Changes in transmural central venous pressure in man during hyperventilation.

We demonstrated that large amounts of blood shift from the forearm veins during hyperventilation (2). If this effect were generalized in the periphery of the body the volume of blood in the central venous reservoir might increase. An increase in pressure in the central veins would be evidence to support this suggestion. The fall in peripheral venous pressure which occurs during hyperventilation (2, 3), however, implies that central venous pressure also decreases. This makes our thesis less attractive. Still, the transmural pressure (4), the net pressure acting to distend the central veins, could increase during overbreathing if the pressure surrounding the veins (intrapleural pressure) decreased more than did the pressure within them. This study was undertaken to assess the nature and magnitude of changes in mean transmural central venous pressure during hyperventilation and to see whether the changes were consistent with our suggestion that blood shifts centrally during overbreathing.