The effect of air travel on the edema of traumatic injuries

Experimental Evidence would argue yes.

Experimental Evidence always comes with strings to bias. There is no free lunch.

The internet is full of bias by organizations that have strings to this type of bias. Internet sources are easy to come by and generally free so the motivation comes from the bias

Scientific evidence would argue no.

Atmospheric pressure is applied to the entire body as so does not favor the flow of fluid from one part to another. There is no alteration of the pressure gradients involving the flow of blood either arteries or veins.

Fluids including edema fluid is not compressible. Gases are compressible so gas in a confined space with expand with negative pressure and contract with positive pressure. The middle ear contains air under normal circumstances but contains fluid when diseased.

The bowels often contain air. Generally the gas can be relieved with any expansion without causing injury. A possible closed loop bowel obstruction could theoretically expand to the extent that gas is withing the closed loop.