Acute effects of autoadjusting and fixed continuous positive airway pressure treatments on cardiorespiratory coupling in obese patients with obstructive sleep apnea

• CPAP and APAP have similar efficacy in reducing apneas in patients with OSA.
• However, CPAP and APAP have different effects on cardiovascular risk factors.
• APAP is not as effective as CPAP in reducing sympathetic modulation during sleep.
• APAP is associated with a lower cardio-respiratory coupling in OSA patients.
• These two factors may explain the different effects on cardiovascular risk factors.

BackgroundTreatment with positive airway pressure devices improved signs and symptoms of obstructive sleep apnea syndrome (OSA); however, auto-adjusting positive pressure (APAP) device was not as effective as continuous positive airway pressure (CPAP) in reducing arterial blood pressure and insulin resistance. The role played by autonomic cardiac regulation remains to be clarified.We aimed to test the effects of CPAP and APAP on autonomic regulation and cardiorespiratory coupling during sleep.MethodsWe retrospectively analyzed full-night polysomnographic studies. 19 patients newly diagnosed with severe OSA (AHI > 30) and 7 obese subjects without OSA (CON) were enrolled. Each OSA subject was assigned to CPAP or APAP treatment and underwent a sleep study after 1 week of treatment. Spectral and cross-spectral analyses of heart rate variability (HRV) and respiration were performed to assess autonomic profile and coherence (K2) between respiration and HF oscillation during sleep in CPAP, APAP and CON groups.ResultsIn CPAP and CON, LFnu and LF/HF, markers of sympathetic modulation, decreased from N2 to N3 and increased during REM sleep (p < 0.001), while in APAP group, sympathetic modulation was significantly higher compared with those of CPAP and CON during all sleep stages. K2 values were lower in APAP compared with those in CPAP and CON.ConclusionAPAP treatment was characterized by a greater sympathetic activation and it was associated with a lower cardio-respiratory coupling compared with CPAP. This might account for the different effects on cardiovascular risk factors induced by the two treatments.