Detection of airway occlusion in simulated obstructive sleep apnea/hypopnea using ultrasound: An in vitro study

Obstructive sleep apnea/hypopnea Syndrome (OSAHS) is the most common form of Sleep Disordered Breathing (SDB) and it is estimated to affect approximately 6% of US adult population. Various methods have been proposed for the development of inexpensive screening methods to detect SDB to reduce the need for costly nocturnal polysomnography (NPSG). By using the existing air in the airway as an ultrasonic contrast agent, we propose a method to examine the narrowing or occlusion of the airway associated with OSAHS events. We describe here an in vitro study that approximates the anatomical and acoustic characteristics of the airway and neck. In this experiment, we simulate the fully open airway as well as apnea and hypopnea events. These in vitro studies results show significant differences in the ultrasonic signals acquired from the open airway model versus those from the model depicting apnea and hypopnea events. Therefore, the findings provide a foundation for development of an ultrasound system to detect SDB in vivo.

I. Introduction

OBSTRUCTIVE- Sleep Apnea/Hypopnea Syndrome is a sleep disorder, characterized by repetitive pharyngeal collapse. It is prevalent in 6% or more of the middle age population [1]. Patients diagnosed with OSAHS have high incidence of obesity, and exhibit increased risk of hypertension, ventricular failure, and stroke. An association between OSAHS and high morbidity and mortality due to cardiovascular and cerebrovascular causes has been established [1]–[3]. Patients with OSAHS suffer from fragmented sleep, habitual snoring, morning headaches, and depression. Risk of auto accidents for OSAHS patients equals about seven fold that of controls without OSAHS [2].