Organismal Responses to Hypoxemic Challenges

  • Robert S. FitzgeraldEmail author
  • Gholam A. Dehghani
  • Samara Kiihl
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 860)


As a counterpoint to the volumes of beautiful work exploring how the carotid bodies (CBs) sense and transduce stimuli into neural traffic, this study explored one organismal reflex response to such stimulation. We challenged the anesthetized, paralyzed, artificially ventilated cat with two forms of acute hypoxemia: 10 % O2/balance N2 (hypoxic hypoxia [HH] and carbon monoxide hypoxia [COH]). HH stimulates both CBs and aortic bodies (ABs), whereas COH stimulates only the ABs. Our design was to stimulate both with HH (HHint), then to stimulate only the ABs with COH (COHint); then, after aortic depressor nerve transaction, only the CBs with HH (HHabr), and finally neither with COH (COHabr). We recorded whole animal responses from Group 1 cats (e.g., cardiac output, arterial blood pressure, pulmonary arterial pressure/and vascular resistance) before and after sectioning the aortic depressor nerves. From Group 2 cats (intact) and Group 3 cats (aortic body resected) we recorded the vascular resistance in several organs (e.g., brain, heart, spleen, stomach, pancreas, adrenal glands, eyes). The HHint challenge was the most effective at keeping perfusion pressures adequate to maintain homeostasis in the face of a systemic wide hypoxemia with locally mediated vasodilation. The spleen and pancreas, however, showed a vasoconstrictive response. The adrenals and eyes showed a CB-mediated vasodilation. The ABs appeared to have a significant impact on the pulmonary vasculature as well as the stomach. Chemoreceptors via the sympathetic nervous system play the major role in this organism’s response to hypoxemia.


Hypoxemia Chemoreceptors Organ vascular resistances 



The authors gratefully acknowledge the support of the National Institutes of Health (NHLBI; HL 0-50712-13) for this study.


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Robert S. Fitzgerald
    • 1
    • 2
    • 3
    Email author
  • Gholam A. Dehghani
    • 1
  • Samara Kiihl
    • 4
  1. 1.Departments of Environmental Health SciencesThe Johns Hopkins University Medical InstitutionsBaltimoreUSA
  2. 2.Departments of PhysiologyThe Johns Hopkins University Medical InstitutionsBaltimoreUSA
  3. 3.Departments of MedicineThe Johns Hopkins University Medical InstitutionsBaltimoreUSA
  4. 4.Departments of BiostatisticsThe Johns Hopkins University Medical InstitutionsBaltimoreUSA

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