United States Patent 3840006

A portable, power driven respirator controls measured amounts of air (and, if desired, admix gas, such as oxygen) to a patient during inhalation events and from the patient during exhalation events. The events are controlled pneumatically and electrically as to time and rate of occurrence, duration and relationship. Quantities, pressures and times are precisely regulated and monitored automatically with some patient override, provision for deep breaths, some manual control and with indicators and alarms.

Buck, Keith E. (Alamo, CA)
Kitrilakis, Sotiris (Berkeley, CA)
Robinson, Thomas C. (Berkeley, CA)
Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
International Classes:
A61M16/00; (IPC1-7): A61M16/00
Field of Search:
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US Patent References:
3414896Respiratory monitor1968-12-03Glick
3307542Lung ventilating equipment1967-03-07Andreasen
3266488Lung ventilating equipment1966-08-16Andreasen
3191595Electrically controlled resuscitator appartus1965-06-29Wilson

Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Dunne G. F.
Attorney, Agent or Firm:
Lothrop & West
What is claimed is

1. A respirator comprising a displacement chamber having a wall movable toward and way from a predetermined location, means urging said wall toward said location, a patient's airway in communication with said chamber, means for supplying said chamber with gas at a pressure to urge said wall away from said location, means for detecting the position of said wall relative to said location and for producing a signal proportional thereto, means for controlling flow of gas from said supplying means to said chamber, and means responsive to said detecting means signal for actuating said controlling means.

2. A respirator as in claim 1 including means for supplying said chamber with another gas at a pressure to press said wall away from said location, second means for controlling said other gas supplying means, and further means responsive to said detecting means signal for actuating said second controlling means.

3. A respirator as in claim 1 in which said detecting means includes an electromechanical device affording an electrical signal in accordance with the instantaneous position of said wall relative to said location.

4. A respirator as in claim 1 in which said controlling means is an electrically actuated valve.

5. A respirator as in claim 1 including a first means for setting a response value at which said detecting means signal actuates said controlling means.

6. A respirator as in claim 5 including a second means for setting another response value at which said detecting means signal actuates said controlling means.

7. A respirator as in claim 6 including means for shifting between said first means and said second means, and timing means for periodically actuating said shifting means.

8. A respirator as in claim 1 including means responsive to said detecting means for delaying the actuation of said controlling means in response thereto.

9. A respirator as in claim 1 including conduit means connecting said chamber to said airway, means in said conduit for opening said airway to and closing said airway from the atmosphere, and means controlled by said detecting means signal for controlling said opening and closing means.

10. A respirator as in claim 9 including a valve in said conduit means, a first timing device, and means controlled by said first timing device for operating said valve.

11. A respirator as in claim 9 including a second timing device, and means controlled by said second timing device for operating said valve.

12. A respirator as in claim 11 including means for synchronizing said first timing device and said second timing device

13. A respirator as in claim 9 including means for regulating the rate of gas flow in said conduit means.

14. A respirator as in claim 9 including means for regulating the pressure of gas flowing in said connecting means.

15. A respirator as in claim 9 including means responsive to air pressure in said airway, and means controlled by said responsive means for setting the maximum value of said air pressure.


There is provided a power driven, portable respirator for use with a human patient who needs assistance in breathing from just a little help to complete help. The patient is furnished for each breath with a selected volume of gas, starting with atmospheric air or compressed air alone or with an added gas, such as oxygen, in any selected proportion. The gas is supplied for inhalation or inspiration (breathing in) automatically at regular intervals of separately selected lengths and at a chosen, variable rate or as triggered by a suitably large and suitably sustained patient effort. An inhaled breath can be held for a suitable time. The inhalation period is followed, usually after a pause, by an exhalation or expiration (breathing out) period of a separately selected length and at a separately selected rate. The breathing in and breathing out periods are compared and a signal is given if the breathing out period is shorter than the breathing in period. Gas pressure is measured during a pause before the beginning of the breathing in event and during a pause before the beginning of the breathing out event. Signals are given if those pressures vary from set values. Automatically or manually the duration of gas inhalation is varied from time to time to afford a deep breath, with a longer than usual inhalation period and a correspondingly lengthened exhalation period. There are various manual adjustments and controls and various indicators and alarms. While some of the operation and control is due to gas pressure, much of the operation and control is accomplished electrically.


It is an object of the invention to provide an improved, portable, power driven respirator especially for human use.

Another object of the invention is to provide a respirator able to supply air or a mixture of gases in measured proportion and automatically continue with air if the mixing gas supply fails.

It is another object of the invention to provide a respirator able to afford inspiration and expiration at timed intervals and for selected periods and rates and with or without patient effort control.

It is a further object of the invention to provide a respirator sensing its operation at intervals between breath cycles to detect anomalies.

