Purpose: Cheyne-Stokes respiration (CSR) in heart failure (HF) patients is characterized by chronic hyperventilation and low-normal to depressed pCO2 levels. Adaptive servoventilation therapy (ASV) was introduced to stabilize respiration in these patients. This study aimed to investigate acute effects of ASV on pCO2 and oxygen saturation (SaO2) in HF patients with CSR and healthy volunteers, respectively. Methods: HF patients (EF ≤ 50%, NYHA ≥ II) with CSR (apnea-hypopnea-index, AHI ≥ 15/h) and healthy volunteers were ventilated using a new ASV device (PaceWace™, ResMed) for 1h. PCO2 and SaO2 were assessed transcutaneously, while vigilance was analyzed using EEG recordings. Results were obtained during ASV ventilation while awake and asleep and compared to those being obtained 30 minutes before and after ventilation. Results: A total of 20 HF patients (19 male, 79±12 years, EF 36±8%, AHI 36±14, mean expiratory airway pressure [EPAP]: 8.9±0.5 cmH2O; mean inspiratory airway pressure [IPAP] support: 17.1±0.5 cmH2O) and 15 healthy volunteers (13 male, 25±4 years, EPAP 8.4±1.8, mean IPAP 14.5±2.4) were included. Figure 1 shows the significant and favorable increase in pCO2 to mid-normal values in ASV treated HF patients while being asleep. Similar results were obtained for healthy volunteers. #p<0.01 for asleep vs. before ASV, after ASV or awake. ![Figure][1] Conclusion: ASV therapy leads to a favorable increase in pCO2 in sleeping subjects, whereas they face hyperventilation being awake. This increase in pCO2 is very favorable in patients with CSA since they are thereby farer away from apneic threshold. [1]: pending:yes