Severity of desaturation events differs between hypopnea and obstructive apnea events and is modulated by their duration in obstructive sleep apnea

Abstract

Purpose: Frequency of apnea and hypopnea events is used to estimate the severity of obstructive sleep apnea (OSA). However, comprehensive information on whether apneas and hypopneas cause an equal biological effect is not available. The purpose of the present work was to evaluate the effect of the breathing cessation event type (i.e., obstructive apnea or hypopnea) and duration on the severity of related SpO₂ desaturation events.

Methods: Type 1 polysomnographies of 395 patients (220 males and 175 females) examined for suspected OSA were analyzed. Desaturation severity related to hypopnea and obstructive apnea events were compared and comparison was controlled for gender, sleep stage, sleeping position, age, and body mass index. Hypopneas and obstructive apneas were further divided into eight different durational categories and related desaturation event characteristics were compared between the categories.

Results: SpO₂ desaturation events caused by obstructive apneas were statistically significantly (p ≤ 0.004) longer, greater in area, and deeper compared to the SpO₂ desaturations caused by hypopneas. The increase in the duration of hypopnea and obstructive apnea events led to increase in the duration and area of related SpO₂ desaturations. The increase in the obstructive apnea event duration also led to increase in the depth of related desaturation event.

Conclusions: Obstructive apneas led to more severe SpO₂ desaturation compared to hypopneas. Increased event duration led to increase in the severity of the related SpO₂ desaturation. In addition to considering event duration, obstructive apneas should have more weight than hypopneas when estimating severity of OSA and associated long-term cardiovascular risk.

Keywords: Apnea-hypopnea index; Desaturation area; Desaturation severity; Severity estimation; Sleep disordered breathing.