The influence of body composition on respiratory muscle, lung function and diaphragm thickness in adults with cystic fibrosis.
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<0.05), VC and TLC than the HS (p<0.01). In addition, although PImax, TDIrel, TDIcont and TR were similar between the patients and the HS, SPImax was lower in the patients (p<0.01). When analyses were made between patients with low versus normal FFM and between patients with low FFM and HS no significant differences were found between overall weight although TDIrel, TDIcont, TR and PAS were all reduced in patients with low FFM (p<0.01).


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.
Enright
Stephanie
S
Wales College of Medicine, Biology, Life and Health Sciences, Cardiff University, Cardiff CF14 4XN, UK. enrights@cardiff.ac.uk
Chatham
Ken
K
Ionescu
Alina A
AA
Unnithan
Viswanath B
VB
Shale
Dennis J
DJ
D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D003550:Cystic Fibrosis / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D012119:Respiration; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000033:anatomy & histology* / Q000502:physiology*