System and method for detecting ventilatory instability

Abstract

Embodiments described herein may include systems and methods for detecting events that may be associated with sleep apnea. Some embodiments are directed to a system and/or method for automated detection of reduction in airflow events using polysomnograph signals, wherein the reduction in airflow events may relate to sleep apnea. The PSG signals may be limited to four signals, including data from an airflow channel, a blood oxygen saturation channel, a chest movement channel, and an abdomen movement channel. Using information from these channels, some embodiments may automatically identify reduction in airflow events.

1 . A method for automated detection of ventilatory instability, comprising:
 calculating an output value of breathes per minute for a data segment based at least in part upon signals of an airflow channel, a chest channel, and/or an abdomen channel and/or combinations thereof;   determining a baseline value for each of the airflow channel, the chest channel, and the abdomen channel based at least in part upon the output value of breathes per minute and/or a measure of the magnitude of the corresponding signals;   determining whether a reduction in airflow above a minimum reduction level relative to the baseline value for the airflow channel has been maintained for a period of time, and identifying a reduction in airflow event if the reduction in airflow is above the minimum reduction level; and   providing an indication of ventilatory instability if the reduction in airflow event is identified and meets a set of criteria.   
     
     
         2 . The method of  claim 1 , further comprising converting the signals of the airflow channel, the chest channel, and/or the abdomen channel to a frequency domain to determine a plurality of frequency spectrums, wherein the plurality of frequency spectrums comprises an airflow channel frequency spectrum, a chest channel frequency spectrum, and/or an abdomen channel frequency spectrum. 
     
     
         3 . The method of  claim 2 , wherein calculating the output value of breathes per minute comprises determining a highest frequency of an average of the plurality of frequency spectrums. 
     
     
         4 . The method of  claim 1 , wherein calculating the output value of breathes per minute comprises averaging an estimate of breathes per minute for each of a plurality of data segments based at least in part upon the signals of the airflow channel, the chest channel, and/or the abdomen channel and/or combinations thereof. 
     
     
         5 . The method of  claim 1 , further comprising determining whether a criterion is met that requires a pulse oximetry channel to change by a defined percentage within a window of time generally relative to the reduction in airflow event. 
     
     
         6 . The method of  claim 5 , further comprising determining whether the pulse oximetry channel has changed by at least 3% relative to its baseline within 30 second of the reduction in airflow event to determine if the criterion is met. 
     
     
         7 . The method of  claim 1 , further comprising determining whether a criterion is met that requires a reduction in the chest channel and/or the abdomen channel relative to the respective baseline values for a defined portion of the reduction in airflow event. 
     
     
         8 . The method of  claim 7 , further comprising determining whether there was at least a 40% reduction relative to the respective baseline values in the chest channel and/or the abdomen channel for at least half of the reduction in airflow event to determine if the criterion is met. 
     
     
         9 . The method of  claim 1 , further comprising discarding invalid data corresponding to the airflow channel, the pulse oximetry channel, the chest channel, and the abdomen channel based on whether certain indicators are present in an associated data segment. 
     
     
         10 . The method of  claim 1 , wherein the data segment comprises a 10 minute data segment. 
     
     
         11 . The method of  claim 1 , wherein the minimum reduction level relative to the baseline value for the airflow channel comprises a 40% reduction relative to the baseline value for the airflow channel. 
     
     
         12 . The method of  claim 1 , comprising determining whether the reduction in airflow above the minimum reduction level relative to the baseline value for the airflow channel has been maintained for 10 seconds or more. 
     
     
         13 - 25 . (canceled) 
     
     
         26 . The method  claim 1 , further comprising determining if the reduction in airflow event is qualified by determining whether a specified amount of change has occurred in the chest channel or the abdomen channel during a window of time including the reduction in airflow event. 
     
     
         27 . The method of  claim 1 , further comprising filtering at least one of the airflow channel, the chest channel, and the abdomen channel. 
     
     
         28 . A method, comprising:
 supplying signals of an airflow channel, a chest channel, an abdomen channel, and a pulse oximetry channel;   calculating a baseline value for each of the airflow channel, the chest channel, and the abdomen channel based at least in part upon a value of breaths per minute and a measure of the magnitude of the corresponding signals;   identifying a reduction in airflow event when a reduction in airflow above a minimum reduction level relative to the baseline value for the airflow channel has been maintained for a threshold period of time;   determining if the reduction in airflow event is qualified by determining whether a specified amount of change has occurred in the chest channel, the abdomen channel, or the pulse oximetry channel during a window of time including the reduction in airflow event;   identifying ventilatory instability based at least in part upon a series of blood oxygen saturation values; and   comparing results from the event detection system and the pulse oximetry pattern recognition system to facilitate adjustment of the pulse oximetry pattern recognition system.   
     
     
         29 . The method of  claim 28 , further comprising calculating the value of breaths per minute for a data segment based on signals of the airflow channel, the chest channel, and/or the abdomen channel and/or combinations thereof. 
     
     
         30 . The method of  claim 28 , further comprising calculating the value of breaths per minute by averaging an estimate of breathes per minute for each of a plurality of data segments based at least in part upon the signals of the airflow channel, the chest channel, and/or the abdomen channel and/or combinations thereof. 
     
     
         31 . The method of  claim 28 , further comprising providing an indication of ventilatory instability on a display if the reduction in airflow event is identified and qualified. 
     
     
         32 . The method of  claim 28 , further comprising:
 converting the signals of the airflow channel, the chest channel, and/or the abdomen channel to a frequency domain; and   determining a plurality of frequency spectrums, wherein the plurality of frequency spectrums comprises an airflow channel frequency spectrum, a chest channel frequency spectrum, and/or an abdomen channel frequency spectrum.   
     
     
         33 . The method of  claim 32 , further comprising calculating an output value of breaths per minute for a data segment based on determining a highest frequency of an average of the plurality of frequency spectrums.