Autonomic modulation of heart rate during obstructive versus central apneas in patients with sleep-disordered breathing

Sleep-disordered breathing is associated with an altered sympathovagal balance determined by the nocturnal cyclic alternating of apneas and hyperventilation. The aim of this study was to determine whether the autonomic modulation of heart rate during obstructive apneas (OA) and central apneas (CA) in patients with sleep-disordered breathing is different. Therefore, by using the time-varying Wigner-Ville transform spectral analysis we described, in 17 patients, the time course of the low-frequency (LF) and the high-frequency (HF) components of the interbeat interval (R-R interval) reflecting, at large, respectively, the sympathetic and the parasym-pathetic modulation, during OA (n = 185) and CA (n = 51) and during the postapneic hyperventilation. In both types of apneas we found cyclic lengthening/shortening in R-R interval, during apneas/postapneic hyperventilation, respectively, with more marked bradycardia during OA (R-R: 1,011 ± 23 versus 893 ± 30 ms2, p < 0.01). In OA the HF oscillations decreased from the apnea to the postapneic hyperventilation (from 1,964 ± 244 to 387 ± 98 ms2, p < 0.0001), whereas the LF oscillations increased (from 2,649 ± 230 to 9,820 ± 716 ms2, p < 0.0001). Conversely, in CA the HF oscillations increased from the apnea to the postapneic hyperventilation (from 452 ± 177 to 1,485 ± 406 ms2, p < 0.0001), whereas the LF component remained unchanged. These results show markedly different autonomic alterations during and after OA versus CA, suggesting a surge in sympathetic modulation after the obstructive episodes.