Methods and apparatus for varying the back-up rate for a ventilator

• US 8,051,852 B2
• Filed: 10/05/2009
• Issued: 11/08/2011
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Bassin, David John
• Primary Examiner(s): Douglas; Steven
• Application Number:
  US12/573,382
• Publication Number:
  US 20100018531A1
• Time in Patent Office: 764 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26
• US Class Current: 128/204.18
• 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 16/0066 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 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/04 Tracheal tubes catheters in general A61M25/00
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0875 Connecting tubes
• CPC Class Codes: A61M 16/20 Valves specially adapted to medical respiratory devices
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/40 Respiratory characteristics

Abstract

A ventilator device delivers ventilatory support to a patient in a back up timed mode when patient respiration is not detected or a spontaneous mode when patient respiration is detected. The timing threshold governing the back-up mode is chosen to deviate from normal expected respiration time for the patient to promote patient initiated ventilation in the spontaneous mode but permit back-up ventilation in the event of apnea. Automated adjustments to the timing threshold during the timed mode are made from the less vigilant timing threshold to a more vigilant threshold at or near a timing of normal expected breathing of the patient. Such adjustments may be made from a minimum to a maximum vigilance timing settings or incrementally there between as a function of time in the timed mode which is preferably the number of delivered machine breaths.

Claims

1. Apparatus for providing back-up support ventilation for a patient comprising

a blower for delivering pressure support ventilation to said patient during a breathing cycle of the patient;

a respiratory detector for detecting breathing and cessation of breathing; and

means for controlling delivery of pressure support upon detecting breathing within a threshold time interval following a preceding detection of cessation of breathing;

said threshold time interval deviating from a normal expected respiration timing for the patient in a manner that promotes patient initiated synchronization of the pressure support ventilation but permits back-up ventilation if breathing is not detected within the threshold time interval.

2. Apparatus in accordance with claim 1 wherein said controlling means adjusts the threshold time interval upon detecting breathing to normalize the threshold time interval toward an expected normal respiration timing for the patient.

3. Apparatus in accordance with claim 2 wherein the threshold time interval is adjusted stepwise as a function of a number of cycles of ventilation delivered in response to upon detecting breathing within a threshold time interval.

4. Apparatus in accordance with claim 1 wherein said controlling means adjusts the threshold time interval upon detecting cessation of breathing to normalize the threshold time interval away from an expected normal respiration timing for the patient.

5. Apparatus in accordance with claim 4 wherein the threshold time interval is adjusted stepwise as a function of a number of cycles of ventilation delivered in response to detecting cessation of breathing.

11. Apparatus in accordance with claim 2 wherein adjustments to the threshold time interval are a function of the adequacy of the patient'"'"'s ventilation.

12. Apparatus in accordance with claim 11 wherein the function of the adequacy of the patient'"'"'s ventilation includes a ratio of a measured ventilation and a target ventilation.

13. Apparatus in accordance with claim 12 wherein the measured ventilation is a minute ventilation and the function is piecewise linear on a ratio of a measured minute ventilation to a target minute ventilation.

14. Apparatus in accordance with claim 2 wherein the threshold time interval is periodically returned to a value that deviates from a normal expected respiration upon detecting breathing.

6. Apparatus in accordance with 5 wherein in response to detecting a single cessation of breathing the threshold time interval is returned to an original threshold time interval that deviates from a normal expected respiration timing for the patient.

7. Apparatus in accordance with claim 6 wherein said controlling means adjusts the threshold time interval upon detecting breathing to normalize the threshold time interval toward an expected normal respiration timing for the patient.

8. Apparatus in accordance with claim 7 wherein adjustments to the threshold time interval are restricted by a maximum respiratory rate that is about 50 percent faster than a rate that deviates from a normal expected respiration rate.

9. Apparatus in accordance with claim 7 wherein adjustments to the threshold time interval are restricted by a minimum respiratory rate that is calculated as a fraction of a normal respiratory rate determined during a learning period.

10. Apparatus in accordance with claim 9 wherein the fraction is about 67%.