PMID: 1212140Nov 1, 1975Paper

Renal effects of continuous negative pressure breathing

Aviation, Space, and Environmental Medicine
M J Kinney

Abstract

Continuous negative pressure breathing (CNPB) was utilized to simulate the thoracic vascular distension of zero G or Space, in 11 anesthetized rats. The animals underwent renal clearance and micropuncture renal nephron studies before, during, and after CNPB. Four rats were pretreated with a high salt diet and I-M desoxycorticosterone (DOCA) in excess. None of these rats diuresed with CNPB. In contrast, five of the seven remaining rats increased the fraction of the filtered sodium excreted (CNa/GFR, p less than 0.05) and their urinary flow rate (V, p less than 0.05). Potassium excretion increased (UK V, p less than 0.05). End proximal tubular fluid specimen's TF/P inulin ratios were unchanged. Whole kidney and single nephron glomerular filtration rates fell 10%. CNPB, a mechanism for atrial distension, appears to cause in the rat a decrease in distal tubular sodium and water reabsorption. Exogenous mineral-corticoid prevents the diuresis, saluresis, and kaluresis. In a separate group of five rats, the CNPB was prolonged or excessive (CNPB greater than 3.5 cm H2O negative pressure); in these, the diuresis ceased and/or antidiuresis occurred. This confirmed the adequacy of other nonatrial volume control mechanisms in regulating re...Continue Reading

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