Thoracic inlet venous valves are typically competent during sudden intrathoracic pressure increases, which may be important for forward blood flow during CPR.
We studied the function of right internal jugular vein valves during cardiac catheterization in 32 patients and external jugular vein valves in vitro from 13 dogs. Patients with normal central venous pressure had competent valves during cough-induced transvalvular pressure gradients of 52.4 +/- 8.6 mm Hg. Ten of 15 patients with elevated central venous pressure had either incompetent or absent internal jugular valves, the latter occurring only in patients with long-standing, severe tricuspid regurgitation. During coughing, competent valves were also demonstrated in the left internal jugular and in the right and left subclavian veins. The excised canine valves were competent at a static transvalvular pressure of 81.8 +/- 3.7 mm Hg. Five of six excised valves remained competent during pulsatile transvalvular pressure of 64.8 +/- 1.9 mm Hg. Thus, thoracic inlet venous valves are usually competent during sudden increases in intrathoracic pressure. These valves may play an important role in establishing the extrathoracic arteriovenous pressure gradient necessary for forward blood flow during cardiopulmonary resuscitation and other states with high intrathoracic pressure.
Fisher et al. (Fri,) studied this question.