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Abstract
BACKGROUND Treatment of the sleep apnoea/hypopnoea syndrome with nasal continuous positive airway pressure (CPAP) conventionally requires a titration procedure in a sleep laboratory. The upper airway has a hysteresis phenomenon which accounts for a decrease in the effective positive pressure level once an initial effective pressure setting has been reached. The aim of this study was to quantify the difference in the initial and final effective pressure settings when the titration sleep study takes into account these possible changes in the effective pressure level.
METHODS Eighty five patients completed the study. During a titration sleep study the pressure was increased by 1 cm H2O in a stepwise fashion until obstructive respiratory events disappeared (effective pressure 1, Peff1). The pressure level was then decreased by increments of 1 cm H2O until breathing abnormalities reappeared. At this time pressure was re-increased by increments of 1 cm H2O to normalise breathing (Peff2).
RESULTS The mean (SD) value of Peff1 was 9.5 (2.6) cm H2O. The pressure was then reduced during 0.5 (0.6) hours to reach the minimal pressure (7.0 (2.0) cm H2O). The pressure obtained after a downward titration had to be re-increased in 79 patients, the Peff2 level being significantly lower than Peff1 (8.9 (2.8) cm H2O, p = 0.0002), mean difference 0.6 (1.5) cm H2O (95% confidence interval 0.29 to 0.93).
CONCLUSION Attempts to decrease the positive pressure level during conventional determination of the effective pressure level allow a significant decrease in the pressure setting. This should be taken into account in each patient who requires an in-laboratory manual CPAP titration procedure.
- sleep apnoea/hypopnoea syndrome
- continuous positive airway pressure (CPAP)
- pressure settings