Exertional Dyspnea in a Young Adult

Abstract

HISTORY: A 23-year-old Caucasian male was referred to the cardiopulmonary clinic for assessment of dyspnea and exercise intolerance. The patient's chief complaint was dyspnea with sport activities and occasionally with stairs and walking. The patient had a chronic history of dyspnea related to unilateral vocal cord paralysis and tracheal stenosis. The patient required mechanical ventilation as well as tracheostomy at birth. PHYSICAL EXAMINATION/EVALUATION OF DYSPNEA: The patient performed pulmonary function testing (spirometry, lung volumes, DLco, and MVV), submaximal steady state exercise testing, and maximal incremental exercise testing. Tidal flow volume loops (TFVL), blood pressure, heart rate (HR), oxygen saturation, cardiac outputs, end-tidal carbon dioxide (PETCO2), gas exchange, venous blood lactate, and ratings of perceived breathlessness (RPB, modified Borg scale 0–10) were collected during the submaximal and maximal exercise testing. DIFFERENTIAL DIAGNOSIS: Exercise intolerance due to mechanical ventilatory limitation Exercise intolerance due to deconditioning TEST AND RESULTS: Pulmonary function tests confirmed variable extrathoracic obstruction. The MVV was markedly limited (33% of predicted). During submaximal exercise, the TFVL showed substantial inspiratory volume reserve but no flow reserve. Dyspnea (RPB=4) during submaximal exercise was not limiting. Lactate threshold (∼ 4 mmol level) was achieved at 75W. The patient achieved a peak work rate of 190W, peak HR of 192 bpm (100% of predicted), and peak VO2of 27 ml/kg/min (71% predicted). VE as a percent of MVV was 119% indicating ventilatory limitation. The TFVL confirmed this finding by revealing severe hyperinflation and utilization of all inspiratory and expiratory flow reserve during peak exercise. Gas exchange data revealed a continuous decline in VE/VCO2, which led to retention of PETCO2. Even so, given severe dyspnea (RPB=10) at peak exercise, leg fatigue was given by the patient as the primary reason for ending exercise. The peak venous blood lactate of 9.9 mmol confirmed the patient's ability to perform enough mechanical work to sustain high rates of glycolysis despite his flow limitation. FINAL WORKING DIAGNOSIS: Reduced exercise capacity due to some deconditioning but predominantly related to flow limitations caused by an extrathoracic constraint. TREATMENT AND OUTCOMES: A focused period of exercise training (base training: HR 133–153 bpm; threshold training: HR 153–163 bpm) was recommended to reduce VE requirements of exercise by decreasing lactate levels and improving functional capacity during submaximal work levels.