Respiratory gas supply apparatus and method

• US 5,048,515 A
• Filed: 11/15/1988
• Issued: 09/17/1991
• Est. Priority Date: 11/15/1988
• Status: Expired due to Fees

• Current Assignee: David W. Sanso
• Original Assignee: David W. Sanso
• Inventors: Sanso, David W.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/271,525
• Time in Patent Office: 1,036 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26
• US Class Current: 128/204.26
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/0677 Gas-saving devices therefor
• CPC Class Codes: A61M 16/0841 for sampling
• CPC Class Codes: A61M 16/0858 Pressure sampling ports
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0024 with an on-off output signal, e.g. from a switch
• CPC Class Codes: A61M 2016/0027 pressure meter

Abstract

A supplemental respiratory gas supply control apparatus and method for providing supplemental gas to an in vivo respiratory system includes a pressure sensor adapted to produce pressure indicative signals indicative of pressures sensed, a gas flow control valve, a sensor communication control valve, and a central control unit adapted to receive pressure indicative signals generated by the pressure sensor and to control the gas control valve and the sensor communication control valve in accordance with the signals received. The gas control valve is connected to a source of supplemental gas at regulated pressure and has two positions, a first position isolating the source of supplemental gas from the single hose cannula and a second position communicating the source of supplementary gas with the cannula hose to provide a flow of supplementary gas to the in vivo respiratory system. The pressure sensor communication control valve has a first mode placing the pressure sensor in communication with the cannula hose to allow the pressure sensor to sense the pressure within the hose and a second mode in which the pressure sensor is placed in communication with the ambient atmsophere. The central control unit initially places the gas control valve in the first position and the sensor communication valve in the first mode to monitor the pressure within the cannula hose.

Claims

1. A method for supplying supplemental respiratory gas through a single hose cannula to an in vivo respiratory system, comprising the steps of:

A. connecting a means for sensing pressure to the cannula hose to measure pressure within the cannula hose;

B. monitoring the pressure within the cannula hose until a time, t_O, of an initial occurrence of a pressure less than atmospheric pressure;

C. continuing to monitor the pressure for a predetermined period of time, Δ

t_c, until a time t₁ ;

D. determining the magnitude of a pressure, P₁, occurring within the cannula hose during the period of time Δ

t_c ;

E. at time t₁, disconnecting the pressure sensing means for the cannula hose;

F. waiting a predetermined period of time Δ

t₁, until a time t₁ '"'"';

G. at time t₁ '"'"', connecting a source of supplemental gas to the cannula hose to begin a supplemental gas administration interval of providing supplemental gas to the in vivo respiratory system;

H. continuing to provide supplemental gas to the in vivo system for a time interval Δ

t_sup, based upon the value P₁, in accordance with a predetermined relation, until a time t₂ ;

I. at time t₂, disconnecting the source of supplemental gas from the cannula hose to end the supplemental gas administration interval;

J. waiting a predetermined period of time Δ

t₂ until a time t₂ '"'"';

K. at a time t₂ '"'"', reconnecting the pressure sensing means to the cannula hose to again monitor the pressure within the cannula hose; and

,

L. successively repeating steps A through K a plurality of times to provide supplemental gas to the in vivo respiratory system on a continuing basis.

2. A method for supplying supplemental gas to an in vivo respiratory system as in claim 1, comprising an additional first step of:

calibrating the pressure sensing means at ambient atmospheric pressure.

3. A method for supplying supplemental gas to an in vivo respiratory system as in claim 1 further comprising the steps of:

starting a timer device immediately upon performance of a step selected from among the steps A through K, to determine a time of expiration of an apneic event characteristic period after performance of the selected step; and

at said time of expiration of the apneic event characteristic period, but only if the performance of the selected step has not reoccurred, activating an aepnic event alarm.

4. A method for supplying supplemental gas to an in vivo respiratory system as in claim 3, in which said apneic event alarm is an acoustic alarm.

