Analytical amplitude/phase markers for neurological sleep apnea events

Utilizing non-linear band-pass filtering, dominant wave forms representing apnea events are found to classify unstable ventilation systems.

Data sets were gathered online from the 'St Vincent's University Hospital, Dublin', which consists of PSG recordings from subjects required to be older than 18 years of age, with no known cardiac disease or autonomic dysfunction, and not taking medication known to interfere with heart rate. Twenty-five subjects were selected for this study. An equation that represents the dominance of the amplitude component on apnea waveforms is described as the Amplitude Waveform AW(t) formula.

Sensitivity values for CSA events are 82.14%, where specificity/precision within this group is 71.43% (P < 0.0001). The upper and lower bound thresholds that delineate the apnea events have a fitting across all apnea cohorts where R² = 75%.

Within the theta bandwidth, the amplitude component of the EEG signal has shown to be the dominant indicator of apnea locations, and the addition of the phase component enables precise identification of apnea events.

Most apnea events occur in clusters that demonstrate a buildup of CO₂ in the bloodstream. The time intervals where breathing cessation leads into an apneic event can be detected in the cortex. Apneic events can be traced as an increasing cortical waveform until breathing is re-established.