title: Air trapping: The major factor limiting diaphragm mobility in chronic obstructive pulmonary disease patients.
abstract: OBJECTIVE
  Patients with COPD can have impaired diaphragm mechanics. A new method of assessing the mobility of the diaphragm, using ultrasound, has recently been validated. This study evaluated the relationship between pulmonary function and diaphragm mobility, as well as that between respiratory muscle strength and diaphragm mobility, in COPD patients.
  
  
  METHODS
  COPD patients with pulmonary hyperinflation (n = 54) and healthy subjects (n = 20) were studied. Patients were tested for pulmonary function, maximal respiratory pressures and diaphragm mobility using ultrasound to measure the craniocaudal displacement of the left branch of the portal vein.
  
  
  RESULTS
  COPD patients had less diaphragm mobility than did healthy individuals (36.5 +/- 10.9 mm vs 46.3 +/- 9.5 mm, P = 0.001). In COPD patients, diaphragm mobility correlated strongly with pulmonary function parameters that quantify air trapping (RV: r = -0.60, P < 0.001; RV/TLC: r = -0.76, P < 0.001), moderately with airway obstruction (FEV(1): r = 0.55, P < 0.001; airway resistance: r = -0.32, P = 0.02) and weakly with pulmonary hyperinflation (TLC: r = -0.28, P = 0.04). No relationship was observed between diaphragm mobility and respiratory muscle strength (maximal inspiratory pressure: r = -0.11, P = 0.43; maximal expiratory pressure: r = 0.03, P = 0.80).
  
  
  CONCLUSIONS
  The results of this study suggest that the reduction in diaphragm mobility in COPD patients is mainly due to air trapping and is not influenced by respiratory muscle strength or pulmonary hyperinflation.
authors.affiliation: Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Wellington Pereira
authors.initials: WP
authors.lastname: Dos Santos Yamaguti
authors.forename: Elaine
authors.initials: E
authors.lastname: Paulin
authors.forename: Simone
authors.initials: S
authors.lastname: Shibao
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Chammas
authors.forename: João Marcos
authors.initials: JM
authors.lastname: Salge
authors.forename: Marcos
authors.initials: M
authors.lastname: Ribeiro
authors.forename: Alberto
authors.initials: A
authors.lastname: Cukier
authors.forename: Celso Ricardo Fernandes
authors.initials: CR
authors.lastname: Carvalho
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003964:Diaphragm / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D011169:Portal Vein; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D012720:Severity of Illness Index; D014463:Ultrasonography