5. A method of supplying supplemental gas to an in vivo respiratory system as in claim 3, in which said apneic event alarm is an optical alarm.

6. A method of supplying supplemental gas to an in vivo respiratory system as in claim 3, in which, beginning at the time of activation of the apneic event alarm, supplemental gas is provided continuously to the in vivo respiratory system.

7. A method for supplying supplemental gas to an in vivo respiratory system as in claim 1, in which the time interval Δ

t_sup of the step of continuing to provide supplemental gas to the in vivo system for the time interval Δ

t_sup, is determined as a direct proportion of the pressure P₁ from an arithmetic formula of the form Δ

t_sup =α

P₁, where α

is an arithmetic constant.

8. A method for supplying supplemental respiratory gas through a single hose cannula as in claim 1 in which the pressure, P₁, determined in step D is an instant pressure at time t₁.

9. A method for supplying supplemental respiratory gas through a single hose cannula as in claim 1 in chich the pressure, P₁, determined in step D is the most negative pressure occurring during the time Δ

t_c.

10. A mehtod for supplying supplemental respiratory gas through a single hose cannula to an in vivo respiratory system, comprising the steps of:

A. connecting a means for sensing pressure to the cannula hose to measure pressure within the cannula hose;

B. monitoring the pressure within the cannula hose until a time, t₀, of an initial occurrence of a pressure less than atmospheric pressure;

C. determining the rate of change of pressure at the time t_O ;

D. at a time t₁, not prior to time t_O, disconnecting the pressure sensing device from the cannula hose;

E. waiting a predetermined period of time Δ

t₁, until a time t₁ '"'"';

F. at time t₁ '"'"', connecting a source of supplental gas to the cannula hose to begin a supplemental gas administration interval of providing supplemental gas to the in vivo respiratory system;

G. continuing to provide supplemental gas to the in vivo system for a time interval Δ

t_sup, based upon the rate of change of pressure determined in step C, in accordance with a predetermined relation, until a time t₂ ;

H. at time t₂, disconnecting the source of supplemental gas from the cannula hose to end the supplemental gas administration interval;

I. waiting a predetermined period of time Δ

t₂ after time t₂, until a time t₂ '"'"';

J. at time t₂ '"'"', reconnecting the pressure sensing means to the cannula hose to again monitor the pressure within the cannula hose; and

,

K. successively repeating steps A through J a plurality of times to provide supplemental gas to the in vivo respiratory system on a continuing basis.

11. A method for supplying supplemental respiratory gas through a single hose cannula to an in vivo respiratory system, comprising the steps of:

A. connecting a means for sensing pressure to the cannula hose to measure pressure within the cannula hose;

B. monitoring the pressure within the cannula hose until a time, t_O, of an initial occurrence of a pressure less than atmospheric pressure;

C. waiting a predetermined period of time, Δ

t_c, until a time t₁ ;

D. determining the magnitude of a pressure, P₁, occuring within the cannula hose during the time Δ

t_c ;

E. at time t₁, disconnecting the pressure sensing means from the cannula hose;

F. at a time t'"'"'₁, not prior to time t₁, connecting a source of supplemental gas to the cannula hose to begin a supplemental gas administration interval of providing supplemental gas to the in vivo respiratory system;

G. continuing to provide supplemental gas to the in vivo system for a time interval Δ

t_sup, based upon the value P₁ in accordance with a predetermined relation, until a time t₂ ;

H. at time t₂, disconnecting the source of supplemental gas from the cannula hose to end the supplemental gas administration interval;

I. at time t₂ '"'"', reconnecting the pressure sensing means to the cannula hose to again monitor the pressure within the cannula hose; and

,

J. successively repeating steps A through I a plurality of times to provide supplemental gas to the in vivo respiratory system on a continuing basis.

