Cardiopulmonary exercise testing: a review of methods and applications in surgical patients

Cardiopulmonary exercise (CPX) testing has a number of medical applications, including the assessment of heart failure and the investigation of unexplained breathlessness. Over the past decade, it has become an important preoperative assessment tool to evaluate functional capacity and predict outcomes in patients undergoing both cardiac and noncardiac surgery. A CPX test is an incremental exercise test during which respiratory variables, including oxygen uptake and carbon dioxide excretion are measured and the ECG is monitored. Among the variables reported from a CPX test are oxygen uptake at anaerobic threshold and peak oxygen uptake. A limited functional capacity as indicated by a low anaerobic threshold or VO(2peak) has been shown to be associated with an increased incidence of perioperative complications in a number of surgical settings. Other reported variables, including the ventilatory equivalents for oxygen (VE/VO(2)) and carbon dioxide (VE/VCO(2)) and the millilitre of oxygen delivered per heartbeat or oxygen pulse [VO(2)/heart rate (HR)] may give indications as to the reasons for exercise limitation. ECG evidence of myocardial ischaemia with increasing workload is also an important indicator of increased perioperative risk. As a noninvasive, low-risk, test of the integrated responses to increasing cardiovascular stress, anaesthesiologists involved in preoperative assessment should have an understanding of its current uses and test outcomes. This review presents the physiological basis for CPX testing, methodology, advantages over other preoperative tests of cardiovascular function and guidance on the interpretation of CPX results in the perioperative setting.