Determining suitable ventilator settings for patients with alveolar hypoventilation during sleep

• US 7,089,937 B2
• Filed: 12/07/2004
• Issued: 08/15/2006
• Est. Priority Date: 03/07/2000
• Status: Expired due to Term

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Berthon-Jones, Michael, Malouf, Gordon, Bassin, David, Bateman, Peter
• Primary Examiner(s): MITCHELL, TEENA KAY
• Application Number:
  US11/005,770
• Publication Number:
  US 20050133032A1
• Time in Patent Office: 616 Days
• Field of Search: 128/200.24, 128/204.18, 128/204.21, 128/204.23, 128/207.14, 128/207.15, 128/207.18, 600/300, 600/301, 600/323, 600/484, 600/529, 600/533, 600/538
• US Class Current: 128/204.23
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• 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 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0858 Pressure sampling ports
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase

Abstract

A method and apparatus for determining suitable settings for a servo-ventilator to be used during sleep. Respiratory characteristics of a patient are measured during an awake learning period. With these measured characteristics, a target ventilation setting may be calculated by alternative methods. The calculated setting may then be used for enforcing a minimum ventilation during a treatment period where ventilatory support is provided with a servo-controlled ventilator.

Claims

1. A method for determining at least one setting of a ventilator to be used during sleep comprising the steps of:

measuring at least one respiratory characteristic of a patient during a learning period while the patient is awake; and

determining at least one setting value from said at least one respiratory characteristic to be used for the operation of said ventilator during a subsequent treatment period of sleep.

2. The method of claim 1 wherein said at least one respiratory characteristic is a measure of ventilation.

3. The method of claim 2 wherein at least one setting value is a target ventilation.

4. The method of claim 3 wherein said target minute ventilation is a function of said measure of ventilation.

5. The method of claim 4 wherein said function is a fixed proportion.

6. The method of claim 5 wherein said fixed proportion is about 90%.

7. The method of claim 2 wherein another said respiratory characteristics is arterial hemoglobin oxygen saturation.

8. The method of claim 7 wherein at least one setting value is calculated from the relationship between said oxygen saturation and said measure of ventilation.

9. The method of claim 2 wherein at least one setting value is derived through a fuzzy expert system with input variables including a target ventilation derived from said measure of ventilation and patient estimation information.

10. The method of claim 9 further comprising the step of analyzing patient estimation information to determine an estimated target ventilation, wherein said setting value is a calculated weighted average of said estimated target ventilation and a second target ventilation derived from said measure of ventilation.

11. The method of claim 3 wherein said step of measuring at least one respiratory characteristic includes deriving measures of spontaneous ventilation and measures of arterial oxygen saturation.

12. The method of claim 11 wherein said step of determining a setting value includes an analysis of a graph of said measures of spontaneous ventilation and measures of arterial oxygen saturation.

13. The method of claim 12 wherein said graph includes a fitted curve derived from said measures of spontaneous ventilation and measures of arterial oxygen saturation using least squares nonlinear regression.

14. The method of claim 13 wherein said curve is an exponential function.

15. The method of claim 13 wherein said measures of spontaneous ventilation are delayed and low-pass filtered to associate changes in said arterial oxygen saturation with changes in said measures of spontaneous ventilation.

16. The method of claim 1 wherein said at least one respiratory characteristic is a measure of respiration rate.

17. The method of claim 16 wherein at least one setting value is a target respiration rate.

18. The method of claim 17 wherein said measure of respiration rate is an average respiration rate.

19. The method of claim 1 wherein said at least one respiratory characteristic is a measure of arterial partial pressure of carbon dioxide.

20. The method of claim 1 wherein at least one setting value is a target ventilation which is a product of a current target ventilation and the measure of arterial partial pressure of carbon dioxide divided by a desired arterial partial pressure of carbon dioxide.