title: Evolution of Diaphragm Thickness during Mechanical Ventilation. Impact of Inspiratory Effort.
abstract: BACKGROUND
  Diaphragm atrophy and dysfunction have been reported in humans during mechanical ventilation, but the prevalence, causes, and functional impact of changes in diaphragm thickness during routine mechanical ventilation for critically ill patients are unknown.
  
  
  OBJECTIVE
  To describe the evolution of diaphragm thickness over time during mechanical ventilation, its impact on diaphragm function, and the influence of inspiratory effort on this phenomenon.
  
  
  METHODS
  In three academic intensive care units, 107 patients were enrolled shortly after initiating ventilation along with 10 nonventilated intensive care unit patients (control subjects). Diaphragm thickness and contractile activity (quantified by the inspiratory thickening fraction) were measured daily by ultrasound.
  
  
  RESULTS
  Over the first week of ventilation, diaphragm thickness decreased by more than 10% in 47 (44%), was unchanged in 47 (44%), and increased by more than 10% in 13 (12%). Thickness did not vary over time following extubation or in nonventilated patients. Low diaphragm contractile activity was associated with rapid decreases in diaphragm thickness, whereas high contractile activity was associated with increases in diaphragm thickness (P = 0.002). Contractile activity decreased with increasing ventilator driving pressure (P = 0.01) and controlled ventilator modes (P = 0.02). Maximal thickening fraction (a measure of diaphragm function) was lower in patients with decreased or increased diaphragm thickness (n = 10) compared with patients with unchanged thickness (n = 10; P = 0.05 for comparison).
  
  
  CONCLUSIONS
  Changes in diaphragm thickness are common during mechanical ventilation and may be associated with diaphragmatic weakness. Titrating ventilatory support to maintain normal levels of inspiratory effort may prevent changes in diaphragm configuration associated with mechanical ventilation.
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|3 Department of Physiology.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Ewan C
authors.initials: EC
authors.lastname: Goligher
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|5 Institute for Health Policy, Management and Evaluation, and.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Eddy
authors.initials: E
authors.lastname: Fan
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.|6 Toronto General Research Institute, Toronto, Ontario, Canada.
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Herridge
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Alistair
authors.initials: A
authors.lastname: Murray
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Stefannie
authors.initials: S
authors.lastname: Vorona
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Debbie
authors.initials: D
authors.lastname: Brace
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|7 Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Nuttapol
authors.initials: N
authors.lastname: Rittayamai
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.|7 Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Ashley
authors.initials: A
authors.lastname: Lanys
authors.affiliation: 2 Department of Medicine.
authors.forename: George
authors.initials: G
authors.lastname: Tomlinson
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Singh
authors.affiliation: 3 Department of Physiology.
authors.forename: Steffen-Sebastian
authors.initials: SS
authors.lastname: Bolz
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|5 Institute for Health Policy, Management and Evaluation, and.|8 Department of Critical Care Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; and.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Rubenfeld
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|3 Department of Physiology.|9 Department of Anesthesia, University of Toronto, Toronto, Ontario, Canada.|10 Department of Critical Care Medicine, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Kavanagh
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|7 Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Brochard
authors.affiliation: 1 Interdepartmental Division of Critical Care Medicine.|2 Department of Medicine.|3 Department of Physiology.|5 Institute for Health Policy, Management and Evaluation, and.|4 Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada.|6 Toronto General Research Institute, Toronto, Ontario, Canada.
authors.forename: Niall D
authors.initials: ND
authors.lastname: Ferguson
mesh_terms: D000368:Aged; D016638:Critical Illness; D003964:Diaphragm / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018908:Muscle Weakness / Q000000981:diagnostic imaging; D012119:Respiration; D012121:Respiration, Artificial; D014463:Ultrasonography
keywords: artificial respiration; diaphragm function; disuse atrophy; myotrauma; weaning