Patent GB-1356212-A (GB)
Title: Apparatus for the monitoring and stimulation of respiration
IPC: A61M16/00
Filed: 1972-02-15
Abstract: 1356212 Respiration monitors and stimulators V LANG 15 Feb 1972 [15 Feb 1971 (2)] 6994/72 Headings ASK, R, and T [Also in Division G1] A respiration monitor and stimulator comprises a respiration sensor 1 or 2, and a counter 9 and timer 10 for determining whether the rate of occurrence of respiratory cycles of greater than a given depth of respiration is less than a given frequency, an alarm relay 11 being operated if the sensed rate is below the predetermined rate so as to switch on a respiration stimulator, and means for indicating the occurrence of a respiratory deficiency. A sensor 1 or 2, such as a thermistor or pressuresensitive transducer, is coupled to a mouth probe 19 or nose probe 20 respectively, the output of the sensor passing via an amplifier 4 to a circuit 5 giving an output pulse for each sensed breath above an adjustable threshold depth. The output of circuit 5 can be monitored by a lamp 7 or by means of an audio transmitter 21. Counter 9 is adjustable to count a predetermined number of breaths, timer 10 being simultaneously adjusted to bring into operation a timing circuit associated with the preset number of breaths. If counter 9 counts the preset number of breaths before timer 10 times out, the timer 10 is reset. If the counter 9 does not count a number of breaths above the threshold depth equal to the preset number before the timer times out, the relay 11 is energised to actuate the stimulator and operate said indicating means. A counter 14 monitors the number of times the relay 11 is energised. If the stimulator does not give rise to spontaneous breathing within a timing period of timer 15, which is adjustable from 10 to 30 seconds, a relay 16 raises an alarm and illuminates a push-button 17 which is used to reset counter 9 timers 10, 15 and relay 16. To prevent irregular jerky breathing resulting from the stimulation being sensed as acceptable respiration and causing turn-off of the stimulator, circuits may be provided to perform the following functions in sequence starting simultaneously with actuation of relay 11; a a circuit 28 blocks the input to timer 10, b counter 9 is reset by circuit 29, c a pulse is transmitted after a preset time delay from a circuit 30 to the input of counter 9, d the input block on timer 10 is removed. Counter 9 must then count one breath less than the preset number before it can reset timer 10 to turn off the stimulator. If a nose probe is used, it may be connected via a two-way electromagnetic valve 34 which normally connects the probe to sensor 1. If respiration is normal, the output of circuit 5 keeps a timer 31 set to zero. If the probe becomes blocked, the valve 34 is operated after timer 31 times out to connect the probe to a gas reservoir or blower 35 to clear the blockage. The input to amplifier 4 is blocked by a circuit 33 whilst the probe blockage is being cleared. The stimulator may comprise an electromagnetic valve 13 cycled by a circuit 12 to cyclically inflate a belt around the patient. Alernatively, electrical stimulation or thermal stimulation may be utilised.