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Possible Pitfalls in the Search for Arterial and Central Chemoreception in Respiration

  • H. Shams
  • J. A. Orr
  • M. R. Fedde
  • P. Scheid
Conference paper

Abstract

We have performed experiments in the cat to test the effects of neutral ( = iso-pH) acid/base infusion on respiration and hemodynamics at unchanged blood pH and Pco2. Stoichiometrically equal quantities of HCl and NaOH were infused into an extracorporeal arteriovenous loop (Series I) or into central veins (Series II), whereby pH and Pco2 in the circulating blood remained constant. Cardiorespiratory parameters and the plasma level of thromboxane (TX)B2, the stable metabolite of TXA2, in right ventricular blood were measured. The first acid/base infusion stimulated breathing largely by increases in respiratory rate, f R, although pH in arterial blood remained virtually unaltered. Right ventricular blood pressure, P rv, rose from 30 to a peak of about 55 mm Hg, with a concomitant rise in the TXB2 level from below detection level to over 500 pg/ml. The second or third infusion evoked no (or small) rises in P rv and TXB2, but ventilation was increased further by the second infusion, again at an unaltered blood pH. After blockade of TX synthesis by Dazmegrel (Series III), no changes were observed, even at the first acid/base infusion, in either P rv or TXB2, and the increase in \({\dot V_E}\) was largely attenuated. The TXA2 mimetic, U46,619, stimulated \({\dot V_E}\) by increases in f R and caused P rv to rise with no change in TXB2. After cooling of both vagus nerves (Series IV), \({\dot V_E}\) remained unaltered, but P rv increased during the first infusion of acid/base.We conclude that acid exposure of blood stimulates TX synthesis and release from platelets, which, in turn leads to hyperventilation and pulmonary hypertension.This ventilatory reflex response to neural acid/base infusion is mediated by vagak apparent fibers.These effects when not properly accounted for can lead to misinterpretation of the results observed in ventilation upon infusion of acids, a tool that is often used to test for arterial chemoreceptor function.

Keywords

Shallow Breathing Ventricular Blood Central Chemoreception Cardiorespiratory Parameter Respiration Research 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York Inc. 1990

Authors and Affiliations

  • H. Shams
  • J. A. Orr
  • M. R. Fedde
  • P. Scheid

There are no affiliations available

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