What does the absence of a dicrotic notch in pulse volume recordings indicate about the patient?

The absence of a dicrotic notch in pulse volume recordings is indicative of arterial obstruction. When the vascular system is functioning normally, the dicrotic notch appears as a small deflection in the pulse tracing that results from the closure of the aortic valve and reflects a normal drop in pressure in the arterial system. If this notch is absent, it suggests that there is an issue with blood flow, typically due to an obstruction in the arteries, which can lead to a diminished or altered hemodynamic response.

In contrast, vasodilation typically leads to an increased blood flow and substantial pulsatile volume, which would preserve the characteristics of the pulse recording including the dicrotic notch. Normal vascular function would also present a clearly defined dicrotic notch. Therefore, while vasodilation does affect blood flow, it does not directly correlate with the absence of a dicrotic notch. Arterial obstruction is the condition that best explains such a finding in pulse volume recordings.