Ultrasound Protocol
PU were performed at three time points during a patient’s ICU stay: (1) as soon after intubation as possible, (2) 48-hours after the initial , and (3) at extubation if the patient’s previous did not already coincide with extubation. The patient was positioned supine with the head of the bed elevated 20 to 40 degrees. All were performed with SonoSite EDGE portable ultrasound system equipped with a P21 (1-5) phased-array transducer (FUJIFILM SonoSite Inc., Bothell, WA).
Four physicians with greater than 3 years of PU experience performed all . They participated in a pre-study 1-hour session to ensure uniformity of the pulmonary classifications, then independently scored 64 virtual patients with video clips. Overall and entity-specific inter-rater agreement calculated. 
Physicians performing the PU were not involved in the patient’s care and were blinded to history, lab data, imaging, treatments, and diagnosis. They were instructed not to examine medication drips or ventilator settings during the ultrasound examination.