Journal article
Quantifying hypoxia-induced chemoreceptor sensitivity in the awake rodent
Journal of applied physiology (1985), Vol.117(7), pp.816-824
10/01/2014
DOI: 10.1152/japplphysiol.00484.2014
PMCID: PMC4187053
PMID: 25080926
Abstract
We evaluated several methods for characterizing hypoxic chemosensitivity in the conscious rat. Adult Sprague-Dawley rats (n = 30) were exposed to normobaric hypoxia [inspired oxygen fraction (Fio2) 0.15, 0.12, and 0.09]. We measured ventilation (V̇e; barometric plethysmography), arterial oxygen saturation (SpO2; pulse oximeter), and oxygen consumption and carbon dioxide production (V̇o2 and V̇co2; analysis of expired air). Linear regression analysis was used to define stimulus-response relationships. Testing was performed on 2 days to assess day-to-day reproducibility. Exposure to graded, steady-state hypoxia caused progressive reductions in SpO2 that were, for any given Fio2, quite variable (SpO2 range, 20-30%) among individuals. Hypoxia produced progressive increases in V̇e caused by increases in both tidal volume (VT) and breathing frequency. Hypoxia also increased the VT:inspiratory time (Ti) ratio, an indicator of central respiratory "drive." Hypoxia caused consistent, progressive declines in V̇o2, V̇co2, and core temperature (>20% at the lowest SpO2). We propose that optimal quantification of carotid chemoreceptor hypoxic sensitivity in the unanesthetized rodent should employ SpO2 [a surrogate for arterial Po2 (PaO2 )] as the stimulus variable and the ventilatory equivalent for V̇co2 (V̇e/V̇co2) and/or mean inspiratory flow rate (VT/Ti) normalized for V̇co2 as the response variables. Both metrics take into account not only the important influence of a falling metabolic rate, but also SpO2, which represents the hypoxic stimulus at the carotid body. Because of the somewhat curvilinear nature of these responses, exposure to multiple levels of graded hypoxia provides the most complete characterization of hypoxic chemosensitivity.
Details
- Title: Subtitle
- Quantifying hypoxia-induced chemoreceptor sensitivity in the awake rodent
- Creators
- Barbara J Morgan - University of Wisconsin–MadisonRussell Adrian - University of Wisconsin–MadisonMelissa L Bates - University of Wisconsin–MadisonJohn M Dopp - University of Wisconsin–MadisonJerome A Dempsey - University of Wisconsin–Madison
- Resource Type
- Journal article
- Publication Details
- Journal of applied physiology (1985), Vol.117(7), pp.816-824
- DOI
- 10.1152/japplphysiol.00484.2014
- PMID
- 25080926
- PMCID
- PMC4187053
- NLM abbreviation
- J Appl Physiol (1985)
- ISSN
- 8750-7587
- eISSN
- 1522-1601
- Grant note
- U01-HL105365 / NHLBI NIH HHS U01 HL105365 / NHLBI NIH HHS
- Language
- English
- Date published
- 10/01/2014
- Academic Unit
- Stead Family Department of Pediatrics; Fraternal Order of Eagles Diabetes Research Center; Health, Sport, and Human Physiology ; Internal Medicine
- Record Identifier
- 9984259392502771
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