Comparison of two in-laboratory titration methods to determine eVective pressure levels in patients with obstructive sleep apnoea

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 eVective positive pressure level once an initial eVective pressure setting has been reached. The aim of this study was to quantify the diVerence in the initial and final eVective pressure settings when the titration sleep study takes into account these possible changes in the eVective 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 (eVective pressure 1, PeV1). 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 (PeV2). Results—The mean (SD) value of PeV1 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 PeV2 level being significantly lower than PeV1 (8.9 (2.8) cm H2O, p = 0.0002), mean diVerence 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 eVective 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. (Thorax 2000;55:741–745)