Normal Doppler spectrum from the brachiocephalic vein in a 4-year-old girl shows a, S, v, and D waves from pressure changes in the right atrium, as well as reduced flow velocity during expiration.
Spectra obtained in the brachiocephalic vein are characterized by waveforms and respiration-related changes similar to those seen in spectra from the superior vena cava (Fig ).

http://radiographics.rsna.org/content/28/3/691.full