Physiologic Effects of an Ambulatory Ventilation System in Chronic Obstructive Pulmonary Disease

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Abstract

Rationale:

Exercise intolerance limits the ability of patients with chronic obstructive pulmonary disease (COPD) to perform daily living activities. Noninvasive ventilation reduces dyspnea and improves exercise performance, but current systems are unsuitable for ambulatory use.

Objectives:

In patients with COPD experiencing exercise-induced desaturation, we evaluated improvements in exercise tolerance facilitated by a wearable, 1-lb, noninvasive open ventilation (NIOV) system featuring a nasal pillow interface during constant work rate (CWR) cycle ergometer exercise and associated effects on dyspnea, respiratory muscle activation, and pulmonary gas exchange efficiency.

Methods:

Fifteen men with COPD (FEV1 = 32.2 ± 12.0% predicted; FEV1/FVC = 31.6 ± 7.1%; exercise oxygen saturation as measured by pulse oximetry [SpO2] = 86.5 ± 2.9%) participated. After incremental testing establishing peak work rate, subjects completed three visits in which they performed CWR exercise to tolerance at 80% peak work rate: (1) unencumbered breathing room air, (2) using NIOV+compressed air, (3) using NIOV+compressed O2, or (4) using O2 via nasal cannula. Assessments included exercise duration, surface inspiratory muscle EMG, SpO2, transcutaneous Pco2, and Borg dyspnea scores.

Measurements and Main Results:

Exercise endurance was 17.6 ± 5.7 minutes using NIOV+O2, greatly prolonged compared with unencumbered (5.6 ± 1.9 min), nasal O2 (11.4 ± 6.8 min), and NIOV+Air (6.3 ± 4.1 min). Isotime SpO2 was higher and intercostal, scalene, and diaphragmatic EMG activity was reduced using NIOV+O2 compared with unencumbered, nasal O2, and NIOV+Air, signifying respiratory muscle unloading. Isotime dyspnea reduction correlated with isotime EMG reduction (r= 0.42,P= 0.0053). There were no significant differences in isotime Vd/Vt or transcutaneous Pco2 among treatments.

Conclusions:

NIOV+O2 yielded substantial exercise endurance improvements accompanied by respiratory muscle unloading and dyspnea reductions in patients with severe hypoxemic COPD.

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