Ventilator pressure optimization method and apparatus

• US 5,937,854 A
• Filed: 01/06/1998
• Issued: 08/17/1999
• Est. Priority Date: 01/06/1998
• Status: Expired due to Term

• Current Assignee: Sensormedics Corporation (Becton Dickinson & Co)
• Original Assignee: Sensormedics Corporation (Becton Dickinson & Co)
• Inventors: Stenzler, Alex
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): ANDERSON, CHARLES WENDELL
• Application Number:
  US09/003,717
• Time in Patent Office: 588 Days
• Field of Search: 128/204.23, 128/204.18, 128/204.21, 128/204.22, 128/204.26, 128/205.24, 128/898, 128/200.24, 600/529-534
• US Class Current: 128/204.23
• 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 2230/40 Respiratory characteristics

Abstract

A method and apparatus for ventilator pressure and optimization administers fixed stepwise pressure changes to the lungs of a patient and measures the lung volume change resulting from each pressure change. Critical opening pressure, critical closing pressure, and overdistention pressure are determined by changes in lung volume corresponding to the fixed stepwise pressure changes.

Claims

1. A method for determining the critical opening pressure of the lungs, comprising the steps of:

(a) applying a known pressure lower than the critical opening pressure to the lungs of a patient through his or her airway;

(b) increasing the pressure applied to the lungs in substantially equal stepwise pressure increments;

(c) measuring the approximate lung volume at each of the stepwise pressure increments;

(d) determining the approximate lung volume increase resulting from the present stepwise pressure increment;

(e) stopping when the lung volume increase resulting from the present stepwise pressure increment differs from the lung volume increase resulting from the previous stepwise pressure increment by more than 20%; and

(f) displaying the final pressure.

2. The method of claim 1, further comprising a step of electronically transmitting the final pressure to a ventilator.

3. A method for determining the critical closing pressure of the lungs, comprising the steps of:

(a) applying a known pressure greater than the critical closing pressure to the lungs of a patient through his or her airway;

(b) decreasing the pressure applied to the lungs in substantially equal stepwise pressure decrements;

(c) measuring the approximate lung volume at each of the stepwise pressure decrements;

(d) determining the approximate lung volume decrease resulting from the present stepwise pressure decrement;

(e) stopping when the lung volume decrease resulting from the present stepwise pressure decrement differs from the lung volume decrease resulting from the previous stepwise pressure decrement by more than 20%; and

(f) displaying the final pressure.

4. The method of claim 3, further comprising a step of electronically transmitting the final pressure to a ventilator.

5. A method for determining the overdistention pressure of the lungs, comprising the steps of:

(a) applying a known pressure lower than the overdistention pressure to the lungs of a patient through his or her airway;

(b) increasing the pressure applied to the lungs in substantially equal stepwise pressure increments;

(c) measuring the approximate lung volume at each of the stepwise pressure increments;

(d) determining the approximate lung volume increase resulting from the present stepwise pressure increment;

(e) stopping when the lung volume increase resulting from the present stepwise pressure increment differs from the lung volume increase resulting from the previous stepwise pressure increment by less than 20%; and

(f) displaying the final pressure.

6. The method of claim 5, further comprising a step of electronically transmitting the final pressure to a ventilator.

7. A method for determining the critical opening pressure of the lungs, comprising the steps of:

(a) applying a known pressure lower than the critical opening pressure to the lungs of a patient;

(b) measuring the approximate lung volume resulting from that pressure;

(c) increasing the pressure to the lungs of a patient by a known increment;

(d) measuring the lung volume resulting from the known increment of pressure;

(e) determining the approximate difference between lung volume measured before the incremental increase in pressure and lung volume after the incremental increase in pressure;

(f) repeating steps (d) and (e);

(g) comparing said differences calculated in steps (e) and (f), stopping when said difference calculated in step (f) differs from the difference calculated in step (e) by more than 20%.

8. A method for determining the critical closing pressure for lung ventilation, comprising the steps of:

(a) applying a known pressure greater than the critical closing pressuer to the lungs of a patient;

(b) measuring the approximate lung volume resulting from that pressure;

(c) decreasing the pressure to the lungs of a patient by a known decrement;

(d) measuring the lung volume resulting from the known decrement of pressure;

(e) determining the approximate difference between lung volume measured before the decremental decrease in pressure and lung volume after the decremental decrease in pressure;

(f) repeating steps (d) and (e);

(g) comparing the differences calculated in steps (e) and (f), stopping when the difference calculated in step (f) differs from the difference calculated in step (e) by more than 20%.

9. A method for determining the overdistention pressure for lung ventilation, comprising the steps of:

(a) applying a known pressure lower than the overdistention pressure to the lungs of a patient;

(b) measuring the approximate lung volume resulting from that pressure;

(c) increasing the pressure to the lungs of a patient by a known increment;

(d) measuring the lung volume resulting from the known increment of pressure;

(e) determining the approximate difference between lung volume measured before the incremental increase in pressure and lung volume after the incremental increase in pressure;

(f) repeating steps (d) and (e);

(g) comparing the differences calculated in steps (e) and (f), stopping when the difference calculated in step (f) differs from the difference calculated in step (e) by less than 20%.

10. A ventilation pressure optimization apparatus, comprising:

(a) a gas supply;

(b) a pressure regulator for varying in substantially equal increments the pressure delivered by the gas supply to a patient;

(c) a lung volume measurement device; and

(d) a computing device connected to said pressure regulator and to said lung volume measuring device;

the computing device controlling the pressure to the patient by incrementally changing the pressure delivered through the pressure regulator to the patient in substantially equal increments, correlating the pressure of each increment with the resulting measurement from the lung volume measuring device, and stopping when the lung volume change between the current pressure increment and the last pressure increment differs from the lung volume change between the last pressure increment and the pressure increment preceding it by a preset amount.

11. The ventilation pressure optimization apparatus of claim 10, wherein said lung volume measurement device is an RIP device.

12. The ventilation pressure optimization apparatus of claim 10, further comprising a display for displaying lung volume measurements and pressure regulator control pressures.

13. The ventilation pressure optimization apparatus of claim 10, wherein said gas supply is a cylinder of atmospheric gas.