Simultaneous recording of ultrasound and polysomnography during natural sleep in patients with obstructive sleep apnea: a pilot study

Tongue base deformation may play a critical role in the phenomenon of obstructive sleep apnea, but polysomnography provides limited information regarding the effect of tongue motion during natural sleep. We reported on preliminary results of combining a novel ultrasound system and polysomnography for simultaneous recordings during natural sleep in volunteers and patients with obstructive sleep apnea. All participants underwent time-synchronized polysomnography and submental transcutaneous ultrasound examinations. The wearable ultrasound device detected the air-mucosal interface of the tongue surface and automatically determined the maximum tongue base thickness in real time. All participants reported no sensation of heat, no sign of skin allergy, and an average of mild disturbance after the ultrasound recordings. In the individual patient with obstructive sleep apnea, we demonstrated a significant difference (P < 0.001) between the ultrasonic tongue base thickness measured during eupnea and that measured during snoring, hypopnea and apnea. The ultrasonic tongue base thickness increased and remained before the occurrence of obstructive apnea. On average, increased tongue base thicknesses of 2.5 (4.1%), 6.0 (9.8%) and 7.7 mm (12.5%) are associated with snoring, hypopnea and apnea, respectively. Our present data demonstrate that simultaneous examination of ultrasonic tongue base thickness and polysomnography is feasible for prolonged recording during natural sleep. The proposed method also enables the detection of significant differences in ultrasonic tongue base thickness between eupnea and obstructive respiratory events evaluated using polysomnography. This novel technique can be used to generate hypotheses for subsequent investigations of the underlying mechanisms and individualized combined therapy for obstructive sleep apnea.

This study has been registered at the Chinese Clinical Trial Registry website with the registration number of ChiCTR-DDT-13003313. The date of registration was 13 July 2013.