Study to Investigate an Association Between Brain Activity and Tidal Volume in Humans (BATMAN)

Not Applicable

Recruiting

Brief Summary: The communication between the lungs and the brain has drawn a lot of attention recently. Animal studies have shown that the breathing cycle is coupled with brain activity, showing that the greater the volume of air delivered to the lungs via a breathing machine greater the brain activity and also the greater the injury to the brain cells.

There is no study in humans that investigates the physiological communication between the volume of air delivered to the lungs and brain activity. This is important because really sick patients receive breathing assistance using breathing machines to keep their oxygen levels within a normal range. Although these machines are life-saving tools, they might result in brain cell injury, leading to cognitive impairment. So, establishing the existence of a physiological communication between the volume of air delivered using these breathing machines and brain activity is the first step to investigating therapies to prevent brain cell injury due to the use of breathing machines to assist breathing.

Detailed Description: Demonstration of a physiological relationship between tidal volume set on the ventilator and hippocampal activity measured as changes in blood-oxygenation level-dependent (BOLD) in the regions of interest (ROIs). The results from this pilot study might assist in creating the foundation for explaining the mechanism of action of ventilation-associated brain injury.

Mechanically ventilated patients who are undergoing MRI examinations under general anesthesia in isocapnic and isoxic conditions will have brain activity investigated under two different tidal volumes, 6 ml/kg and 12 ml/kg applied for 3-5 minutes. Positive end-expiratory pressure will be adjusted to maintain plateau pressure \<30 cm H2O.

Recruitment & Eligibility

Inclusion Criteria

Patients scheduled to undergo an MRI scan of their head under general anesthesia
Age > 18 years

Exclusion Criteria

Stroke, and/or brain tumor in the regions of interest that has not been diagnosed before the MRI scan
Previous medical history of dementia
Previous medical history of brain surgery
Acute or chronic spinal cord Injury
Previous Vagotomy
Phrenic nerve injury

Arm && Interventions

Group	Intervention	Description
Group 1: tidal volume delivered at 6 ml/kg for 3-5 minutes, followed by 12ml/kg for 3-5 minutes	Tidal Volume set on ventilator	The clinical MRI examination will be obtained before commencing with the study protocol. The study protocol will commence once the scheduled MRI scan is finished. The study-related procedures will add 10 minutes after the scheduled MRI scans are finished with two different tidal volumes with maintaining isocapnia and isooxia. Study procedure: tidal volume delivered at 6 ml/kg for 5 minutes, followed by 12ml/kg for 5 minutes
Group 2: tidal volume delivered at 12 ml/kg for 3-5 minutes, followed by 6ml/kg for 3-5 minutes	Tidal Volume set on ventilator	The clinical MRI examination will be obtained before commencing with the study protocol. The study protocol will commence once the scheduled MRI scan is finished. The study-related procedures will add 10 minutes after the scheduled MRI scans are finished with two different tidal volumes with maintaining isocapnia and isooxia. Study procedure: tidal volume delivered at 12 ml/kg for 5 minutes, followed by 6ml/kg for 5 minutes

Primary Outcome Measures

Name	Time	Method
establish a correlation between the tidal volume delivered and changes in the blood-oxygenation level-dependent (BOLD) on regions of interest (ROIs) during an MRI scan.	10 minutes	correlation between the tidal volume delivered and changes in the blood-oxygenation level-dependent (BOLD) on regions of interest (ROIs)

Secondary Outcome Measures

Name	Time	Method
establish whether the changes in BOLD signal in multiple ROIs correlate with changes in tidal volume via a multi-correlation analysis (independent component analysis)	10 minutes	establish whether the changes in BOLD signal in multiple ROIs correlate with changes in tidal volume via a multi-correlation analysis