning of the inhalation phase is 
synchronous with the QRS complex, while in diastolic ventilation the end 
of inhalation is synchronous with the QRS complex. 
During inhalation, the expiration valve is closed and the fresh gas flows 
into the lungs. During exhalation, the expiration valve is open and the 
alveolar gas is entrained and carried away from the lungs by the flow of 
fresh gas. 
The functional design of the control device for performing 
pulse-synchronized ventilation according to FIG. 23 is shown in FIG. 24. 
The control device contains signal preparation, evaluating electronics, 
control electronics, and display elements and operating elements (key 
recognition). The signal-preparation electronics has the task of receiving 
the electrical EKG signal delivered by the electrocardiograph or blood 
pressure measuring device, encoding it, and displaying the QRS complex in 
order then to deliver a defined control pulse to the evaluation 
electronics. The signal preparation electronics contains a threshold value 
detector and a timer which provides a control pulse with the necessary 
length and amplitude. This makes it possible to use EKG devices with 
analog or digital signals. In this way it is possible to use all 
commercial EKG units or blood pressure measuring devices for the 
ventilator system according to the invention for pulse-synchronized 
ventilation. 
The evaluation electronics is the central component of the control device. 
The evaluation electronics contains the following functional units: 
central processing unit, clock, RAM, interfaces for inputs and outputs, 
timer, interruption-control circuit, and possibly a read-only memory 
(ROM). The evaluation electronics receives the pulse delivered by the 
signal preparation electronics and, from the duration of the AZ interval 
of two ORS complexes, calculates the duration between two heartbeats. The 
evaluation electronics is also connected with the operating elements, with 
which the inhalation/exhalation ratio as well as the operating mode may be 
determined, and it monitors the display elements. In the evaluation 
electronics, the duration of inhalation and exhalation corresponding to 
the set inhalation/exhalation ratio is determined, as well as the time 
between the EKG signals and the operating mode to be used. The evaluation 
electronics transmits the required signal for opening and closing the 
expiration valve. Control for the expiration valve is provided as a 
function of the pulse frequency (EKG signals) and the set predetermined 
inhalation/exhalation ratio (FE ratio). With the FE ratio, the ventilation 
cycle can be synchronized with the systole or diastole. In contrast to a 
EKG trigger with initially adjustable, then fixed delay, with the control 
device and its control according to the invention, independence from the 
heart rate is ensured. It is possible to perform ventilation with a freely 
selectable frequency. The ratio between the inhalation and exhalation time 
is adjustable, for example in a range from 1:4 to 4:1. The duration of 
inhalation and exhalation is determined by the set FE ratio. The correct 
point in time for switching from inhalation to exhalation, i.e. the 
opening of the expiration valve, results from the set mode (systolic or 
diastolic inhalation) and the set I/E ratio. The control electronics 
performs the necessary adjustments to the control signal supplied by the 
evaluation electronics, in order to control the expiration valves of 
commercially available ventilators. The key recognition of the control 
device makes it possible to use operating elements to set the ratio of 
inhalation to exhalation. In addition, operating elements are provided for 
adjusting the operating mode. Key recognition is detected in the 
evaluation electronics and changed. 
The control device also has display elements for displaying the operating 
mode, the set I/E ratio. In addition, incoming QRS complexes (EKG signals) 
as well as the position of the expiration valve are displayed. All the 
display elements are controlled by the central evaluation electronics of 
the control device. The evaluation electronics of the control device 
require an external program. 
The control device distinguishes between two operating modes. 
"Systolic" operating mode: inhalation takes place during systole. 
"Diastolic" operating mode: inhalation takes place during diastole. 
It is possible to switch between the two operating modes by means of 
operating elements; for this purpose the evaluation electronics can be 
controlled by key recognition; see FIG. 24. 
In the "diastolic" operating mode, immediately after an EKG signal is 
recognized (QRS complex), the expiration valve is opened; see FIG. 23, 
curve IV. 
