What could cause a higher pitch signal when performing a CW Doppler at the Prox Dorsalis Pedis level?

A higher pitch signal in Continuous Wave (CW) Doppler is primarily influenced by the angle of incidence of the ultrasound beam. When the probe is positioned at a steeper angle relative to the direction of blood flow—essentially standing it up—the frequency of the reflected sound waves changes due to the Doppler effect. This increased angle results in a higher frequency shift, which is perceived as a higher pitch signal.

The other potential causes are less likely to produce a higher pitch signal. If the probe is positioned too far from the vessel, the Doppler signals would likely weaken rather than increase in frequency. Turbulence in blood flow can create a broadening of the frequency spectrum, often resulting in a less consistent signal rather than a simple increase in pitch. An elevated blood pressure does not directly correlate with the pitch of the Doppler signal; it may influence the overall velocity of flow but not the perceived frequency shift in a straightforward manner. Therefore, adjusting the angle of incidence has the most direct effect on achieving a higher pitch signal in this scenario.