How to evaluate exertional breathlessness using normative reference equations in research.

Abstract

Breathlessness is a common, distressing and limiting symptom in people with advanced disease, but is challenging to assess as the symptom intensity depends on the level of exertion (symptom stimulus) during the assessment. This review outlines how to use recently developed normative reference equations to evaluate breathlessness responses, accounting for level of exertion, for valid assessment in symptom research. Published normative reference equations are freely available to predict the breathlessness intensity response (on a 0-10 Borg scale) among healthy people after a 6-minute walking test (6MWT) or an incremental cycle cardiopulmonary exercise test (iCPET). The predicted normal values account for individual characteristics (including age, sex, height, and body mass) and level of exertion (walk distance for 6MWT; power output, oxygen uptake, or minute ventilation at any point during the iCPET). The equations can be used to (1) construct a matched healthy control dataset for a study; (2) determine how abnormal an individual's exertional breathlessness is compared with healthy controls; (3) identify abnormal exertional breathlessness (rating>upper limit of normal); and (4) validly compare exertional breathlessness levels across individuals and groups. Methods for standardized and valid assessment of exertional breathlessness have emerged for improved symptoms research.