unlikely in an individual at risk, e.g. with residual exercise intolerance after pulmonary embolism [44–46]. CPET as an adjunct to the investigation of ischaemic heart disease There is some limited evidence that a downward deflection of the V′O2–WR relationship and a plateau in the O2 pulse profile are occasionally associated with ischaemic heart disease [47, 48], as discussed later in this Monograph [49]. Concomitant (or subsequent) ECG abnormalities may occur, particularly in more advanced disease [50]. Although there are other more sensitive and specific modalities to investigate coronary artery disease, those abnormalities should be valued in an individual at risk. CPET to uncover dysfunctional breathing and/or hyperventilation Non-physiological changes and increased variability in breathing pattern, which are frequently accompanied by varied degrees of alveolar hyperventilation, can be identified in patients undergoing CPET due to unexplained dyspnoea [51–53]. Although those abnormalities are not always idiopathic (i.e. “primary”) [54], once identified they might avoid potentially iatrogenic and costly procedures in patients who have frequently been extensively investigated. Risk assessment Prognosis in cardiopulmonary diseases As a consequence of marked advances in the pharmacological and non-pharmacological treatment of heart failure in the past 10 years [55], there have been substantial changes in the variables (and their cut-offs) for predicting poor outcome (as detailed later in this Monograph, in chapters covering responses that are diagnostic for cardiac diseases [49] and exercise testing in the evaluation of lung and heart disease patients [56]). For example, lower peak V′O2 thresholds compared with those used in seminal studies [57] are now used in multi-parametric models of risk estimation [58, 59]. A flattening submaximal V′O2 trajectory has been shown to be useful to predict poor prognosis in heart failure with either reduced, mid-range or preserved ejection fraction [60]. Moreover, submaximal ventilatory (high V′E–V′CO2 indices, oscillatory ventilation) and gas exchange variables (low PETCO2) have been recognised as independent predictors of poor prognosis [61]. Similar variables (with the exception of oscillatory ventilation) have proved valuable as prognosticators in PAH [62]. Limited evidence suggests that high excessive exertional ventilation also predicts poor outcome in COPD (in association with resting hyperinflation) [63] and ILD (in association with low peak exercise capacity and mechanical constraints) [35]. Pre-operative assessment In the pre-operative assessment of lung resection surgery, some more recent reports described a role for high V′E–V′CO2 indices in the prediction of a negative outcome in patients with intermediate peak V′O 2 values [64, 65] HARVIE and LEVETT [66] provide a chapter on pre-operative evaluation (including lung transplantation) later in this Monograph. The value of traditional variables previously found to be useful in the pre-operative assessment of major abdominal surgery (low peak V′O 2 and/or V′O 2 ΘT) has been extended to colorectal, hepatobiliary, urological and abdominal aortic aneurysm surgery (as recently reviewed in [67, 68]). xiv https://doi.org/10.1183/2312508X.10015318