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

Study Overview
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Brief Summary
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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.

Official Title
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Ultrasonographic Assessment of the Optic Nerve Sheath Diameter During Variations in PetCO2 and Controlled Internal Jugular Venous Occlusion: A Volunteer Study

Conditions
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Elevated Intracranial Pressure (ICP)

Intervention / Treatment
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* Other: Ultrasonographic of the optic nerve sheath diameter
* Other: RespirAct™
* Other: Neck collar


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Ultrasonographic of the optic nerve sheath diameter|On both eyes of all subjects in supine position by two investigators.|
|Other: RespirAct™|Carbon dioxide Manipulation by RespirAct™ sequential gas delivery breathing circuit at each CO2 levels (normocapnia, Hypercapnia I and II and hypocapnia).|
|Other: Neck collar|Internal jugular compression using a Neck collar will be applied at each CO2 levels (normocapnia, Hypercapnia I and II and hypocapnia) and ONSD measurements will be done before and after the collar.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Optic nerve sheath diameter at Normocapnia |  | 1 day | 
| Optic nerve sheath diameter at Hypercapnia |  | 1 day | 
| Optic nerve sheath diameter at Hypocapnia |  | 1 day |