Departmental Bulletin Paper Correlation between peak expiratory flow and abdominal muscle thickness in elderly subjects.

Ishida, Hiroshi  ,  Kurozumi, Chiharu  ,  Moriyoshi, Hikaru  ,  Suehiro, Tadanobu  ,  Watanabe, Susumu

IntroductionHigh expiratory flow plays an important role in expelling foreign substances and excessive mucus from the lungs and airways in order to minimize the risk of infection. Activity of the abdominal muscles is important for the generation of high expiratory flow. This muscle group includes the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA). However, little is known about the contribution of each abdominal muscle to forced expiration.ObjectiveThe aim of the present study was to determine whether abdominal muscle thickness at rest is correlated with peak expiratory flow (PEF) in elderly subjects.MethodsThe present study examined whether PEF was associated with the thickness of specific abdominal muscles in 24 elderly women who could walk independently. Muscle thickness was measured at rest in the supine position. The thicknesses of the right RA, EO, IO, and TrA were measured using B-mode ultrasound at the end of a relaxed expiration in the supine position. PEF was obtained using a peak flow meter in the sitting position. The correlation between normalized PEF and normalized abdominal muscle thickness was determined using Pearson’s correlation coefficient.ResultsCorrelation coefficients when comparing PEF and the RA, EO, IO, and TrA were 0.434 (P = 0.034), 0.323 (P = 0.124), 0.539 (P = 0.007), and 0.470 (P = 0.021), respectively.ConclusionOur results indicate that the muscle thickness of the IO correlates most with fast forced expiration production in the elderly subjects, TrA and RA have intermediate correlations, while EO is the least correlated. Thus, the action of the IO and TrA in increasing IAP, as well as the action of the RA on the rib cage, might be more highly associated with PEF than the action of the EO on the rib cage in elderly subjects.

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