ductus venosus attempt in a patient who won't cooperate

What happens when we attempt duplex ultrasound imaging of the ductus venosus in a 3rd trimester pregnancy who just cant hold her breath?These images tell the story:During cessation of respiration (breath holding):Observe the nice tracing/ waveformAnd when the patient continues respiratory activity: Note the interruption of the waveform. Possibly the sampling gate has shifted to another nearby vessel. see also: http://www.ultrasound-images.com/fetus-general.htm#How%20to%20spot%20the%20Normal%20ductus%20venosus:
Source: cochinblogs - Category: Radiologists Source Type: blogs