Low-concentration carbon dioxide is an effective adjunct to positive airway pressure in the treatment of refractory mixed central and obstructive sleep- disordered breathing

To assess the efficacy of added carbon dioxide as adjunctive therapy to positive airway pressure-refractory mixed obstructive and central sleep-disordered breathing, using a prototype device-the positive airway pressure gas modulator. Open-label evaluation of low concentrations of carbon dioxide added to a positive airway pressure circuit. Physician-attended polysomnographic titration in a free-standing sleep laboratory with end-tidal and transcutaneous carbon-dioxide monitoring. Six adult men (age 54 +/- 5.7 years) with severe poorly controlled mixed sleep-disordered breathing in the absence of renal or heart failure. Flow-independent addition of incremental concentrations of carbon dioxide during sleep. The respiratory disturbance index before treatment was 66 +/- 14.5 events per hour of sleep, with a nocturnal desaturation low of 84.6% +/- 10.1%. Residual respiratory disturbance index on best treatment was 43 +/- 9 events per hour of sleep. There was an immediate (