An additional object of the invention is to provide a respirator affording special deep breaths from time to time.

A still further object of the invention is to provide a respirator of considerable flexibility in setting and quick response, one easily regulated and controlled and also compatable with the needs of various patients.

A still further object of the invention is to provide a respirator affording numerous advantages over respirators heretofore available.

Other objects, as well as the foregoing, are attained in the embodiment of the invention described in the accompanying description and shown in the accompanying drawings.

In the drawings,

FIG. 1 is a diagrammatic disclosure of much of the pneumatic circuitry of the respirator, may of the parts being illustrated in cross-section on a diametrical, transverse plane;

FIG. 2 is a cross-section on an axial plane through a combined volume chamber and accumulator reservoir;

FIG. 3 is a cross-section on a diametrical plane through a diaphragm controlled valve;

FIG. 4 is a cross-section on a diametrical plane through a variable resistance valve;

FIG. 5 is a cross-section on a diametrical plane through a release valve;

FIGS. 6 and 7, when FIG. 6 is placed immediately to the left of FIG. 7, illustrate diagrammatically a portion of the pneumatic and electrical circuitry of the respirator; and

FIGS. 8 and 9, when FIG. 8 is placed immediately to the left of FIG. 9, show additional electrical and pneumatic circuitry involved in the respirator.

The principal pneumatic arrangement of the respirator is especially disclosed in FIG. 1 and in FIG. 6 in which there is provided an electric motor 6 of the usual sort receiving power from any suitable, standard source (such as 115 volt AC or 12 volt DC) through a conductor 7 controlled by a switch 8 operated by a coil 9, return conductors being omitted for clarity. The motor 6 through a shaft 11 drives an air compressor 12 preferably of the positive displacement type. This receives atmospheric air through an inlet 13 and through a filter 14 and through a duct 16 to the pump inlet. The received air is compressed and leaves the pump through an outlet conduit 17 from which it passes through an acoustic filter 18 and control valve to a conduit 19. To assure that the discharge pressure is not excessive, a line 21 from the pump outlet leads through a pressure relief valve 22 and a pipe 23 to the atmosphere.

It is often arranged that an alternative or auxiliary source of air under pressure be provided. For example, a compressed air reservoir 26 is connected by a pipe 27 through a pressure control valve 28 to the conduit 19. When the auxiliary compressed air supply is utilized, its pressure is transmitted through a line 29 to a pressure responsive switch 31 effective through a conductor 32 to control the energization of the coil 9. When there is pressure available from the source 26 the coil 9 is energized to open the switch 8 and to shut off the electric motor 6. When there is no pressure from the source 26, the motor 6 is energized. Either the electric motor driven compressor is utilized as an air source or the compressed air reservoir 26 is utilized as an air source, the switch over being automatic.

From the conduit 19 compressed air flow is into a reservoir 36 or accumulator constructed, in one form, as shown in detail in FIG. 2. In this arrangement there is provided a drum-like, circular-cylindrical wall 37 having some atmospheric openings 38 therein and being provided with a lower flange 39 abutting one side of a flexible diaphragm 41, the other side of which is abutted by a head 42, related to the side wall 37 by fasteners 43 which clamp the diaphragm periphery. There is a diaphragm piston 44 having a central hub 46 with a rolling diaphragm seal 47 clamped between the piston 44 and the hub and also clamped between the head 42 and a central sleeve 48.

Opposite the head 42 and spanning the space enclosed by the wall 37 is a central disk 49 having an edge shoulder 51 seated against the drum wall 37 for centralization and also carrying a number of cups 52 (but one being illustrated for clarity) each serving as a holder for an expansion coil spring 53 also abutting the piston 44. The tendency is for the springs 53 to urge the piston 44 and the head 42 into a closed approach to provide a minimum volume of the reservoir or accumulator 36.

The conduit 19 supplies air under sufficient pressure to the chamber 36 so that the piston 44 is lifted, as seen in FIG. 2, against the urgency of the multiple springs 53 thus increasing the volume of the chamber or accumulator 36 and holding a supply of compressed air at a pressure as limited by the relief valve 22.

From the chamber 36 compressed air is lead by a pipe 56 through an air inlet valve 57 controlled by an electrical coil 58 and flows into a pipe 59 extending into and communicating with a volume control chamber 61 or measuring chamber comparable to the chamber 36. The chamber 61 is partly defined by a head 62 having a flange 63 engaged by the fasteners 43. The flange abuts a defining diaphragm 64 resting on a drum wall 66 having atmospheric openings 67 therein and lodged against another shoulder 68 on the central disk 49. When the fasteners 43 are tight the heads 62 and 42 are pressed against their respective diaphragms 64 and 41 and the drum walls 66 and 67 are tightly engaged with and position the central disk 49.

