Respiratory analysis in patients with obstructive sleep apnea syndrome (OSAS): mixed vs. predominant obstructive vs. pure obstructive

Abstract

Introduction Mixed apnea has been classified as a subtype of obstructive apnea by current guideline. However, recent study suggested that different breathing patterns before sleep onset were demonstrated between mixed apnea and pure obstructive apnea. We aim to investigate the respiratory signal patterns among 3 subtypes of obstructive sleep apnea (OSA). Materials and methods We enrolled 60 patients who were not only diagnosed with OSA by polysomnography but also underwent nasal continuous positive airway pressure (CPAP) therapy more than at least 6 months. Ten healthy subjects were also included. Patients were divided into 3 types of OSA: pure-OSA (obstructive apnea 100%), predominant- OSA (70% −100%), mixed-OSA (mixed apnea > 30% of total apneuic events). Respiration signal was calculated as respiratory interval, which means time difference between discrete respirations during 30 s. Stable sleep time, which was defined by two conditions, was extracted from total sleep duration. First, respiration rate has to fit within 12 ∼ 20 per minute. Second, respiration interval was ranged from 3 to 5 s. We compared the synchrony of thorax-abdominal movements during sleep among 3 OSA subtypes and healthy subjects. Results Out of 60 patients, 50 (90%) patients were male. Mean age was 56.3i3/410.5 years and mean apnea–hypopnea index (AHI) was 41.7i3/416.0/h. The proportion of stable sleep time was significantly decreased in both predominant-OSA and mixed-OSA groups (P Conclusion We reports that mix-OSA reveals not only unstable respiratory pattern but also desynchronized movement of thorax and abdominal wall during sleep, compared to patients with pure-OSA or predominant-OSA and normal subjects. Current study provides some evidence for the different pathophysiology of respiration according to OSA subtypes.