Assessment of Brain Function Changes During PEEP-Based Respiratory Therapy in Critically Ill Patients Using Multimodal Neurophysiological Monitoring

Acute brain injury is frequently accompanied by respiratory dysfunction requiring mechanical ventilation because of impaired consciousness, respiratory insufficiency, or the need for airway protection. Positive end-expiratory pressure (PEEP) and lung recruitment maneuvers (RM) are commonly applied to improve oxygenation and prevent alveolar collapse. Although these interventions are essential components of lung-protective ventilation, increases in intrathoracic pressure may influence venous return, systemic hemodynamics, cerebral perfusion, carbon dioxide homeostasis, and cerebral blood flow. Such physiological alterations may subsequently affect cortical activity and neurovascular coupling, particularly in patients with impaired cerebrovascular regulation. However, the cerebral effects of ventilator interventions remain incompletely understood in neurocritical care populations.

This prospective, single-center study is designed to investigate brain-lung interactions during mechanical ventilation in patients admitted to a neurocritical care unit. The study focuses on the dynamic relationships among ventilator settings, cerebral electrophysiological activity, cerebral hemodynamics, and systemic physiological responses during clinically indicated recruitment maneuvers and PEEP adjustments.

During routine respiratory management, participants will undergo predefined ventilator interventions consisting of recruitment maneuvers and PEEP modifications according to the study protocol. Physiological signals will be continuously recorded throughout baseline, intervention, and recovery periods. This design allows assessment of cerebral responses to controlled changes in intrathoracic pressure and respiratory support while minimizing interference with standard clinical care.

Multimodal physiological monitoring will be performed simultaneously throughout the study period. Monitoring modalities include scalp electroencephalography (EEG), transcranial Doppler ultrasonography (TCD), invasive arterial blood pressure monitoring, end-tidal carbon dioxide monitoring, pulse oximetry, and routine intensive care monitoring. Physiological signals from multiple monitoring devices will be synchronized and recorded using a dedicated multimodal data acquisition platform. High-resolution recordings of cerebral electrophysiological activity, cerebral blood flow velocity, arterial blood pressure, respiratory parameters, and end-tidal carbon dioxide will allow assessment of rapid physiological responses occurring during ventilator interventions. Continuous acquisition of synchronized physiological signals will permit integrated evaluation of respiratory, cardiovascular, and cerebral responses.

EEG recordings will be analyzed using quantitative electrophysiological methods to characterize cortical activity. Spectral analysis will be performed to assess changes across conventional frequency bands, including relative delta activity and other power-based indices reflecting alterations in cortical functional state. Cerebral blood flow dynamics will be evaluated using TCD-derived cerebral blood flow velocity measurements. Simultaneous recordings of arterial blood pressure and end-tidal carbon dioxide will provide complementary information regarding cerebral perfusion and respiratory physiology.