Interrelationships of cardiac output, blood pressure, and peripheral resistance during normal respiration in normotensive and hypertensive individuals.

The effects of normal respiration upon the heart, blood pressure, and peripheral circulation were studied in normotensive and hypertensive subjects. Changes of right and left ventricular output were measured by the ballistocardiogram and the pressure-pulse method of Remington, peripheral blood flow by plethysmographs. The central and peripheral changes were interrelated and evidence is presented that the latter are chiefly due to the effects of intrathoracic pressure upon cardiac filling. F OR MANY years it has been known that quiet respiration is accompanied by certain changes in the dynamics of the circulation. On inspiration the output of the right ventricle increases, that of the left decreases,'-6 arterial pressure falls7-" and regional blood flow is diminished.'2-'4 During expiration the direction of the changes is reversed. Their origin has been attributed to the effects of variations of intrathoracic pressure upon the filling of the right heart which in turn affects the filling of the left heart.2-6 The depth, type and rate of respiration7' 11 influence the magnitude of the changes to some degree. There is no information on the effects of quiet respiration upon peripheral resistance. Most of the above studies have been made on laboratory animals. Rather drastic procedures were used and either central or peripheral circulatory changes were investigated. The present study represents an attempt to interrelate all the changes in man, using technics designed to cause as little disturbance to the subject as possible. In addition, the reactions of normo-tensive and hypertensive individuals were compared. 278 METHODS Simultaneous measurements were made of the variations of the output of each ventricle, of arterial pressure and of volume flow through various peripheral areas. Blood pressure was measured directly by a Hamilton optical manometer"' through a 20 gage hypodermic needle in the brachial artery. Respiration was recorded by a pneumograph strapped about the thorax. Directional changes in regional blood flow were estimated with photoelectric ple-thysmographs applied usually to the lobe of the ear, the toe tip and finger tip. In a few instances they were followed in the forearm and hand with an air plethysmograph. Similar changes were found in other regions of the body, i.e., the scrotum, cheek, tongue, and rectovaginal septum. These instruments did not provide quantitative measurements of blood flow, but directional changes were estimated from the diastolic volume of the part. All electrical signals were led through direct current amplifiers into Sanborn galvanometers; recordings were made on a photokymograph …