Brain Monitoring During PEEP-Based Respiratory Therapy in Critically Ill Patients

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

Mechanical ventilation is commonly used in critically ill patients with acute brain injury. Positive end-expiratory pressure (PEEP) and lung recruitment maneuvers are important ventilator strategies for improving oxygenation, but they may also influence cerebral blood flow, systemic hemodynamics, carbon dioxide levels, and brain electrical activity. The effects of PEEP-related ventilator changes on cortical function in neurocritical care patients remain insufficiently understood.

This prospective observational physiological study will evaluate changes in brain electrical activity and cerebral blood flow during clinically indicated lung recruitment maneuvers and PEEP adjustments in mechanically ventilated neurocritical care patients. Multimodal monitoring will include electroencephalography (EEG), transcranial Doppler ultrasound, invasive arterial blood pressure, end-tidal carbon dioxide, and routine clinical variables.

EEG-derived measures, including delta power ratio and related frequency-domain indicators, will be used to describe cortical activity. Cerebral blood flow velocity and low-frequency neurovascular coupling measures will be explored as secondary physiological outcomes. The study will examine whether PEEP-related changes are associated with alterations in EEG activity, cerebral blood flow, and neurovascular coupling, and whether these responses differ according to clinical status.

The results may help improve understanding of brain-lung interactions during mechanical ventilation and inform future studies on individualized ventilation strategies in neurocritical care.

Study Overview

• Status: Recruiting
• Conditions: Acute Brain Injury; Mechanical Ventilation; Neurocritical Care
• Intervention / Treatment: Procedure: Recruitment Maneuver; Procedure: Positive End-Expiratory Pressure Adjustment

Detailed Description

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.

A central component of the study is the investigation of neurovascular coupling during mechanical ventilation. Integrated analysis of EEG activity and cerebral blood flow oscillations will be performed to characterize physiological coupling between neuronal activity and cerebral circulation. Relationships among cerebral electrophysiological activity, cerebral blood flow velocity, systemic hemodynamics, respiratory variables, and ventilator settings will be explored to better understand mechanisms underlying brain-lung interactions. These analyses will provide insight into how ventilator-induced physiological changes may influence cerebral function and cerebrovascular regulation in critically ill patients.

By providing simultaneous assessment of respiratory, hemodynamic, and neurophysiological responses during ventilator interventions, this study aims to improve understanding of the physiological mechanisms linking mechanical ventilation and brain function. The findings may contribute to the development of individualized ventilatory strategies that optimize respiratory support while preserving cerebral physiological stability in patients with acute brain injury.

• Study Type: Interventional
• Enrollment (Estimated): 50
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Min Xu; Phone Number: +8613864708968; Email: xuminicu@163.com

Study Locations

• China
  • Shandong
    • Dongying, Shandong, China, 257034
      • Recruiting
      • Shengli Oilfield Central Hospital
      • Contact: min xu; Phone Number: +86 13864708968; Email: xuminicu@163.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age ≥18 years.
• Admission to the neurocritical care unit with acute brain injury requiring intensive care management.
• Receiving invasive mechanical ventilation.
• Undergoing clinically indicated recruitment maneuvers and positive end-expiratory pressure (PEEP) adjustments.
• Availability of an adequate temporal acoustic window for transcranial Doppler monitoring.
• Written informed consent obtained from the participant or a legally authorized representative.

Exclusion Criteria:

• Pregnancy.
• Hemodynamic instability precluding recruitment maneuvers or PEEP adjustments.
• Severe cardiac dysfunction judged by the treating physician to contraindicate study procedures.
• Inability to obtain adequate transcranial Doppler signals.
• Conditions preventing EEG monitoring, including extensive scalp injury or dressings that preclude electrode placement.
• Withdrawal of informed consent.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: PEEP-Based Respiratory Intervention

Procedure: Recruitment Maneuver; A standardized lung recruitment maneuver performed during mechanical ventilation to transiently increase airway pressure and reopen collapsed alveoli. Physiological responses are continuously monitored using multimodal neuromonitoring and hemodynamic monitoring systems.; Procedure: Positive End-Expiratory Pressure Adjustment; Positive end-expiratory pressure (PEEP) levels are adjusted according to the study protocol during mechanical ventilation. Cerebral electrophysiological activity, cerebral blood flow, systemic hemodynamics, and respiratory parameters are continuously recorded during PEEP modifications.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in EEG Delta Power Ratio During PEEP-Based Respiratory Interventions	Change in electroencephalography (EEG)-derived delta power ratio (DPR) measured before, during, and after recruitment maneuvers and positive end-expiratory pressure (PEEP) adjustments. DPR is calculated as the proportion of delta-band power relative to total EEG power and is used as an indicator of cortical electrophysiological activity.	During ventilator interventions (baseline, intervention, and recovery periods; approximately 30 minutes)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Cerebral Blood Flow Velocity	Changes in cerebral blood flow velocity measured by transcranial Doppler ultrasonography during recruitment maneuvers and PEEP adjustments.	During ventilator interventions (approximately 30 minutes)
Change in Neurovascular Coupling Index	Changes in neurovascular coupling quantified by phase-amplitude coupling analysis between low-frequency cerebral blood flow oscillations and EEG activity.	During ventilator interventions (approximately 30 minutes)
Change in Mean Arterial Pressure	Changes in invasive mean arterial pressure during recruitment maneuvers and PEEP adjustments.	During ventilator interventions (approximately 30 minutes)

Collaborators and Investigators

• Sponsor: Shengli Oilfield Hospital

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2024
• Primary Completion (Estimated): February 1, 2027
• Study Completion (Estimated): February 1, 2027

Study Registration Dates

• First Submitted: July 16, 2026
• First Submitted That Met QC Criteria: July 16, 2026
• First Posted (Actual): July 21, 2026

Study Record Updates

• Last Update Posted (Actual): July 21, 2026
• Last Update Submitted That Met QC Criteria: July 16, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Mechanical Ventilation; Electroencephalography; Neurocritical Care; Cerebral Blood Flow; Transcranial Doppler; Neurovascular Coupling; Positive End-Expiratory Pressure; Brain-Lung Interaction
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Craniocerebral Trauma; Trauma, Nervous System; Brain Injuries
• Other Study ID Numbers: XJS-2024-08

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No