12. A method for supplying supplemental respiratory gas through a single hose cannula to an in vivo respiratory system, comprising the steps of:

A. connecting a means for sensing pressure to the cannula hose to measure pressure within the cannula hose;

B. monitoring the pressure within the cannula hose until a time, t_O, of an initial occurrence of a pressure less than atmospheric pressure;

C. waiting a predetermined period of time, Δ

t_c, after time t_O, until a time t₁ ;

D. determining the magnitude of a pressure, P₁, occurring within the cannula hose during the time Δ

t_c ;

E. at time t₁, disconnecting the pressure sensing device from the cannula hose;

F. at time t₁ '"'"', connecting a source of supplemental gas to the cannula hose to begin a supplemental gas administration interval of providing supplemental gas to the in vivo respiratory system;

G. continuing to provide supplemental gas to the in vivo system for a time interval Δ

t_sup, based upon the value P₁ in accordance with a predetermined relation, after t₁ '"'"', until a time t₂ ;

H. at time t₂, disconnecting the source of supplemental gas from the cannula hose to end the supplemental gas administration interval;

I. at a time t'"'"'₂ ;

not prior to time t₂, reconnecting the pressure sensor device to the cannula hose to again continuously monitor the pressure within the cannula hose; and

,

J. sucessively repeating steps A through I a plurality of times to provide supplemental gas to the in vivo respiratory system on a continuing basis.

13. A method for controlling the supply of a supplemental respiratory gas through a single hose cannula to an in vivo respiratory system, comprising the steps of:

A. connecting a means for sensing pressure to the cannula hose to measure pressure within the cannula hose;

B. monitoring the pressure within the canula hose until a time, t₀, of an initial occurrence of a pressure less than atmospheric pressure;

C. at time t₁, not prior to t₀, disconnecting the pressure sensing device from the cannula hose;

D. at a time t₁ '"'"', not prior to t₁, connecting a source of supplemental gas to the cannula hose to begin a supplemental gas administration interval of providing supplemental gas to the in vivo respiratory system;

E. continuing to provide supplemental gas to the in vivo system for a time interval Δ

t_sup, until a time t₂ ;

at time t₂, disconnecting the source of supplemental gas from the cannula hose to end the supplemental gas administration interval;

H. waiting a predetermined period of time Δ

t₂, until a time t₂ '"'"';

I. successively repeating the steps A through H a plurality of times to provide supplemental gas to the in vivo system on a continuing basis.

14. An apparatus for supplying supplemental respiratory gas from a gas source through a single hose cannula to an in vivo respiratory system during successive respiratory cycles, each cycle beginning with a respiratory demand by the in vivo respiratory system characterized by a negative pressure occurrence at an interface between the cannula hose and the in vivo system, comprising:

means for sensing pressure and generating a pressure indicative signal representative of the magnitude of the pressure sensed;

alternative communication means responsive to first control signals to switch between two alternative modes, a first mode communicating said pressure sensing means with the cannula hose so that a pressure with in the hose can be monitored and a second mode communicating said pressure sensing means with ambient atmospheric pressure;

means for connecting the apparatus to a source of supplemental gas;

valve means responsive to second control signals to switch between two alternative positions, said valve means isolating the source of supplemental gas from the cannula hose when in the first position and allowing supplemental gas from the source to flow into the cannula hose when in the second position;

control means, including timing means, for receiving said pressure indicative signal and selectively generating said first and second control signals, said control means responsive to initiation of operation of the apparatus to generate said first control signal to place said alternative communication means in said first mode and said second control signal to place said valve means in said first position to cause said pressure sensing means to sense a pressure within the cannula hose, said control means thereafter receiving said pressure indicative signal and generating said first and second control signals in accordance with said pressure indicative signal, said control means responsive to initial reception of a pressure indicative signal indicative of a pressure less than atmospheric pressure, at a time t₀, to initiate a sequential, supplemental-gas-administration cycle by generating a firt control signal at a time t₁, a predetermined time interval Δ

t_c after time t_O, to switch said alternative communication means to its second mode;

generating a second control signal at a time t₁ '"'"', a predetermined time interval Δ

