Exercise intolerance is complex but can be overcome  

Multiple interlinked physiological systems can contribute to exercise intolerance for people with respiratory disease, but that means there may be ways to “get more juice out of the system,” says international expert and physiologist Susan Ward, Emeritus Professor at the UK’s University of Leeds.

Speaking in a session at the TSANZSRS Annual Scientific Meeting on Saturday, Professor Ward explained how muscular exercise for respiratory patients depends on an integrated pathway of systems linking intramuscular energy exchange with pulmonary gas exchange.

Failure at any one of those points can result in exercise intolerance. So a patient with COPD, which is where most of the evidence in the field is focused, may have exercise intolerance which is not purely a result of pulmonary obstruction.

“The intriguing thing to me is the number of things going on which really are quite surprising,” she  told the limbic in an interview. Cardiac dysfunction, for example, can contribute to exercise intolerance in the presence of pulmonary disease, even if there is no clinical manifestation of heart failure.

Cardiopulmonary exercise testing (CPET) can guide physicians to identify exercise-limiting impairments, so that they can be accurately targeted. “If you want to design a good programme for intervention, you can’t do it if you don’t know where the deficits are,” she said.

For example, “You could have slight impairment with cardiac output, but if it’s got enough output to go to the cardiac muscle, it’s not the thing that’s going to stop you.” The key factor is to work out what is limiting a patient’s activity most.

Simple deconditioning can be a major factor, and is difficult to disentangle from system dysfunctions, says Professor Ward. “The exercise component of pulmonary rehabilitation could offset a lot of impairment,” she said. However, patients quickly become deconditioned again unless they maintain exercise after the programme has ended.

The “bottom line” for respiratory patients is that abilities important for quality of life, such as walking speed, can be increased, if physicians know what to target.

The “ceiling” on physical activity may depend on respiratory function, and there’s no way to reverse the obstruction element of COPD. “But given that ceiling on how high breathing can go, the amount of energy you can get out can be significantly increased,” she said.

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