New guidelines outline best tests of exercise ability in CF

Physical exercise is a critical part of maintaining health for people living with CF

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A trio of people run together in this exercise illustration.

An international team of scientists has published new guidelines for how best to perform exercise testing in people with cystic fibrosis (CF).

Guidance and standard operating procedures for functional exercise testing in cystic fibrosis” was published in European Respiratory Review.

“Our goal is that all people with CF of an appropriate age have access to regular exercise testing to better understand their health and be given individualised exercise advice,” Zoe Saynor, PhD, first author of the guidelines at the University of Portsmouth in the U.K., said in a press release.

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Getting physical exercise is a critical part of maintaining health for people with CF. In order to help facilitate adequate exercise, current guidelines suggest that people with CF who are older than 10 years should have their exercise abilities evaluated at least once per year. However, until now there haven’t been established guidelines for how to do this type of testing.

“Current guidelines recommend every person with cystic fibrosis should have access to an exercise test at least once a year. That doesn’t happen in most parts of the world, including in many clinics here in the UK,” Saynor said. “It’s important that everyone is on the same page when it comes to exercise and activity plans, so that the quality of treatment doesn’t vary depending on where a person is from.”

The new guidelines were created through a collaborative effort by dozens of experts across the globe.

“The big focus of the project was to change and improve clinical practice across the world, so we’ve been working together collectively over a number of years. We wanted to involve colleagues from areas with different medical care systems, and from both low and middle-income countries, to ensure our recommendations had as much stakeholder involvement as possible,” Saynor said.

CPET: The gold standard of measuring aerobic exercise

According to the guidelines, the gold standard for measuring aerobic exercise capacity in people with CF is cardiopulmonary exercise testing, or CPET. In a traditional CPET setup, a patient exercises while hooked up to equipment that monitors how much oxygen they take in, which is key for assessing aerobic fitness.

The guidelines note that when CPET cannot be performed, for example due to lack of equipment or lung infections that could contaminate the equipment, a stationary bicycle is recommended to measure the maximum workload. It also can provide assessment of heart rate and blood oxygen saturation.

It important to assess patients’ subjective experiences of effort and shortness of breath during these tests, the guidelines highlight. The experts recommended a standardized tool called the Dalhousie scale for this purpose.

In addition to CPET, the modified shuttle test — an assessment where a patient walks on a treadmill that gets increasingly faster every minute — also may be suitable for measuring aerobic exercise capacity in people with CF. The guidelines specifically suggest using a version of the shuttle test that includes 25 different speeds.

The 6-minute walking distance test, which measures the distance a person can walk in six minutes, may be useful for people with CF who have advanced lung disease or are undergoing lung transplant. But it probably isn’t as useful for people with milder disease, according to the guidelines. The guidelines state that the three-minute step test, an older assessment of aerobic exercise ability, should not be used in modern clinical practice for people with CF.

In addition to measuring aerobic exercise capacity, the guidelines also highlight the importance of measuring other aspects of fitness such as muscle strength. Sit-to-stand tests and measures of grip strength may be helpful in this regard, though the guidelines note there isn’t as much evidence supporting these tests in CF as there is for aerobic tests like CPET. As such, the guidelines emphasize a need for further research into how best to perform muscle strength testing in CF patients.

The guidelines also note a need for future testing to examine how modern treatments, such as CFTR modulators, affect exercise abilities for people with CF. Such testing “represents an important next step in advancing the understanding of how the pathophysiology [disease processes] of CF, ageing and new treatments truly impact physical function, as well as moving closer to the goal of individualised exercise prescription and personalised medicine that incorporates the needs and wishes of [people with] CF,” the guidelines state.

Standardization of exercise tests makes studies easier

The guidelines note that better standardization of how exercise tests are performed around the world will make it easier to conduct large studies to address these questions.

“Moving towards a consensus internationally on the choices of validated exercise tests, standardised protocols and objective measures in exercise testing will assist in developing robust multicentre research opportunities,” said Jenny Hauser, president of CF Physio, a nonprofit that aims to improve physical therapy in CF.

“The guidelines will improve equity in practice across CF centres, and will help clinicians in appropriately supporting their patients to develop individualised exercise programs for improved health outcomes,” she said.