Effects of Hyperinflation on the Oxygen Pulse as a Marker of Cardiac Performance in COPD

¹ Division of Pulmonary, Critical Care and Sleep Medicine. Caritas St Elizabeth's Medical Center. Tufts University School of Medicine, Boston, MA.
² Division of Pulmonary, Critical Care and Sleep Medicine. Caritas St Elizabeth's Medical Center. Tufts University School of Medicine, Boston, MA.; and Departamento de Fisiología. Instituto Nacional de Enfermedades Respiratorias, México, D.F.

^* To whom correspondence should be addressed. E-mail: vpinto{at}copdnet.org.

	Abstract

A decreased inspiratory to total lung capacity ratio (IC/TLC) is associated with dynamic hyperinflation (DH) and decreased exercise capacity. We hypothesized that static (low IC/TLC) and dynamic hyperinflation impair cardiac function assessed by O₂ pulse at rest and during cardiopulmonary exercise test (CPET).

We measured lung function, body mass index, handgrip strength and CPET parameters [oxygen uptake (ml·kg^-1·min^-1), O₂ pulse (ml·beat^-1)] in 87 COPD patients (ATS/ERS/GOLD 3–4) and 46 controls. The patients were divided into those with IC/TLC >25% or 25%.

The IC/TLC at rest and at peak exercise was associated with O₂ pulse (r=0.65, p<0.001 and r=0.68, p<0.001). Patients with IC/TLC 25% (n=45) had significantly lower exercise capacity, peak O₂ pulse, O₂ pulse, peak IC, peak IC/TLC, and IC/TLC%compared to patients with IC/TLC >25% and controls. During CPET, the O₂ pulse was lower at iso-work in patients with IC/TLC 25% than in those with IC/TLC >25%.

Resting hyperinflation (IC/TLC) is associated with lower O₂ pulse, peak exercise IC/TLC and exercise capacity in patients with severe COPD. Our results support an interaction between hyperinflation and decreased cardiac function that may contribute to exercise limitation in these patients.

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