Practicality and clinical utility of cardiopulmonary exercise testing to investigate complex breathlessness in severe asthma

Abstract

Background: breathlessness does not always correlate with asthma severity and is often driven by co-existing conditions such as breathing pattern disorder (BPD) or de-conditioning. Cardiopulmonary exercise testing (CPET) may help in elucidating the causes of breathlessness. Aim: to assess the utility of CPET in the management of complex breathlessness in severe asthma. Methods: well characterised severe asthmatics with prominent breathlessness and exercise limitation underwent standard CPET protocol in a tertiary centre. Results: CPET was performed in 16 patients [mean age 43yrs (range 26-60), 9 females, mean BMI 33.4±6.5kg/m2, FEV1 (L) 2.7±1.1, FEV1%-pred 83.9±25.9%, FEV1/FVC ratio 73.8±9.6 (range 55-86), inhaled corticosteroid dose 1.5±0.7mg/day, oral corticosteroid courses per annum 3.6±3, FeNO 48.1±44 ppb, blood eosinophils 0.5±0.6x109/L]. Twelve (75%) patients completed CPET (loaded exercise time 9.7±2.8, peak heart rate 89±12% predicted). The V’O2 at peak was 85±24 %predicted; at anaerobic threshold 53±11 (range 42-70), and the breathing reserve was 15± 31%. Of the 4 cases that did not complete CPET, 2 had BPD. The CPET diagnoses included BPD in 81% and hyperventilation 56%, deconditioning 12.5%, reduced functional capacity due to obesity 6.5%, and ventilation limitation due to underlying lung disease 6.5%. There were no adverse effects post testing. Results altered diagnosis in 62.5% of cases; reinforced diagnosis in 25%; and did not alter diagnosis in 12.5% (normal CPET). Conclusion: CPET was practical to conduct and aided in elucidating the causes of breathlessness in severe asthma, which facilitated appropriate management.