DETERMINING SUITABLE VENTILATOR SETTINGS FOR PATIENTS WITH ALVEOLAR HYPOVENTILATION DURING SLEEP
A method and apparatus for determining suitable settings for a servo-ventilator to be used during sleep. Respiratory characteristics of a patient are measured during an awake learning period. With these measured characteristics, a target ventilation setting may be calculated by alternative methods. The calculated setting may then be used for enforcing a minimum ventilation during a treatment period where ventilatory support is provided with a servo-controlled ventilator.
1 - 49 . (canceled)
50 . A method for determining at least one setting of a ventilator to be used during sleep comprising the steps of:
measuring at least one respiratory characteristic of a patient during a learning period; and
determining at least one setting value from said at least one respiratory characteristic to be used for the operation of said ventilator during a subsequent treatment period of sleep.
51 . The method of claim 50 wherein said at least one respiratory characteristic is a measure of ventilation.
52 . The method of claim 51 wherein at least one setting value is a target ventilation.
53 . The method of claim 52 wherein said target minute ventilation is a function of said measure of ventilation.
54 . The method of claim 53 wherein said function is a fixed proportion.
55 . The method of claim 54 wherein said fixed proportion is about 90 %.
56 . The method of claim 51 wherein another said respiratory characteristics is arterial hemoglobin oxygen saturation.
57 . The method of claim 56 wherein at least one setting value is calculated from the relationship between said oxygen saturation and said measure of ventilation.
58 . The method of claim 51 wherein at least one setting value is derived through a fuzzy expert system with input variables including a target ventilation derived from said measure of ventilation and patient estimation information.
59 . The method of claim 58 further comprising the step of analyzing patient estimation information to determine an estimated target ventilation, wherein said setting value is a calculated weighted average of said estimated target ventilation and a second target ventilation derived from said measure of ventilation.
60 . The method of claim 52 wherein said step of measuring at least one respiratory characteristic includes deriving measures of spontaneous ventilation and measures of arterial oxygen saturation.
61 . The method of claim 60 wherein said step of determining a setting value includes an analysis of a graph of said measures of spontaneous ventilation and measures of arterial oxygen saturation.
62 . The method of claim 61 wherein said graph includes a fitted curve derived from said measures of spontaneous ventilation and measures of arterial oxygen saturation using least squares nonlinear regression.
63 . The method of claim 62 wherein said curve is an exponential function.
64 . The method of claim 62 wherein said measures of spontaneous ventilation are delayed and low-pass filtered to associate changes in said arterial oxygen saturation with changes in said measures of spontaneous ventilation.
65 . The method of claim 50 wherein said at least one respiratory characteristic is a measure of respiration rate.
66 . The method of claim 65 wherein at least one setting value is a target respiration rate.
67 . The method of claim 66 wherein said measure of respiration rate is an average respiration rate.
68 . The method of claim 50 wherein said at least one respiratory characteristic is a measure of arterial partial pressure of carbon dioxide.
69 . The method of claim 50 wherein at least one setting value is a target ventilation which is a product of a current target ventilation and the measure of arterial partial pressure of carbon dioxide divided by a desired arterial partial pressure of carbon dioxide.