Rheoplethysmographic studies of digital venous tone and venous activity.

Abstract

Abstract It has been shown that partial obstruction to digital venous outflow resulted in slight increase in tone and constriction of the precapillary digital vessels and from slight to marked increase in postcapillary vascular tone and constriction. The digital veins were among the postcapillary vessels. The mechanism for the increase in venomotor tone as well as the tone of the other vessels remains unknown. Four types of volume-time course curves for the initial pulse cycles after inflation of the digital collecting cuff were described. These included the patterns for (1) the resting, relaxed state of the digital vessels, (2) the dilated state, (3) the constricted state (Types A and B), and (4) the obstruction to digital flow. These curves have significant rheoplethysmographic, physiologic, and pathologic connotations. Noradrenalin was found to constrict the postcapillary digital vessels, including the veins, but the veins were not constricted as much as the precapillary vessels for the doses used. The orienting reflex, psychogenic and neurogenic reflexes, and deep inspiration were found to produce constriction of the postcapillary vessels, including the digital veins, as well as the precapillary vessels. It was found rheoplethysmographically that the pre- and postcapillary vessels constrict and/or dilate discordantly or disproportionately in the same manner described for the afferent and efferent arterioles of the kidney. This phenomenon probably exists for other organs as well. The phenomenon is most likely concerned with the regulation of water and solute loss into, and absorption from, the intercellular spaces, and with interstitial fluid circulation and lymph flow in healthy and diseased states. The value of digital rheoplethysmography in the study of the peripheral circulation was further emphasized by these observations.