Abstract
BackgroundTo evaluate the impact of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP) in animals with different respiratory mechanics, baseline ICP and volume status.MethodsA total of 50 male adult Bama miniature pigs were involved in four different protocols (n = 20, 12, 12, and 6, respectively). Under the monitoring of ICP, brain tissue oxygen tension and hemodynamical parameters, PEEP was applied in increments of 5 cm H2O from 5 to 25 cm H2O. Measurements were taken in pigs with normal ICP and normovolemia (Series I), or with intracranial hypertension (via inflating intracranial balloon catheter) and normovolemia (Series II), or with intracranial hypertension and hypovolemia (via exsanguination) (Series III). Pigs randomized to the control group received only hydrochloride instillation while the intervention group received additional chest wall strapping. Common carotid arterial blood flow before and after exsanguination at each PEEP level was measured in pigs with intracranial hypertension and chest wall strapping (Series IV).ResultsICP was elevated by increased PEEP in both normal ICP and intracranial hypertension conditions in animals with normal blood volume, while resulted in decreased ICP with PEEP increments in animals with hypovolemia. Increasing PEEP resulted in a decrease in brain tissue oxygen tension in both normovolemic and hypovolemic conditions. The impacts of PEEP on hemodynamical parameters, ICP and brain tissue oxygen tension became more evident with increased chest wall elastance. Compare to normovolemic condition, common carotid arterial blood flow was further lowered when PEEP was raised in the condition of hypovolemia.ConclusionsThe impacts of PEEP on ICP and cerebral oxygenation are determined by both volume status and respiratory mechanics. Potential conditions that may increase chest wall elastance should also be ruled out to avoid the deleterious effects of PEEP.
Highlights
To evaluate the impact of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP) in ani‐ mals with different respiratory mechanics, baseline ICP and volume status
We found that respiratory mechanics determine the effect of PEEP on ICP: in pigs with normal ICP, an increase of PEEP resulted in increased ICP, where the influence was more evident in the condition of increased Chest wall elastance (ECW)
Details of respiratory mechanics, hemodynamical parameters and blood gas analysis were shown in Additional file 2. ECW was significantly increased by chest wall strapping, while no difference in Lung elastance (EL) was observed between the control and chest wall strapping groups (Additional file 2: Tables S1–S3)
Summary
To evaluate the impact of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP) in ani‐ mals with different respiratory mechanics, baseline ICP and volume status. Chen et al BMC Neuroscience (2021) 22:72 oxygenation and on the other hand may potentially impair intracranial pressure (ICP) and cerebral blood perfusion. It is still unclear how positive end-expiratory pressure (PEEP) affects the ICP and cerebral oxygenation. The transmission of PEEP into the thoracic cavity is determined by respiratory mechanics: it has been shown that increased lung elastance (EL) and decreased chest wall elastance (ECW) can minimize the effect of PEEP on pleural pressure [19]. An increased ERS may attribute to either the increase in EL due to pulmonary diseases such as acute respiratory distress syndrome (ARDS), or the rise in E CW due to chest wall impairment such as intra-abdominal hypertension, or both [20]. EL and ECW were not differentiated in previous studies [3, 10, 11, 14]
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