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Many adults with single-ventricle congenital heart disease who have undergone a Fontan procedure have abnormal pulmonary function resembling restrictive lung disease. Whether this contributes to ventilatory limitations and increased dyspnea has not been comprehensively studied. We recruited 17 Fontan participants and 17 healthy age- and sex-matched sedentary controls. All participants underwent complete pulmonary function testing followed by a symptom-limited incremental cardiopulmonary cycle exercise test with detailed assessments of dyspnea and operating lung volumes. Fontan participants and controls were well matched for age, sex, body mass index, height, and self-reported physical activity levels (all P > 0.05), although Fontan participants had markedly reduced cardiorespiratory fitness and peak work rates ( P < 0.001). Fontan participants had lower values for most pulmonary function measurements relative to controls with 65% of Fontan participants showing evidence of a restrictive ventilatory defect. Relative to controls, Fontan participants had significantly higher breathing frequency, end-inspiratory lung volume (% total lung capacity), ventilatory inefficiency (high ventilatory equivalent for CO 2 ), and dyspnea intensity ratings at standardized absolute submaximal work rates. There were no between-group differences in qualitative descriptors of dyspnea. The restrictive ventilatory defect in Fontan participants likely contributes to their increased breathing frequency and end-inspiratory lung volume during exercise. This abnormal ventilatory response coupled with greater ventilatory inefficiency may explain the increased dyspnea intensity ratings in those with a Fontan circulation. Interventions that enhance the ventilatory response to exercise in Fontan patients may help optimize exercise rehabilitation interventions, resulting in improved exercise tolerance and exertional symptoms. NEW & NOTEWORTHY This is the first study to comprehensively characterize both ventilatory and sensory responses to exercise in adults that have undergone the Fontan procedure. The majority of Fontan participants had a restrictive ventilatory defect. Compared with well-matched controls, Fontan participants had increased breathing frequency, end-inspiratory lung volume, and ventilatory inefficiency. These abnormal ventilatory responses likely form the mechanistic basis for the increased dyspnea intensity ratings observed in our Fontan participants during exercise.

No studies of cystic fibrosis (CF) have systematically characterized the evolution of the qualitative dimensions of exertional dyspnea. Adults with CF (n = 25) and control individuals matched for sex, age, and body mass index (n = 25) underwent cardiopulmonary cycle exercise testing with a detailed evaluation of ventilatory and dyspnea responses. The qualitative dimensions of dyspnea were examined during each exercise stage by having subjects select phrases that best described their breathing (i.e., "work/effort," "unsatisfied inspiration," and "unsatisfied expiration"). Subjects also selected phrases that described the quality of their breathing at peak exercise using an established 15-item questionnaire, which was then clustered into different categories. Subjects with CF had greater ventilatory requirements, higher end-inspiratory and end-expiratory lung volumes (% total lung capacity), and an earlier inflection/plateau in tidal volume during exercise compared with control subjects. Increased work/effort was the dominant qualitative descriptor in both groups throughout exercise. Unsatisfied inspiration was selected by 48% of subjects with CF and 40% of controls at some point during exercise. The onset of unsatisfied inspiration in these subjects occurred at a significantly lower relative exercise intensity in subjects with CF vs. controls (72 ± 21 vs. 94 ± 11% Wmax, P < 0.01). Chest tightness was the only qualitative descriptor cluster that was selected more frequently by subjects with CF vs. controls (36 vs. 0%, respectively, P < 0.05) at peak exercise. Therapeutic interventions that reduce ventilatory requirements and improve lung volumes may delay the onset of distressing sensations such as unsatisfied inspiration and chest tightness in adults with CF., (Copyright © 2016 the American Physiological Society.)

Understanding sex differences in the qualitative dimensions of exertional dyspnea may provide insight into why women are more affected by this symptom than men. This study explored the evolution of the qualitative dimensions of dyspnea in 70 healthy, young, physically active adults (35 M and 35 F). Participants rated the intensity of their breathing discomfort (Borg 0-10 scale) and selected phrases that best described their breathing from a standardized list (work/effort, unsatisfied inspiration, and unsatisfied expiration) throughout each stage of a symptom-limited incremental-cycle exercise test. Following exercise, participants selected phrases that described their breathing at maximal exercise from a list of 15 standardized phrases. Intensity of breathing discomfort was significantly higher in women for a given ventilation, but differences disappeared when ventilation was expressed as a percentage of maximum voluntary ventilation. The dominant qualitative descriptor in both sexes throughout exercise was increased work/effort of breathing. At peak exercise, women were significantly more likely to select the following phrases: "my breathing feels shallow," "I cannot get enough air in," "I cannot take a deep breath in," and "my breath does not go in all the way." Women adopted a more rapid and shallow breathing pattern and had significantly higher end-inspiratory lung volumes relative to total lung capacity throughout exercise relative to men. These findings suggest that men and women do not differ in their perceived quality of dyspnea during submaximal exercise, but subjective differences appear at maximal exercise and may be related, at least in part, to underlying sex differences in breathing patterns and operating lung volumes during exercise., (Copyright © 2015 the American Physiological Society.)