Identifying limitations to exercise with incremental cardiopulmonary exercise testing: a scoping review

Abstract

Cardiopulmonary exercise testing (CPET) is a comprehensive and invaluable assessment used to identify the mechanisms that limit exercise capacity. However, its interpretation remains poorly standardised. This scoping review aims to investigate which limitations to exercise are differentiated by the use of incremental CPET in literature and which criteria are used to identify them. We performed a systematic, electronic literature search of PubMed, Embase, Cochrane CENTRAL, Web of Science and Scopus. All types of publications that reported identification criteria for at least one limitation to exercise based on clinical parameters and CPET variables were eligible for inclusion. 86 publications were included, of which 57 were primary literature and 29 were secondary literature. In general, at the level of the cardiovascular system, a distinction was often made between a normal physiological limitation and a pathological one. Within the respiratory system, ventilatory limitation, commonly identified by a low breathing reserve, and gas exchange limitation, mostly identified by a high minute ventilation/carbon dioxide production slope and/or oxygen desaturation, were often described. Multiple terms were used to describe a limitation in the peripheral muscle, but all variables used to identify this limitation lacked specificity. Deconditioning was a frequently mentioned exercise limiting factor, but there was no consensus on how to identify it through CPET. There is large heterogeneity in the terminology, the classification and the identification criteria of limitations to exercise that are distinguished using incremental CPET. Standardising the interpretation of CPET is essential to establish an objective and consistent framework.

FIGURE 1

PRISMA flowchart of the included publications. CPET: cardiopulmonary exercise testing.

FIGURE 2

Bar chart of most commonly reported limitations to exercise. Limitations to exercise at the level of the respiratory and cardiovascular system that were reported twice or less were included in the category “other”, while for limitations at the level of the peripheral muscle and other limitations only limitations mentioned once were included in this category. ^#: Pulmonary vascular limitation was categorised as a limitation at the level of the respiratory system, but it also involves the cardiovascular system. EIB: exercise-induced bronchoconstriction.

FIGURE 3

Citation network diagram illustrating the sources of the used identification criteria for limitation(s) to exercise of included publications. Blue dots represent publications included in this scoping review, red dots are publications that were referred to but were not included, because they did not meet the selection criteria or were not retrieved. The size of the dot is relative to the amount of times the publication was referenced to. Publications that did not reference any source for the identification criteria they used nor were referenced to by other publications were left out this diagram.