Study design (if review, criteria of inclusion for studies)
Randomised or quasi-randomised clinical controlled trials comparing different inspiratory muscle training regimens with each other or a control in people with cystic fibrosis.
List of included studies (10)
Albinni 2004; Amelina 2006; Asher 1983; Bieli 2017; Chatham 1997; de Jong 2001; Enright 2004; Heward 2000; Sawyer 1993
Participants
People with CF, of any age, diagnosed by clinical criteria, sweat test or genotyping or both.
Interventions
Inspiratory muscle training (IMT) (as achieved by voluntary isocapnic hyperpnoea, resistive loading or threshold loading) vs each other or with no or sham IMT
Outcome measures
Primary outcomes: 1. Health-related quality of life - Chronic Respiratory Disease Questionnaire (emotion); Chronic Respiratory Disease Questionnaire (mastery); 2. Pulmonary function tests (performed at rest): i) forced expiratory volume at one second (FEV1) ii) forced vital capacity (FVC) 3. Exercise tolerance: i) field-based tests ii) laboratory-based tests
Main results
Authors identified 20 studies, of which 10 studies with 238 participants met the review's inclusion criteria. There was wide variation in the methodological and written quality of the included studies. Four of the 10 included studies were published as abstracts only and lacked concise details, thus limiting the information available. Eight studies were parallel studies and two of a crossâover design. Respiratory muscle training interventions varied dramatically, with frequency, intensity and duration ranging from thrice weekly to twice daily, 20% to 80% of maximal effort, and 10 to 30 minutes, respectively. Participant numbers ranged from 11 to 39 participants in the included studies; five studies were in adults only, one in children only and four in a combination of children and adults. No differences between treatment and control were reported in the primary outcome of pulmonary function (forced expiratory volume in one second and forced vital capacity) or postural stability (very lowâquality evidence). Although no change was reported in exercise capacity as assessed by the maximum rate of oxygen use and distance completed in a six minute walk test, a 10% improvement in exercise duration was found when working at 60% of maximal effort in one study (n = 20) (very lowâquality evidence). In a further study (n = 18), when working at 80% of maximal effort, healthârelated quality of life improved in the mastery and emotion domains (very lowâquality evidence). With regards to the review's secondary outcomes, one study (n = 11) found a change in intramural pressure, functional residual capacity and maximal inspiratory pressure following training (very lowâquality evidence). Another study (n=36) reported improvements in maximal inspiratory pressure following training (P < 0.001) (very lowâquality evidence). A further study (n = 22) reported that respiratory muscle endurance was longer in the training group (P < 0.01). No studies reported significant differences on any other secondary outcomes. Metaâanalyses could not be performed due to a lack of consistency and insufficient detail in reported outcome measures.
Authors' conclusions
There is insufficient evidence to suggest whether this intervention is beneficial or not. Healthcare practitioners should consider the use of respiratory muscle training on a caseâbyâcase basis. Further research of reputable methodological quality is needed to determine the effectiveness of respiratory muscle training in people with cystic fibrosis. Researchers should consider the following clinical outcomes in future studies; respiratory muscle function, pulmonary function, exercise capacity, hospital admissions, and healthârelated quality of life. Sensoryâperceptual changes, such as respiratory effort sensation (e.g. rating of perceived breathlessness) and peripheral effort sensation (e.g. rating of perceived exertion) may also help to elucidate mechanisms underpinning the effectiveness of respiratory muscle training.