Abutting the diaphragm 64 there is a piston 71 engaged by an expansion spring 72 having its other end seated in a cup 73 carried by the disk 49. A plurality of the springs 72 and cups 73 are utilized (but one set being illustrated) and these are preferably interspersed with the cups 52 and springs 53. While the springs 72 normally urge a minimum volume for the chamber 61, air supplied thereto under pressure is effective to overcome the urgency of the springs 72 and enlarges the chamber 61 by forcing the piston 71 to approach the central disk 49.

It is important to know the instantaneous position of the piston 71. For that reason there is provided on the central disk 49 a stationary housing 74 containing an electrical coil 75 (FIG. 6) and serving as a mounting 76 for some electrical connectors. Related to the housing 74 is a movable induction core 77 (such as a core magnetically affecting the coil 75) joined by a rod 78 and a closed aligning spring 79 to an anchor 81 on the piston 71. The arrangement is such that as the position of the induction core 77 is axially varied in accordance with changes in position of the piston 71, a correspondingly varying electrical signal is furnished across appropriate conductors extending into and from the mounting 76. In this fashion there can be obtained a remote indication of the instantaneous axial position of the piston 71 which corresponds to the instantaneous volume of the chamber 61.

In some instances, the respirator is preferably operated not only on compressed atmospheric air from a pump or tank but also with oxygen or some other mixing gas and with any desired relative proportion between atmospheric air and the mixing gas. For that reason there is provided a source 83 (FIG. 6) of mixing gas such as pure oxygen under pressure. This is supplied through a conduit 84 and through a pressure regulating valve 86 to a pipe 87. Further flow is through a control valve 88 operated by an electrical coil 89. When open the valve 88 permits the mixing gas or oxygen to flow into the pipe 59 and thus into the chamber 61 of the measuring device.

The atmospheric air under pressure or the oxygen under pressure or the mixture thereof under pressure, generally referred to as the pressure gas, can leave the chamber 61 through a conduit 91 as the piston 71 approaches the head 62 under influence of the springs 72. The conduit 91 is connected to the inlet 92 of a flow rate valve 93 (FIGS. 1, 3, 6 and 7). Within the valve 93 there is a poppet 94 operating in an interior chamber 95. The poppet is carried on a stem 96 and is adapted to close or to throttle the inlet 92. The stem extends through a support and is connected to a diaphragm 97 subject to pressure differential on opposite sides thereof. The freely movable diaphragm is clamped between a body 98 and a cap 99 and divides a chamber 101 from a chamber 102. The diaphragm is biased in one direction by a spring 103 urging the diaphragm toward the cap 99.

Within the chamber 101 the pressure is that derived from a conduit 104 joined to the reservoir pipe 56 and extending through an inhalation valve 106 operated by an electrical coil 107. The valve 106 has one outlet pipe 108 extending to the interior chamber 95 and has another outlet pipe 109 extending into the interior chamber 101.

The chamber 95 is also connected by a conduit 111 to a variable resistance valve 113 (FIG. 4). The conduit 111 terminates in a valve seat, flow through which is controlled by a valve disk 114 having flat sides 116 and guides 117 to prevent its rotation. The disk 114 is mounted on a steep pitched or quick thread 118 of an adjusting stem 119 to which a control knob 121 is fastened. The chamber 112 and the chamber 102 are connected in common by a conduit 122.

From the chamber 112 the pressure gas flows through a pipe 123 into a relief conduit 124 (FIGS. 1 and 7) connected to the inlet 126 of a variable pressure relief valve 127. Within the body of the valve 127 there is a seat 128 with which cooperates a valve disk 129 held in position by a coil spring 131 also abutting a cup 132 carried non-rotatably on the end of a valve rod 133 having steep threads 134. Against the threads a frictional drive screw 136 bears so that the shaft 133 can be turned only with some difficulty by an operator manipulating a knob 137 at the end of the rod 133. Disposed on the flanged lower end of the cup 132 is a loose ring 138 having frictional engagement with the interior wall 139 of the chamber 140 within the valve. The ring 138 is urged downwardly along the valve axis by gravity. The ring 138 has a central bore 141 larger in diameter than the cup 132 and its axial position on the cup is confined not only by the flange 142 on the lower end of the cup but is likewise confined by a pin 143 at the upper end of the cup.

The chamber 140 has a port 144 leading to the atmosphere so that when grossly excessive pressure lifts the valve disk 129 off of its seat 128 against the urgency of the spring 131, as set by the instantaneous position of the knob 137, air can flow past the cut 132 by lifting the ring 138 and so discharge to the atmosphere through the port 144. In this way, the pressure that exists within the pipe 123 is maintained at not to exceed a chosen value. Pressure gas from the pipe 123 flows through an outlet unit 150 including a bacteria filter 151 and, if desired, a humidifier 152 and into a line 153 connected to an airway conduit 154 connected to the customary face or breathing mask (not shown) applied to the patient.

