Process for determining the mechanical properties of the respiratory system of a respirated patient and device for carrying out the process

• US 5,876,352 A
• Filed: 11/20/1997
• Issued: 03/02/1999
• Est. Priority Date: 05/17/1997
• Status: Expired due to Fees

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Weismann, Dieter
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): ASTORINO, MICHAEL C
• Application Number:
  US08/975,334
• Time in Patent Office: 467 Days
• Field of Search: 600/529, 600/532, 600/533, 600/538, 600/539, 600/541, 600/542, 600/540
• US Class Current: 600/529
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2230/46 Resistance or compliance of the lungs

Abstract

A process and device for determining mechanical properties of a respiratory system of a patient connected to a respirator, wherein a short-term occlusion of the patient'"'"'s airways is performed during an inspiration phase and/or an expiration phase. Initiating of the occlusion is at different points in time within the breathing cycle and during a plurality of breaths. The respiratory flow and the inhaled or exhaled volume of the patient is determined at the beginning of this occlusion. The airway pressure is also measured during this occlusion. The change occurring over time in the airway pressure during a measurement time falling within the occlusion time is determined. Also determined is the course over time of the change occurring over time of the muscle pressure of the patient from the measured values. The course over time of the muscle pressure is calculated by integrating this course over time.

Claims

1. Process for determining mechanical properties of a respiratory system of a patient connected to a respiration device, the process comprising the steps of:

performing a plurality of occlusions of an airway of the patient during a plurality of breaths, each of said occlusions occurring in a separate one of said plurality of breaths, each of said occlusions also occurring at a different point in a respective one of said plurality of breaths;

determining respiratory flow and volume of the patient at a beginning of said each occlusion;

measuring airway pressure during said each occlusion;

determining a change occurring over time in said airway pressure during a measurement time within said each occlusion;

determining a change occurring over time in muscle pressure of the patient from said change in airway pressure.

2. A process in accordance with claim 1, wherein:

performing said occlusion of said airway during one of an inspiration phase and an expiration phase, a duration of said occlusion is short-term relative to one of said plurality of breaths;

said volume is one of inhaled and exhaled tidal volume;

said change in muscle pressure is determined for a plurality of points in a breathing cycle from measured and determined values;

muscle pressure is determined by integrating said change in muscle pressure, said integrating is performed over said breathing cycle to calculate a plurality of muscle pressures during said breathing cycle.

3. Process in accordance with claim 1, wherein:

muscle pressure is determined by integrating said change in muscle pressure, said integrating is performed over a breathing cycle to calculate a plurality of muscle pressures during said breathing cycle;

said muscle pressures are added to said measured airway pressures to form a total pressure;

said volume is one of inhaled and exhaled tidal volume;

a compliance of lungs of the patient is calculated from a derivation of values for said total pressure according to said tidal volume.

4. Process in accordance with claim 1, wherein:

a reference breath is determined for the patient;

said occlusion is triggered only when a particular breath is within a predetermined deviation from said reference breath.

5. Process in accordance with claim 3, wherein:

a reference breath is determined for the patient;

said occlusion is triggered only when a particular breath is within a predetermined deviation from said reference breath.

6. Process in accordance with claim 1, wherein:

a reference breath is determined for the patient;

evaluation of measured results is performed only when a particular breath is within a predetermined deviation from said reference breath.

7. Process in accordance with claim 1, wherein:

said volume is corrected by an effect due to one of a compliance and a resistance of the ventilator breathing system.

8. Device for determining mechanical properties of a respiratory system of a patient connected to a respiration device, the device comprising:

a control unit for bringing about a plurality of short-term occlusions of the patient'"'"'s airways during one of an inspiration phase and/or an expiration phase of a plurality of breaths, each occlusion being in a separate one of said plurality of breaths, said control unit having means to initiate said occlusion at different points in time within each of said plurality of breaths;

a flow sensor for measuring respiratory flows, and one of inhaled or exhaled total volumes;

a pressure sensor for measuring airway pressures of the patient during said each of said plurality of breaths;

an evaluating unit for detecting a change occurring over time in said airway pressures during a measurement time of said each occlusion, said evaluating unit also determining a change occurring over time in muscle pressures of the patient from said respiratory flows, said total volumes and changes in said airway pressures.

9. A device in accordance with claim 8, wherein:

said evaluating unit calculates muscle pressures by integrating said change in muscle pressures;

said change in muscle pressures is determined for a plurality of points in a breathing cycle;

said integrating is performed over said breathing cycle to calculate a plurality of muscle pressures during said breathing cycle.

10. Device in accordance with claim 8, wherein:

said evaluating unit calculates muscle pressures by integrating said change in muscle pressures;

said integrating of said evaluating unit is performed over a breathing cycle to calculate a plurality of muscle pressures during said breathing cycle, said evaluating unit has means to add said muscle pressures to said airway pressures to form total pressures and to calculate a compliance of the patient'"'"'s lungs from said total pressures according to said tidal volumes.

11. Device in accordance with claim 8, wherein:

said control unit has means for storing a representation of preceding breaths of the patient and to initiate said each occlusion only if a particular breath is substantially identical to said preceding breaths.

12. Device in accordance with claim 8, wherein:

said evaluating unit has means for storing a representation of preceding breaths of the patient and to evaluate measured values only if a particular breath is substantially identical to said preceding breaths.

13. Device in accordance with claim 8, wherein:

said evaluating unit has means to correct said volumes by an effect due to one of compliance and resistance of the ventilator breathing system.

14. Device in accordance with claim 8, wherein:

said flow and pressure sensors are arranged at a patient connection of the respirator.

15. Device in accordance with claim 8, wherein:

said sensors are part of the respirator.

16. Device for determining mechanical properties of a respiratory system of a patient connected to a respiration device, the device comprising:

a control unit for bringing about a plurality of short-term occlusions of the patient'"'"'s airways during one of an inspiration phase and/or an expiration phase of a plurality of breaths, each occlusion being in a separate one of said plurality of breaths, said control unit having means to initiate said occlusion at different points in time within each of said plurality of breaths;

a flow sensor for measuring respiratory flows, and one of inhaled or exhaled total volumes;

a pressure sensor for measuring airway pressures of the patient during said each of said plurality of breaths;

an evaluating unit for detecting a change occurring over time in said airway pressures during a measurement time of said each occlusion, said evaluating unit also determining a change occurring over time in muscle pressures of the patient from said respiratory flows, said total volumes and changes in said airway pressures, said evaluating unit also calculating muscle pressures by integrating said change in muscle pressures.

17. A device in accordance with claim 16, wherein:

said change in muscle pressures is determined for a plurality of points in a breathing cycle;

said integrating is performed over said breathing cycle to calculate a plurality of muscle pressures during said breathing cycle.

18. Device in accordance with claim 16, wherein:

said integrating of said evaluating unit is performed over a breathing cycle to calculate a plurality of muscle pressures during said breathing cycle, said evaluating unit has means to add said muscle pressures to said airway pressures to form total pressures and to calculate a compliance of the patient'"'"'s lungs from said total pressures according to said tidal volumes.