Respiratory muscle training for cystic fibrosis

Cystic Fibrosis (CF) is the most frequent autosomal recessive disease in White populations. It is caused by mutations of the CF transmembrane conductance regulator (CFTR) gene, which results in dehydrated and viscous secretions. People with CF suffer from impairment in fluid balance and temperature homeostasis in respiratory, reproductive, and digestive functions. The higher number of deaths in CF is attributable to respiratory or cardiorespiratory causes. Viscous secretions in the lung alter clearancecausing bacterial colonization and chronic pulmonary infection. In the long term, this condition leads to a progressive worsening of pulmonary function, which eventually results in respiratory failure. Pharmacological management of CF, including individualized combinations of medications (e.g., antibiotics and mucoactive agents) alongside airway clearance to optimize secretion mobilization, leads to an increase in life expectancyIn this scenario, exercise interventions such as respiratory muscle training (RMT) are becoming a key approach in CF management to optimize health outcomes and to prevent complications of CF syndrome. 

This review investigated the effectiveness of respiratory muscle training on clinical status in patients with CF.

This review is important for

People with CF experiencing difficulty in breathing, their loved ones/caregivers, health professionals caring for this population, general practitioners, researchers, and policymakers.

Outcomes of this review

This is an update of Cochrane Systematic Reviews (CSRs) published in 2008, 2011, 2013, and 2018. The outcomes analyzed were pulmonary function; exercise capacity; health-related quality of life; respiratory muscle function, strength, and endurance; frequency and duration of respiratory infections and hospitalizations; compliance; death or survival; adverse effects; costs; oxygen saturations; and postural stability measured.

The CSR included 10 studies published and/or registered up to October 5, 2020, with a total of 238 participants from children to adults. The results of these studies could not be combined since they published insufficient details, and the authors did not use the same standard measurements. No study found any difference in lung function; one of the studies reported an improvement in exercise duration, and another found improvement in quality of life. Two studies found a significant improvement in respiratory muscle function. 

These results were inconclusive because (i) there was no consistency and homogeneity in the methods of the included studies; (ii) none of the studies analyzed all the aspects completely; and (iii) some of the studies lacked information about age and pulmonary function. The applicability of the results is limited also due to (a) the recent introduction of CFTR modulating therapy and the consequent changes in the CF population; and (b) the population may not be representative of the actual CF population of patients.

Author’s conclusion of the review

The evidence to support the intervention as beneficial or not is insufficient; therefore, no recommendation can be made. In clinical practice, the use of respiratory muscle training should be determined individually for each patient. 

Future recommendations 

The authors recommend that further research must follow a more rigorous method and adopt standardized measurements to assess the effects of respiratory muscle training in people with cystic fibrosis. In particular,additional research should address (a) respiratory muscle function; (b) pulmonary function; (c) exercise capacity; (d) hospitalizations; (e) quality of life; (f) perceived dyspnoea; and (g) perceived exertion. Moreover, to address the representativity issue, the authors recommend that studies targeting specifically either pediatric or older-adult patients be carried out.

Comment by Robin Kuruvila Sentinella