Acute effects of different continuous positive airway pressures (CPAP) on cardiovascular autonomic control in healthy subjects

Abstract

CPAP is associated with cardiovascular and respiratory changes and plays a key role in the management of respiratory failure. Scanty data are available on the effects of CPAP on autonomic control in healthy subjects.The aim of this study was to evaluate the effects of different pressures on cardiorespiratory and autonomic variables in young volunteers.In 11 subjects we recorded ECG, continuous blood pressure (BP), respiration and end tidal CO2 (etCO2) at baseline (B) and during CPAP application using a face mask. Three different CPAP pressures (4,8 and 12 cmH20) were delivered in random order in each session.Spectral analysis of heart rate variability (HRV) was used to assess sympathovagal balance: low frequency (LF) and high frequency (HF) oscillations are markers of sympathetic and parasympathetic modulation respectively. Spontaneous baroreflex sensitivity (BRS) was calculated using the spectral alpha index.CPAP induced a significant decrease in heart rate (HR) and an increase in total power (TP) compared to B. No changes in HR and TP were observed among the different pressures. LF, HF, respiratory frequency and BRS were not affected by CPAP. EtCO2 and BP were unmodified during the experiments.The data suggest that CPAP acutely modifies HR and TP independently by changes in sympathovagal balance and BRS; direct mechanical effects induced by CPAP might explain these preliminary data. ASI Grant