Also connected to the airway conduit 154 by an extension 165 of the line 153 is an exhalation valve 157 (FIG. 1). This includes a valve seat 158 over which is disposed an inflatable and deflatable flexible balloon valve 159. When the balloon is inflated, flow through the valve 157 is inhibited but when the balloon is deflated flow continues through the valve 157 (FIG. 7) and through a duct 161 to the atmosphere.

In order that the balloon valve 159 can be properly controlled, some air under pressure flows from the reservoir conduit 56 through the conduit 104 into a pipe 167 so that there is always available pressure in the conduit 167 from the pressure gas source. The conduit 167 has a connector 168 joined through a needle valve 169 to a pipe 171. The needle valve has a needle 172 positioned by a manual control 173 so that the restriction of the needle is variable and so that the flow from the connector 168 to the pipe 171 can be throttled. There is a vent connector 174 joined to the pipe 171 and discharging through a restricted orifice 176 and through a pipe 177 to the atmosphere.

Shunting the needle valve 169 is a conductor 178 extending through a control valve 179 also connected to the pipe 171 and operated by an electrical coil 181 and in turn connected through a conduit 182 to the balloon valve 159. Depending upon the position of the core 183 of the valve 179 is the inflation or deflation of the balloon valve 159. When the valve is in the position shown in FIG. 1 the pressure in the lines 56, 104, 167 and 178, a fairly high pressure, is available to inflate the balloon 159 but when the valve 179 is switched to its other position then the balloon is connected to the pipe 171 which has a relatively low pressure a little higher than the atmosphere, depending upon the adjustment of the valve knob 173 and the drain through the connector 174, the restriction 176 and the pipe 177.

The circuitry just described for flow both to and away from the patient airway conduit 154 forms the fundamental air circuitry, i.e., the pressure or inhalation and discharge or exhalation gas circuitry of the respirator. Particular controls, electrically operated, are employed to program the respirator either to cycle automatically when the patient is unable to do his own breathing or to respond to stimuli from the patient so that his breathing can be assisted although primarily timed by him. There are also controls for operation by a doctor or attendant.

Consideration of the electrical controls can start with the arrangement of the position responsive coil 75 (FIG. 6) reflecting the instantaneous location of the piston 71 and so is responsive to the actual volume of the chamber 61. To supply the coil 75, conductors 186 and 187 from a suitable source of low voltage (usually plus and minus 15 volts) energize an oscillator 188 connected by a conductor 189 to the coil 75. From the coil a lead 191 supplies a demodulator 192, the output of which is impressed upon a conductor 193. The conductor 193 extends to an air volume detector 194 thus made responsive to the instantaneous position of the piston 71 and the volume of the chamber 61.

Supplied to the air volume detector 194 is a signal from a tidal volume controller 196 including a variable resistor 197 joined through a two-position switch 198 and a conductor 199 to the detector 194. The variable resistor 197 can be set to any desired value within its range to control the quantity or amount of the tidal volume of gas selected to be involved in a single breathing cycle. The switch 198 in its other position is joined to a conductor 201 going to a variable resistor 202 of a deep breath increment control generally designated 203 and effective to give a variable limit to the expanded air volume of a "deep" breath over and above the normal or preset tidal air volume. The switch 198 is responsive to a deep breath increment control having a terminal A 206 for receiving a timed signal later to be described. In normal position the deep breath control 204 directly connects the tidal volume control 196 to the air volume detector 194 whereas when sometimes moved into its other extreme position the deep breath increment control 204 connects the increment control 203 directly to the air volume detector 194.

The conductor 193 from the position coil demodulator 192 also connects to an oxygen volume detector 207 further connected to receive a signal through a conductor 208 from an oxygen-to-air ratio control 209. This is inclusive of a variable resistor 211 having a lead 212 joined to the conductor 199 and also having a conductor 213 extending to a two-position switch 214 to which the conductor 208 is attached. Another conductor 216 is available at the switch 214 and extends to the controller 209.

Parallel to the switch 214 is an alarm switch 217 connected to a source of current by a conductor 218 and also having a lead 219 extending through a disabling switch 221 to a terminal B 222, later to be described. The switches 214 and 217 are ganged by a connection 223 and respond to a solenoid 224 joined by a conductor 226 to a pressure switch 227 having a pipe 228 joined to the conduit 84 and so responsive to the pressure of oxygen in the conduit 84. Should the oxygen pressure fall to a dangerously low value, the pressure switch 227 causes the solenoid 224 to move the switches 214 and 217 simultaneously into the positions shown in FIG. 6, thus de-energizing the oxygen volume detector 207 leaving the air volume detector 194 solely effective and also energizing the terminal B 222 to afford a later described alarm.

