Traditional sonography has the patient on a examination couch, usually in the centre of the room with machine on the patients right. POCUS in the ED can replicate this, or for procedures have the screen on the patients left, operator on the patients right however access around the patient on the hospital trolley bed is preserved.
In general practice we are often more constrained. Rooms can be small, beds are often fixed or too heavy to move easily and if not electric can be hard/unsafe for the elderly to climb.
Time constraints of a consultation also come into play – it can take a very long time for someone in winter layers to take everything off, lie down on the examination couch and then dress again.
So for pure reasons of anatomical access, safety, timeliness and privacy there are some scans that just need to go to the formal sonographer due to pure patient positioning reasons.
I have also been using a sitting position for lung POCUS, the patient sitting sideways on a chair without arms, allowing access to the back and infra-axillary lung windows. This however must affect rib spacing and ?increased lower zone consolidation compared to the ideal lying down with hands behind head in a trolley. Some articles do suggest a lying or sitting position equally valid and points out that sitting is preferred for the very dyspnoeic. This is another article from a early researcher/adopter of LungPOCUS, Volpicelli, who states there is no difference in lying/sitting/standing as fluid shifts occur slowly in the lungs.