ADJUSTMENT OF TARGET VENTILATION IN A SERVOVENTILATOR

• US 20090013999A1
• Filed: 09/02/2005
• Published: 01/15/2009
• Est. Priority Date: 09/03/2004
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Bassin, David John
• Granted Patent: US 9,205,210 B2
• Time in Patent Office: Days
• US Class Current: 128/204.180
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• 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 16/022 Control means therefor
• 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 2016/003 with a flowmeter
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards

Abstract

A servoventilator control slowly changes the target ventilation over a period of time, according to a preprogrammed schedule adapted to be set by the physician. Preferably, the target ventilation stays constant at an initial target ventilation for an initial hold time, and then increases at a constant rate until it reaches a final target ventilation, whereupon it stays constant thereafter. If the pressure support level is too high, possibly indicating glottic or upper airway closure, the rate of increase of target ventilation may be lowered or the final target ventilation not reached.

Claims

1. A method for determining suitable ventilator settings in patients with alveolar hypoventilation during sleep, and for delivery of those settings comprising the steps of:

measuring the ventilation of a patient during at least a latter portion of a learning period while the patient is awake;

determining a target ventilation from said measure of ventilation; and

slowly changing the target ventilation over a period of time, according to a programmed schedule implemented in a ventilator controller.

2. The method for determining suitable ventilator settings of claim 1, wherein the step of changing the target ventilation over a period of time, increases the ventilation from a first level to a second level, then stays at the second level.

3. The method for determining suitable ventilator settings of claim 2, wherein the target ventilation stays constant at a first level, for a predetermined initial hold time, and then increases at a constant rate until it reaches a second level, whereupon it stays constant thereafter.

4. The method for determining suitable ventilator settings of claim 1, wherein a rate of increase of the initial target ventilation is lowered if the pressure support level is too high to extend the time to reach a final target ventilation.

5. A method of non-invasive ventilation of a patient comprising the steps of:

(i) ventilating a patient at a first level of ventilation for a first duration exceeding several breathing cycles; and

(ii) at the expiration of the first duration, changing the level of ventilation from the first level to a second level over a second duration.

6. The method of non-invasive ventilation of claim 5, wherein the second duration is several weeks.

7. The method of non-invasive ventilation of claim 5, wherein the change in level of ventilation is an increase.

8. The method of non-invasive ventilation of claim 5, wherein the change in level of ventilation is automatically controlled.

9. A method for determining suitable ventilator settings in patients with alveolar hypoventilation during sleep, and for delivery of those settings comprising:

(i) using a ventilator to learn the patient'"'"'s awake ventilation;

(ii) setting an initial target ventilation to a proportion of said awake ventilation;

(iii) setting a final target ventilation to the initial target ventilation multiplied by the ratio of a desired PCO₂ value to a current PCO₂ value;

(iv) setting a target ventilation ramp time to a value, depending on the clinical urgency of lowering the PCO₂ and the amount by which it is desired to lower the PCO₂.

10. A servoventilator apparatus comprising an electric motor having an impeller under the control of a controller circuit, that allows a flow of pressurized air to pass along an air delivery conduit to a patient interface;

a pressure sense tube between the patient interface and a pressure sensor that allows the controller to sense pressure in the patient interface;

a controller that determines the flow rate of air along the air delivery conduit via a flow sensor;

means to allow setting appropriate target ventilations and ramp times,

wherein the controller provides ventilation of a patient at a first level of ventilation for a first duration exceeding several breathing cycles; and

at the expiration of the first duration, changes the level of ventilation from the first level to a second level over a second duration.

11. A bilevel ventilation apparatus having a pressure support level and a controller programmed to increase the pressure support level at a selected rate after an initial hold time until it reaches a final pressure support level.