The protocol I posted came from @TheDude Dr. Hepworth’s protocol for CTV - #4 by TheDude. I don’t know if it’s changed since then.
Your doctor should be able to order Hepworth’s protocol (maybe by calling it Dr. Hepworths IJV US protocol), but Dr. Hepworth usually uses Health Images in Cherry Creek to do the jugular ultrasounds he orders. There are a couple of techs there who are very familiar with it. It doesn’t say this in the description, but the valsalva maneuver is also used during the US i.e. at various times during the US, the tech will tell the patient to hold his/her breath & put pressure into the neck. I don’t know the reason for this, but perhaps it helps exhibit the velocity rates of blood flow at those points more clearly.