Sleep apnea: tracking effects of a first session of CPAP therapy by means of Granger causality

Abstract Connectivity between physiological networks is an issue of particular importance for understanding the complex interaction brain-heart. In this paper, this interaction was analyzed in patients diagnosed with obstructive sleep apnea (OSA) and compared with a group of healthy subjects. Polysomnography signals were characterized employing Granger causality computation to measure the directed connectivity between five brain wave and three heart activity spectral subbands. Polysomnography recordings from 10 control subjects and 28 obstructive sleep apnea patients were employed. The latter were recorded before and after going through a first session of continuous positive air pressure (CPAP) therapy in a split-night study. Results showed that CPAP therapy allowed for recovery of connections mainly in subsystems involving the theta subband. Other differences between control and OSA patient groups were established in connections that involve lower frequency range of heart activity. This detailed information will aid in the initial diagnosis for OSA, and determine the role of cardiac activity in sleep dynamics based on the use of three subbands analysis.