Balancing lung and brain: physiological strategies for ARDS management in acute brain injury

Acute respiratory distress syndrome (ARDS) is a common and clinically significant complication in patients with acute brain injury (ABI), affecting up to one-third of critically ill individuals and contributing to increased mortality, prolonged mechanical ventilation, and worse neurological outcomes. The coexistence of ARDS and ABI creates a fundamental therapeutic dilemma: strategies that protect the lung may adversely affect cerebral physiology, whilst neuroprotective targets may compromise respiratory management. This narrative review examined the pathophysiological interactions between the injured lung and brain, highlighting the competing effects of key ventilatory variables. Lung-protective ventilation, including low tidal volume and higher positive end-expiratory pressure (PEEP), reduces ventilator-induced lung injury but may increase arterial carbon dioxide (PaCO₂), resulting in intracranial hypertension and impaired cerebral perfusion. Conversely, strict control of PaCO₂ and optimisation of cerebral perfusion may necessitate deviations from conventional ARDS strategies. Oxygenation targets further illustrate this tension, as both hypoxaemia and hyperoxaemia can exacerbate secondary brain injury. We synthesised current evidence on respiratory support, including non-invasive strategies, invasive mechanical ventilation, rescue therapies such as prone positioning and extracorporeal support, and pharmacological interventions, with emphasis on their differential effects on pulmonary and cerebral physiology. Attention was also given to the role of multimodal neuromonitoring, including intracranial pressure and brain tissue oxygenation, as tools to individualise ventilatory management and reconcile competing organ priorities. Overall, available data support a shift from protocolised approaches towards physiology-driven, patient-specific strategies that integrate lung mechanics, gas exchange and cerebral haemodynamics in patients with concomitant ARDS and ABI. Future studies should incorporate combined lung and brain endpoints to define strategies that simultaneously minimise ventilator-induced lung injury and secondary brain injury.