Bedside Ultrasound Assessment of Positive End-Expiratory Pressure–induced Lung Recruitment

TLDR

Lung ultrasound is increasingly used at the bedside to evaluate alveolar‑interstitial syndrome, consolidation, pneumonia, pneumothorax, and pleural effusion in critically ill patients. The study aimed to compare the pressure‑volume curve method with lung ultrasound for assessing PEEP‑induced lung recruitment in patients with ARDS/ALI. In a prospective cohort of 40 patients (30 ARDS, 10 ALI), PV curves and LUS were performed at PEEP 0 and 15 cm H₂O, with LUS patterns classified into consolidation, irregular B lines, coalescent B lines, or normal aeration, and a regional reaeration score calculated. A strong correlation (ρ = 0.88) was found between PV‑curve–derived recruitment and the ultrasound reaeration score, with scores ≥ +8 predicting > 600 ml recruitment and scores ≤ +4 indicating 75–450 ml, and a significant association (ρ = 0.63) between the score and PaO₂ improvement, indicating that LUS can estimate recruitment but cannot detect hyperinflation and should not be used alone for PEEP titration.

Abstract

In the critically ill patients, lung ultrasound (LUS) is increasingly being used at the bedside for assessing alveolar-interstitial syndrome, lung consolidation, pneumonia, pneumothorax, and pleural effusion. It could be an easily repeatable noninvasive tool for assessing lung recruitment.Our goal was to compare the pressure-volume (PV) curve method with LUS for assessing positive end-expiratory pressure (PEEP)-induced lung recruitment in patients with acute respiratory distress syndrome/acute lung injury (ARDS/ALI).Thirty patients with ARDS and 10 patients with ALI were prospectively studied. PV curves and LUS were performed in PEEP 0 and PEEP 15 cm H₂O₂. PEEP-induced lung recruitment was measured using the PV curve method.Four LUS entities were defined: consolidation; multiple, irregularly spaced B lines; multiple coalescent B lines; and normal aeration. For each of the 12 lung regions examined, PEEP-induced ultrasound changes were measured, and an ultrasound reaeration score was calculated. A highly significant correlation was found between PEEP-induced lung recruitment measured by PV curves and ultrasound reaeration score (Rho = 0.88; P < 0.0001). An ultrasound reaeration score of +8 or higher was associated with a PEEP-induced lung recruitment greater than 600 ml. An ultrasound lung reaeration score of +4 or less was associated with a PEEP-induced lung recruitment ranging from 75 to 450 ml. A statistically significant correlation was found between LUS reaeration score and PEEP-induced increase in Pa(O₂) (Rho = 0.63; P < 0.05).PEEP-induced lung recruitment can be adequately estimated with bedside LUS. Because LUS cannot assess PEEP-induced lung hyperinflation, it should not be the sole method for PEEP titration.