Effects of hyperinflation on the oxygen pulse as a marker of cardiac performance in COPD

Abstract

A decreased inspiratory capacity (IC)/total lung capacity (TLC) ratio is associated with dynamic hyperinflation and decreased exercise capacity. The present authors hypothesised that static (low IC/TLC) and dynamic hyperinflation impair cardiac function as assessed by oxygen pulse at rest and during cardiopulmonary exercise testing (CPET). Lung function, body mass index, hand grip strength and CPET parameters were measured (oxygen uptake (mL x kg(-1) x min(-1)) and oxygen pulse (mL x beat(-1))) in 87 chronic obstructive pulmonary disease (COPD) patients (American Thoracic Society/European Respiratory Society/Global Initiative for Chronic Obstructive Lung Disease stage 3-4) and 46 controls. The patients were divided into those with IC/TLC > 25% or < or = 25%. The IC/TLC ratio at rest and at peak exercise was associated significantly with oxygen pulse. Patients with IC/TLC < or = 25% (n = 45) had significantly lower exercise capacity, peak oxygen pulse, peak minus baseline oxygen pulse, peak IC, peak IC/TLC ratio and % change from baseline to peak IC/TLC ratio compared with patients with IC/TLC > 25% and controls. During CPET, the oxygen pulse was lower at iso-work in patients with IC/TLC < or = 25% than in those with IC/TLC > 25%. Resting hyperinflation (inspiratory capacity/total lung capacity) is associated with lower oxygen pulse, peak exercise inspiratory capacity/total lung capacity and exercise capacity in patients with severe chronic obstructive pulmonary disease. The present results support an interaction between hyperinflation and decreased cardiac function that may contribute to exercise limitation in these patients.

Fat-Free Mass Depletion Is Associated With Poor Exercise Capacity Irrespective of Dynamic Hyperinflation in COPD Patients

“…A poor cardiovascular response to exercise was related to dynamic hyperinflation on exertion in patients with severe COPD, 5 and this finding has been recently confirmed and extended by our group in patients with a wide range of air-flow obstruction. 6 In the present series, the depleted patients, compared with nondepleted patients, significantly differed in cardiovascular response to exercise, for a given level of hyperinflation at rest and on exertion, indicating that a low FFM may independently affect cardiovascular function.…”

“…The patients with an IC/TLC at the peak of exercise of Յ 0.25 may be defined as "heavy hyperinflators." 5,6 On the basis of the age of our population sample, a value of 10 mL/kg/min may be considered as a threshold value of normality for the peak O 2 pulse. 27 A P value of Ͻ .05 was taken as significant.…”

“…4 Furthermore, the ventilatory constraints occurring during exercise have the potential for significant negative effects on cardiovascular function. 5,6 Additionally, a fat-free mass (FFM) depletion commonly occurs in COPD patients, resulting from several factors, such as systemic inflammatory mediators, disuse atrophy, poor nutrition, and oral corticosteroid medication. 7 Importantly, the reduction in FFM may also contribute to impairment of exercise capacity in these patients.…”

Effects of emphysema on oxygen uptake during maximal exercise in COPD

“…In that study, however, the severity of emphysema was not established because there was no radiologic assessment [20].…”

“…Vassaux et al [20] measured oxygen pulse at rest and at peak exercise in 87 patients with severe or very severe COPD, and in 46 age-and sex-matched controls. They find that patients with very severe hyperinflation at rest (IC/TLC B 25%) have significantly lower peak oxygen pulse than both patients with IC/TLC [ 25% and controls.…”