title: Use of Angle-Independent M-Mode Sonography for Assessment of Diaphragm Displacement.
abstract: OBJECTIVE
  Sonographic assessment of diaphragm displacement has conventionally been conducted with M-mode sonography via an anterior subcostal approach. This method is subject to measurement errors when diaphragm displacement is not in line with the M-mode plane. We aimed to compare measurements obtained by offline angle-independent (anatomic) M-mode sonography with conventional M-mode sonography.
  
  
  METHODS
  Fifty healthy adults were imaged with conventional and angle-independent M-mode sonography of the bilateral hemidiaphragms at 60% maximal inspiratory capacity using an inspiratory spirometer.
  
  
  RESULTS
  Left hemidiaphragm displacement was successfully imaged by conventional M-mode sonography in only 70% (n = 35), as lung expansion obscured imaging, whereas 92% (n = 46) were assessable by angle-independent M-mode sonography. All right hemidiaphragm displacement could be assessed. Conventional M-mode results were higher than angle-independent M-mode results on the right (mean ± SD, 4.9 ± 1.4 versus 4.6 ± 1.2 cm, respectively; P= .003) and left (5.4 ± 1.3 versus 4.6 ± 1.0 cm; P < .001). Displacement values were different for right versus left hemidiaphragms on conventional M-mode sonography (mean difference, 0.6 ± 0.2 cm; P = .005), with only mild agreement (R2= 0.35; P < .001). There was no laterality seen in the diaphragm displacement on angle-independent M-mode sonography (mean difference, 0.1 ± 0.1 cm; P = .47), with good agreement (R2= 0.76; P < .001).
  
  
  CONCLUSIONS
  Angle-independent M-mode sonography leads to better visualization and assessment of the left hemidiaphragm. It records lower displacement than conventional M-mode sonography in the bilateral diaphragms, likely because of fewer orientation and translation errors. Future study is indicated to assess the clinical utility of angle-independent M-mode sonography in a population with diaphragm dysfunction.
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota USA.|Department of Intensive Care, Nepean Hospital, Sydney, New South Wales, Australia.
authors.forename: Sam R
authors.initials: SR
authors.lastname: Orde
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota USA.
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Boon
authors.affiliation: Department of Family Medicine, Mayo Clinic, Rochester, Minnesota USA.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Firth
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota USA.
authors.forename: Hector R
authors.initials: HR
authors.lastname: Villarraga
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota USA sekiguchi.hiroshi@mayo.edu.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sekiguchi
mesh_terms: D000328:Adult; D003964:Diaphragm / Q000000981:diagnostic imaging* / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D012016:Reference Values; D015203:Reproducibility of Results; D014463:Ultrasonography / Q000379:methods*
keywords: M-mode sonography; diaphragm; musculoskeletal ultrasound; sonography