Initial Adherence to Autotitrating Positive Airway Pressure Therapy: Influence of Upper Airway Narrowing

OBJECTIVES: There is still debate concerning the reason for the high initial failure rate of positive airway pressure (PAP) treatment. The objective of this study is to investigate the factors of the initial adherence to PAP, with an emphasis on the role of upper airway narrowing. METHODS: The patients were divided into two groups according to the continuation of therapy within the first three months of treatment. The demographic and polysomnographic findings, the minimal nasal cross sectional area (MCA), the degree of palatine tonsilar hypertrophy (PTH) and the modified Mallampati grade of the oropharynx inlet (Orophx) were compared between the study groups. RESULTS: Among 36 patients, 23 continued the auto-adjusting positive airway pressure (APAP) therapy (the adherent group) and 13 discontinued APAP within three months (the non-adherent group). The apnea-hypopnea index (AHI) was significantly higher in the adherent group than in the non-adherent group (P<0.001). The AHI distributions of the two groups are extremely different. Thirteen of the 23 patients in the adherent group had an AHI of more than 60/hr, while none of the patients in the non-adherent group had an AHI of more than 60/hr. In the patients with an AHI from 15 to 60/hr, the MCA at the wide side of the nasal cavity and the sum of the MCAs of both sides were significantly larger in the adherent group than those values in the non-adherent group (P=0.004). The PTH and the Orophx were not significantly different between the two groups. CONCLUSION: AHI is a definite significant factor of adherence to APAP therapy. The dimension of the nasal cavity has an influence on initial APAP adherence in the patients who have a not too high level of AHI.