• Robinder G Khemani, Justin Hotz, Rica Morzov, Rutger C Flink, Asvari Kamerkar, Marie LaFortune, Gerrard F Rafferty, Patrick A Ross, and Christopher J L Newth.
• Department of Anesthesiology and Critical Care, Children's Hospital Los Angeles, 4650 Sunset Blvd Mailstop 12, Los Angeles, CA, 90027, USA. rkhemani@chla.usc.edu.
• Intensive Care Med. 2016 Aug 1; 42 (8): 1214-22.

PurposePressure support is often used for extubation readiness testing, to overcome perceived imposed work of breathing from endotracheal tubes. We sought to determine whether effort of breathing on continuous positive airway pressure (CPAP) of 5 cmH2O is higher than post-extubation effort, and if this is confounded by endotracheal tube size or post-extubation noninvasive respiratory support.MethodsProspective trial in intubated children. Using esophageal manometry we compared effort of breathing with pressure rate product under four conditions: pressure support 10/5 cmH2O, CPAP 5 cmH2O (CPAP), and spontaneous breathing 5 and 60 min post-extubation. Subgroup analysis excluded post-extubation upper airway obstruction (UAO) and stratified by endotracheal tube size and post-extubation noninvasive respiratory support.ResultsWe included 409 children. Pressure rate product on pressure support [100 (IQR 60, 175)] was lower than CPAP [200 (120, 300)], which was lower than 5 min [300 (150, 500)] and 60 min [255 (175, 400)] post-extubation (all p < 0.01). Excluding 107 patients with post-extubation UAO (where pressure rate product after extubation is expected to be higher), pressure support still underestimated post-extubation effort by 126-147 %, and CPAP underestimated post-extubation effort by 17-25 %. For all endotracheal tube subgroups, ≤3.5 mmID (n = 152), 4-4.5 mmID (n = 102), and ≥5.0 mmID (n = 48), pressure rate product on pressure support was lower than CPAP and post-extubation (all p < 0.0001), while CPAP pressure rate product was not different from post-extubation (all p < 0.05). These findings were similar for patients extubated to noninvasive respiratory support, where pressure rate product on pressure support before extubation was significantly lower than pressure rate product post-extubation on noninvasive respiratory support (p < 0.0001, n = 81).ConclusionsRegardless of endotracheal tube size, pressure support during extubation readiness tests significantly underestimates post-extubation effort of breathing.

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