Treatment of Positive Airway Pressure Treatment-Associated Respiratory Instability with Enhanced Expiratory Rebreathing Space (EERS)

Abstract

Hypocapnia is an important mediator of sleep-dependent respiratory instability. Positive pressure-associated ventilatory control instability results in poor control of sleep apnea and persistent sleep fragmentation. We tested the adjunctive efficacy of low volumes of dead space (enhanced expiratory rebreathing space [EERS]) using a non-vented mask to minimize sleep hypocapnia. Retrospective chart review. American Academy of Sleep Medicine accredited sleep center and laboratory. Enhanced expiratory rebreathing space 204 patients diagnosed with continuous positive pressure (CPAP)-refractory sleep apnea between 1/1/04 and 7/1/06 were included in this retrospective review. All patients had in-lab attended polysomnography for diagnosis, conventional CPAP titration, and further assessments of added EERS. EERS volume was titrated to control of disease, which was typically obtained when end-tidal (ET) CO₂ during sleep was 1-2 mm Hg above wake eupneic CO₂ levels. The clinic records were reviewed for clinical outcomes. Poor laboratory response to, and initial clinical abandonment of CPAP, was very common (89.2%) in this group of patients, who as a group demonstrated mild resting wake hypocapnia (ETCO₂ = 38.1 ± 3.1 mm Hg). Minimizing sleep hypocapnia by adding 100-150 mL EERS (mean ETCO₂) at optimal therapy 38.6 ± 2.9 mm Hg) markedly improved polysomnographic control of sleep apnea, without inducing tachypnea or tachycardia. Follow-up (range 30-1872 days) showed improved clinical tolerance, compliance, and sustained clinical improvement. Leak and sleep fragmentation modified clinical outcomes. EERS is a potentially useful adjunctive therapy for positive pressure-associated respiratory instability and salvage of some CPAP treatment failures.