The detectors 194 and 207 have related functions. The air volume detector 194 when energized affords a signal through a conductor 231 to one side of an and gate 232. The other side of the and gate is joined to a conductor 233 from which a signal comes from a terminal C 234 later to be described. When there are signals in both the conductors 231 and 233 the and gate 232 supplies a signal through a conductor 236 to an exclusive or gate 237 connected through a conductor 238 and an amplifier 239 and by a lead 241 to the electrical coil 58 and so actuates the air valve 57.

In a comparable fashion, there is a parallel and gate 242 joined by a lead 243 to the oxygen volume detector 207 and joined by a lead 244 to the conductor 233. When signals are received by the and gate 242 through the conductors 243 and 244 a signal is impressed upon a conductor 246 having one branch 247 extended to the exclusive or gate 237. The conductor 246 continues through an amplifier 248 to the electrical coil 89 of the oxygen valve 88.

With the foregoing arrangement the net result is that the particular position of the piston 71 (or the instantaneous volume of the chamber 61) is effective to control the valve 88 for oxygen and the valve 57 for air. By proper setting of the oxygen-to-air ratio control 209 the valves 57 and 88 are respectively opened and closed at a selected point during the reciprocation of the piston 71. Oxygen is supplied to the chamber 61 for a selected fraction of the total piston travel whereas air is supplied to the chamber 61 for the remaining part of the piston travel. In this way there is afforded a precise, volumetrically measured ratio of supplied air and supplied oxygen. Should the oxygen supply fail, as indicated by an excessively low oxygen pressure in the pipe 84, then the oxygen supplying mechanism is shut down but the air supplying mechanism continues to function and the tidal volume is then represented by unmixed air.

The conductor 193 from the position demodulator 192 is joined by a lead to a chamber-empty detector 251 also having an input conductor 252 extending from a variable resistance 253 between ground and a suitable electrical source 254. This affords a variable setting for choosing the minimum volume of the chamber 61 selected to trigger the functioning of the apparatus. A signal from the detector 251 is supplied through a conductor 256 to an inflation-hold timer 257 incorporating a timing unit 258 having a variable control 259 thereon. The mechanism can be preset or can be adjusted at any time to select the duration of a period of pause in the inflation portion of the cycle. The output signal from the inflation-hold timer 257 is supplied through a conductor 260 to a terminal D 261, later to be described.

In a somewhat comparable fashion, the air volume detector 194 has a branch conductor 262 extending from the conductor 231 to a terminal E 263 connected as later described.

In the operation of the coil 75, when the chamber 61 is substantially at its maximum volume the detector 194 responds by sending a signal through the conductor 231 and the conductor 262 to the terminal E 263 which, as shown in FIG. 8, is joined by a conductor 266 to an and gate 267. The and gate 267 is also supplied through a conductor 268 joined to a terminal F 269 which, as will later be described, receives a signal triggered by the selected ratio of exhalation time to inhalation time. When both signals are available at the and gate 267 an impulse is supplied through a conductor 271 to the enable section 272 of an inhalation gate 273. The gate 273 is merely enabled by receipt of a signal through the conductor 271 indicating that the mechanism is in condition for the inhalation portion of the breathing cycle.

In order to afford an output signal from the inhalation gate 273 it is first necessary to have a timing signal. Consequently, there is provided a respiration rate timer 274. This has a variable timing controller 276 which can be manually set or adjusted at the option of the operator.

Periodically, as set, this affords a signal through an output section 278 and through a conductor 279 to the trigger unit 281 of the enabled inhalation unit 273. The triggering impulse in the conductor 279 is likewise supplied through a conductor 282 to a terminal G 283 connected to an alarm mechanism later to be described.

An impulse from the enabled and triggered inhalation controller 273 is supplied by the out section 284 thereof through a conductor 286 into the start section 287 of an inhalation controller 288 having a time limit mechanism 289 connected thereto. This is usually set at an arbitrary, predetermined value, for example five seconds. The inhalation mechanism 288 furnishes a pulse from an out section 291 extending through a conductor 292 to a terminal H 293. This appears also in FIG. 7. The pulse from the inhalation controller 288 continues through a conductor 294 and an amplifier 296 and through a conductor 297 to control the electrical coil 107 for the valve 106. Thus, the valve 106 moves between extreme positions in accordance with a signal from the out section 291 of the inhalation controller 288.

