It seems people don't have the same number of valves and that they are not present at the same locations and that they are often not needed, very confusing as to what impact these valves have, faulty of missing or too many or none at all, confusing?
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The ones in your jugulars are inverted in *function* from those, because most of the time, they are above your heart (no handstands please). They block reflux from going up. Extra spurious valves only slow the flow, and may even be 1-way in the wrong direction or not work at all if they are malformations.
When you lie down (asleep) the jugular is inflated and the valve, if present, may be necessary to protect your brain from reflux. Because the flow is not constant, timing may also be important, and you may get reflux when that valve is open and most of the flow is downwards.
From Internal Jugular Valve and Central Catheter Placement
Fukazawa, Kyota M.D.; Aguina, Luz M.D.; Pretto, Ernesto A. Jr. M.D., M.P.H.
"We report a case of difficult central venous catheter placement in the presence of a large venous valve located in the right IJV. An IJV valve is present in 88-100% of cases, and its function is to prevent retrograde flow from the right atrium to the brain.1 The anatomic location of these valves is usually in the distal portion of the IJV, just proximal to the jugular bulb.2 Because the IJV valve is mostly located in the retroclavicular space, the ultrasound assessment of this valve is difficult with large ultrasound probes. In the majority of cases, the valve leaflet is bicuspid (77-98%), but tricuspid (0-7%) or unicuspid (1.4-16%) valves have been reported.2–4 Normally, valve cusps are thin (100 μm) translucent structures surrounded by a thickened ridge of tissue in which cusps attach to the vein.2 Complete valve closure occurs during diastole when atrial contraction transmits pressure backward into the superior vena cava.2 When intrathoracic pressure is increased, as in this patient (ascites and positive pressure ventilation), competent IJV valves prevent excessive backward flow to the brain.2 IJV valves can be competent up to a static pressure of 100 mmHg, such as in cases of coughing or Valsalva maneuver.5 However, the large venous valve might cause protrusion of the valve cusp into the lumen under increased venous pressure. In this circumstance, the large venous valve could potentially cause difficult central catheter placement, and if multiple or forceful attempts to overcome resistance are performed, the possibility of damage exists. In this case, ultrasound examination and guidance allowed us to visualize the exact location of the IJV. As a result, the procedure was aborted before any damage was done."
What if you are one of the 0-12% who have no IJV valve? Hope you have enough flow to swamp the reflux and prevent it. Pump hard on the left? Seems they expect reflux when you're old.
Not a doctor.
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