Is pulse rate measurable in the capillary bed and venous vasculature?

Question

Pulse rate is easily felt when gently pressing the arteries in the wrist or neck region (Fig. 1).

^{Fig. 1. Feeling the pulse at the radial artery. Source: Wikipedia}

Arteries supply the thin vasculature in the capillary bed where the blood flow encounters a large increase in resistance due to the narrow vasculature and blood flow is reduced, albeit the pressure may still be relatively high. The capillary bed, in turn, feeds the venous system (Fig. 2), characterized by a low blood pressure and relatively slow and continuous blood flow. This steady, slow blood flow is apparent during blood sampling procedures from the veins in the arm, where I have never noticed any pulsatile flow by visual observation (anecdotal evidence, but quite representative I'm sure).

^{Fig. 2. Blood vessels. Source: Aruba trial.}

Is there an observable/measurable pulse in the capillaries and veins, or is blood flow continuous in these vessels?

^{PS. This question was re-formulated based on a deleted question posted by @laggingreflex and credits go to OP.}

Answer 1

In the capillary bed? Absolutely! In the venous return? Depends!

I had to build one of these for class. In short: you can tell how oxygenated the blood is by its color, but you have to correct for how much blood there is: The dilation of the arterioles and capillaries with the heartbeat increases the size of the area being measured, and changes all sorts of properties including conductance. There's a neat heartbeat monitoring method method that involves putting two electrodes on your arm, one at the wrist and one at the elbow, and measuring the increase in conductivity every time your heart beats and your arm swells.

Depending on heart rate and all sorts of other things, there's not usually a detectable heartbeat in the veins right outside the heart (see the CVP, which is pretty much flat). However, the jugular venous pressure is the pressure of the internal jugular vein that drains the head, and that has heartbeat oscillations (not one-to-one, there are "echoes" and other weirdnesses because it's almost connected to the heart. See here for more).

In sum: The capillary bed absolutely swells and contracts with each heartbeat, but in the veins blood usually just oozes along. There are a couple exceptions but mostly they're silent.

(The Korotkoff sounds you're talking about are a fluid dynamics thing. When the veins are regular-sized they're wide enough to permit laminar flow(where all the blood moves in a straight line), which is smooth but still pulsatile. Like these guys the blood flow starts and stops but is in sync with itself. When you compress them you increase the Reynolds number and you get turbulent flow, which you can hear because it's making noise.)