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Journal of applied physiology1976; 40(2); 184-190; doi: 10.1152/jappl.1976.40.2.184

Hypoventilation in ponies after carotid body denervation.

Abstract: Seven ponies were subjected to carotid body denervation (CD) and two ponies were sham operated (S). Measurement of arterial blood gases and arterial blood and cerebrospinal fluid (CSF) acid-base balance were made prior to and 1,2,4,9, and 17 wks after surgery in unanesthetized animals. Resting ventilation and ventilatory responsiveness to hypoxia and NaCN infusion were assessed prior to and 2,9, and 17 wks after surgery. Alveolar hypoventilation in the CD ponies was marked 1-2 wk after surgery when VE and VA were reduced 40% and 10%, respectively, from control and PaCO2 was 12-15 mmHg above control. However, the effect was not nearly as great 4, 9, and 17 wk after surgery when the PaCO2 stabilized at approximately 6 mmHg above control PaCO2. Arterial blood pH was normal in the hypercapnic CD ponies, but CSF pH remained acid relative to normal throughout the 17-wk period. Changes in ventilatory responsiveness to hypoxia and NaCN tended to parallel changes in resting ventilation. These findings suggest: 1) the carotid bodies are essential in ponies to maintain normal ventilation: 2) in CD ponies peripheral chemosensitivity is partially regained at some unestablished locus; and 3) pH compensating mechanisms in chronically hypercapnic ponies function relatively better in blood than in CSF.
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Publication Date: 1976-02-01 PubMed ID: 2576DOI: 10.1152/jappl.1976.40.2.184Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Objective:

This research study aimed to investigate the effects of carotid body denervation (removal of the carotid bodies) on the ventilation, blood gases, and acid-base balance in ponies.

Explanation:

The researchers conducted a study involving nine ponies, seven of which underwent carotid body denervation (CD), whereas two ponies underwent a sham operation (S). The following measurements and assessments were made before and at different time points after the surgery:

1. Arterial blood gases and acid-base balance: Measurements of arterial blood gases and the acid-base balance in the blood and cerebrospinal fluid (CSF) were taken. These measurements provide valuable information about the levels of oxygen, carbon dioxide, and other chemicals in the blood and CSF.

2. Ventilation: The resting ventilation (the rate and depth of breathing at rest) was assessed. Additionally, the researchers evaluated the ponies’ ventilatory responsiveness to hypoxia (low oxygen levels) and NaCN infusion (a chemical that stimulates the carotid bodies).

The results of the study were as follows:

1. Alveolar hypoventilation: In the CD ponies, there was a marked decrease in alveolar hypoventilation (reduced breathing) observed 1-2 weeks after the surgery. This was evident through a decrease in ventilation (VE) and alveolar ventilation (VA) by 40% and 10% respectively, compared to control ponies. The arterial partial pressure of carbon dioxide (PaCO2) was also elevated by 12-15 mmHg above control levels. However, the impact on ventilation was less significant at 4, 9, and 17 weeks after the surgery, with PaCO2 stabilizing at around 6 mmHg above control levels.

2. Acid-base balance: Despite the hypercapnia (elevated PaCO2), arterial blood pH in the CD ponies remained normal. However, the pH in the CSF, which surrounds the brain and spinal cord, remained acidic relative to normal throughout the 17-week period.

3. Ventilatory responsiveness: Changes in ventilatory responsiveness to hypoxia and NaCN tended to parallel the changes in resting ventilation. This suggests that the impaired ventilation observed in the CD ponies also affected their response to certain stimuli that would typically affect breathing rate.

The researchers draw the following conclusions based on their findings:

1. The carotid bodies, which are small organs located near the carotid arteries that play a crucial role in sensing and responding to changes in oxygen and carbon dioxide levels in the blood, are essential in maintaining normal ventilation in ponies.

2. In CD ponies, peripheral chemosensitivity, which is the sensitivity of peripheral chemoreceptors (such as the carotid bodies) to changes in blood chemical levels, is partially regained at an unknown location. This suggests that other compensatory mechanisms may come into play to partly restore the ponies’ ability to respond to changes in oxygen and carbon dioxide levels.

3. pH compensating mechanisms, which help maintain the acid-base balance, function relatively better in blood compared to CSF in chronically hypercapnic ponies. This indicates that the body has better mechanisms for compensating for changes in pH in the blood compared to the CSF.

Overall, this study provides insights into the important role of carotid bodies in maintaining ventilation and highlights the complex mechanisms involved in regulating blood gases and acid-base balance in ponies.

Cite This Article

APA
Bisgard GE, Forster HV, Orr JA, Buss DD, Rawlings CA, Rasmussen B. (1976). Hypoventilation in ponies after carotid body denervation. J Appl Physiol, 40(2), 184-190. https://doi.org/10.1152/jappl.1976.40.2.184

Publication

Journal of applied physiology
ISSN: 0021-8987
NlmUniqueID: 0376576
Country: United States
Language: English
Volume: 40
Issue: 2
Pages: 184-190

Researcher Affiliations

Bisgard, G E
    Forster, H V
      Orr, J A
        Buss, D D
          Rawlings, C A
            Rasmussen, B

              MeSH Terms

              • Acid-Base Equilibrium
              • Animals
              • Aorta / innervation
              • Blood Gas Analysis
              • Carbon Dioxide / blood
              • Carbon Dioxide / cerebrospinal fluid
              • Carotid Body / physiology
              • Cyanides / pharmacology
              • Denervation
              • Horses / physiology
              • Hydrogen-Ion Concentration
              • Hypoxia
              • Lactates / blood
              • Lactates / cerebrospinal fluid
              • Oxygen / blood
              • Respiration / drug effects

              Citations

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