Effects of emphysema on oxygen uptake during maximal exercise in COPD

Abstract

The objective of the study is to assess the effects of emphysema on peak oxygen uptake ( _ VO 2peak ) during a cardiopulmonary exercise test in patients with chronic obstructive pulmonary disease (COPD). We measured _ VO 2peak and oxygen pulse in 80 patients with stable COPD exercising maximally. Oxygen saturation was measured by pulse oximetry (SpO 2 ), and the ventilatory response assessed by the ratio of tidal volume (V T ) at peak to slow vital capacity (SVC) at baseline, and by the percent increase of peak V T over baseline. Computed tomography imaging (CT scan) served as the reference diagnostic standard for emphysema. Based on the panel-grading (PG) method, emphysema was rated absent or mild (PG B 30, n = 54), or moderate to severe (PG [ 30, n = 26).Multiple quantile regression was applied to estimate the effects of PG [ 30 on _ VO 2peak . At peak exercise, the patients with PG [ 30 had significantly lower _ VO 2 , oxygen pulse and SpO 2 , and featured a blunted ventilatory response with respect to those with PG B 30 (p \ 0.001). With multiple quantile regression, the effects of PG [ 30 on _ VO 2Peak were only partially explained by the degree of lung hyperinflation, a substantial component being imputable to impairment of lung diffusing capacity. In conclusion, chronic obstructive pulmonary disease patients with moderate to severe emphysema feature significantly lower exercise tolerance than those with no or mild emphysema. Our findings underscore the need of tailoring therapeutic interventions for COPD to the predominant clinical phenotype to improve exercise capacity.

Combining Dynamic Hyperinflation with Dead Space Volume during Maximal Exercise in Patients with Chronic Obstructive Pulmonary Disease

“…In their study, the patients with COPD had high RV% predicted and high emphysema score measured with high resolution computed tomography (HRCT). They hypothesized that V Tpeak /FEV 1 > 1 or elevated V Tpeak /IC was due to DH occurring at peak exercise in patients with severe emphysema, which is comparable with our study and another study using V Tpeak /SVC to assess the severity of emphysema evaluated with HRCT [36] (Figure 3). However, it has been reported that the change in V D /V T from rest to peak exercise was not related to the severity of emphysema [35].…”

“…VTpeak% could be more powerful than VTpeak/FEV1 and VTpeak/SVC (Figure 3). 299 bolded boxes, from this study; blue boxes, from references [35] and [36]. Solid lines, significantly correlated; 303 dashed lines, not significantly correlated.…”

“…previous studies have suggested that the OCD and the COPD assessment test should be used 321 simultaneously when undertaking clinical evaluations of patients with COPD, and that the OCD in 322 ramp-slope selection should be used for dyspneic patients when undertaking CPET [13,19]. 323 Black bolded boxes, from this study; blue boxes, from References [35,36]. Solid lines, significantly correlated; dashed lines, not significantly correlated.…”

“…Solid lines, significantly correlated; 303 dashed lines, not significantly correlated. Black lines, from this study; blue lines, from reference [35]; green 304 line, from reference [36]. VT%, tidal volume and total lung capacity (TLC) ratio; EELV%, end-expiratory lung…”

“…another study using VTpeak/SVC to assess the severity of emphysema evaluated with HRCT [36] ( Figure 294 3). However, it has been reported that the change in VD/VT from rest to peak exercise was not related to 295…”