Depending on the FE ratio, the expiration valve is then closed again after 
a certain period of time ta, so that inhalation takes place during 
diastole. After the next QRS complex arrives, the expiration valve is 
opened again. 
In the "systolic" operating mode, following recognition of the QRS complex, 
the expiration valve is closed; see FIG. 23, curve III. In this operating 
mode, depending on the FE ratio, the expiration valve is opened again 
after a certain period of time tb, so that inhalation takes place during 
systole. After the next QRS complex arrives, the expiration valve is 
closed again. 
The control device monitors the actual functionality itself. In order to 
achieve maximum safety, the monitoring functions of the connected 
ventilator system are active. If improper functioning of the ventilator 
system is detected, the control device is switched off automatically and 
the conventional ventilator begins independently to provide conventional 
ventilation. 
The evaluation electronics of the control device constantly tests the times 
for inhalation and exhalation and the arrival of new EKG signals. Only 
when several correct ventilation cycles have been recorded does the 
control unit take over the monitoring of the ventilator. Then the shutoff 
to the ventilator is closed, indicated by a pilot light. In the event of 
power failure, the shutoff disconnects the control device from the 
ventilator, which then starts operating independently again. 
In the event of an absence of EKG signals, continuation of conventional 
ventilation with the ventilator is likewise initialed without control by 
the control device, until new EKG pulses reach the control device. 
To avoid dangerous pressures in the lungs, the inhalation time is 
monitored. In cases of excessive inhalation times, the ventilator likewise 
automatically takes over control once again, i.e. the control device is 
switched off. In those cases in which the EKG pulses arrive too rapidly, 
efficient ventilation is no longer guaranteed. In this case as well, the 
control device can shut off automatically and the conventional ventilator 
automatically takes over further ventilation. In the event of EKG pulses 
following one another at intervals that are too short, however, several 
such short pulses must follow one another to trigger a shutoff, since only 
then do they indicate a prolonged state. 
To monitor the central airway pressure, the tube is provided near the 
distal end, on the outside, with a pressure sensor, especially an 
electronic pressure sensor, equipped with an electronic device for signal 
processing of the measured values detected. In addition, the electronic 
pressure sensor can supply the recorded measured value of the central 
airway pressure in the trachea to the control device. Then the control 
device, in addition to the given safety mechanisms, can monitor the 
function of the overall system and correct it as necessary. Further 
details of the provision of a tube with an external pressure sensor are 
described in German Patent Application P 43 10 799.0. In addition, it is 
possible with the aid of the central airway pressure measured continuously 
in the trachea using the tube with integrated pressure sensor and the 
electrical signals obtained therefrom, to operate the ventilator system as 
a function of the prevailing central airway pressure of the patient. In 
particular, it is possible to supply the electrical signals, corresponding 
to the central airway pressure determined, to the ventilator system to 
actuate a trigger for a defined pressure drop in the ventilator system. 
With continuously controlled mechanical ventilation of a patient, the 
electrical signals recorded, which correspond to the measured central 
airway pressure, can be fed into the ventilator system to control the 
pressure limitation and upper pressure limit functions, so that the 
ventilator system, when a predetermined pressure is reached, either shuts 
off the supply of fresh gas or switches to exhalation. In particular, 
capacitive pressure sensors with integrated electronic signal processing 
are suitable, manufactured as ready-to-install modules. The pressure 
sensors operate using the difference principle, i.e. pressure differences 
are determined and converted into electronic signals. The analog signals 
from the measured parameters are converted into digital signals with the 
aid of an analog-digital converter, amplified, and evaluated in 
microprocessors. These electronics are designed in the form of a chip and 
connected with the pressure sensor as a measurement sensor to form a small 
module, measuring 9.times.1.2.times.0.8 mm for example, so that they can 
be mounted or installed easily on the outside of the tube wall. 
The control device can also be designed according to the invention in such 
fashion that it is capable of controlling the expiration valve in such 
manner that a definite positive-end expiratory pressure (PEEP) can be 
adjusted for the patient. 
