METHODS AND APPARATUS FOR THE SYSTEMIC CONTROL OF VENTILATORY SUPPORT IN THE PRESENCE OF RESPIRATORY INSUFFICIENCY

• US 20150000667A1
• Filed: 09/19/2014
• Published: 01/01/2015
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Bassin, David John
• Granted Patent: US 10,449,312 B2
• Time in Patent Office: Days
• US Class Current: 128/204.23
• CPC Class Codes: A61B 5/087 Measuring breath flow
• 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 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0875 Connecting tubes
• CPC Class Codes: A61M 2016/0033 electrical
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/40 Respiratory characteristics

Abstract

A method and apparatus for providing ventilatory assistance to a spontaneously breathing patient an error signal (56) is computed that is the difference between a function of respiratory airflow (54) over a period of time and a target value (52). Using a servo loop, air is delivered to the patient at a pressure that is a function of the error signal, the phase of the current breathing cycle, and a loop gain that varies depending on the magnitude of the error signal. The loop gain increases with the magnitude of the error signal, and the gain is greater for error signals below a ventilation target than for error signals above the ventilation target value. The target value (52) is an alveolar ventilation that takes into account the patient'"'"'s physiologic dead space.

Claims

1. A method for providing ventilatory assistance to a spontaneously breathing patient comprising continuously repeating the steps of:

determining respiratory airflow,

computing a measure of the difference between a function of respiratory airflow over a period of time and a target value,

determining the phase of the current breathing cycle, and

delivering air to the patient at a pressure that is a function of the product of (a) said difference measure, (b) the amplitude at the determined phase of the current breathing cycle of an amplitude-versus-phase template that is appropriate for a normal breathing cycle, and (c) a gain factor that varies depending on the magnitude of said difference measure.

2. A method for providing ventilator assistance in accordance with claim 1 wherein said gain factor increases with the magnitude of said difference measure.

3. A method for providing ventilator assistance in accordance with claim 2 wherein for equal difference measures below and above said target value, the gain factor is greater for difference measures below said target value.

4. A method for providing ventilator assistance in accordance with claim 3 wherein said target value is an alveolar ventilation that takes into account the patient'"'"'s physiologic dead space.

5. A method for providing ventilator assistance in accordance with claim 1 wherein the phase of the current breathing cycle is determined by relating respiratory airflow and its rate of change to different phases of a normal breathing cycle.

6. A method for providing ventilator assistance in accordance with claim 5 wherein said relating step includes application of a set of fuzzy logic rules.

7. A method for providing ventilator assistance in accordance with claim 1 wherein said difference measure is a clipped integral of the respiratory airflow minus said target value, and for either polarity of said difference measure the pressure of the delivered air is changed in a respective direction that tends to reduce said difference measure.

8. A method for providing ventilator assistance in accordance with claim 1 wherein said target value is an alveolar ventilation that takes into account the patient'"'"'s physiologic dead space.

9. Apparatus for providing ventilator assistance to a spontaneously breathing patient comprising:

processing means for computing a measure of the difference between a function of respiratory airflow over a period of time and a target value, and for determining the phase of the current breathy cycle, and

a control mechanism for causing a blower to deliver air to the patient at a pressure that is a function of said difference measure, the amplitude at the determined phase of the current breathing cycle of an amplitude-versus-phase template that is appropriate for a normal breathing cycle, and a gain factor that varies depending on the magnitude of said difference measure.

10. Apparatus for providing ventilator assistance in accordance with claim 9 wherein said gain factor increases with the magnitude of said difference measure.

11. Apparatus for providing ventilator assistance in accordance with claim 10 wherein for equal difference measures below and above said target value, the gain factor is greater for difference measures below said target value.

12. Apparatus for providing ventilator assistance in accordance with claim 11 wherein said target value is an alveolar ventilation that takes into account the patient'"'"'s physiologic dead space.

13. Apparatus for providing ventilator assistance in accordance with claim 9 wherein said processing means determines the phase of the current breathing cycle by relating respiratory airflow and its rate of change to different phases of a normal breathing cycle.

14. Apparatus for providing ventilator assistance in accordance with claim 13 wherein processing means utilizes a set of fuzzy logic rules.

15. Apparatus for providing ventilator assistance in accordance with claim 9 wherein said difference measure is a clipped integral of the respiratory airflow minus said target value, and for either polarity of said difference measure sid control mechanism causes the pressure of the delivered air to be changed into a respective direction that tends to reduce said difference measure.

16. Apparatus for providing ventilator assistance in accordance with claim 9 wherein said target value is an alveolar ventilation that takes into account the patient'"'"'s physiologic dead space.