Optic Nerve Sheath Diameter (ONSD) With the Raised PCO2 and Internal Jugular Venous Occlusion

Elevated intracranial pressure (ICP) is a common and potentially life threatening condition arising from a variety of pathological conditions including traumatic brain injury (TBI), intracranial hemorrhage, subarachnoid hemorrhage and brain tumors. Monitoring the ICP is the most important aspect of the management of these patients. Recently, transorbital ultrasonography has gained popularity as a noninvasive bedside exam that has been shown to be useful in the diagnosis of raised ICP by evaluating the change in the optic nerve sheath diameter (ONSD). Transorbital ultrasonographic measurement of ONSD appears to be a noninvasive, relatively inexpensive bedside examination for the diagnosis of raised ICP. The investigators aimed to determine the changes in ONSD with acute controlled changes in ICP in healthy volunteers. The controlled changes in ICP will be produced by manipulating the PCO2 with the use of Respiract and jugular venous compression with the use of custom made neck collar.

Inclusion criteria

Adult healthy volunteers who are above the age of 18 ASA 1 Body mass index (BMI) less than and equal to 35 Neurologically normal subjects with no symptoms other than occasional non-severe headache

Exclusion criteria

BMI above 35 Lack of informed consent Language barrier Medical students and/or anesthesia residents going through the department as part of their rotation Pregnancy Frequent migraine headache