Medical ventilator with autonomous control of oxygenation
View Patent ↗A portable critical care medical ventilator with autonomous control of oxygenation is provided. The system and method provide for significantly reducing the O 2 required to maintain an adequate O 2 concentration and as a result delivery of O 2 to the body's tissues and does not require the clinician to enter initial values.
1. A method for delivering oxygen to a patient with a mechanical ventilator, the method comprising:
(a) supplying fractionally inspired oxygen (FlO 2 ) to a patient based on a target oxygen saturation (SpO 2 ), wherein the target SpO 2 is set a lower limit of clinical acceptability of SpO 2 for the patient to conserve oxygen;
(b) monitoring SpO 2 returned from the patient;
(c) determining an error between the monitored SpO 2 and the target SpO 2 and while the error is greater than a predetermined error iteratively performing,
(d) determining a gain factor such that increases to FlO 2 are greater than decreases for a magnitude of the determined error;
(e) determining a correction factor by multiplying the determined gain factor by the magnitude of the error;
(f) applying the correction factor to the supplied FlO 2 ; and further comprising
waiting a first predetermined time period before iteratively performing steps (c)-(f).
2. The method as in claim 1 , wherein the first predetermined time period is about 40 seconds.
3. The method as in claim 1 , wherein the gain factor is determined such that increases to FlO 2 are three times as great as decreases for the magnitude of the determined error.
4. The method as in claim 3 , wherein if the correction factor is greater than a predetermined correction factor threshold, set the correction factor to the predetermined correction factor threshold.
5. The method as in claim 4 , wherein the predetermined threshold is about 20 percent.
6. The method as in claim 4 , further comprising, wherein if the supplied FlO 2 is adjusted more than a predetermined alert threshold with a second predetermined time period, issuing an alert to an operator of the mechanical ventilator.
7. The method as in claim 6 , wherein the predetermined alert threshold is about 10 percent.
8. The method as in claim 6 , wherein the predetermined alert threshold is about 10 percent and the second predetermined time period is about 10 minutes.
9. The method as in claim 3 , further comprising:
determining if the monitored SpO 2 is below a predetermined safety threshold, wherein if the monitored SpO 2 is below the predetermined safety threshold for a predetermined safety time period, adjusting the FlO 2 to 1.0.
10. The method as in claim 9 , wherein the predetermined safety threshold is about 88 percent.
11. The method as in claim 10 , wherein the predetermined safety time period is about 20 seconds.
12. A system for delivering oxygen to a patient comprising:
a ventilator for supplying fractionally inspired oxygen (FlO 2 ) to a patient based on a target oxygen saturation (SpO 2 ), wherein the target SpO 2 is set at the lower limit of clinical acceptability of SpO 2 for the patient to conserve oxygen; and
an O 2 concentrator coupled to the ventilator for supplying oxygen to the ventilator,
wherein the ventilator monitors SpO 2 returned from the patient, determines an error between the monitored SpO 2 and the target SpO 2 and while the error is greater than a predetermined error, the ventilator iteratively determines a gain factor such that increases to FlO 2 are greater than decreases for a magnitude of the determined error, determines a correction factor by multiplying the determined gain factor by the magnitude of the error and applies the correction factor to the supplied FlO 2 , and wherein the ventilator waits a first predetermined time period before iteratively applying the corrector factor to the supplied FlO 2 .
13. The system as in claim 12 , further comprising a patient ventilation circuit including a supply tube for supplying FlO 2 to the patient from the ventilator and a bidirectional connection for sending sensed or measured parameters of the patient to the ventilator.
14. The system as in claim 12 , wherein the ventilator controls an output of the O 2 concentrator to maintain the corrected supplied FlO 2 .
15. The system as in claim 12 , wherein the ventilator mixes an output of the O 2 concentrator with ambient air to maintain the corrected supplied FlO 2 .
16. The system as in claim 12 , wherein the first predetermined time period is about 40 seconds.
17. The system as in claim 12 , wherein the gain factor is determined such that increases to FlO 2 are three times as great as decreases for the magnitude of the determined error.
18. The system as in claim 17 , wherein if the correction factor is greater than a predetermined correction factor threshold, the ventilator sets the correction factor to the predetermined correction factor threshold.
19. The system as in claim 18 , wherein the predetermined threshold is about 20 percent.
20. The system as in claim 18 , wherein if the supplied FlO 2 is adjusted more than a predetermined alert threshold with a second predetermined time period, the ventilator issues an alert to an operator of the ventilator.
21. The system as in claim 20 , wherein the predetermined alert threshold is about 10 percent.
22. The system as in claim 20 , wherein the predetermined alert threshold is about 10 percent and the second predetermined time period is about 10 minutes.
23. The system as in claim 17 , wherein the ventilator determines if the monitored SpO 2 is below a predetermined safety threshold, and if the monitored SpO 2 is below the predetermined safety threshold for a predetermined safety time period, adjusts the FlO 2 to 1.0.
24. The system as in claim 23 , wherein the predetermined safety threshold is about 88 percent.
25. The system as in claim 24 , wherein the predetermined safety time period is about 20 seconds.