In addition, the controller 288 has a not-out section 301 joined by a conductor 302 to the start section 303 of an exhalation controller 304. Included in the controller 304 is a timer 306. Customarily, this is not variable but is preset to a selected time limit, for example 10 seconds. From an out section 307 of the exhalation controller 304 a signal goes through a conductor 308 to a terminal C 234, also shown in FIG. 6. The signal then from the exhalation controller 304 is supplied through the terminal C 234 to both of the and gates 232 and 242 so that they can function as previously described. The impulse in the conductor 308 also is received (FIG. 9) in the start section 311 of a blocking controller 312. This has an out section 313 if uninhibited furnishing an impulse to a conductor 314 to which is connected a lead 316 having a terminal J 317. This appears also in FIG. 7 and is joined through a conductor 318 to an amplifier 319 and through a further conductor 321 to the electrical coil 181 effective to move the valve 179 between its extreme positions.

The conductor 314 (FIG. 9) goes to the start section 323 of an airway disconnect alarm device 324 having a timer section 326 usually preset to a short time, for example one tenth of a second, so that until the expiration of such time after the reception of a start impulse in the section 323 the airway disconnect alarm device 324 affords in its out section 327 an impulse delivered through a conductor 328 to an and gate 329. The other impulse to the and gate 329 is received through a conductor 331 having a terminal K 332. This also appears in FIG. 7 joined to a conductor 333 receiving a signal from a pressure switch 334 having a connection 336 to the airway conduit 154.

Should the pressure in the connection 336 drop due to a mechanical disconnection in the airway 154 (FIG. 1) to the patient, that drop in pressure is immediately productive of a signal through the conductor 333, the terminal K 332 and the conductor 331 to the and gate 329. If the and gate 329 also has a pulse through the conductor 328 from the out section 327 of the airway disconnect alarm structure 324, a signal then is given through a conductor 337 to the set section 338 of an alarm board 339. A corresponding signal is sent from the out section 341 thereof to a conductor 342 energizing an appropriate alarm light 343. This affords to the operator an alarm very promptly after the occurrence of any airway disconnect.

With the control of the inhalation valve 106 and the exhalation valve 179 automatically timed by the respiration rate timer 274 as already described, a continuous train of repetitive, timed breathing cycles can be indefinitely continued. There is, however, a preference for affording a patient a larger or deep breath from time to time. This can be accomplished either by manual control or by automatic control.

The manual control for this function is provided through a conductor 351 (FIG. 8, center bottom), extending from a suitable electrical source, by a manual switch 352 when closed giving a signal in a conductor 353 extending to the set portion 354 of a signal controller 356 in a synchronizing logic board 357. Also able to give a signal to the conductor 353 and the set portion 354 is an automatic deep breath timer 358 having a variable timing unit 359 thereon and at intervals providing a signal in a conductor 361 joined to the conductor 353.

When an impulse from either source is received at the set portion 354, there is transmitted from the out portion 362 of the controller 356 a signal traveling through a conductor 363 to one side of a synchronizing and gate 364.

When there is a signal from the out section 291 of the inhalation controller 288 in the conductor 292, the signal is also sent through a conductor 366 to a timing unit 367 which transmits a timed signal partly through a conductor 368 to one side of another and gate 369. Also the element 367 takes part of the incoming signal from the conductor 366 and at a predetermined increment of time thereafter transmits the signal through a conductor 371 to the other side of the and gate 364. Thus, when both signals are available at the and gate 364 there is an impulse therefrom going through a conductor 372 into the set portion 373 of a controller 374. From the out section 375 of the controller 374 the signal travels through a conductor 376 to the other side of the and gate 369. This, when dually energized, provides a signal in a conductor 377 to a conductor 378 having a lead 379 extending to the reset section 381 of the controller 374. The reset conductor 378 extends through a manual switch 383 to a suitable source 384 of current. At any time the synchronizing controller 357 can be reset by manually depressing the switch 383 momentarily.

The signal from the out portion 375 of the controller 374 appearing in the conductor 376 is also transmitted through a conductor 386 (see FIGS. 8 and 9) to the terminate section 387 of the exhalation timing board 312. Also, a conductor 388 joined to the conductor 386 extends to the terminal A 206 (FIG. 6). From the terminal A 206 this signal goes through the conductor 205 to the deep breath increment control 204 thus moving the switch 198 from its normal tidal volume control position, as shown, to its alternate deep breath increment position. This introduces the variable, predetermined, deep breath quantity signal from the control 202 through the conductor 201 into the conductor 199 for effect as previously described.

A requirement is for the duration of exhalation to be greater than the duration of inhalation not only during ordinary breathing but also following a deep breath. This is done by having a deep breath inhalation portion of a breathing cycle followed immediately by a correspondingly lengthened exhalation portion of that cycle.

