The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

with a mercury manometer. Pulse rates were obtained from electrocardiograms taken simultaneously with the other measurements.Cardiac output was calculated from the oxygen consumption and the arteriovenous oxygen difference according to Fick's formula (2). Two radio-opaque cardiac catheters were introduced through the external jugular veins and, with the aid of fluoroscopy, the distal ends were placed in the right auricle and in the pulmonary artery, respectively. The proximal ends of the catheters were connected with saline manometers for the recording of mean pressures. The location of the catheters and their zero pressures were verified at post-mortem examination. To ensure maximal mixing of the blood returning to the heart, samples of venous blood were taken from the pulmonary artery. Arterial blood was obtained from the cannulated femoral artery. In the course of each experiment, 100 to 150 cc. of blood were withdrawn and replaced with isotonic saline solution. The Van Slyke-Neill technic (3) was used in the analysis of blood Qa and CO2. Hematocrits were determined by the Wintrobe method (4), arterial blood being employed.Control measurements were made when the blood pressure and respiration of the animal became stabilized. The animals were then covered with chipped-ice packs. Body temperatures were recorded from thermometers placed deeply in the rectosigmoid area and protected from the ice packs. The mean cooling period was about two hours during which the body temperatures fell to 290 C. The animal was then dried, covered with thin sheets, and exposed to radiant heat. However, the body temperatures continued to fall to 270 C, before beginning to rise.The mean rewarming period lasted five to six hours, at the end of which body temperatures usually had returned to 37°C. Ten or 11 determinations were obtained in each experiment, measurements being taken after each 2 degree change of body temperature. Evaluation of the methodMeasurements of right auricular and pulmonary arterial pressures represent only the approximate mean values. The changes in pressure were considered to be of greater significance. During periods of extreme bradypnea resulting from severe respiratory center depression, great variations in concentration of blood gases occur during each respiratory cycle, and this produces errors in the direct Fick method. This inaccuracy is further increased by the fact that the usual means of collecting blood samples makes it impossible to obtain exactly 293

No abstract

An elevation of the body temperature evokes many physiological changes, as a direct result of the increased rate of metabolism and the greater demand for oxygen and substrate, and indirectly in warm blooded animals because of the elicitation of thermolytic mechanisms. An understanding of the interrelationships between these factors is of obvious importance in an appreciation of the dynamics of hyperthermia and in the establishment of a rationale for its treatment. Despite many important contributions to this problem, there is a paucity of information concerning the effect of hyperthermia on the cardiac output and the right intracardiac pressures. We have therefore undertaken an analytical study of the circulation in hyperthermia in an effort to assay these adjustments more satisfactorily. Our present experiments have been limited to a study of the changes which occur following exposure to radiant heat since this method of producing hyperthermia seemed to be the simplest, being free from incidental effects produced by pyrogens and by other methods. A few experiments were done with short wave diathermy. METHODHyperthermia was induced in nine dogs. Six dogs, anesthetized with sodium pentobarbital, were exposed to radiant heat from several light bulbs until the body temperatures (about 380 C) gradually increased to 42°C during a two-hour interval. Body temperatures were reduced during the following one-to two-hour periods by using cold wet cloths applied to the body and by draft-producing electric fans. (1). Measurements similar to the above were also obtained in a series of three dogs heated by short wave diathermy,5 but unless specified, the results given below refer only to those experiments in which radiant heat was employed. Similar measurements were made on three control anesthetized dogs kept at room temperature. DISCUSSION OF RESULTS Oxygen consumptionMany studies have demonstrated a close parallel between the rise in body temperature and the increased oxygen consumption (2-4) which accompanies the acceleration of cellular metabolism during fever. In our experiments (Figure 1) an average increase of 57% was observed at a body temperature of 420 C, the greatest increase being 100%o in one instance. During the cooling period oxygen consumption decreased simultaneously with the fall in body temperature and returned to control levels as the temperature of the animal again reached 380 C. In the control series only slight and insignificant changes in oxygen consumption took place.Respiration and content of blood gases The production of hyperthermia was accompanied by an increase in respiratory rate and 5 The Burdick Corporation generously supplied the short wave equipment. 301

No abstract

No abstract

No abstract

No abstract