Pulmonary poorly communicating fraction: relationships with exercise capacity and gas exchange

Aim: The “poorly communicating fraction” (PCF) (Plethysmographic total lung capacity (TLC) - single breath alveolar volume difference) is a marker of pulmonary ventilation inhomogeneity. Aim of this study was to investigate relationships between PCF, exercise capacity and gas exchange in patients with airway obstruction (AO) and not. Population: In 117 patients (M/F 83/34, aged 65.6+7.7, 52 with AO (FEV 1 /VC 79.0+9.1%pred) plethysmographic study, D L CO, bike ramp exercise were studied. Results: The PCF (1.11±0.657 L, 18.1±9.5 %predTLC) was correlated to smoke (pack/yrs r=0.24, p L CO%pred (r= -0.49, p O2 %pred (r= -0.24, p E /V’ CO2 intercept (r= 0.37, p 15 %predTLC (95 percentile of non AO) was considered high. High PCF patients (1.64±0.56 L; 27.2±8.4 %predTLC) are older (p 1 /VC %pred, D L CO%pred and PaO2. They showed higher Peak RR (p E /V’ CO2 intercept (p O2 and Watts. Twenty-seven over sixty-six patients though with normal FEV 1 /VC %pred had high PCF (23.3±5.9 vs 9.9±3.5%). They are older (p Conclusions: PCF is correlated with smoke, hyperinflation, D L CO and to reduce exercise capacity and gas exchange. Also in patients without AO an increased PCF is predictor of hyperinflation at rest and reduced exercise performance.