t₁ after time t₁, to switch said valve means from said first position to said second position to begin an interval of supplemental respiratory gas administration;

generating said second control signal at a time t₂, a time interval Δ

t_sup after time t₁ '"'"', to switch said valve means from the second position to the first position to end the interval of supplemental gas administration and thereby define a period of supplemental gas administration, Δ

t_sup ;

generating a first control signal, at a time t₂ '"'"', a predetermined time interval Δ

t₂ after time t₂, to switch said alternative communication means to its first mode to communicate the pressure sensing means with the cannula hose and allow said pressure sensing means to generate a pressure indicative signal indicative of the pressure within the cannula hose;

said control unit thereafter responsive to said pressure indicative signal to initiate continuing, successive, supplemental-gas-administration cycles in response to demand by the in vivo respiratory system.

15. A supplemental respiratory gas supply apparatus as in claim 14 further comprising:

means for calibrating said control means at ambient atmospheric pressure.

16. A supplemental respiratory gas supply apparatus as in claim 14 in which the supplemental-gas-administration interval, Δ

t_sup, defined by said sequential cycle of said control means is a predetermined constant time period.

17. A supplemental respiratory gas supply apparatus as in claim 14 in which the supplemental gas administration interval, Δ

t_sup, defined by said sequential of said control means is a time period determined as a function of the most negative pressure magnitude occurring during time interval Δ

t_c.

18. A supplemental respiratory gas supply apparatus as in claim 14 in which the supplemental gas administration interval, Δ

t_sup, defined by said sequential of said control means is a time period determined as a function of the rate of change of pressure with time at the time of the initial reception of a pressure indicative signal indicative of a pressure lower than atmospheric pressure, t_O.

19. A supplemental respiratory gas supply apparatus as in claim 14 in which the time interval Δ

t_c is determined by electrical impedance and mechanical inertia of the supplemental respiratory gas supply apparatus, including the control means.

20. A supplemental respiratory gas supply apparatus as in claim 14 in which the supplemental-gas-administration interval, Δ

t_sup, defined by said sequential cycle of said control means, is a time period determined as a function of a pressure, P₁, indicated by the pressure sensor at the time, t₁, that said alternative communication means is switched to its second mode.

21. A supplemental respiratory gas supply apparatus as in claim 20, in which the supplemental-gas-administration interval defined by said sequential cycle of said control device, Δ

t_sup, is directly proportional to the amount by which the pressure, P₁, indicated by the pressure sensing means at the time said alternative communication means is switched to its second mode, t₁, is below atmospheric pressure.

22. An apparatus for supplying supplemental respiratory gas as in claim 14 in which said valve means is in the first position when in repose in a power off condition so that, in the event of a power failure, supplemental respiratory gas is continuously provided to the in vivo respiratory system.

23. An apparatus for supplying supplemental respiratory gas through a single hose cannula to an in vivo respiratory system comprising:

means for sensing pressure and generating a pressure indicative signal representative of the magnitude of the pressure sensed;

means for providing alternative fluid communication, said alternative communication means having two modes, a first mode in which said alternative communication means provides fluid communication between said pressure sensing means and an interior portion of the cannula hose so that said pressure sensing means senses a pressure in the portion of the cannula hose and generates a pressure signal indicative thereof, and a second mode in said alternative communication means provides fluid communication between said pressure sensing means and an ambient atmosphere so that said pressure sensing means generates a pressure indicative signal indicative of ambient atmospheric pressure, said alternative communication means responsive to a first and second control signal to switch to the first and second mode, respectively;

means for controlling a flow of supplemental gas, said gas flow control means in fluid communication with a source of supplemental respiratory gas and having two positions, a first position in which said flow control means isolates the supplemental gas source from the cannula hose and a second position in which said gas flow control means provides fluid communication between the gas source and the cannula hose so that supplemental respiratory gas flows into the cannula hose, said gas flow control means responsive to a third and fourth control signal to switch to the first and second position, respectively;

