Method and apparatus for demand oxygen system monitoring and control

• US 5,165,397 A
• Filed: 07/31/1990
• Issued: 11/24/1992
• Est. Priority Date: 12/15/1988
• Status: Expired due to Fees

• Current Assignee: Leon J. Arp
• Original Assignee: Leon J. Arp
• Inventors: Arp, Leon J.
• Primary Examiner(s): Wiecking, David A.
• Assistant Examiner(s): KELLEY, STEVEN SHAUN
• Application Number:
  US07/561,367
• Time in Patent Office: 847 Days
• Field of Search: 128/204.18-204.26, 128/716, 128/722, 128/723, 364/413.03, 364/413.05
• US Class Current: 128/204.21
• 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 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit
• CPC Class Codes: A61M 2016/1025 the O2 concentration

Abstract

An apparatus and method for controlling a respirating gas supply system responsive to a patient'"'"'s respiration. The ratio of the time of the gas supply valve open to the time of the valve closed is measured and an automatic oxygen flow override is provided if the ratio is outside a set range. Various indicators quickly indicate to the operator what system or systems have failed and/or the condition of the patient'"'"'s respiration. The apparatus can operate in two modes: a pre-flush mode which would begin gas flow to the patient at the end of exhalation and end gas flow at the end of inhalation and an inhalation mode which would begin gas flow at the beginning of inhalation and end gas flow at the end of inhalation.

Claims

1. A method for monitoring and controlling gas flow to a patient comprising the steps of:

(a) connecting the apparatus for monitoring and controlling gas flow and a patient to gas and power sources;

(b) connecting the patient requiring inhalation of supplemental oxygen to a patient-machine interface such as a nasal cannula or face mask with said patient-machine interface attached to a length of respiration sensor tubing and to a length of oxygen delivery tubing;

(c) connecting said respiration sensor tubing to a respiration sensor tubing port and said oxygen delivery tubing to an oxygen output port located on the outside of the case of the apparatus with the opposite end of said respiration sensor tubing port connected to a respiration sensor and the opposite end of said oxygen output port connected to an oxygen flow controlling valve in the apparatus;

(d) generating a signal responsive to a respiration cycle of said patient, said respiration cycle consisting of inhalation by said patient followed by exhalation by said patient, followed by a short pause period of time just prior to beginning of the next inhalation of said patient;

(e) detecting, monitoring, and evaluating the amplitude and slope of said signal produced by said respiration sensor, said evaluation of said signal produced by said respiration sensor to be done by a control means including a microprocessor multiple times to determine if said signal from said respiration sensor was produced by inhalation by said patient or if said signal from said respiration sensor was produced by an artifact source such as ambulatory motion of said patient or by the motion of the oxygen delivery tubing or respiration sensor tubing connecting the apparatus to said patient, said control means and said microprocessor operable in a first operating mode a second operating mode;

(f) if a first operating mode was selected, then producing a first control signal responsive to said signal at the start of inhalation in response to said slope having a first predetermined sign and said amplitude crossing a first predetermined value to start the flow of gas to said patient and producing a second control signal responsive to said signal at the end of inhalation in response to said slope having a second predetermined sign and said amplitude crossing a second predetermined value to stop the flow of gas to said patient;

(g) if said second operating mode was selected, then producing a first control signal responsive to said signal at the end of exhalation in response to said slope having a first predetermined sign and said amplitude crossing a third predetermined value to start the flow of gas to said patient, said flow of gas starting at the end of said exhalation by said patient and continuing during the short pause period just prior to the beginning of the next inhalation by said patient to cause the flow of said gas to wash out any exhaled carbon dioxide in said patient'"'"'s nasal cavity and any carbon dioxide in a nasal cannula or face mask interface used for connecting the said flow of gas from said oxygen output port to said patient, and producing a second control signal responsive to said signal at the beginning of exhalation in response to said slope having a second predetermined sign and said amplitude crossing a fourth predetermined value to stop the flow of gas to said patient during exhalation by said patient, said second predetermined sign being different than said first predetermined sign;

(h) operating a normally open valve interposed in said oxygen output port in response to said first control signal for turning gas flow in said delivery means on and in response to said second control signal for turning gas flow in said delivery means off;

(i) predetermining an acceptable ratio of inhalation time over exhalation time for a patient;

(j) determining the actual ratio of the inhalation time over exhalation time during the inhalation phase of a respiratory cycle for the patient;

(k) comparing said actual ratio to said acceptable ratio to automatically determine the adequacy or inadequacy of the oxygen flow to the patient;

(l) automatically starting the flow of oxygen to the patient if the oxygen flow has been determined to be inadequate;

(m) automatically activating visible and audible alarms if the flow of oxygen to the patient has been determined to be inadequate;

(n) automatically interrupting driving power source to said valve to force said valve open thus allowing oxygen to flow to the patient if the flow of oxygen to the patient was not started automatically after determining that the flow has been inadequate;

(o) activating visible and audible alarms if the oxygen source is inadequate or not present;

(p) automatically starting the flow of oxygen to the patient in case of low operating voltage, or interruption of the driving power,

(q) detecting and using said signal having a slope opposite to the said slope of the signal produced during the inhalation phase to turn off the flow of oxygen to a patient; and

(r) repeating steps (h) through (q) for a plurality of consecutive respiratory cycles.

