• Martin Dres, Bruno-Pierre Dubé, Ewan Goligher, Stefannie Vorona, Suela Demiri, Elise Morawiec, Julien Mayaux, Laurent Brochard, Thomas Similowski, and Alexandre Demoule.
• From Public Assistance - Paris Hospital, Pitie-Salpetriere Hospital, Pneumology and Critical Care Department, Paris, France (M.D., B.-P.D., S.D., E.M., J.M., T.S., A.D.) Sorbonne University, Experimental and Clinical Neurophysiology Research Unit 1158, Paris, France (M.D., S.D., T.S., A.D.) St. Michael's Hospital, Li Ka Shing Knowledge Institute, Keenan Research Centre, Toronto, Ontario, Canada (M.D., L.B.) Medicine Department, Pneumology Department, Hotel Dieu Hospital, Montreal University Hospital Center, Montréal, Québec, Canada (B.-P.D.) Montreal University Hospital Center Research Center, Montréal, Québec, Canada (B.-P.D.) the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada (E.G., L.B.) the Department of Medicine, Division of Respirology, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada (E.G., S.V.).
• Anesthesiology. 2020 May 1; 132 (5): 1114-1125.

BackgroundThe assessment of diaphragm function with diaphragm ultrasound seems to bring important clinical information to describe diaphragm work and weakness. When the diaphragm is weak, extradiaphragmatic muscles may play an important role, but whether ultrasound can also assess their activity and function is unknown. This study aimed to (1) evaluate the feasibility of measuring the thickening of the parasternal intercostal and investigate the responsiveness of this muscle to assisted ventilation; and (2) evaluate whether a combined evaluation of the parasternal and the diaphragm could predict failure of a spontaneous breathing trial.MethodsFirst, an exploratory evaluation of the parasternal in 23 healthy subjects. Second, the responsiveness of parasternal to several pressure support levels were studied in 16 patients. Last, parasternal activity was compared in presence or absence of diaphragm dysfunction (assessed by magnetic stimulation of the phrenic nerves and ultrasound) and in case of success/failure of a spontaneous breathing trial in 54 patients.ResultsThe parasternal was easily accessible in all patients. The interobserver reproducibility was good (intraclass correlation coefficient, 0.77 (95% CI, 0.53 to 0.89). There was a progressive decrease in parasternal muscle thickening fraction with increasing levels of pressure support (Spearman ρ = -0.61 [95% CI, -0.74 to -0.44]; P < 0.0001) and an inverse correlation between parasternal muscle thickening fraction and the pressure generating capacity of the diaphragm (Spearman ρ = -0.79 [95% CI, -0.87 to -0.66]; P < 0.0001). The parasternal muscle thickening fraction was higher in patients with diaphragm dysfunction: 17% (10 to 25) versus 5% (3 to 8), P < 0.0001. The pressure generating capacity of the diaphragm, the diaphragm thickening fraction and the parasternal thickening fraction similarly predicted failure or the spontaneous breathing trial.ConclusionsUltrasound assessment of the parasternal intercostal muscle is feasible in the intensive care unit and provides novel information regarding the respiratory capacity load balance.

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