Methods for controlling mechanical lung ventilation
A method for controlling mechanical lung ventilation is described. The method may include intermittently switching the airway pressure of a patient from a first baseline pressure level to a second baseline pressure and vice-versa such that the patient is able to breathe spontaneously in both first and second baseline pressure levels; detecting an inspiration effort by the patient within a predetermined period of time before a switching event of the intermittently switching the airway pressure; and controlling, responsive to detecting a breathing effort, a flow control valve and an exhalation valve to adjust a length of the first period of time according to a delay time so a patient inspiration-exhalation cycle is completed prior to the switching event.
1. A method for controlling mechanical ventilation, the method comprising:
controlling, by a control unit, a flow control valve and an exhalation valve of a ventilator to intermittently switch an airway pressure, supplied to an airway connector configured to deliver a breathing gas to an airway of a patient, between a substantially constant first baseline pressure level and a substantially constant second baseline pressure level, the first and second baseline pressure levels being higher than an atmospheric pressure, wherein the control unit is configured to switch between first first baseline pressure and the second baseline pressure at the end of a preset first period of time;
detecting, by the control unit, a spontaneous patient breathing effort through the airway connector within a predetermined period of time of a switching event at the end of the first period of time, wherein the predetermined period of time is substantially shorter than the first period of time;
controlling, by the control unit, responsive to detecting the breathing effort, the flow control valve and the exhalation valve to extend a length of the first period of time according to a delay time so a patient inspiration-exhalation cycle is completed prior to the switching event; and
controlling, by the control unit, the flow control valve and the exhalation valve to switch a respective level of the airway pressure to the first or second baseline pressure level after the adjusted first period of time.
2. The method of claim 1 , wherein the breathing effort comprises an expiratory flow, the method further comprising:
measuring the expiratory flow from a beginning of the breathing effort; and
determining the delay time based on the measured expiratory flow.
3. The method of claim 2 , further comprising:
comparing the measured expiratory flow to a preset flow trigger level;
controlling, by the control unit, responsive to the measured expiratory flow being equal or less than the preset flow trigger level, the exhalation valve to initiate the switching event by reducing the substantially constant first baseline pressure.
4. The method of claim 3 , wherein controlling the exhalation valve to initiate the switching event comprises:
switching reducing substantially constant the first baseline pressure to the substantially constant second baseline pressure after the delay time when the measured expired flow is equal or less than the preset flow trigger level.
5. The method of claim 3 , wherein the delay time is set to allow completion of a preset percentage of the expiratory flow.
6. The method of claim 1 , further comprising:
increasing the first period of time by the delay time so that the inspiration-exhalation cycle is completed during the delay time.
7. The method of claim 6 , wherein the breathing effort comprises an inspiratory flow, and wherein the first baseline pressure level is higher than the second baseline pressure level.
8. The method of claim 7 , further comprising:
opening the flow control valve to sustain an inspiration of the patient at the substantially constant first baseline pressure level during the predetermined period of time before the switching event; and
simultaneously keeping the exhalation valve of the ventilator closed to maintain the respective level of the airway pressure at the substantially constant first baseline pressure level.
9. The method of claim 1 , wherein the breathing effort comprises an expiratory flow, the method further comprising:
controlling, by the control unit, an opening of the exhalation valve to allow complete exhalation at the first baseline pressure level; and
opening the exhalation valve after the delay time to release the respective level of the airway pressure from the substantially constant first baseline pressure level to the substantially constant second baseline pressure level.
10. A system for controlling mechanical ventilation, the system comprising:
one or more processors; and
a memory including instructions that, when executed by the one or more processors, cause the one or more processors to:
control a flow control valve and an exhalation valve of a ventilator to intermittently switch an airway pressure, supplied to an airway connector configured to deliver a breathing gas to an airway of a patient, between a substantially constant first baseline pressure level and a substantially constant second baseline pressure level, the first and second baseline pressure levels being higher than an atmospheric pressure, wherein the instructions are configured to switch between the first baseline pressure and the second baseline pressure at the end of a preset first period of time;
detect a spontaneous patient breathing effort through the airway connector within a predetermined period of time of a switching event at the end of the first period of time, wherein the predetermined period of time is substantially shorter than the first period of time;
control responsive to detecting the breathing effort, the flow control valve and the exhalation valve to extend a length of the first period of time according to a delay time so a patient inspiration-exhalation cycle is completed prior to the switching event; and
control the flow control valve and the exhalation valve to switch a respective level of the airway pressure to the first or second baseline pressure level after the adjusted first period of time.