Consequently, from the conductor 386 (FIG. 8) there is extended a conductor 391 joined through a resistor 392 to a conductor 393 also joined to the conductor 292 through a resistor 394. Signals from both the conductors 292 and 391 thus appear in the conductor 393 and are transferred to an integrator 396 (FIG. 9). In the integrator 396 during the inhalation event the incoming signal (regular or deep breath) increases the integrator value at a corresponding rate to a high level. During ensuing exhalation, the integrator value decreases at the same rate to a low or zero value. Exhalation being longer than inhalation, the residual exhalation time affords a low or zero signal from the integrator 396 to a unit 397. This unit signals through a conductor 398 only when there is a low or no signal from the integrator 396, i.e., during the end of respiration. An or gate 399 receives the signal from the conductor 398 and can receive a signal directly from the conductor 391 through a conductor 400 shunting the integrator 396. A conductor 401 goes to the terminal F 269 (also in FIG. 8) and carries the signal from the or gate 399 through conductor 268 to one side of the and gate 267. Signals simultaneously from the conductors 266 and 268 thus energize the inhalation control 273.

Signals in the conductors 398 and 400 (FIG. 9) travel through conductors 402 and 403 having inverters 404 and 406 therein to conductors 407 and 408 and so into an and gate 409. A conductor 411 extends to the and gate 409 from the terminal G 283. A signal from the respiration rate timer 278 through the conductors 279 and 282 is transmitted through the terminal G 283 and the conductor 411 to the and gate 409. If then there are no signals to the or gate 399, the resulting inverter signals in the conductors 407 and 408 cause the and gate 409 to signal through a conductor 412 into the set section 413 of an alarm board 414 thus responding when exhalation time is less than inhalation time. A signal at the set section 413 provides a signal in the out section 416 of the board 414. This is carried by a conductor 417 to an indicator or alarm light 418.

From the inflation hold timer 257 (FIG. 6) a signal through the conductor 260 is available at the terminal D 261 which also appears in FIG. 8. A conductor 421 goes from the terminal D 261 to an or gate 422 having an output conductor 423 joined to the terminate section 424 of the inhalation timer 288 so that upon receipt of a signal at the termination section 424 either the signal from the output section 291 or the signal from the non-output section 301 is terminated so that either portion of the cycle can be interrupted for a new start of a complete cycle, a sort of "catch" breath.

Also effective upon the or gate 422 is a signal derived through a conductor 426 connected to the source 384 through a manual switch 427. A manual signal can thus be given to the terminate section 424 of the inhalation controller 288.

A further signal can be received by the or gate 422 through a conductor 428 and joined by a conductor 429 to a terminal L 431. This appears also in FIG. 7 and therein is joined through a conductor 432 to a maximum inspiration pressure switch 433. Air conduits 434 and 436 connect to opposite sides of the switch 433 and shunt a restricted orifice 437 in the conduit 124 which discharges to the atmosphere. Thus, upon attainment of the maximum desired inhalation pressure, the switch 433 is effective to send a signal through the conductor 432, the terminal L 431 and the conductor 429 and the conductor 428 to the or gate 422 thus activating the terminate section 424 of the controller 288.

Also, receipt of a maximum pressure signal at the terminal L 431 (FIG. 9) supplies energy through the conductor 429 to the other branch of the conductor 428 and so to the set section 438 of an alarm 439 for maximum inspiration pressure. The signal at the set section 438 provides a corresponding signal in the out section 441 of the board 439 and through a conductor 442 energizes an alarm light 443.

As shown in FIG. 8 (top center), the conductor 286 joins to a branch conductor 444 going to an or gate 445 having an output conductor 446 extending to the termination section 447 of the exhalation controller 304. Thus, a signal from the inhalation section 273 through the conductor 286 and the conductor 444 sends a signal through the conductor 446 to the terminate section 447 thus ending the exhalation signal.

The or gate 445 also has an input through a conductor 448 extending from a current source and including a hand switch 449 so that the termination section 447 can be manually energized through the or gate 445. In addition, the or gate 445 can receive a signal through a conductor 451 (FIG. 8) from the output section 452 of a patient effort control 453. As shown particularly in FIG. 7, the airway 154 is joined by a duct 454 to a pressure responsive patient effort switch 456. This is effective to emit a signal when the patient by inhalation reduces the pressure in the airway and so at the switch 456. Under that condition a signal is sent through a conductor 457 to a terminal M 458 which also appears in FIG. 8.

A signal at the terminal 458 is transmitted through a conductor 459 having a control switch 461 therein and also inclusive of a variable potential control 462. If the signal from the patient switch 456 (FIG. 7) is maintained for sufficient time, then the impulse is effective through a conductor 463 on the start section 464 of the control 453.

If the patient effort continues long enough, as regulated by the time required to charge a capacitor 465 through a resistor 462, there is then a pulse, timed by a timer 466, from the out section 452 through the conductor 451. As before, this goes through the or gate 445 and by means of the conductor 446 actuates the termination section 447 of the exhalation control 304. Upon exertion of sufficient effort for sufficient time the patient can initiate inhalation by impressing a signal from the out section 291 through the conductor 292 and the terminal 293 H to actuate the inhalation valve 106 to provide air through the valve 94 and the regulator 114 to the airway 154 and the patient.

