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A portable critical care medical ventilator with autonomous control of oxygenation is provided. The system and method provide for significantly reducing the O2 required to maintain an adequate O2 concentration and as a result delivery of O2 to the body's tissues and does not require the clinician to

A portable critical care medical ventilator with autonomous control of oxygenation is provided. The system and method provide for significantly reducing the O2 required to maintain an adequate O2 concentration and as a result delivery of O2 to the body's tissues and does not require the clinician to enter initial values.

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1. A method for delivering oxygen to a patient with a mechanical ventilator, the method comprising: (a) supplying fractionally inspired oxygen (FlO2) to a patient based on a target oxygen saturation (SpO2), wherein the target SpO2 is set a lower limit of clinical acceptability of SpO2 for the patien

1. A method for delivering oxygen to a patient with a mechanical ventilator, the method comprising: (a) supplying fractionally inspired oxygen (FlO2) to a patient based on a target oxygen saturation (SpO2), wherein the target SpO2 is set a lower limit of clinical acceptability of SpO2 for the patient to conserve oxygen;(b) monitoring SpO2 returned from the patient;(c) determining an error between the monitored SpO2 and the target SpO2 and while the error is greater than a predetermined error iteratively performing,(d) determining a gain factor such that increases to FlO2 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 FlO2; and further comprisingwaiting 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 FlO2 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 FlO2 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 SpO2 is below a predetermined safety threshold, wherein if the monitored SpO2 is below the predetermined safety threshold for a predetermined safety time period, adjusting the FlO2 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 (FlO2) to a patient based on a target oxygen saturation (SpO2), wherein the target SpO2 is set at the lower limit of clinical acceptability of SpO2 for the patient to conserve oxygen; andan O2 concentrator coupled to the ventilator for supplying oxygen to the ventilator,wherein the ventilator monitors SpO2 returned from the patient, determines an error between the monitored SpO2 and the target SpO2 and while the error is greater than a predetermined error, the ventilator iteratively determines a gain factor such that increases to FlO2 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 FlO2, and wherein the ventilator waits a first predetermined time period before iteratively applying the corrector factor to the supplied FlO2. 13. The system as in claim 12, further comprising a patient ventilation circuit including a supply tube for supplying FlO2 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 O2 concentrator to maintain the corrected supplied FlO2. 15. The system as in claim 12, wherein the ventilator mixes an output of the O2 concentrator with ambient air to maintain the corrected supplied FlO2. 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 FlO2 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 FlO2 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 SpO2 is below a predetermined safety threshold, and if the monitored SpO2 is below the predetermined safety threshold for a predetermined safety time period, adjusts the FlO2 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.