Decision making for position-dependent obstructive sleep apnea syndrome on the basis of patient information and physical examinations of the upper airway, acquired on an outpatient basis.

Conclusions: Patients with body mass index (BMI) < 25 kg/m and obstructive sleep apnea syndrome (OSAS) are highly suspicious for position-dependent OSAS. Diagnosis of position-dependent/position-independent OSAS can be difficult in patients satisfying both 'BMI >25 kg/m' and 'any of tongue enlargement (TE), palatine tonsil hypertrophy (PTH) and obstruction by Muller's maneuver (OMM)'. Polysomnography is warranted in such patients.

Objectives: The objective was to retrospectively elucidate criteria for differentiating position-dependent OSAS on the basis of patient information and physical examinations of the upper airway obtainable in clinics.

Methods: The 643 patients were categorized as positional patients (PPs) or non-positional patients (NPPs). The patient background factors examined were sex, age, BMI, and hypertension. TE, PTH, pharyngeal tonsil hypertrophy, and OMM were evaluated. Cross-validation was performed using even-numbered registrations as the training set group (Group A) and odd-numbered registrations as the test case group (Group B).

Results: In Group A, patients with BMI <25 kg/m were clearly more frequent among PP than among NPP. In Group A with BMI ≥25 kg/m, significant differences were found for TE, PTH and OMM. Significant differences were found between 0 and 1/2/3 for number of factors. Results generated from Group A were validated in Group B.