Young Chronic E-Cigarette Users Display Cardiopulmonary Abnormalities During Exercise and Blunted Recruitment of Pulmonary Diffusing Capacity.

Abstract

The prevalence of e-cigarette use is increasing, and e-cigarette users with no history of tobacco smoking report greater respiratory symptoms. Traditional evaluation of resting pulmonary function may fail to detect subclinical abnormalities. To what extent do young, otherwise healthy chronic e-cigarette users with no tobacco smoking history exhibit altered cardiopulmonary function during exercise and blunted recruitment of pulmonary diffusing capacity for carbon monoxide (Dlco)? Twenty chronic e-cigarette users (mean age, 23 ± 4 years) with no tobacco smoking history and 20 age-, height-, and sex-matched control participants underwent a pulmonary function test and cardiopulmonary exercise test. Key outcomes included exercise capacity (V˙O_2peak), ventilatory efficiency (minute ventilation/CO₂ output nadir), exertional dyspnea, and operating lung volumes during exercise. A secondary aim investigated recruitment of resting Dlco and its components, measured as the change from the seated to supine posture. Adjusted linear regression models were used to evaluate the effect of group on key outcome variables at rest and during exercise. Both groups presented with normal pulmonary function (all, P_group > .05). E-cigarette users exhibited a lower V˙O_2peak (P_group = .017), elevated minute ventilation/carbon dioxide output nadir (P_group = .037), and greater exertional dyspnea (P_group < .001, P_{group∗workload} < .001), whereas operating lung volumes did not differ from control participants (all, P > .05). E-cigarette users also displayed a blunted Dlco recruitment to a postural change (P_{group∗posture} = .036). Between-group differences in dyspnea and Dlco recruitment were independent of V˙O_2peak. Young, otherwise healthy chronic e-cigarette users exhibit evidence of abnormal cardiopulmonary responses to exercise and blunted Dlco recruitment. These findings suggest early cardiopulmonary impairment and pulmonary vascular dysfunction in young e-cigarette users.