2. The apparatus for controlling gas flow from a gas storing means to a patient as recited in claim 1, wherein said amplitude of said signal is less than a selected one of the following:

said first predetermined value if said first respiration signal was previously generated, and

said second predetermined value if said second respiration signal was previously generated.

3. The apparatus for controlling gas flow from a gas storing means to a patient as recited in claim 2, wherein, after a next crossing, said amplitude of said signal is greater than the non-selected one of said first predetermined value and said second predetermined value.

4. The method of claim 1, further comprising the steps of connecting the said oxygen delivery tubing to the output port of a respiratory gas humidifier, and with a length of tubing, to connect the said oxygen delivery port of the apparatus to the input of said respiratory gas humidifier.

5. An apparatus to monitor and control the flow of gas to a patient comprising:

(a) a gas pressure regulator means for connection between a source of pressurized gas and the apparatus hereafter defined for the purpose of limiting, to a safe level, the pressure of gas delivered to a patient through the apparatus;

(b) visible and audible alarm means for alerting and/or warning the patient and/or attending personnel of abnormal operation of the apparatus;

(c) warning indicator means to indicate and to warn the patient and/or attending personnel that the alarm "on-off" selector switch is in the "alarm off" position, thereby disabling the visible and audible alarm means intended for alerting and/or warning the patient and/or attending personnel of abnormal operation of the apparatus;

(d) a gas source sensor means to detect the presence or absence of an adequate source of gas for proper operation of the apparatus and to provide a signal to activate visible and audible alarm means in the event that the gas source becomes inadequate for the safe operation of the apparatus;

(e) respiration sensing means responsive to a respiration cycle of said patient, said respiration cycle consisting of inhalation by said patient followed by exhalation by said patient, followed by a short pause period of time just prior to the beginning of the next inhalation of said patient for generating a first respiration signal during the time of inhalation by said patient and a second respiration signal during the time of exhalation by said patient;

(f) control means including a microprocessor for detecting, monitoring and evaluating the amplitude and slope of an electrical signal produced by said respiration sensing means, said evaluation of said signal produced by said respiration sensing means to be done multiple times so as to detect and determine if said signal from said respiration sensing means was produced by inhalation by said patient or if said signal from said respiration sensing means was produced by an artifact source such as ambulatory motion of said patient or by the motion of the gas delivery tubing or respiration sensing tubing connecting the apparatus to said patient, said control means and said microprocessor operable in a first operating mode and a second operating mode, said first operating mode responsive to a first respiration signal generated by said respiration sensing means at the start of inhalation for producing a first control signal in response to said slope having a first predetermined sign and said amplitude crossing a first predetermined value to start the flow of gas to said patient and responsive to a second respiration signal generated at the end of inhalation for producing a second control signal in response to said slope having a second predetermined sign and said amplitude crossing a second predetermined value to stop the flow of gas to said patient, said second selectable operating mode responsive to a first respiration signal from said respiration sensing means and generated at the end of exhalation for producing a first control signal in response to said slope having a first predetermined sign and said amplitude crossing a third predetermined value to start the flow of gas to said patient at the end of said exhalation by said patient and continuing during the short pause period of time just prior to the beginning of the next inhalation of said patient, said flow of gas starting at the end of said exhalation by said patient and continuing during the short pause period just prior to the beginning of the next inhalation by said patient to cause the flow of said gas to wash out any exhaled carbon dioxide in said patient'"'"'s nasal cavity and any carbon dioxide in a nasal cannula or face mark interface used for connecting the said flow of gas from said gas flow controlling device to said patient, said second operating mode responsive to a second respiration signal generated by said respiration sensing means at the beginning of exhalation for producing a second control signal in response to said slope having a second predetermined sign and said amplitude crossing a fourth predetermined value to stop the flow of gas to said patient during exhalation of said patient, said second predetermined sign different than said first predetermined sign;

(g) a normally open valve interposed in said gas delivery means and responsive to said first control signal for turning gas flow in said delivery means on and responsive to said second control signal for turning gas flow in said delivery means off;

(h) offset and gain controlling amplification means for modification of the output signal of the inhalation and exhalation sensing means;

(i) inhalation slope and level detector means for determining the beginning of the spontaneous inhalation phase in a patient'"'"'s respiratory cycle;

(j) exhalation slope and level detector means for determining the beginning of the spontaneous exhalation phase in a patient'"'"'s respiratory cycle;

(k) indicator means for visible and/or audible signalling of the proper operation of the inhalation and exhalation sensing means;

(l) gas flow controlling valve means for controlling the flow of a gas;

(m) oxygen flow controlling valve driver means for controlling the operation of the gas flow controlling valve means;

