The modified Borg/6-min walk distance ratio: a method to assess exertional breathlessness and leg discomfort using the 6-min walk test

Dyspnea, dysfunctional breathing disorders, and the Bayesian brain hypothesis

Clinicians frequently evaluate patients who present with dyspnea. This term describes uncomfortable breathing during physical activity, and the intensity or degree of dyspnea can vary in an individual depending on circumstances and between individuals. In some cases, the level of dyspnea appears out of proportion to other information relevant to the cardiorespiratory system, and this situation has been described as dysfunctional breathing. The Bayesian brain hypothesis helps clinicians understand this symptom in these patients. This hypothesis suggests that prior experiences with dyspnea during physical activity or a respiratory disorder provide the background that is used to interpret current symptoms. This review outlines problems associated with the use of the term "dyspnea" and briefly describes how the Bayesian brain hypothesis might help clinicians understand this symptom better.

How to evaluate exertional breathlessness using normative reference equations in research

PURPOSE OF REVIEW

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.

RECENT FINDINGS

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.

SUMMARY

Methods for standardized and valid assessment of exertional breathlessness have emerged for improved symptoms research.