Assessing the exertion required to induce breathlessness in a population with advanced cancer: matching measures to the level of physical function

Abstract Background The aim of the study was to assess four evidence-based assessments utilising exercise challenges that induce breathlessness, each with progressively less demanding levels of exertion, which can be tailored to people with a range of functional capabilities in the setting of advanced cancer for research studies. Functional cut off points for these assessments have not previously been defined. Methods A cross sectional study of four exercise tests attempted by all participants: 6 min walk test (6MWT); (derived) 2 min walk test (2MWT); arm exercises; and reading numbers aloud. Performance status (Australia-modified Karnofsky Performance Status (AKPS)), baseline breathlessness using the modified Medical Research Council (mMRC) breathlessness scale, and a visual analogue scale of intensity and unpleasantness of breathlessness were measured. Co-morbidity was codified using the Charlson Co-morbidity Index. Percentage of people completing each test by AKPS level of function and baseline mMRC breathlessness scores were quantified. Results In the 68 participants, poorer function decreased the proportion of people able to complete the exercise tests. For completion rates ≥80%, of 6MWT and 2MWT, only people with an AKPS 70–90 had completion. For arm exercises, this included people with an AKPS as low as ≥50; and for reading numbers, it included people with an AKPS of 40 but not below. Conclusions Walking tests have poor utility in people with high levels of functional impairment. For people with high levels of dependence, reading numbers should be used in evaluating exercise-induced breathlessness in research studies. These data also suggest that people’s exertional limitations have been under-estimated as cancer progresses