Ultrasound imaging and use of B-lines for functional lung evaluation in neurocritical care: a prospective, observational study.

CONTEXT: Lung ultrasound imaging can be used to evaluate pulmonary water content and pulmonary consolidation in ICU patients, but data from neurocritical care are lacking. OBJECTIVE: To evaluate the utility of lung ultrasound to estimate the PaO2/FiO2 ratio and its diagnostic accuracy compared with chest radiograph and thoracic computed tomography (CT). DESIGN: Prospective, observational study. SETTING: University hospital neurocritical care unit. PATIENTS: Forty-five consecutive patients. MAIN OUTCOME MEASURES: The relationship between the number of B-lines and the PaO2/FiO2 ratio as measure of lung water content, and the diagnosis of pulmonary consolidation. RESULTS: Evaluation of lung water content as determined by the number of 'B-lines' has a linear relationship with the PaO2/FiO2 ratio (r = -0.8; P < 0.01). Lung ultrasound has a diagnostic accuracy similar to that of chest radiograph (99 vs. 96%), using thoracic CT as the reference technique. CONCLUSION: In neurocritical care, the use of lung ultrasound allows detection of increased lung water content when more than three 'B-lines' are present within the same lung field. This is associated with a reduction in PaO2/FiO2 ratio. Lung ultrasound can be used to diagnose pulmonary consolidation with an accuracy similar to the chest radiograph.