Abstract
Introduction: A recent ERS statement on standardisation of cardiopulmonary exercise testing (CPET) in chronic lung diseases (Radtke et al 2019) discussed the criteria for determining maximal effort. A CPET with a respiratory exchange ratio (RER) >1.05 is considered maximal using these criteria; V’O2 85% predicted, and HR We hypothesise that using an RER >1.05 as maximal will result in misinterpretation. Methods: Retrospective analysis of CPETs performed at Birmingham Heartlands Hospital in 2019. Inclusion criteria: patient limited, RER >1.15 at peak, >6 mins. Exclusion criteria: highly variable RER indicating dysfunctional breathing. V’O2, V’E, and HR were measured at RERs of 1.00, 1.05, 1.10, 1.15, 1.20 and peak. CPET data between different points of RER were compared with Friedman tests. Results: CPET was performed in 422 patients. 199 had an RER > 1.15 at peak. 23 patients were excluded due to dysfunctional breathing. Of the 176 patients analysed, 138 reached an RER >1.20. At peak 76.5% of patients had abnormal findings as per ERS statement, at an RER of 1.05 this was 96.5% and at an RER of 1.15 this was 86.9% Discussion: Using an RER of 1.05 as a maximal effort underestimates some patients’ true exercise capacity. This will have an impact on diagnosis and risk stratification.
Published Version
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