BACKGROUND: The prevalence of e-cigarette use is increasing, and young adults who report e-cigarette use and no history of tobacco smoking report greater respiratory symptoms. Traditional evaluation of resting pulmonary function may fail to detect subclinical abnormalities.

RESEARCH QUESTION: To what extent do otherwise healthy, young adults who report regular e-cigarette use and no tobacco smoking history exhibit altered cardiopulmonary function during exercise and blunted recruitment of pulmonary diffusing capacity for carbon monoxide (Dlco)?

STUDY DESIGN AND METHODS: Twenty participants with chronic e-cigarette exposure (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), ventilatory efficiency (minute ventilation/CO 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.

RESULTS: Both groups presented with normal pulmonary function (all, P > .05). Individuals who use e-cigarettes exhibited a lower V˙O (P = .017), elevated minute ventilation/carbon dioxide output nadir (P = .037), and greater exertional dyspnea (P < .001, P < .001), whereas operating lung volumes did not differ from control participants (all, P > .05). Individuals who use e-cigarettes also displayed a blunted Dlco recruitment to a postural change (P = .036). Between-group differences in dyspnea and Dlco recruitment were independent of V˙O.

INTERPRETATION: In this study, otherwise healthy young adults who report regular e-cigarette use exhibited evidence of abnormal cardiopulmonary responses to exercise and blunted Dlco recruitment. These findings suggest early cardiopulmonary impairment and pulmonary vascular dysfunction in young adults with chronic e-cigarette exposure.