means for receiving said pressure indicative signal, determining when said pressure indicative signal is indicative of a negative pressure less than atmospheric pressure, and, upon receiving such a negative pressure indicative signal, generating a cycle signal continuously until its termination at the end of a cycle time interval;

means for controlling the mode of said flow control means in response to said cycle signal, said mode control means operative to receive said cycle signal and generate said third and fourth control signals in such a manner as to switch said flow control means in the second position and maintain said flow control means in said second position continuously from a time said cycle signal is initially generated until a gas disconnect time following the time of initial generation of said cycle signal by a predetermined gas-connect-delay interval, switching said flow control means from said first position to said second position at said gas connect time and maintaining said flow control means in said second position continuously while said cycle signal continues to be generated over a remainder of the cycle time interval, and upon the termination of said cycle signal, switching said flow control means from the second position to the first position and maintain said flow control means in the second position until said cycle signal is again generated; and

means for controlling the mode of said alternative communication means in response to said cycle signal, said mode control means operative to receive said cycle signal and to generate said first and second control signals in such a manner as to switch said alternative communication means from the first mode to the second mode immediately upon generation of said cycle signal and to continuously maintain said alternative communication means in said second position while said cycle signal is generated over the cycle time interval and for an additional predetermined fixed sensor-connect-delay interval, and thereafter switching said alternative communication means to the first mode and maintaining said flow control means in the first mode continuously until the cycle signal is again generated.

24. An apparatus for supplying supplemental respiratory gas through a single hose cannula as in claim 23 in which said cycle signal is of a duration which is a multiple of a pre-determined incremental time period.

25. An apparatus for supplying supplemental gas, as in claim 23 in which said cycle signaling means comprises:

means for retaining a negative peak in said pressure indicative signals, said peak retaining means interposed between said pressure sensing means and said comparing and signaling means and operative to receive said pressure indicative signal and to produce a modified pressure indicative signal, said modified pressure indicative signal indicative of a pressure identical to the pressure indicated by said pressure indicative signal of said pressure sensing means except beginning at a time when the rate of pressure increase indicated by said pressure indicative signal exceeds a predetermined rate of increase, said modified pressure indicative signal indicating a pressure increasing at a constant predetermined rate of pressure increase equal to said predetermined rate beginning at said time of excess rate increase until a time said modified pressure indicative signal is again indicative of a pressure identical to the pressure indicated by said pressure indicative signal, said modified pressure signal thence remaining identical to the pressure indicated by said pressure indicative signal until a pressure increase indicated by said pressure indicative signal again exceeds the predetermined rate of increase; and

means for comparing and signaling, adapted to receive both said modified pressure indicative signal and a calibrated atmospheric pressure indicative signal and compare said pressure indicative signal to said calibrated atmospheric pressure indicative signal and to generate a cycle signal when said pressure indicative signal is indicative of a pressure less than atmospheric pressure.

26. An apparatus for supplying supplemental respiratory gas as in claim 25 in which said supplemental respiratory gas control means is in the second position when in repose in a power off condition so that, in an ocurrence of power failure, supplemental respiratory gas is continuously provided to the in vivo respiratory system.

27. An apparatus for supplying supplemental respiratory gas as in claim 25 in which said alternative communication means and said supplemental gas control means each comprise a poppet valve.

28. An apparatus for supplying supplemental gas, as in claim 25 in which said cycle signal is of a duration which is a multiple of a pre-determined incremental time period.

29. An apparatus for supplying supplemental respiratory gas as in claim 25 further comprising:

means for switching said alternative communication means to the second mode when power is first supplied to the apparatus;

latch means to produce a first latch signal when power is first supplied to the apparatus and to produce a second latch signal upon generation of a cycle signal; and

,

ramp signal generating means operative to receive said latch signals and, in response to said first latch signal, to generate a trial calibration atmospheric pressure indicative signal beginning at a pressure indicative value higher than a predetermined atmospheric pressure indicative value and indicative of a pressure decreasing at a constant rate over time until receiving said second latch signal and thereafter to generate a constant calibrated atmospheric pressure indicative signal until the power is cut off.

