Upper Airway Collapsibility and OSA: A Novel Method in Detecting Pharyngeal Wall Floppiness

Abstract

Objectives:

Upper airway collapse is the major reason of obstructive sleep apnea (OSA). However, the site and mechanism of the obstruction remains unclear. To measure the pharyngeal wall floppiness under different pressures, a novel method and technique is introduced in the present study.

Methods:

Forty-seven normal subjects (male: 32; mean age, 37.9 years) and 49 OSA patients (male: 6; mean age, 41.45 years) were recruited in this prospective clinical study. The pharyngeal cavity volumes were measured by means of acoustic reflection under positive (10 cmH₂O) and negative (–10 cmH₂O) pressures. The pharyngeal wall floppiness was calculated from the difference of pharyngeal cavity volumes under positive and negative pressures divided by the sum of the volumes under different pressures.

Results:

The pharyngeal wall floppiness was 0.19 ± 0.11 in normal subjects and 0.24 ± 0.07 in OSA group with a significant difference (P < .01). There was moderate positive correlation between pharyngeal wall floppiness and age or body mass index (BMI) in normal subjects. In OSA patients, the pharyngeal wall floppiness had a weak negative correlation to age, whereas it had moderate positive correlation to sleep apnea severity (apnea-hypopnea index), BMI or neck circumference, respectively.

Conclusions:

The OSA population had greater pharyngeal wall floppiness. The age dependent of pharyngeal wall floppiness in normal subjects implied that aging might play important roles in the development of OSA. The measurement of pharyngeal wall floppiness could be a useful and valuable parameter in diagnosis of OSA and predicting the adherence in continuous positive airway pressure (CPAP) treatment.