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Purpose: The aim of the present study was to assess the rate of diffuse alveolar damage (DAD) on open lung biopsy (OLB) performed in the ICU for nonresolving ARDS., Methods: A single-center retrospective study of patients meeting the Berlin definition criteria for ARDS who had undergone OLB for nonresolving ARDS. Patients were classified into mild, moderate and severe ARDS categories and according to the presence or absence of DAD on the OLB. The ARDS categories were assessed at baseline and at the time of the OLB. The OLBs were reviewed by two pathologists blinded to the ARDS classification. The primary endpoint was the rate of DAD according to the ARDS stage in the patients with nonresolving ARDS who had OLB. The secondary endpoint was the ability of DAD to predict ARDS among all the patients who had OLB. The same clinico-histopathological confrontation was cross validated in another ICU., Results: From January 1998 to August 2013, 113 patients underwent OLB for acute hypoxemic respiratory failure, 83 of whom met the inclusion criteria for ARDS. At the time the OLB was performed, 11 of these patients had mild, 56 moderate, and 16 severe ARDS, respectively. The median (1st-3rd quartiles) time to OLB was 13 (10-18) and 9 (6-14) days from the onset of respiratory symptoms and from ARDS onset, respectively, with no statistical difference between the three ARDS groups. DAD was found in 48 (58 %) patients with ARDS, 4 (36 %) in the mild, 33 (59 %) in the moderate, and 11 (69 %) in the severe stage (P = 0.23). For the 113 patients who underwent OLB, the sensitivity and specificity of DAD to the Berlin definition was 0.58 (0.46-0.69) and 0.73 (0.54-0.88), respectively. Similar results were found in the other ICU., Conclusions: DAD is present in the majority of patients with nonresolving ARDs and its frequency is no different across the three ARDS stages. On this basis, the systematic use of steroids in nonresolving ARDS is not recommended.

Objective: To assess a sigmoidal equation for describing airway closure., Design: Experimental study., Setting: University laboratory., Participants: Eight piglets mechanically ventilated on zero end-expiratory pressure (ZEEP)., Interventions: Control and lung saline lavage., Measurements and Results: Lungs were inflated up to transpulmonary pressure of 30 cmH(2)O at constant flow (0.12l s(-1)) then deflated at the same flow rate up to the point at which oesophageal pressure was constant, which was assumed to represent complete airway closure. The deflation volume-transpulmonary pressure curve was fitted to: (1) a sigmoidal equation focusing on inflexion point and pressure at maximal compliance increase and (2) an exponential equation above an inflexion point determined by eyeballing. Data deviate from the exponential equation at the point of airway closure onset. The zero-volume intercept was determined. Complete airway closure was reached at -8.3+/-3.5cmH(2)O in control conditions and at -1.3+/-3.7 cmH(2)O after lavage (p < 0.05). Between control and lavage, onset of airway closure was 3.0+/-1.9 vs. 6.0+/-2.8 cmH(2)O (p <0.05), inflexion point 3.2+/-1.8 vs. 7.7+/-2.6 cmH(2)O (p <0.001), pressure at maximal compliance increase -1.9+/-0.7 vs. -0.03+/-2.1cmH(2)O (p <0.05) and zero-volume intercept -1.5+/-1.4 vs. 0.3+/-2.3cmH(2)O (p <0.05)., Conclusions: During mechanical ventilation airways stay open and close around ZEEP in control but are closed above ZEEP after lavage. Inflexion point might reflect onset of airways closure in control. Pressure at maximal compliance increase was not a marker of complete airways closure. In control and lavage, pressure at maximal compliance increase and zero-volume intercept were reasonably equivalent.