Non-invasive method for optimizing the respiration of atelectatic lungs

• US 6,612,995 B2
• Filed: 07/26/2001
• Issued: 09/02/2003
• Est. Priority Date: 01/29/1999
• Status: Expired

• Current Assignee: Maquet Critical Care AB (Getinge AB)
• Original Assignee: Siemens-Elema AB (Siemens AG)
• Inventors: Leonhardt, Steffen, Bohm, Stephan
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/917,232
• Publication Number:
  US 20020110849A1
• Time in Patent Office: 768 Days
• Field of Search: 600/529, 600/532, 600/538, 128/204.21, 128/204.23, 128/200.24
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)

Abstract

The invention relates to a method and an apparatus to identify alveolar opening and collapse of a lung. To automatically generate the settings of ventilator parameters in a simple and gentle way, the hemoglobin oxygen saturation and/or the endtidal CO₂ concentration and/or the CO₂ output are-measured and processed to detect alveolar opening and closing. From the knowledge of the corresponding airway pressures, a central processing unit may generate the settings of ventilation parameters such that gas exchange is maximal while the mechanical stress of the lung tissue is minimal.

Claims

1. Method for determining the alveolar opening or closing of a lung ventilated by an artificial ventilator, comprising the steps of:

measuring the hemoglobin oxygen saturation (SO₂), and

changing the airway pressure (P_aw) wherein from the observation of the resulting course of the measured hemoglobin oxygen saturation (SO₂) the airway pressure level at which alveolar opening or closing occurs is determined.

2. Method according to claim 1, wherein the inspiratory oxygen fraction (fiO₂) at the artificial ventilator is adjusted such that the measured hemoglobin oxygen saturation (SO₂) is approximately equal to a given reference value, and wherein the airway pressure is changed and from the resulting course of the adjusted inspiratory oxygen fraction (fiO₂) an airway pressure level is determined, which corresponds to the alveolar opening or the alveolar closing of the lung.

3. Method according to claim 2, wherein the airway pressure is increased continuously and wherein an alveolar opening of the lung is detected, if the gradient of the resulting course of the adjusted inspiratory oxygen fraction (fiO₂) reaches a negative minimum.

4. Method according to claim 2, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the gradient of the resulting course of the adjusted inspiratory oxygen fraction (fiO₂) reaches a positive maximum.

5. Method according to claim 3, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the gradient of the resulting course of the adjusted inspiratory oxygen fraction (fiO₂) reaches a positive maximum.

6. Method for determining the alveolar opening or closing of a lung ventilated by an artificial ventilator, comprising the steps of:

measuring the endtidal CO₂ concentration in the expired gas (etCO₂), and

changing the airway pressure (p_aw), wherein from the observation of the resulting course of the measured endtidal CO₂ concentration the airway pressure level at which alveolar opening or closing occurs is determined.

7. Method according to claim 6, wherein the airway pressure is increased continuously and wherein an alveolar opening of the lung is detected, if the positive gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

8. Method according to claim 7, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the negative gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

9. Method according to claim 6, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the negative gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

10. Method for determining the alveolar opening or closing of a lung ventilated by an artificial ventilator, comprising the steps of:

measuring the CO₂ output (CO₂ volume exhaled per unit time), and

changing the airway pressure (p_aw), wherein from the observation of the resulting course of the measured CO₂ output the airway pressure level at which alveolar opening or closing occurs is determined.

11. Method according to claim 10, wherein the airway pressure is increased continuously and wherein an alveolar opening of the lung is detected, if the positive gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

12. Method according to claim 11, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the negative gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

13. Method according to claim 10, wherein the airway pressure is decreased continuously and wherein an alveolar closing of the lung is detected, if the negative gradient of the resulting course of the measured endtidal CO₂ concentration and/or the CO₂ output reaches a maximal change.

14. Apparatus for determining the alveolar opening or closing of a lung, comprising:

an artificial ventilator for ventilating a lung,

a saturation sensor for measuring the hemoglobin oxygen saturation (SO₂), and

a data processor which determines during a change of the airway pressure (p_aw) from the resulting course of the measured hemoglobin oxygen saturation (SO₂) the airway pressure level at which alveolar opening or closing occurs.

15. Apparatus according to claim 14, comprising a feedback control loop which controls the inspiratory oxygen fraction (fiO₂) delivered to the patient such that the measured hemoglobin oxygen saturation (SO₂) is approximately equal to a given reference value, and wherein the data processor determines the airway pressure at which alveolar opening occurs from the course of the required inspiratory oxygen fraction (fiO₂) during a change of the airway pressure.

16. Apparatus for determining the alveolar opening or closing of a lung, comprising:

an artificial ventilator for ventilating a lung,

a sensor to measure endtidal CO₂ concentration (etCO₂), and

a data processor which determines during a change of the airway pressure (p_aw) from the resulting course of the measured endtidal CO₂ concentration the airway pressure level at which alveolar opening or closing occurs.

17. Apparatus for determining the alveolar opening or closing of a lung, comprising:

an artificial ventilator for ventilating a lung,

a sensor to measure CO₂ output (CO₂ volume exhaled per unit time), and

a data processor which determines during a change of the airway pressure (p_aw) from the resulting course of the measured CO₂ output the airway pressure level at which alveolar opening or closing occurs.