Effective Continuous Positive Airway Pressure Changes Related to Sleep Stage and Body Position in Obstructive Sleep Apnea during Upward and Downward Titration: An Experimental Study.

Background and Purpose The aim of this study was to determine how the sleep stage and body position influence the effective pressure (Peff) in standard upward titration and experimental downward titration. Methods This study applied successful manual titration of continuous positive airway pressure over 3 hours [including at least 15 min in supine rapid eye movement (REM) sleep] followed by consecutive downward titration for at least 1 hour to 22 patients with moderate-tosevere obstructive sleep apnea. We analyzed baseline polysomnography variables and compared the effective pressures (Peff1(upward) and Peff2(downwa)(rd)) between non-REM and REM sleep and between supine and lateral positions using the paired t-test or Wilcoxon signed-rank test. Results During upward titration, Peff1 increased during REM sleep compared to non-REM sleep [9.5 +/- 2.9 vs. 8.9 +/- 2.7 cm H2O (mean +/- SD), Delta Peff1(Rem-non-REM)=0.6 +/- 1.1 cm H2O; p=0.024]. During downward titration, Peff2 was higher in a supine than a lateral position (7.3 +/- 1.7 vs. 4.8 +/- 1.5 cm H2O, Delta Peff2(supine)(-lateral)=2.5 +/- 1.3 cm H2O; p=0.068). When comparing both upward and downward titration conditions, we found that Peff2 was significantly lower than Peff1 in all sleep stages, especially during REM sleep (Peff1(REM) vs. Peff2(REM)=9.5 +/- 2.9 vs. 7.4 +/- 3.3 cm H2O) with an overall difference of 2.1 +/- 1.7 cm H2O (p<0.001). Peff in supine sleep decreased from 9.4 +/- 3.0 cm H2O (Peff1(supine)) to 7.6 +/- 3.3 cm H2O (Peff2(s)(upine)), with an overall difference of 1.8 +/- 1.6 cm H2O (p<0.001). Conclusions This study has revealed that the collapsibility of the upper airway is influenced by sleep stage and body position. After achieving an initial Peff1, a lower pressure was acceptable to maintain airway patency during the rest of the sleep. The observed pressure decrease may support the use of an automated titration device that integrates real-time positional and sleep-stage factors, and the use of a lower pressure may improve fixed-pressure-related intolerance.