Determining suitable ventilator settings for patients with alveolar hypoventilation during sleep

Abstract

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.