Final answer:
The syndrome where a pregnant or obese patient may pass out while supine is called supine hypotensive syndrome, caused by compression of the inferior vena cava. A related condition is orthostatic hypotension, which involves a blood pressure drop and dizziness upon standing.
Step-by-step explanation:
The syndrome in which a patient, often someone who is pregnant or obese, may pass out while lying in a supine position is known as supine hypotensive syndrome. This condition occurs because the weight of the abdomen (due to pregnancy or obesity) can compress the inferior vena cava when the patient lies on their back, reducing venous return to the heart and subsequently reducing cardiac output. The decrease in blood flow can lead to a drop in blood pressure and fainting. Patients such as the aforementioned, often find relief by lying in a side position rather than on their back.
Orthostatic hypotension is a related condition where blood pressure drops significantly upon standing. This could cause dizziness or fainting due to a temporary decrease in blood flow to the brain. Both conditions are examples of how body positioning can impact cardiovascular dynamics, particularly in susceptible individuals like pregnant women or those who are overweight.