Apparatus for monitoring respiratory muscle activity

• US 5,316,009 A
• Filed: 07/01/1992
• Issued: 05/31/1994
• Est. Priority Date: 07/05/1991
• Status: Expired due to Term

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Yamada, Yoshitsugu
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US07/907,399
• Time in Patent Office: 699 Days
• Field of Search: 128/716, 128/720, 128/725, 128/204.23, 128/205.23
• US Class Current: 600/533
• CPC Class Codes: A61B 5/087 Measuring breath flow

Abstract

A respiratory muscle activity monitoring apparatus is provided with a pressure sensor for detecting pressure in an air passage connecting a lung ventilator and the airway system of a patient and a flow rate sensor for detecting flow rate in the air passage. An arithmetic constant detecting unit detects resistance Rrs and elastance Ers of the respiratory system including the airway and thorax beforehand by using detection signals from the pressure sensor and the flow rate sensor while the lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped. Using airway opening pressure Paw detected by the pressure sensor and flow rate dV/dt detected by the flow rate sensor, a developed pressure calculating unit calculates pressure Pmus developed by the respiratory muscles during mechanical ventilation as well as during spontaneous breathing from the expression: Pmus=-Paw+Rrs(dV/dt)+Ers ∫(dV/dt)dt. An output unit displays and/or records the obtained Pmus together with waveform signal detected by the pressure sensor along a common time axis. Furthermore, by detecting a tidal volume VT from flow rate, work Wmus is calculated as follows: Wmus=-∫Paw(dV/dt)dt+∫Rrs(dV/dt)² dt+(1/2)Ers(VT)²

Claims

1. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in an air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

developed pressure calculating means for calculating pressure Pmus developed by the respiratory muscles during lung ventilation from the following expression

space="preserve" listing-type="equation">Pmus=-Paw+Rrs(dV/dt)+∫

(dV/dt)dt

where Paw is airway opening pressure detected by said pressure sensor and dV/dt is flow rate detected by said flow rate sensor; and

output means for outputting the obtained Pmus together with the detection signal generated by said pressure sensor along a common time axis.

2. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in an air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

developed pressure calculating means for calculating pressure Pmus developed by the respiratory muscles during lung ventilation from the following expression

space="preserve" listing-type="equation">Pmus=-Paw+Rrs(dV/dt)+∫

(dV/dt)dt

where Paw is airway opening pressure detected by said pressure sensor and dV/dt is flow rate detected by said flow rate sensor;

time difference calculating means for detecting a time point when the obtained Pmus starts to decrease as an inspiration initial point, detecting a time when the level of the detection signal generated by said pressure sensor starts to increase as a air-supplying initial point, and obtaining a time difference between said inspiration initial point and said air-supplying initial point; and

output means for outputting data of said time difference.

3. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in an air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

developed pressure calculating means for calculating pressure Pmus developed by the respiratory muscles during lung ventilation from the following expression

space="preserve" listing-type="equation">Pmus=-Paw-Rrs(dV/dt)-∫

(dV/dt)dt

where Paw is airway opening pressure detected by said pressure sensor and dV/dt is flow rate detected by said flow rate sensor;

pressure-time product calculating means for detecting a time point when the obtained Pmus starts to decrease as an inspiration initial point, detecting a time point when the obtained Pmus starts to increase as an inspiration terminal point, and calculating pressure-time product between said inspiration initial point and said inspiration terminal point from the following expression

space="preserve" listing-type="equation">PTP=∫

Pmus dt;

and

output means for outputting data of said pressure-time product.

4. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

developed pressure calculating means for calculating pressure Pmus developed by the respiratory muscles during lung ventilation from the following expression

space="preserve" listing-type="equation">Pmus=-Paw+Rrs(dV/dt)+Ers∫

(dV/dt)dt

where Paw is airway opening pressure detected by said pressure sensor and dV/dt is flow rate detected by said flow rate sensor; and

expiration initiation detecting means for detecting a time point when the obtained Pmus starts to increase as an expiration initial point and outputting a signal indicating initiation of expiration.

5. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

tidal volume detecting means for detecting a tidal volume by integrating said detection signal generated by said flow rate sensor;

work calculating means for calculating work Wmus performed by the respiratory muscles over an inspiratory period from the following expression

space="preserve" listing-type="equation">Wmus=-Paw(dV/dt)dt+Rrs∫

(dV/dt).sup.2 dt+(1/2)Ers(VT).sup.2

where Paw is airway opening pressure detected by said pressure sensor, dV/dt is flow rate detected by said flow rate sensor, and VT is a tidal volume detected by said tidal volume detecting means; and

output means for outputting the obtained work Wmus.

6. An apparatus for monitoring respiratory muscle activity according to claim 5, wherein said work calculating means calculates a mean value of work Wmus obtained in a plurality of inspiratory phases, and said output mean outputs said mean value.

7. An apparatus for monitoring respiratory muscle activity comprising:

a pressure sensor for detecting air pressure in an air passage connecting a lung ventilator and an airway system of a patient and generating a detection signal in response thereto;

a flow rate sensor for detecting flow rate in said air passage and generating a detection signal in response thereto;

arithmetic constant detecting means for detecting resistance Rrs and elastance Ers of a respiratory system of the patient including the airway and thorax beforehand by using the detection signal generated by said pressure sensor and the detection signal generated by said flow rate sensor while said lung ventilator is supplying air to the patient whose spontaneous breathing is temporarily stopped;

developed pressure calculating means for calculating pressure Pmus developed by the respiratory muscles during lung ventilation from the following expression

space="preserve" listing-type="equation">Pmus=-Paw+Rrs(dV/dt)+Ers∫

(dV/dt)dt

where Paw is airway opening pressure detected by said pressure sensor and dV/dt is flow rate detected by said flow rate sensor; and

output means capable of selectively outputting the generated detection signals of said pressure sensor and flow rate sensor and data calculated by said calculating means.

8. An apparatus for monitoring respiratory muscle activity as defined by claim 7, further comprising:

time difference calculating means for detecting a time point when the obtained Pmus starts to decrease as an inspiration initial pint, detecting a time when the level of detection signal from said pressure sensor starts to increase as a air-supplying initial point, and obtaining a time difference between said inspiration initial point and said air-supplying initial point and wherein the output means outputs data of said time difference.

9. An apparatus for monitoring respiratory muscle activity as defined in claim 7, further comprising:

expiration initiation detecting means for detecting a time point when the obtained Pmus starts to increase as an expiration initial point and wherein the output means outputs a signal indicating initiation of expiration.