System and method for detecting ventilatory instability
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 system, comprising:
a processing device configured to:
calculate an output value of breathes per minute for a data segment based on signals of an airflow channel, a chest channel, and/or an abdomen channel and/or combinations thereof;
calculate 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 a measure of the magnitude of the corresponding signal;
determine 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 identify a reduction in airflow event if the reduction in airflow is above the minimum reduction level;
determine 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; and
provide an indication of ventilatory instability if the reduction in airflow event is identified and qualified.
2. The system of claim 1 , comprising a filter capable of filtering the airflow channel, the chest channel, and/or the abdomen channel.
3. The system of claim 2 , comprising a filter capable of band-pass filtering and low-pass filtering the airflow channel, the chest channel, and the abdomen channel, while passing the pulse oximetry channel.
4. The system of claim 1 , comprising a monitor capable of displaying the indication of ventilatory instability.
5. The system of claim 1 , wherein the processing device is configured to determine whether the indication of ventilatory instability corresponds to central sleep apnea or obstructive sleep apnea based on signals of the chest channel and abdomen channel being in a phase or out of phase.
6. The system of claim 1 , comprising an integral polysomnograph system capable of providing the signals of the airflow channel, the chest channel, and the abdomen channel.
7. The system of claim 1 , comprising a pulse oximetry sensor; an airflow sensor, a chest sensor, and an abdomen sensor.
8. A system, comprising:
a polysomnograph system capable of supplying signals of an airflow channel, a chest channel, an abdomen channel, and a pulse oximetry channel;
an event detection system including a processing device configured to:
calculate 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 breathes per minute and a measure of the magnitude of the corresponding signal;
identify 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; and
determine 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; and
a pulse oximetry pattern recognition system capable of identifying ventilatory instability based at least in part upon a series of blood oxygen saturation values; and
a system calibration component capable of comparing results from the event detection system and the pulse oximetry pattern recognition system to facilitate adjustment of the pulse oximetry pattern recognition system.
9. The system of claim 8 , wherein the processing device of the event detection system is configured to calculate the value of breathes 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.
10. The system of claim 9 , wherein the processing device of the event detection system is configured to calculate the value of breathes 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.
11. The system of claim 9 , comprising a display, wherein the event detection system is configured to provide an indication ofventilatory instability on the display if the reduction in airflow event is identified and qualified.
12. The system of claim 8 , wherein the processing device of the event detection system is configured to convert the signals of the airflow channel, the chest channel, and/or the abdomen channel to a frequency domain, and wherein the event detection system is configured 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.
13. The system of claim 12 , wherein the processing device of the event detection system is configured to calculate the value of breathes per minute for a data segment based on determining a highest frequency of respective averages of the plurality of frequency spectrums.
14. The system of claim 8 wherein the system calibration component is capable of adjusting features of the pulse oximetry pattern recognition system to achieve a desired correspondence between respective results of the pulse oximetry pattern recognition system and the event detection system.