The influence of body composition on respiratory muscle, lung function and diaphragm thickness in adults with cystic fibrosis

Abstract Background: Weight loss and loss of fat-free mass (FFM) are associated with peripheral muscle wasting in cystic fibrosis (CF) although whether this co-exists with loss of diaphragm mass remains unclear. Methods: FFM was determined by dual-energy X-ray absorptiometry and bioelectrical impedance in 40 adults with CF and 30 age-matched healthy subjects (HS). Diaphragm thickness at functional residual capacity (FRC) [TDIrel] and total lung capacity (TLC) [TDIcont] and thickening ratio (TR) were assessed by ultrasonography. Inspiratory muscle strength and work capacity were determined by maximal inspiratory pressure (PImax), and sustained PImax (SPImax); pulmonary function (RV, VC and TLC) and physical activity status (PAS) were also determined. Results: When the CF patients were assessed as a group (low and normal FFM) they had similar age, weight, height and PAS compared to the HS, although patients had lower FFM ( p p p p Conclusions: PImax is relatively well preserved in adults with CF although there is a relationship between the loss of inspiratory muscle work capacity, FFM, PAS and pulmonary function. Furthermore loss of FFM is associated with loss of diaphragm muscle mass.