Expiratory Flow Limitation in Obstructive Sleep Apnea and COPD: A Quantitative Method to Detect Pattern Differences Using the Negative Expiratory Pressure Technique.

Ahmet Baydur

doi:10.2174/1874306401206010111

Abstract

Background:Expiratory flow limitation (EFL), determined by the negative expiratory pressure (NEP) technique, can exhibit overlapping patterns in COPD, obstructive sleep apnea (OSA) and non-OSA obesity. We assessed the ability of a quantitative method to assess EFL to discriminate COPD from obese and OSA patients during NEP (-2 to -3 cm H2O) testing.Methods:EFL was quantified by measuring the area under the preceding control tidal breath (Vt) subtended by the NEP curve (%AUC). To quantify mean lost flow, the ratio of %AUC to percentage of control Vt over which EFL occurred (%EFL) (= %AUC/%EFL) was computed. Percent EFL, %AUC, and %AUC/%EFL was compared in 42 patients with COPD, 28 obese subjects without OSA, 50 with OSA (26 mild-moderate, 24 severe) and 19 control subjects, in seated and supine postures.Results:All patients exhibited %EFL values significantly higher than control subjects, corrected for age and gender (ANOVA). All but the COPD group exhibited higher %EFL while supine, but not %AUC or %AUC/%EFL. Amongst seated subjects, %EFL was highest in COPD, and amongst supine groups, it was greatest in OSA and COPD. %AUC/%EFL was significantly higher in mild-moderate OSA than in COPD only while seated. %AUC or %AUC/%EFL did not discriminate amongst other cohorts in either posture.Conclusions:Computation of %EFL helps distinguish EFL in COPD, obese and OSA patients from those of control subjects. Computation of %AUC and %AUC/%EFL is useful in determining the magnitude of extrathoracic FL in individuals with obesity and OSA, but does not distinguish between cohorts.

Highlights

The major factor contributing to the generation of sleep disordered breathing is increased upper airway collapsibility [1,2,3,4]
In chronic obstructive pulmonary disease (COPD), Expiratory flow limitation (EFL) is defined as absence of change in expiratory flow during application of negative expiratory pressure (NEP), and is a clinically important factor contributing to dyspnea by leading to hyperinflation and inspiratory muscle dysfunction
COPD patients and control subjects were excluded if they had symptoms of sleep apnea, and did not undergo sleep studies

Summary

Introduction

The major factor contributing to the generation of sleep disordered breathing is increased upper airway collapsibility [1,2,3,4]. Expiratory flow limitation (EFL) during quiet breathing in various respiratory disorders can be demonstrated by the negative expiratory pressure (NEP) technique [5,6,7,8,9]. No study has questioned the reliability and accuracy of the NEP technique [10]. It can be detected during quiet breathing using. Expiratory flow limitation (EFL), determined by the negative expiratory pressure (NEP) technique, can exhibit overlapping patterns in COPD, obstructive sleep apnea (OSA) and non-OSA obesity. We assessed the ability of a quantitative method to assess EFL to discriminate COPD from obese and OSA patients during NEP (-2 to 3 cm H2O) testing

Objectives

Methods

Results

Conclusion