Ventilation system having true valve control for controlling ventilation pressures

A ventilation system with positive and negative ventilation pressures controllable through a control unit is to be improved with respect to its adaptability, in particular in the generation of high pulse repetition frequencies above the natural breathing frequency. A gas transport element is provided in connection with a ring line which contains an inhalation valve in an inspiration branch and an exhalation valve in an expiration branch. The desired improvement is obtained by the fact that the gas transport element is arranged in the ring line with constant direction of delivery. By alternate control of the inhalation valve and exhalation valve in a closed system inspiration and expiration pulses are produced. In addition, a controllable valve unit is indicated in which the inhalation valve and the exhalation valve are actuated as diaphragm valves by combined injector and ejector units of low inertia.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates in general to respirators and in particular to a new 
and useful ventilation system for persons in which there is a ring line 
having a gas transport device which is a blower which operates 
continuously to provide a continuous circulation of the gas from a gas 
supply and to an improved control providing a control flow in inspiration 
and expiration branches connected to the ring line. 
The invention relates to a ventilation system with positive and negative 
ventilation pressures controllable through a control unit, which pressures 
are produced by a gas transport element, a ring line being provided which 
comprises in an inspiration branch an inhalation valve and in an 
expiration branch an exhalation valve. In addition, an advantageous 
controllable valve unit for use in such a ventilation system is provided. 
From German Pat. No. 917,210 an apparatus for artificial ventilation is 
known where a ventilation connection is connected via positively coupled 
valves controlled as a function of pressure in an open system alternately 
with the intake side and with the discharge side of an injector. 
German Pat. No. 946,258 describes a respirator with an inspiration and an 
expiration branch, which branches are connected to a pressure blower and 
with a suction blower. By a gate valve control acting in both branches, 
positive and negative ventilation pressures of appropriate duration are 
produced. This, too is an open system, which has the disadvantage of high 
respiratory gas consumption. 
Such systems are not usable because of the control sluggishness of their 
mechanical parts when a relatively high pulse repetition frequency of the 
ventilation pulses at high slope steepness is to be achieved. 
In German AS No. 24 24 025 a ventilation apparatus with inspiration branch 
and expiration branch is described, which branches form part of a closed 
cycle conduit. In the inspiration branch there is an inhalation valve, and 
in the expiration branch, an exhalation valve. For pressure generation 
there is used a blower of reversible direction of rotation which is 
connected alternately to the inspiration branch by its pressure side, and 
after reversal of direction, to the expiration branch by its suction side. 
Such an arrangement requires a complicated system of reversing the 
direction of rotation of the blower and is usable only for relatively slow 
pulse repetition frequencies. 
SUMMARY OF THE INVENTION 
The invention proceeds from the technical problem of providing, with the 
use of a single delivering element, a pneumatically quick-acting 
ventilation system which permits ventilation at relatively high pulse 
repetition frequencies (above 200 inspiration pulses per minute)and with a 
high slope steepness of the respiration pulses. 
For the solution of this problem, it is provided that the gas transport 
element in the ring line is arranged drivable with constant delivery 
direction, and that by alternate control of the inhalation valve and 
exhalation valve inspiration and expiration pulses are generated in a 
closed system. 
Such a ventilation system is adaptable with respect to the pneumatic 
energy; and, due to the connection of a gas transport element with only 
one delivering direction, its overall construction is simple. With it, 
even high-frequency ventilation pulses can be produced with sufficient 
positive and negative pressure values. 
Gas transport elements in ring lines are known in anesthesia equipment 
through U.S. Pat. No. 4,127,121 among others. There, however, the gas 
transport element serves exclusively to circulate a flushing gas flow; it 
does not produce the inspiration and expiration pulses required in a 
ventilation system. 
In the inspiration phase, the gas transport element, which may expediently 
be designed as a medium pressure blower, produces, in the delivery 
direction, a positive pressure which, with the inhalation valve open and 
the exhalation valve closed, forces the respiratory gas into the lung of 
the ventilated patient via the inspiration branch. Conversely, with the 
inhalation valve closed and the exhalation valve open, the lung is 
evacuated via the expiration branch by the negative pressure present at 
the suction side of the gas transport element. The duration of the 
inspiration and expiration phases or respectively the magnitude of the 
produced negative and positive pressures can advantageously be adjusted by 
a suitable adjustment of the delivery output and of the pulse width for 
the inspiration and expiration pulses. 
