Value of cardiopulmonary exercise testing in interstitial lung diseases

Abstract

Introduction: Exertional dyspnea (ED) is a common symptom throughout the course of interstitial lung diseases (ILD). The pathophysiology behind this symptom can pertain to impairments in cardiovascular, peripheral muscle or respiratory systems. Aim: To evaluate the clinical utility of cardiopulmonary exercise testing (CPET) in the assessment of ED in ILD patients. Material and Methods: Retrospective study conducted within our ILD outpatient clinic. Clinical records (January 2015 - December 2017) were reviewed and data regarding demographics, modified Medical Research Council dyspnea scale scores, pulmonary function tests (PFT) and CPET results were retrieved. Results: From a total of 187 patients we included 19 (10.2%) that underwent CPET for the study of ED. Patients were mainly male (74%) with an average age of 54 years. Silicosis (37%), sarcoidosis (26%) and systemic vasculitis (26%) were the most frequent diagnosis. Baseline PFTs were normal (63%) or revealed only mild obstructive (26%) or restrictive (11%) patterns. DLCO was slightly decreased in 26% of patients. In all cases ED was considered out of proportion to the PFTs results. A cyclo-ergometer incremental protocol CPET was performed and considered normal in 32%; 26% presented respiratory limitation and 32% peripheral muscle deconditioning. On average the VO2 was 82.6%, the mean ventilatory reserve was 35L/min, the anaerobic threshold (AT) was 46.7%, VE/VCO2 at AT was 32.3% and the peak P(A-a)O2 was 20mmHg. Conclusions: CPET proved a valuable tool in detailing the pathophysiology of ED in our ILD patients. Peripheral muscle deconditioning was a frequent finding that would have otherwise remained unaddressed.