Indications for exercise testing: a critical perspective

Abstract

Since the first European Respiratory Society (ERS) Task Force guidelines on ‘‘Clinical Exercise Testing’’ were published in 1997 [1], exercise testing has become increasingly used for the functional evaluation of patients with a wide range of chronic lung and heart diseases characterised by exercise intolerance, such as chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), primary pulmonary hypertension (PPH), cystic fibrosis (CF) and chronic heart failure (CHF). Physiological indices of system function measured or estimated during cardiopulmonary exercise testing (CPET), as well as the distance covered during walking tests, such as the 6-min walk test (6MWT) and the shuttle walk test (SWT), have been shown to provide valuable information regarding functional status, prognosis and outcome evaluation of therapeutic interventions. Importantly, such exercise-based interrogation has proved to be superior to resting spirometric and electrocardiographic measures. The widespread popularity of exercise testing in clinical practice reflects, to a considerable degree, developments related to the following. 1) The availability of computerised systems that allow accurate noninvasive measurement and display of pulmonary gas exchange responses on a breath-by-breath basis in real time. 2) The standardisation of exercise protocols, such as the maximal incremental cycle-ergometer, treadmill test and walking tests (e.g. 6MWT and SWT). 3) Disease-specific interpretative strategies for the identification of system function and limiting foci pertinent to differential diagnosis, prognosis and therapeutic intervention. These advances have been variously captured in a range of key consensus statements [1–3]. Therefore, it was timely that the second ERS Task Force on clinical exercise testing recently presented a consensus statement entitled ‘‘Recommendations on the use of exercise testing in clinical practice’’ [4]. This was an evidence-based document targeted at the practising clinician to better inform decisions on whether, when and how to employ exercise testing. As set out in the introduction section, the purpose of the document was ‘‘to present recommendations on the clinical use of exercise testing in patients with cardiopulmonary disease, with particular emphasis on the evidence base for functional evaluation, prognosis and assessment of interventions’’ to ‘‘allow resolution of practical issues that often confront the clinician, such as: 1) When should an evaluation of exercise intolerance be sought?; 2) Which particular form of test should be asked for?; and 3) What cluster of variables should be selected when evaluating prognosis for a particular disease or the effect of a particular intervention?’’ The aims of this chapter, therefore, are to: 1) briefly discuss the major indications for exercise testing in clinical practice; 2) critically address the major exercise outcomes; and 3) identify areas of uncertainty that may direct future research.