REQUIRED LEVELS OF NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE DURING TREATMENT OF OBSTRUCTIVE SLEEP-APNEA

The improvement in the severity of obstructive sleep-related breathing disorders during nasal continuous positive airway pressure (NCPAP) th erapy can account for the decrease in the required NCPAP level with ti me. The aim of this study was to prospectively quantify the changes in the required NCPAP level over time of use in sleep apnoea-hypopnoea s yndrome (SAHS). Forty sleep apnoea-hypopnoea patients were evaluated b efore and during the time course of NCPAP therapy. The effective NCPAP level was defined as the positive pressure level that abolished apnoe ic and hypopnoeic events and snoring in all sleep stages and sleep pos itions. This pressure level was determined within 2 weeks after baseli ne diagnostic sleep study. Sleep studies with NCPAP and NCPAP titratio n were performed after 2 (n=40), 8 (n=40), and 20 (n=24) months of NCP AP therapy. The initial effective NCPAP level was 9.6+/-0.4 cmH(2)O. I t progressively decreased to 8.8+/-0.4, 7.9+/-0.4 and 7.7+/-0.5 after 2, 8 and 20 months, respectively; the difference being significant bet ween the first three NCPAP nights. There was a poor relationship betwe en the changes in the effective NCPAP and changes in weight recorded a t the different visits. There was a weak negative relationship between the changes in NCPAP and the previous NCPAP level. In 13 patients, th e apnoea-hypopnoea index (AHI) remained >10 n.h(-1) at the first NCPAP trial because the effective NCPAP level was not tolerated. Despite a suboptimal NCPAP level, their sleep architecture improved, and they al l reported a subjective improvement in diurnal hypersomnolence. After 2 months of NCPAP therapy, the AHI was <10 n.h(-1) in 11 of these subo ptimally treated patients. We conclude that the required NCPAP level p rogressively decreases with use. The changes in body weight may play a minor role in the change in the effective NCPAP level.