A signal from the or gate 445, however derived, is not only effective upon the terminate section 447 of the exhalation controller 304, but also travels in a conductor 471 and at the respiration rate controller 274 is effective upon a pulse section 472 thereof. The signal immediately resets the timer 274 and starts a new cycle thereof. Similarly, the conductor 471 (FIG. 9) sends a signal to a reset section 473 of a failure-to-cycle control 474. This mechanism includes a timer 476 having a preset time interval, for example 15 seconds. In the event there is a signal from the timer 476 without a prior resetting signal from the or gate 445, then there is a signal fron the out section 477 of the control 474. Through a conductor 478, this signal goes to the set section 479 of a failure-to-cycle alarm control 481. This then sends a signal from the out section 482 thereof through a conductor 483 to a signal lamp 484, alerting an operator that the machine has somehow failed to cycle within the preset period.

Also joined to the conductor 471 (FIG. 9) is a conductor 486 joined to an alarm control 487 responsive to end expiration pressure and incorporating a timing unit 488. This is set, for example, to afford a timing interval of 0.03 seconds. There is an out section 489 of the control 487 joined through a conductor 491 to an and gate 492, the other signal to which is received through a conductor 493 joined to a terminal N 494, also appearing in FIG. 7. This terminal N 494 is connected by a conductor 496 with a pressure responsive switch 497. On one side this has a conduit 498 joined to the airway conduit 154 and on the other side has a conduit 499 joined to the conduit 171. A differential pressure in the switch 497 greater than a preset amount, such as 5 centimeters of water column, is effective to provide a signal in the conductor 496 to the terminal N 494 and from the terminal N 494 through the conductor 493 to the and gate 492. The combined signals therein cause emission of a signal in a conductor 501 leading to the set section 502 of an end expiration pressure alarm control 503. An out section 504 of the control 503 is joined through a conductor 506 to an alarm light 507. In this way, if the pressure at the end of expiration is inordinate, an alarm by illumination of the lamp 507 is afforded.

As shown in FIG. 6 (left center), the relay switch 217 is closed when the oxygen pressure is too low and affords a signal through the conductor 219 at the terminal B 222. The same terminal B 222 appears in FIG. 9. When there is a signal at that terminal, the signal is transmitted through a conductor 508 into the set portion 509 of an alarm board 511 having an out section 512. A signal in such section is manifest through a conductor 513 at an alarm lamp 514 so that as soon as the pressure switch 227 (FIG. 6) responds to deficient oxygen pressure the lamp 514 is illuminated.

There is a further alarm. From the source of low voltage (5 volts) a conductor 516 (FIG. 9, center) extends through a normally closed switch 517 and through a manual switch 518 to a conductor 519. The switch 517 is opened by an energized coil 521 supplied by the normal commercial source of power. When commercial power is available, the switch 517 is held open, but when the main power fails the switch 517 closes. When that occurs the conductor 519 is energized and affords a signal to a set section 522 of a power disconnect line board 523. An out section 524 thereof then furnishes a signal through a conductor 525 to an alarm light 526. Thus, when the normal operating power is off, the light 526 is illuminated by the local five volt stand by power.

In addition to the visual alarm lights there is provided an audible alarm bell 527 (FIG. 9, lower right).

All of the conductors to the individual optical alarms such as 342, 506, 422, 513, 525, 483 and 417 are connected through respective ones of a number of capacitors 528 with a conductor 529 extending to the set section 531 of an audible alarm board 532. A signal in the set section 531 produces a corresponding signal in the out section 533 thereof and energizes a conductor 534 to sound the alarm bell 527 whenever any one of the visual signals is effective. Because of the customary surroundings of this type of mechanism, it is usually highly desirable to shut off the audible alarm without necessarily disabling any of the other alarms. For that reason there is a conductor 536 extending from the local low voltage source through a hand switch 537, such as a push button, and leading to the reset section 538 of the board 532. When a signal is by hand sent into the reset section 538, there is no longer a signal in the out section 533 and the audible alarm 527 stops.

It is also preferred to provide a simple means for canceling all of the alarms. Also derived from the local low voltage source through a conductor 539 is a signal effective upon closure of a hand switch 541 or push button to energize a common conductor 542. This is joined through a diode 543 to the conductor 536, to the reset section 538, and also is joined through individual conductors, such as 544, to the reset section 538 and the reset sections 546 of each of the control boards 339, 503, 439, 511, 523, 481 and 414. Thus, by momentarily closing switch 541 all of the alarm signals can be canceled.