Related Experiment Video
Updated: Apr 24, 2026
14:09
Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
20.7K
Case report: (Pre)syncopal symptoms associated with a negative internal jugular venous pressure
Niels D Olesen1, Johannes J van Lieshout2, James P Fisher3
1Department of Anesthesia, Rigshospitalet, University of Copenhagen Copenhagen, Denmark.
Frontiers in Physiology
|September 6, 2014
Summary
A siphon may not support cerebral blood flow. Negative internal jugular venous pressure causes venous collapse, limiting blood flow to the brain, especially during upright posture.
Area of Science:
- Physiology
- Neuroscience
- Vascular Biology
Background:
- Cerebral blood flow (CBF) regulation is crucial for brain function.
- A proposed siphon mechanism involving internal jugular venous (IJV) pressure was hypothesized to support CBF.
- However, near-zero IJV pressure in upright humans questioned this mechanism.
Purpose of the Study:
- To investigate the relationship between IJV pressure and CBF regulation.
- To determine if negative IJV pressure impacts cerebral hemodynamics.
- To test the hypothesis that venous collapse limits CBF.
Main Methods:
- Measured IJV pressure, middle cerebral artery mean blood velocity (MCA Vmean), and frontal lobe oxygenation (ScO2) in healthy males.
- Assessed changes in these parameters in supine and seated positions.
- Observed a subject experiencing presyncope to analyze extreme IJV pressure changes.
Main Results:
- IJV pressure decreased from 9 mmHg (supine) to 3 mmHg (seated).
- MCA Vmean and ScO2 decreased significantly with seated posture.
- A presyncopal subject exhibited a sharp drop in IJV pressure to -17 mmHg, with concurrent MCA Vmean decrease.
Conclusions:
- Negative IJV pressure, essential for siphon formation, may cause venous collapse within the dura.
- This venous collapse appears to limit, rather than support, cerebral blood flow.
- Findings challenge the siphon hypothesis and highlight the role of venous pressure in CBF regulation.
Related Concept Videos
01:27Assessment of the Cardiovascular System III: Palpation
1.5K
Palpation involves feeling the body to evaluate texture, size, consistency, and tenderness for assessing cardiovascular health. The following steps are organized in a head-to-toe order:
Jugular Venous Pressure (JVP) Measurement
Position the patient at a thirty- to forty-five-degree angle or in a semi-fowler's position. Look for the highest point of pulsation in the internal jugular vein and measure the vertical distance to the angle of Loius or sternal angle. A normal JVP is 3-4 cm above...
Jugular Venous Pressure (JVP) Measurement
Position the patient at a thirty- to forty-five-degree angle or in a semi-fowler's position. Look for the highest point of pulsation in the internal jugular vein and measure the vertical distance to the angle of Loius or sternal angle. A normal JVP is 3-4 cm above...
1.5K
01:30Alterations in Blood Pressure
2.1K
Alterations in blood pressure, such as hypertension (high blood pressure) and hypotension (low blood pressure), significantly affect human health. Understanding these conditions' classifications, causes, and symptoms is essential for effective management and treatment.
Hypertension (High blood pressure)
Hypertension occurs when blood pressure readings consistently exceed the normal range. It is diagnosed when systolic blood pressure (the top number, indicating pressure while the heart...
Hypertension (High blood pressure)
Hypertension occurs when blood pressure readings consistently exceed the normal range. It is diagnosed when systolic blood pressure (the top number, indicating pressure while the heart...
2.1K
01:17Measurement of Blood Pressure
3.9K
Assessing blood pressure is a standard procedure executed in virtually all medical environments. The method utilized today was established over a hundred years ago by an innovative Russian doctor, Dr. Nikolai Korotkoff. The soft ticking noise, known as Korotkoff sounds, heard while taking blood pressure readings results from turbulent blood flow within the vessels. The apparatus required for this procedure includes a sphygmomanometer, a blood pressure cuff attached to a gauge, and a...
3.9K
01:19Veins of Head and Neck
7.6K
The blood drainage from the head and neck is primarily managed by three pairs of veins: the external jugular, internal jugular, and vertebral veins. The external jugular veins drain superficial scalp and face structures, passing over the sternocleidomastoid muscles to empty into the subclavian veins.
On the other hand, the vertebral veins, unlike their arterial counterparts, are not primarily responsible for brain drainage. Instead, they drain the cervical vertebrae, spinal cord, and some small...
On the other hand, the vertebral veins, unlike their arterial counterparts, are not primarily responsible for brain drainage. Instead, they drain the cervical vertebrae, spinal cord, and some small...
7.6K
01:28Special considerations while measuring blood pressure
1.5K
When assessing blood pressure (BP), healthcare professionals must consider various factors and potential unexpected outcomes to ensure accurate readings and provide proper patient care. Adhering to these guidelines is essential to achieving the most reliable results.
Monitoring Both Arms:
Monitoring BP in both arms during the initial assessment is advisable, as the systolic value may differ by five to ten mm Hg between arms. For subsequent BP assessments, use the arm with the higher reading.
Monitoring Both Arms:
Monitoring BP in both arms during the initial assessment is advisable, as the systolic value may differ by five to ten mm Hg between arms. For subsequent BP assessments, use the arm with the higher reading.
1.5K
01:29Cardiovascular System Abnormal Findings I: Inspection and Palpation
1.3K
In a cardiovascular examination, inspection and palpation are crucial for identifying abnormalities.
Abnormal findings observed during an inspection
Abnormal findings observed during an inspection
1.3K