Study of the upper airway anatomy using magnetic resonance imaging in Indian obese patients with obstructive sleep apnea – A pilot study

Background

Obstructive sleep apnea (OSA) is very common in obese patients. However, why some obese patients have severe OSA while others do not is unclear. Research is limited regarding which structures contribute to upper airway narrowing, especially in Asian patients where bony restrictions is thought to be important.

Methods

Nineteen consecutive patients with BMI ≥35 kg/m², and newly diagnosed with OSA based on overnight polysomnography were studied using non-contrast magnetic resonance imaging (MRI) of the upper airway during wakefulness.

Results

Patients were divided into two groups, one with severe OSA comprising 11 patients and one without severe OSA having 8 patients. The retro-palatal airway was narrowest in both groups. Patients with severe OSA had a significantly narrower retroglossal airway (0.99 ± 0.48 cm² vs 2.61 ± 2.02 cm², p = 0.02), primarily due to a narrower anteroposterior diameter at this level (p = 0.03). The tongue volume (p = 0.91), lateral pharyngeal wall volume (p = 0.26), tongue length (p = 0.93), soft palate length (p = 0.13), and dynamic change of upper airway with inspiration (p = 0.31) were not significantly different between the two groups.

Conclusions

While the retro-palatal airway is equally narrow in both groups of patients, patients with severe OSA also have a significantly narrower retro-glossal airway. This finding could represent either a generalized reduction in airway area in whole of the oropharynx or multiple-level obstruction; probably aggravating upper airway collapse during sleep, predisposing some Asian obese patients to develop severe OSA.