30. An apparatus for supplying of a supplemental respiratory gas through a single hose cannula to an in vivo respiratory system as in claim 23 in which said cycle time interval is determined based upon a momentary rate of change of the pressure signal at the time of said negative pressure indication.

31. In a supplemental respiratory gas supply apparatus for providing supplemental respiratory gas to an invivo respiratory system through a cannula hose in response to demands of the invivo system, the system having a pressure sensor, a source of supplemental respiratory gas at a pressure greater than atmospheric pressure and control means, said control means operational to connect and disconnect said sensor to the cannula hose at a point of sensor communication to monitor pressure within the hose and to connect and disconnect said gas source to said cannula hose to introduce supplemental gas into the hose during periods of supplemental gas administration, the improvement comprising:

said control means disconnecting said sensor from said cannula hose during the periods of supplemental gas administration and including means for maintaining said sensor disconnected from said hose during a predetermined sensor-connect-delay interval after disconnecting said source from said hose thereby allowing pressure gradients within the hose resulting from the introduction of respiratory gas into the hose to reduce sufficiently to assure pressure at the point of sensor communication is not sufficient to damage or aggravate drift of the sensor before connecting said sensor to said hose to monitor pressure within the hose.

32. In a supplemental respiratory gas supply apparatus for providing supplemental respiratory gas to an in vivo respiratory system through a cannula hose in response to demands of the in vivo system characterized by an occurrence of negative pressure at a point of interface between the cannula hose and the in vivo system, the system having a means for sensing pressure within the cannula hose, a source of supplemental respiratory gas and a control means, said control means operational to connect said gas source to the cannula hose to introduce supplemental gas into the hose over periods of supplemental gas supply intervals and to disconnect said source from said hose to end the duration of supply intervals, a method of control comprising the steps of;

monitoring the pressure within the cannula hose to detect an initial occurrence of negative pressure;

determining the largest magnitude of negative pressure occurring over a sample period following said initial occurrence of negative pressure; and

thereafter introducing supplemental gas into the hose for a supply interval of a duration determined by said largest magnitude of negative pressure.

33. A method for controlling a supplemental respiratory gas supply apparatus for providing supplemental respiratory gas to an in vivo respiratory system through a cannula hose in response to demands of the in vivo system characterized by an occurrence of negative pressure at a point of interface between the cannula hose and the in vivo system, the system having a means for sensing pressure within the cannula hsoe, a source of supplemental respiratory gas and a control means, said control means operational to connect said gas source to the cannula hose, to introduce supplemental gas into the hose over periods of supplemental gas supply intervals and to disconnect said source from said hose to end the duration of supply intervals, comprising the steps of;

monitoring the pressure within the cannula hose to detect an initial occurrence of negative pressure;

determining the rate of change of pressure at the time of said initial occurrence; and

,

thereafter introducing supplemental gas into the hose for a supply interval of a duration determined by said rate of charge of pressure.

34. A method for controlling a supplemental respiratory gas supply apparatus for providing supplemental respiratory gas to an in vivo respiratory system through a cannula hose in response to demands of the in vivo system characterized by an occurrence of negative pressure at a point of interface between the cannula hose and the in vivo system, the system having a means for sensing pressure within the cannula hose, a source of supplemental respiratory gas and a control means, said control means operational to connect said gas source to the cannula hose to introduce supplemental gas into the hose over periods of supplemental gas supply intervals and to disconnect said source from said hose to end the duration of supply intervals, comprising the steps of;

monitoring the pressure within the cannula hose to detect an initial occurrence of negative pressure;

determining the magnitude of an instant pressure occurring within the hose at a predetermined time after said initial occurrence; and

thereafter introducing supplemental gas into the hose for a supply interval which is determined by the magnitude of said pressure.