0604 CO2 Rebreathing Through a Novel Continuous Positive Airway Pressure Breathing Circuit Improves Central Sleep Apnea and Cheyne-Stokes Respiration

Abstract Introduction CSA/CSR have been associated with increased morbidity and mortality. Current non-invasive therapies can mitigate but seldom eliminate CSA/CSR. CSA/CSR often develops in patients with reduced CO2 ventilatory reserve for which exogenous CO2 administration during sleep can increase ventilatory reserve and stabilize CSA/CSR. Nevertheless, treatment with exogenous CO2 is hampered by bulky delivery systems that require CO2 replenishment. We hypothesized that these limitations could be overcome and CSA/CSR could be treated if rebreathed their own CO2 from a novel positive airway pressure (PAP) breathing circuit. Methods Eight men with predominantly CSA/CSR from heart failure (N=7) and traumatic brain injury (N=1) were recruited (age, 72.3±10.0yr; BMI, 31.2±7.0kg/m2; mean±SD) for an abbreviated polysomnogram (PSG) on low-level CPAP. A novel CPAP breathing circuit was designed to accumulate expired CO2 by limiting CO2 washout through a servo-controlled exhalation valve. Leak flow was toggled every ~10 minutes during non-REM sleep to alternate between CO2 rebreathing and room air. Effects of leak flow on CO2 rebreathing and sleep disordered breathing outcomes (apnea-hypopnea index: AHI_4%; respiratory disturbance index: RDI; %CSR; End-tidal CO2: ETCO2) were examined. Results Baseline sleep parameters showed a median AHI_4% of 37±17.8/hr with central AHI of 15.3±7.1/hr, and CSR% of 44±16.8% of total sleep time (TST). The mean nocturnal SpO2 was 93.6±1.9% with time spent below 90% of 6.1±8.3% and mean nadir of 80.1±4%. TST was 87.2±25min on room air and was 32.4±24.2min on CO2 rebreathing. CO2 rebreathing increased ETCO2 (40.5±2.9 vs. 35.9±1.8mmHg) by reducing leak flow (22.2±2.4 vs. 7.9±0.6LPM), and was associated with reductions in AHI_4% (27.0±14.6 vs. 6.1±7.3/hr) and RDI (38.1±13.4 vs. 11.2±10.0/hr). Conclusion CO2 rebreathing through a novel PAP circuit improved CSA/CSR markedly by limiting leak flow, reversing baseline hypocapnia, normalizing ETCO2 and increasing CO2 ventilatory reserve. Extended trials are required to determine the safety and efficacy of treatment with this servo-controlled low-level PAP CO2 rebreathing circuit. Support (if any) Periodic Breathing LLC and Christina Streett, R.PSG.T.