Mechanical ventilation in acute brain injury

Acute brain injury (ABI) includes traumatic brain injury, subarachnoid and intracerebral haemorrhage, ischaemic stroke and global hypoxic-ischaemic injury, and patients often require admission to intensive care. Although pathologically heterogeneous, they share common mechanisms of primary injury followed by secondary brain injury. Systemic derangements such as hypoxaemia, dysregulated carbon dioxide tension and elevated intracranial pressure (ICP) may exacerbate secondary injury and should be avoided. Patients with ABI often require invasive mechanical ventilation (IMV), and of these up to 19-22% may develop acute respiratory distress syndrome. Lung-protective ventilation (LPV) strategies using low tidal volumes and moderate positive end-expiratory pressure to minimise ventilator-induced lung injury are established practices in patients requiring IMV. However, strict application of LPV principles may conflict with neuro-protective goals, particularly carbon dioxide control to optimise cerebral blood flow and avoid rises in ICP. This review examines the physiological tension between lung and brain protection, focusing on neuro-respiratory interactions and brain-lung crosstalk. We synthesise the evidence on ventilatory strategies in the context of patients with ABI, discuss the implications for neurological and pulmonary outcomes, and highlight the need for an integrated, individualised approach to ventilation in these patients.