System And Method For Detecting Ventilatory Instability

• US 20100063366A1
• Filed: 09/10/2008
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Pinto, Yu-Jung, Ochs, James, Batchelder, Keith
• Granted Patent: US 8,398,555 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence

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.

Claims

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. A system, comprising:

a processing device capable of calculating 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 at least in part by determining a baseline value for each of the airflow channel, the chest channel, and/or 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 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.

14. The system of claim 13, comprising a filter capable of filtering the airflow channel, the chest channel, and/or the abdomen channel.

15. The system of claim 14, 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.

16. The system of claim 13, comprising a monitor capable of displaying the indication of ventilatory instability.

17. The system of claim 13, wherein the processing device is capable of determining whether the indication of ventilatory instability corresponds to central sleep apnea or obstructive sleep apnea based on signals of the chest channel and/or abdomen channel.

18. The system of claim 13, comprising an integral polysomnograph system capable of providing the signals of the airflow channel, the chest channel, and the abdomen channel.

19. The system of claim 13, comprising a pulse oximetry sensor;

an airflow sensor, a chest sensor, and an abdomen sensor.

20. A system, comprising:

a polysomnograph system capable of supplying signals of an airflow channel, a chest channel, an abdomen channel, and/or a pulse oximetry channel, and/or combinations thereof;

a pulse oximetry pattern recognition system capable of identifying ventilatory instability based at least in part upon a series of blood oxygen saturation values;

an event detection system capable of identifying ventilatory instability events based at least in part upon data from the airflow channel, the chest channel, the abdomen channel, and/or the pulse oximetry channel, and/or combinations thereof; 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.