In order to adjust the PEEP, the expiration valve is opened only partially, 
so that a corresponding certain residual pressure PEEP remains in the 
airways. 
The PEEP can be adjusted using the operating elements in the evaluation 
electronics of the control device; see FIG. 24. The evaluation electronics 
is capable of calculating the degree of opening of the expiration valve 
that is then required. This extension stage for the adjustment of the PEEP 
can be used on all ventilators that have a controllable expiration valve. 
When pressure sensors are used in conjunction with the tube, it is possible 
to design the control device so that it can measure the exhalation 
pressure with the aid of the pressure sensors on the exhalation leg of the 
ventilator build-up, and this measurement signal is used in evaluation to 
increase the reliability of the overall system. In addition, it is also 
possible to use the pressure sensors to monitor the adjusted PEEP. 
While in conventional ventilators the expiration valve has heretofore 
formed a single unit with the fresh gas source and the corresponding 
operating and adjusting elements, and the control device according the 
invention is connected in addition, it is also possible to equip the 
control device according to the invention directly with an expiration 
valve of its own. In this manner, the expiration valve together with the 
control device is independent of the ventilator system and can likewise 
perform ventilation itself. 
FIG. 25 shows schematically the diagram of a control device with an 
internal expiration valve 60. The double-lumen tube 1 with ventilation 
passage 12 and inspiration passage as well as nozzle 17 at the transition 
of the distal end of the inspiration passage to the exhalation passage is 
used, with the aid of the control device, for pulse-synchronized 
ventilation with a retrograde gas flow. With an oxygen/air mixer, the 
correct gas mixture is selected from the oxygen/air supply, the desired 
fresh gas flow can be set with the flow regulator, and fed through line 80 
to inspiration passage 11. The control device which uses the EKG signals 
obtained from the electrocardiograph EKG unit to control ventilation, 
controls directly the expiration valve 60 mounted at the proximal outlet 
of ventilation passage 12. An arrangement according to FIG. 25 permits 
pulse-synchronized ventilation with continuous exhalational retrograde 
flow only with an expiration valve, but without a conventional ventilator. 
In order to be able to operate the control device completely 
independently, i.e. even without a EKG unit or blood pressure measuring 
device, according to the invention an internal clock is provided that is 
associated with the control device. The design of a control device with an 
internal clock is shown in the block diagram in FIG. 26. Instead of an 
electrocardiogram or blood pressure measuring device, a clock is provided. 
The pulses generated by the clock are picked up by the evaluation 
electronics. From the clock frequency and the set FE ratio, the evaluation 
electronics calculates the time for opening and closing the expiration 
valve. The operating elements and the evaluation electronics can be used 
to adjust the clock frequency for example between 2/min and 200/min. The 
control unit with the clock can be integrated for example into the system 
according to FIG. 25, so that the EKG device shown there can be 
eliminated. In this manner it is possible to provide a ventilator system 
that may be used as a stand-alone version, in other words without a 
conventional ventilator. When a clock is used in conjunction with the 
control device, see FIG. 26, non-pulse-synchronized ventilation with a 
continuous exhalational retrograde gas flow is also possible. 
The control device according to the invention, in the various expansion 
stages, serves to control pulse-synchronized ventilation with continuous 
retrograde gas flow in conjunction with a double-lumen tube, in which the 
inspiration passage is equipped at the distal end with a nozzle that blows 
into the distal outlet opening of the ventilation passage. With the aid of 
the control device, an expiration valve that is provided either externally 
in a commercially available ventilator or is connected internally directly 
with the control device, see FIG. 25, is opened and closed. The control 
for the exhalation device is provided pulse-synchronously, so that 
inhalation takes place during either systole or diastole. In order to 
record the phases of the heart, the control device is connected with an 
EKG unit or a blood pressure measuring device. 
The control device is designed so that it can also be operated as a 
stand-alone device with an integrated expiration valve and its own clock 
(asynchronous); see FIG. 26. In addition, the residual pressure in the 
airways can be adjusted with this device. Direct measurement and control 
of central airway pressure using pressure sensors is also possible.