Treatment of positive airway pressure treatment-associated respiratory instability with enhanced expiratory rebreathing space (EERS)

J Clin Sleep Med. 2010 Dec 15;6(6):529-38.


Study objectives: 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.

Design: Retrospective chart review.

Setting: American Academy of Sleep Medicine accredited sleep center and laboratory.

Intervention: Enhanced expiratory rebreathing space

Measurements and results: 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.

Conclusions: EERS is a potentially useful adjunctive therapy for positive pressure-associated respiratory instability and salvage of some CPAP treatment failures.

Keywords: Respiratory chemoreflex; dead space; end-tidal CO2; hypocapnia; non-vented mask; positive airway pressure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Blood Gas Analysis
  • Cohort Studies
  • Continuous Positive Airway Pressure / adverse effects*
  • Continuous Positive Airway Pressure / methods
  • Female
  • Humans
  • Hypocapnia / etiology*
  • Hypocapnia / physiopathology
  • Hypocapnia / therapy*
  • Logistic Models
  • Male
  • Masks
  • Middle Aged
  • Oxygen Inhalation Therapy / instrumentation
  • Oxygen Inhalation Therapy / methods*
  • Polysomnography / methods
  • Respiratory Dead Space*
  • Retrospective Studies
  • Severity of Illness Index
  • Sleep Apnea, Obstructive / diagnosis
  • Sleep Apnea, Obstructive / therapy*
  • Treatment Outcome