Abstract
BackgroundThe effects of positive end-expiratory pressure (PEEP) on lung ultrasound (LUS) patterns, and their relationship with intracranial pressure (ICP) in brain injured patients have not been completely clarified. The primary aim of this study was to assess the effect of two levels of PEEP (5 and 15 cmH2O) on global (LUStot) and regional (anterior, lateral, and posterior areas) LUS scores and their correlation with changes of invasive ICP. Secondary aims included: the evaluation of the effect of PEEP on respiratory mechanics, arterial partial pressure of carbon dioxide (PaCO2) and hemodynamics; the correlation between changes in ICP and LUS as well as respiratory parameters; the identification of factors at baseline as potential predictors of ICP response to higher PEEP.MethodsProspective, observational study including adult mechanically ventilated patients with acute brain injury requiring invasive ICP. Total and regional LUS scores, ICP, respiratory mechanics, and arterial blood gases values were analyzed at PEEP 5 and 15 cmH2O.ResultsThirty patients were included; 19 of them (63.3%) were male, with median age of 65 years [interquartile range (IQR) = 66.7–76.0]. PEEP from 5 to 15 cmH2O reduced LUS score in the posterior regions (LUSp, median value from 7 [5–8] to 4.5 [3.7–6], p = 0.002). Changes in ICP were significantly correlated with changes in LUStot (rho = 0.631, p = 0.0002), LUSp (rho = 0.663, p < 0.0001), respiratory system compliance (rho = − 0.599, p < 0.0001), mean arterial pressure (rho = − 0.833, p < 0.0001) and PaCO2 (rho = 0.819, p < 0.0001). Baseline LUStot score predicted the increase of ICP with PEEP.ConclusionsLUS-together with the evaluation of respiratory and clinical variables-can assist the clinicians in the bedside assessment and prediction of the effect of PEEP on ICP in patients with acute brain injury.
Highlights
The effects of positive end-expiratory pressure (PEEP) on lung ultrasound (LUS) patterns, and their relationship with intracranial pressure (ICP) in brain injured patients have not been completely clarified
In a small physiological study using quantitative Computed Tomography [7], we showed that PEEP could be safe in brain injured patients when promoting alveolar recruitment, without causing alveolar hyperdistention, decreased mean arterial pressure and cerebral blood flow
Inclusion and exclusion criteria Patients were screened for inclusion from August 1st 2020 to September 1st 2021, and considered eligible if they were > 18 years old, required mechanical ventilation and were admitted to the intensive care unit (ICU) of San Martino Policlinico Hospital, IRCCS for Oncology and Neuroscience, Genoa, Italy, after acute brain injury requiring invasive ICP monitoring, and if underwent LUS evaluation based on clinical indications at two different levels of PEEP (5 and 15 c mH20)
Summary
The effects of positive end-expiratory pressure (PEEP) on lung ultrasound (LUS) patterns, and their relationship with intracranial pressure (ICP) in brain injured patients have not been completely clarified. Secondary aims included: the evaluation of the effect of PEEP on respiratory mechanics, arterial partial pressure of carbon dioxide (PaCO2) and hemodynamics; the correlation between changes in ICP and LUS as well as respiratory parameters; the identification of factors at baseline as potential predictors of ICP response to higher PEEP. Concerns regarding the potential detrimental effects of PEEP on cerebral hemodynamics include different pathophysiological mechanisms: the risk for increased intrathoracic.
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