11. The system of claim 10 , wherein the breathing effort comprises an expiratory flow, wherein the instructions, when executed, further cause the one or more processors to:
measure the expiratory flow from a beginning of the breathing effort; and
determine the delay time based on the measured expiratory flow.
12. The system of claim 11 , wherein the instructions, when executed, further cause the one or more processors to:
comparing the measured expiratory flow to a preset flow trigger level;
controlling, responsive to the measured expiratory flow being equal or less than the preset flow trigger level, the exhalation valve to initiate the switching event by reducing the substantially constant first baseline pressure.
13. The system of claim 12 , wherein controlling the exhalation valve to initiate the switching event comprises:
switching reducing the substantially constant first baseline pressure after the delay time when the measured expired flow is equal or less than the preset flow trigger level.
14. The system of claim 12 , wherein the delay time is set to allow completion of a preset percentage of the expiratory flow.
15. The system of claim 10 , further comprising:
increasing the first period of time by the delay time so that the inspiration-exhalation cycle is completed during the delay time.
16. The system of claim 15 , wherein the breathing effort comprises an inspiratory flow, and wherein the first baseline pressure level is higher than the second baseline pressure level, wherein the instructions, when executed, further cause the one or more processors to:
open the flow control valve of the ventilator to sustain an inspiration of the patient at the substantially constant first baseline pressure level during the predetermined period of time before the switching event, the flow; and
keep the exhalation valve of the ventilator closed to maintain the respective level of the airway pressure at the substantially constant first baseline pressure level.
17. The system of claim 15 , wherein the breathing effort comprises an inspiratory flow, and wherein the first baseline pressure level is higher than the second baseline pressure level, and wherein the instructions, when executed, further cause the one or more processors to:
open the flow control valve of the ventilator to sustain an inspiration of the patient at the substantially constant first baseline pressure level during the predetermined period of time before the switching event; and
simultaneously keep the exhalation valve of the ventilator closed to maintain the respective level of the airway pressure at the substantially constant first baseline pressure level.
18. The system of claim 10 , wherein the breathing effort comprises an expiratory flow, and wherein the instructions, when executed, further cause the one or more processors to:
control an opening of the exhalation valve to allow complete exhalation at the first baseline pressure level; and
open the exhalation valve after the delay time to release the respective level of the airway pressure from the substantially constant first baseline pressure level to the substantially constant second baseline pressure level.
19. A non-transitory machine-readable medium comprising instructions stored therein, which when executed by a machine, cause the machine to perform operations comprising:
controlling, by a control unit, a flow control valve and an exhalation valve of a ventilator to intermittently switch an airway pressure, supplied to an airway connector configured to deliver a breathing gas to an airway of a patient, between a substantially constant first baseline pressure level and a substantially constant second baseline pressure level, the first and second baseline pressure levels being higher than an atmospheric pressure, wherein the control unit is configured to switch between first baseline pressure and the second baseline pressure at the end of a preset first period of time;
detecting, by the control unit, a spontaneous patient breathing effort through the airway connector within a predetermined period of time of a switching event at the end of the first period of time, wherein the predetermined period of time is substantially shorter than the first period of time;
controlling, by the control unit, responsive to detecting the breathing effort, the flow control valve and the exhalation valve to extend a length of the first period of time according to a delay time so a patient inspiration-exhalation cycle is completed prior to the switching event; and
controlling, by the control unit, the flow control valve and the exhalation valve to switch a respective level of the airway pressure to the first or second baseline pressure level after the adjusted first period of time.
20. The non-transitory machine-readable medium of claim 19 , wherein the breathing effort comprises an expiratory flow, wherein the operations further comprise:
measuring the expiratory flow;
determining the delay time based on the measured expiratory flow; and
adjusting the first period of time by the delay time so that the inspiration-exhalation cycle is completed during the delay time, and the respective level of the airway pressure is switched from the first baseline pressure to the second baseline pressure after the delay time.