In the basic arrangement, the patient to be ventilated is connected via a 
T-piece to a closed respiratory cycle of the ring line. This respiratory 
cycle is fed from an external fresh gas source compensates spent oxygen 
and any leakages in the ring system. The mode of operation here concerned 
is the volume limited closed one. In further development of the invention 
it may be provided to install gas storage elements in the inspiration 
branch and in the expiration branch. In that case a pressure accumulator 
before the inhalation valve and a vacuum accumulator behind the exhalation 
valve are maintained under positive pressure and under corresponding 
negative pressure, respectively. This makes possible spontaneous through 
breathing, in which during the inspiration phase additional respiratory 
gas is taken from the pressure accumulator and during the expiration phase 
is passed into the vacuum accumulator. In this case, spontaneous breathing 
is superimposed on forced ventilation by the ventilation system. 
If by an appropriate adjustment of the control device the inhalation valve 
as well as the exhalation valve are open, the patient can breathe through 
spontaneously without forced ventilation. The T-piece forming the 
ventilation connection may expediently be designed as an injector, if, 
with the inhalation and exhalation valves open, an intermittent positive 
pressure ventilation is to be achieved. If the storage capacity of the 
pressure accumulator and of the vacuum accumulator is within the range of 
the lung compliance, through breathing is possible without any substantial 
respiratory resistances. In this mode the ventilation system operates as a 
half closed system. 
In the connecting line between the inhalation valve and the exhalation 
valve there may expediently be arranged, as an additional safety, at least 
one compensation valve which opens toward the atmosphere and permits free 
through breathing when the permissible inspiration pressure is exceeded 
and when the permissible expiration pressure is not achieved. Instead of 
one double action compensating valve, two single action compensating 
valves may be arranged, one compensating valve opening when the 
permissible inspiration pressure is exceeded and the other compensating 
valve opening when the permissible expiration pressure is not produced. 
While in the mode of operation of the closed system the middle position can 
be influenced only by dosage of the fresh gas supply, in the mode of the 
"half-closed system" the middle position can expediently be adjusted for 
example by arranging in the inspiration branch behind the gas transport 
element an adjustable overpressure valve and in the expiration branch 
before the gas transport element an underpressure regulator. The middle 
position then results from the adjusted overpressure and underpressure and 
from the ratio of the open times of the inhalation valve and exhalation 
valve, respectively. 
To prevent contamination of the ring line by room air, the underpressure 
regulator can expediently be provided in the form of a by-pass control 
between the suction side and pressure side of the blower. In this mode of 
operation the ventilation system represents a pressure limited half-closed 
ventilation form. 
A controllable valve unit which can be used in the indicated ventilation 
system, or if desired independently thereof, is expediently constructed so 
that the inhalation valve and the exhalation valve are designed as 
diaphragm valves with pneumatic drive, the diaphragm separating an 
auxiliary control space from a gas conduction space,and where the 
auxiliary space contains means for overpressure and underpressure 
generation. In an expedient form of realization, combined injector and 
ejector pairs are used in such a controllable valve unit. Their nozzles 
can be connected by the control device to a compressed air source, the 
control must preferably actuating solenoid valves arranged accordingly. In 
such a construction, inspiration and expiration pulses of high slope 
steepness and high pulse repetition frequency can be generated. 
The controllable valve unit with its inhalation and exhalation valves can 
be used in the inspiration branch and expiration branch of any known 
ventilation apparatus, but it is especially suitable for use in the 
indicated ventilation system of the initially described kind when high 
pulse repetition frequencies above the natural ventilation frequency and 
high slope steepness of the pulses are to be produced. 
By the features of the invention, a ventilating system is provided which in 
the mode of operation as a closed ring system has the special feature of 
low gas consumption and which moreover can be used selectively as pressure 
limited closed or volume limited half closed system. 
Accordingly it is an object of the invention to provide an improved 
ventilating system of a respirator and to provide an improved control 
device therefor. 
A further object of the invention is to provide a control device in a 
ventilating system which is simple in design, rugged in construction and 
economical to manufacture. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in particular, the invention embodied therein 
comprises a ventilating system for persons in which there is a ring line 
generally designated 7 in FIG. 1 in which gas is moved by a gas transport 
device such as a blower 1 which is connected at the inlet side of the gas 
transport to a gas supply through a valve 18. In accordance with the 
invention an inspiration branch 2 is connected to the ring line 7 adjacent 
the discharge line 7a of the gas transport device 1 and an expiration 
branch 3 is connected to the ring line 7 adjacent the inlet line to the 
gas transport device 1. The pressures in the respective inspiration and 
expiration lines and through a line 11 which is connectable to the 
patient, is regulated by an inhalation valve 4 and an exhalation valve 5 
connected to respective inspiration and expiration lines 2 and 3 and to 
respective inhalation valve 4 and exhalation valve 5. A feature of the 
construction is the T-piece 6 which operates with valves 4,5, from a 
control 19 which includes a compressed air source 35 as shown in FIG. 2 
which acts in respective control spaces 22 or 23 for varying gases which 
are delivered to inspiration line 2, expiration line 3 and the patient 
connecting line 11. 