(n) memory means for receiving and retaining cyclical output signals from the inhalation slope and level detector means, the exhalation slope and level detector means, and for controlling the operation of an oxygen flow controlling valve driver means;

(o) power interruption switch means for interrupting the flow of operating power to the gas flow controlling valve means in the event of a malfunction or failure of the oxygen flow controlling valve driver means;

(p) memory means for power interruption which controls the operation of the power interruption switch means to provide automatic power interruption to the oxygen flow controlling valve driver means and the gas flow controlling valve means;

(q) automatic power-up reset means to activate the "power on" section of the memory means for power interruption which controls the operation of the power interruption switch means at the time driving power is turned on to operate the apparatus;

(r) manual power-up reset means to provide for manual override by the operator of the apparatus controlled power interruption switch means;

(s) power interruption valve open over valve closed ratio detector is such that inadequate gas flow to the patient has been provided by the apparatus and to then generate and transmit a "power off" command signal to the memory for power interruption means, said memory for power interruption means then generates and transmits a "power off" control signal to the power interruption switch means for the purpose of automatically interrupting the operation of the gas flow controlling valve means and thereby starting a continuous flow of gas to be inhaled by the patient;

(t) "no" gas flow indicator means to provide indication to the patient and/or attending personnel that no gas is flowing to the patient;

(u) gas flow "on" indicator means to provide indication to the patient and/or attending personnel that gas is flowing to the patient;

(v) start of gas flow valve open over valve closed ratio detector means to detect when the valve open over valve closed ratio is such that inadequate gas flow to the patient has been provided by the apparatus and to then automatically generate and transmit a controlling signal to the "on" input of the memory for operating mode means for the purpose of causing the memory for operating mode means to generate and transmit a controlling signal to the oxygen flow controlling valve driver means to cause the flow of gas to the patient to be turned on, the controlling signal generated by the start of gas flow valve open over valve closed ratio detector means is also delivered to the "alarm on" input of the memory for alarm and low input voltage means for the purpose of causing the memory for alarm and low input voltage means to generate and deliver a control signal to activate the visible and audible alarm means of the apparatus;

(w) direct current power supply means for accepting either alternating current input source or direct current input source to supply a constant voltage, direct current output to operate the apparatus, and

(x) a low voltage detector means for monitoring the output voltage of the direct current power supply means and to generate and deliver a control signal to activate the visible and audible alarm means and to simultaneously start the flow of gas to the patient in the event that the output voltage of the power supply should fall to a level below that which will guarantee proper operation of the device.

6. The apparatus of claim 5, further comprising the inclusion of:

(a) an oxygen flow controlling valve means for controlling the flow of a oxygen;

said oxygen flow controlling valve means to be a normally open valve when driving and control power to the valve is absent, and

(b) an oxygen flow controlling valve driver means for controlling the operation of the oxygen flow controlling valve means;

said oxygen flow controlling valve driver means to supply power continuously to actuate the valve means during the exhalation phase of a patient'"'"'s breathing cycle, thus causing the valve means to close.

7. The apparatus of claim 5, further comprising the inclusion of:

(a) an oxygen flow controlling valve means for controlling the flow of an oxygen;

said oxygen flow controlling valve means to be a normally closed valve when driving and control power to the valve means is absent, and

(b) an oxygen flow controlling valve driver means for controlling the operation of an oxygen flow controlling valve means;

said oxygen flow controlling valve driver means to supply power continuously to actuate the valve during the inhalation phase of a patient'"'"'s breathing cycle, thus causing the valve means to open.

8. The apparatus of claim 5, further comprising the inclusion of:

(a) an oxygen flow controlling valve means for controlling the flow of oxygen;

said oxygen flow controlling valve means to be a normally open valve when driving and control power to the valve is absent at the time the device is first turned on, said oxygen flow controlling valve mean requiring only a momentary pulse of electrical current to close said valve means, and a second momentary pulse of electrical current to open the valve means, and

(b) an oxygen flow controlling valve driver means for controlling the operation of an oxygen flow controlling valve means;

said oxygen flow controlling valve driver means to supply only a momentary pulse of electrical current to close said valve during the exhalation phase of a patient'"'"'s breathing cycle, and a second momentary pulse of electrical current to open the valve means during the inhalation phase of a patient'"'"'s breathing cycle.

9. The apparatus of claim 5, further comprising the inclusion of:

(a) an oxygen flow controlling valve means for controlling the flow of oxygen;

said oxygen flow controlling valve means to be a normally closed valve when driving and control power to the valve is absent at the time the device is first turned on, said oxygen flow controlling valve means requiring only a momentary pulse of electrical current to open said valve, and a second momentary pulse of electrical current to close the valve, and

(b) an oxygen flow controlling valve driver means for controlling the operation of an oxygen flow controlling valve means;

said oxygen flow controlling valve means to supply only a momentary pulse of electrical current to open the oxygen flow controlling valve means during the inhalation phase of a patient'"'"'s breathing cycle, and a second momentary pulse of electrical current to close the valve means during the exhalation phase of a patient'"'"'s breathing cycle.