The Effect of Continuous Negative Pressure Breathing on Water and Electrolyte Excretion by the Human Kidney

Abstract

The effects of decreased intrathoracic pressure on arterial blood pressure (1), venous pressure (2, 3), cardiac output (4), and pulmonary pressure and volume (5) have been investigated in the past. The present study was prompted by the association of marked diuresis with continuous negative pressure breathing in anesthetized animals (6) and the observation that in unanesthetized man continuous positive pressure breathing leads to an oliguria (7). The purpose of this investigation was to demonstrate that human subjects like anesthetized animals have an increased urine flow in response to continuous negative pressure breathing. Observations were made on the renal excretion of water, sodium and potassium, urinary pH, and endogenous creatinine clearance in the hope that the mechanism of the diuresis might be elucidated. METHODSSixteen experiments and six control studies were done with eight normal males who ranged in age from 18 years to 43 years. The subjects received their usual breakfast without added salt on the morning of the experiment. The study was carried out with the subject in the recumbent position in a constant temperature environment In order to obtain an adequate urine volume and a steady state, each subject was maintained on 50 cc. and in some cases 100 cc. of 0.14 per cent saline by mouth (8) and expiration was applied through a standard U. S. Air Force pressure breathing oxygen mask attached by a short tubing to a 40 liter cylinder. This cylinder was ventilated by a suction pump with fresh air at the rate of 100 to 160 liters per minute and rebreathing was prevented by means of a two-way valve in the face mask. The desired negative pressure, which in these experiments was a mean pressure of 15 to 18 centimeters of water, was obtained by varying the air inlet to the container. Control studies duplicated the procedure exactly except that the negative pressure breathing was omitted. Repeat studies were done in all but two subjects.The urine volume for each 15-minute interval was noted and the pH of each sample was determined by means of a glass-calomel electrode pH meter which had an accuracy of 0.1 pH units. Sodium and potassium determinations were made on each urine specimen with an internal standard Perkin Elmer flame photometer. The endogenous creatinine content of the blood and urine was measured by the method of Bonsnes and Taussky (9). The creatinine clearance was used for convenience in these studies with an awareness of both its accuracy and its limitations. The pulse and respiratory rates were followed and periodic observations of the blood pressure were made with a standard sphygmomanometer. RESULTS

Effect of Altered Intrathoracic Pressure on Renal Hemodynamics, Electrolyte Excretion and Water Clearance*

“…The results of this study confirm earlier demonstrations of the alterations in urine flow that are associated with changes in intrathoracic pressure (1)(2)(3)(11)(12)(13). Although earlier reports suggested that water excretion was altered independent of electrolyte excretion and unrelated to changes in renal hemodynamics, these two factors were not completely evaluated.…”

“…It has been suggested in earlier reports that the intrathoracic portion of the cardiovascular system contains a volume receptor area (1,3). Further study has demonstrated that the left atrium is one such receptor area (4,5).…”

“…Continuous positive pressure was administered through a positive pressure demand valve system. Continuous negative pressure was obtained by breathing room air through a system which incorporated a large drum in which the negative pressure was maintained by a suction pump (3). The positive pressure breathing experiments were carried out with the subject in the seated position throughout the study (control, test, and recovery periods).…”

“…Continuous positive pressure breathing is associated with a decrease in the rate of urine flow in dog (1) and man (2), whereas breathing against a constant negative pressure produces an increased rate of urine flow in the same species (1,3). A decrease in urea clearance accompanies the antidiuresis of positive pressure breathing and suggests an altered rate of glomerular filtration (1).…”

“…A decrease in urea clearance accompanies the antidiuresis of positive pressure breathing and suggests an altered rate of glomerular filtration (1). The diuresis of negative pressure breathing is not associated with marked changes in endogenous creatinine clearance or sodium and potassium excretion (1,3).…”