Diffusing Capacity for Carbon Monoxide is Linked to Ventilatory Demand in Patients with Chronic Obstructive Pulmonary Disease

AbstractDyspnea is deemed to result from an imbalance between ventilatory demand and capacity. The single-breath diffusing capacity for carbon monoxide (DLCO) is often the best correlate to dyspnea in COPD. We hypothesized that DLCO contributes to the assessment of ventilatory demand, which is linked to physiological dead space /tidal volume (VD/VT) ratio. An additional objective was to assess the validity of non-invasive measurement of transcutaneous PCO2 allowing the calculation of this ratio. Forty-two subjects (median [range] age: 66 [43–80] years; 12 females) suffering mainly from moderate-to-severe COPD (GOLD stage 2 or 3: n = 36) underwent pulmonary function and incremental exercise tests while taking their regular COPD treatment. DLCO% predicted correlated with both resting and peak physiological VD/VT ratios (r = −0.55, p = 0.0015 and r = −0.40, p = 0.032; respectively). The peak physiological VD/VT ratio contributed to increase ventilation (increased ventilatory demand), to increase dynamic hype...