Some circulatory responses to Valsalva's manoeuvre in patients with polyneuritis and spinal cord disease.

Arterial blood pressure was recorded through a Cournand needle inserted into the brachial artery. Distensibility of the capacity vessels was measured by comparing the increase in hand volume resulting from intermittent obstruction of the venous return from the hand with the simultaneous rise in venous pressure of the hand. Hand volume changes were measured with a waterfilled plethysmograph of 516 litres capacity. The water was stirred continuously and its temperature maintained at 34 + 0 5°C. The patient lay supine with the hand in the plethysmograph at the level of the manubriosternal joint. The water within the plethysmograph exerted a hydrostatic pressure of 8 to 11 cm. water upon the dorsum of the hand. Hand volume changes were derived from pressure changes of the air contained within the turret of the plethysmograph. Ambient temperature was constant throughout each investigation, within the range 22 to 250C. Venous pressure was measured through a nylon catheter of 0-8 mm. internal diameter introduced percutaneously on the dorsal or radial aspect of the radiocarpal joint and directed peripherally. The catheter was made to negotiate at least one venous valve and the end of the catheter lay about 5 cm. distal to the site at which the vein was punctured. Care was taken that the end of the catheter was not wedged in a venous tributary. The catheter was periodically flushed with 0-2 ml. of a solution of saline containing 0 01 mg./ml. of heparin. All pressures were measured with capacitance transducers (Southern Instruments), and records were obtained with a four-channel direct-writing pen unit. The pens were 16 cm. long, worked in an arc of 4 cm., and had a peak to peak response time of 0 07 second. The paper speed usually used was 5 mm./second. An occluding pneumatic cuff was placed round the wrist immediately proximal to the plethysmograph and intermittently inflated to 40 mm. Hg for 10 to 20 seconds. During each period of venous occlusion the hand volume and venous pressure were continuously recorded. EXPRESSION OF RESULTS The increase in hand volume was expressed graphically against the increase in hand venous pressure. The measured increase in hand venous pressure included the transmitted rise in pressure within the plethysmograph as a consequence of increase in hand volume. The true rise in venous pressure was therefore derived by subtracting the rise in pressure within the plethysmograph from the total rise in venous pressure. As the rise of pressure within the plethysmograph during an episode of occlusion of venous return never exceeded 70% of the total rise in venous pressure, this correction was small. The transmural hand venous pressure, or venous distending pressure, was derived by subtracting the hydrostatic pressure, due to the column of water within the plethysmograph above the back of the hand, from the venous pressure.Thishydrostatic pressure always exceeded the resting hand venous pressure. As the hydrostatic pressure was directly transmitted to both hand tissues and hand veins the venous distending pressure was near zero between episodes of venous occlusion, indicating that the veins were collapsed (Ryder, Molle, and Ferris, 1944).