In FIG. 1, the gas transport element such as the medium pressure blower 1 
is arranged, which together with the inspiration branch 2, the expiration 
branch 3 as well as the inhalation valve 4, exhalation valve 5 and T-piece 
6 is connected to the ring line 7. The direction of rotation of blower 1 
and hence the gas transport direction is indicated by an arrow 20. The 
inspiration branch 2 begins at the outlet of blower 1 and ends at T-piece 
6. The expiration branch 3 leads from the T-piece 6 to the suction side of 
blower 1. 
In the inspiration branch 2, in the flow direction behind the blower 1 and 
before a humidifier 8, there is an adjustable overpressure valve 9. Behind 
the humidifier 8 and before the inhalation valve 4 a pressure accumulator 
10 is connected to the inspiration branch 2. The T-piece 6 connects the 
inspiration and expiration branches 2 and 3, and by its projection 11 
permits ventilation of a person, which can be effected in known manner via 
a line and to a breathing mask or a tracheal tube (not shown). 
The exhalation valve 5 is located at the beginning of the expiration branch 
3 and is followed by a CO.sub.2 absorber 12. A vacuum accumulator 13 is 
connected to the expiration branch 3 between the CO.sub.2 absorber 12 and 
the exhalation valve 5. Behind the CO.sub.2 absorber 12 lies a vacuum 
regulator 14. A by-pass line 15 and a line 16 behind the blower 1, bridges 
the regulator 14 with the suction and pressure side of the blower 1. 
Before the suction side of blower 1, moreover, a fresh gas transport 
element in the form of valve 18 is connected from the gas supply to the 
expiration branch 3 for dosed feeding of respiratory gas into the ring 
line 7. 
The control unit 19, constructed in known manner with electronic components 
for control of the inhalation valve 4 and of the exhalation valve 5 is 
used. 
By a controllable rotary drive 17 of blower 1, not explained in detail in 
the drawing, the ventilation system illustrated in FIG. 1 permits an 
appropriate adaptation to the pressure values and duration of the 
inspiration and expiration pulses. The vacuum created by blower 1 in the 
expiration branch 3 is adjustable by the vacuum regulator 14. The 
repetition frequency and duration of the inspiration phase and expiration 
phase are determined by the alternate actuation of inhalation valve 4 and 
exhalation valve 5 by the control unit 19. The overpressure valve 9 
permits adjustment of the middle position. 
In FIG. 2, the inhalation valve 4 is shown open and the exhalation valve 5 
closed. Both valves, 4,5 are diaphragm valves, the diaphragms 20 and 21 
separating an auxiliary or control space 22 and 23 from a gas conduction 
space 24 formed by the remaining inspiration branch 2 and the remaining 
expiration branch 3. 
Arranged in the auxiliary spaces 22 and 23, which lead into the surrounding 
atmosphere via outlet nipples 25 and 26, are combined injector and ejector 
units 27 and 28, each comprising an ejector nozzle 29, 32 and an injector 
nozzle 30, 31. These nozzles are connected via connecting lines 36, 37, 
38, 39 to respective solenoid valves 33 and 34. A compressed air source 
35, which creates a positive pressure of about 2 to 5 bars, is to be 
connected to the solenoid valves 33, 34 by a branch connecting line 40. 
In the shown inhalation phase with inhalation valve 4 open and exhalation 
valve 5 closed, a negative pressure is created in the auxiliary space 22 
and a positive pressure in the auxiliary space 23. For this purpose the 
compressed air source 35 is connected by the closed solenoid valve 33 with 
the ejector nozzle 29 and with the injector nozzle 30 of the combined 
injectorejector units 27,28. Air is pumped through the ejector nozzle 29 
out of the auxiliary space 22 and conducted through the outlet nipple 25 
into the surrounding space. With that a vacuum is created which opens the 
diaphragm 20 and thereby connects the inspiration branch 2 with the 
projection 11. 
The compressed air supply to the injector nozzle 30 brings about the intake 
of ambient air from the outlet nipple 26 into the auxiliary space 23, so 
that a corresponding positive pressure is built up, which closes diaphragm 
21 and hence shuts off the expiration branch 3. In this state of operation 
the ejector nozzle 32 and injector nozzle 31 are maintained pressureless 
by the opened solenoid valve 34. 
At the end of the inhalation pulse duration preset in the control unit 19, 
solenoid valve 34 is closed and solenoid valve 33 is opened. Thus, under 
reversal of the described processes, there occurs the initiation of the 
expiration phase by opening of the exhalation valve 5, and at the same 
time the inhalation valve 4 changes over to the closed position. 
Such a controllable valve unit, as described in the foregoing with 
reference to FIG. 2, is especially low in inertia and therefore can 
realize the high pulse repetition frequencies desired in high frequency 
ventilation with high slope steepness of the individual pulses. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.