Effects of respiration upon the venæ cavæ of certain mammals, as studied by means of x‐ray cinematography

Abstract

THE problem indicated in the title was suggested by the previous work of one of us (K. J. F.), who was also responsible for the operative procedure. The solution of the problem was made possible by the use of X-ray cinematography, the technique of which has been largely developed, since 1926, by the other of us (R. J.).The effects of respiration upon the calibre and volume of the thoracic inferior vena cava of the cat, dog, and rabbit have already been estimated by an indirect method (K. J. F.), and the findings corroborated, in the case of the cat, by X-ray cinematography (R. J.) [Franklin, 1933]. Although it is incorrect to draw too general a conclusion from so small a number of experiments, it seems probable that the volume of this vein in these three species is diminished rather than increased in inpiration, especially if inspiration is at all deep. It is of interest to note that E yster and Hicks [1933], on other grounds, came to the belief that in dogs "the importance of breathing in reference to venous return has been exaggerated in the usual theoretical discussions of this subject."The thoracic inferior vena cava may also be constricted to some extent at its diaphragmatic end in certain species (e.g. cat and dog) when inspiration is at all deep. This effect is not to be regarded as of outstanding importance, for it depends primarily upon the degree of development of a particular anatomical feature, and the animals examined showed considerable variation in this respect [Franklin, 1934]. In the present series of experiments an inspiratory constriction of the diaphragmatic end of the thoracic inferior vena cava was clearly visible on the X-ray screen RESPIRATION AND VENE CAVAiJ. in the case of the second dog (Plate I, fig. 2). The post-mortem examination showed that this animal had a moderately well-developed "caval band," and this was almost certainly responsible for the constriction.The experiments described below were undertaken in order to add to the knowledge already acquired of the effects of respiration upon the calibre and volume of the vens cave. The particular portions of the caval system about which further information was required were the superior vena cava, and the intrahepatic portion of the inferior vena cava. For the greater part of this work there was only one suitable technique, namely, X-ray cinematography, and this technique was therefore employed.It is perhaps important to emphasize the fact that the rate of flow of blood in the ven,% cave was not primarily under consideration; a study of the X-ray film of experimental pulmonary embolism made by Naegeli and Janker at Bonn [Naegeli, 1931] shows that the movement of fluid within the ven&e cave is a complicated one, and we have, therefore, been content to study chiefly the changes in calibre and kindred problems.

Observations on laminar flow in veins

“…(ii) The distortion of vessels by external forces appeared to be the main cause of the degree of disturbance seen in the portal vein and to contribute to the disturbance in the thoracic inferior vena cava. Movement of the diaphragm has been shown by X-ray cinematography to cause lengthening and narrowing of the vena cava (Franklin & Janker, 1934) in inspiration, and the reverse change appeared to occur in the portal vein in our observations. Inflation of the lungs also caused lateral distortion of the vena cava, as reported above, but without confirmatory evidence in the intact animal we cannot say that this is a normal phenomenon in vena cava or portal vein.…”

Relationship of the diaphragm to the inferior vena cava in human embryos and fetuses

“…Franklin (1937) presents a thorough review of the early work on this problem. The structural arrangement of the right crus as it inserts into the posterior caval wall has been a point of much discussion.…”

“…Keith (1902) attributed a pumping action in the inferior vena cava to contraction of the right crus during inspiration and proposed that it is an important mechanism for return of blood to the right heart. Franklin (1934), Franklin and Janker (1934, 1936, and Norhagen (1963) observed the caval region of the diaphragm in animals radiographically and described a constriction of the inferior vena cava during deep inspiration. Surgical section of the right phrenic nerve resulted in the absence of caval constriction during inspiration (Norhagen, 1963).…”