Methods and apparatus with improved ventilatory support cycling

1. A ventilator that delivers air at different pressures to a patient during inspiratory and expiratory cycles of breathing, the ventilator comprising: a blower; a controller; and a memory containing instructions configured to operate the controller to control one or more of a motor current or motor speed associated with the blower and cycling between inspiratory and expiratory operation, and wherein the ventilator cycles from inspiratory to expiratory operation as a result of the patient's inspiratory flow passing a threshold flow level and the threshold flow level generally continuously increases for a predetermined amount of time during the inspiratory cycle.

2. A ventilator in accordance with claim 1 wherein the threshold flow level increases linearly during at least a portion of the inspiratory cycle.

3. A ventilator in accordance with claim 2 wherein cycling from inspiratory to expiratory operation is prevented during the initial portion of an inspiratory cycle.

4. A ventilator in accordance with claim 1 wherein the threshold flow level increases from a minimum level to a maximum level, both of which are functions of peak flow.

5. A ventilator in accordance with claim 1 wherein the threshold flow level increases from a minimum level to a maximum level, each of which is a respective percentage of peak flow.

6. A ventilator in accordance with claim 1 wherein the threshold flow level increases from a minimum level to a maximum level, each of which is a respective predefined amount above a zero level.

7. A ventilator in accordance with claim 1 wherein the threshold flow level increases from a minimum level to a maximum level as a function of elapsed inspiratory time.

8. A ventilator in accordance with claim 1 wherein the threshold flow level increases from a minimum level to a maximum level as a function of both elapsed inspiratory time and an expected maximum inspiratory time.

9. A ventilator in accordance with claim 1 wherein the rate at which the threshold flow level increases from a minimum level to a maximum level is adjustable for individual patient needs.

10. A ventilator in accordance with claim 1 wherein the rate at which the threshold flow level increases from a minimum level to a maximum level is determined from previous breaths.

11. A ventilator in accordance with claim 10 wherein the rate at which the threshold flow level increases from a minimum level to a maximum level is based on the average inspiration time of a predetermined number of previous normal breaths.

12. A ventilator in accordance with claim 1 wherein the threshold flow level is positive for at least a portion of the inspiratory cycle.

13. A ventilator in accordance with claim 1 wherein the threshold flow level is a function of the inspiratory peak flow or time.

14. The ventilator of claim 1 wherein the controller is select from the group consisting of a processor, an integrated chip in which the instructions are coded and an integrated chip in which the instructions are loaded as software.

15. The ventilator of claim 1 wherein the threshold flow level generally continuously increases without decreasing for a predetermined amount of time during the inspiratory cycle.

16. A method for operating a ventilator that delivers air at different pressures to a patient during inspiratory and expiratory cycles of breathing, comprising: controlling, using a controller, cycling between inspiratory and expiratory operations; cycling from inspiratory to expiratory operation as a result of the patient's inspiratory flow passing a threshold flow level; and generally continuously increasing the threshold level for a predetermined period of time within an inspiratory cycle.

17. A method in accordance with claim 16 wherein the threshold increases linearly during at least a portion of the inspiratory cycle.

18. A method in accordance with claim 16 wherein cycling from inspiratory to expiratory operation is prevented during the initial portion of an inspiratory cycle.

19. A method in accordance with claim 16 wherein the threshold level increases from a minimum level to a maximum level, both of which are functions of peak flow.

20. A method in accordance with claim 16 wherein the threshold level increases from a minimum level to a maximum level, each of which is a respective percentage of peak flow.

21. A method in accordance with claim 16 wherein the threshold level increases from a minimum level to a maximum level, each of which is a respective predefined amount above a zero level.

22. A method in accordance with claim 16 wherein the threshold level increases from a minimum level to a maximum level as a function of elapsed inspiratory time.

23. A method in accordance with claim 16 wherein the threshold level increases from a minimum level to a maximum level as a function of both elapsed inspiratory time and an expected maximum inspiratory time.

24. A method in accordance with claim 16 wherein the rate at which the threshold level increases from a minimum level to a maximum level is adjustable for individual patient needs.

25. A method in accordance with claim 16 wherein the rate at which the threshold level increases from minimum level to a maximum level is determined from previous breaths.

26. A method in accordance with claim 25 wherein the rate at which the threshold level increases from a minimum level to a maximum level is based on the average inspiration time of a predetermined number of previous normal breaths.

27. A method in accordance with claim 16 wherein the threshold level is positive for at least a portion of the inspiratory cycle.

28. A method in accordance with claim 16 wherein the threshold level is a function of the inspiratory peak flow and time.