Related Experiment Video
Updated: Aug 18, 2026

MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges
Published on: December 17, 2014
[Normal ventilatory response to hypoxia and hypercapnia at an altitude of 2240 meters]
J C Vázquez-García1, S L Arellano-Vega, J Regalado-Pineda
1Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias, INER, México DF.
Objective:
To evaluate the ventilatory response to hypoxia and hypercapnia in healthy residents of Mexico City at 2240 m above sea level.
Methods:
15 healthy subjects, 10 women and 5 men, were studied (mean age 38; range 26-76). All completed one or two tests of ventilatory response to hypoxia and hypercapnia as described by Rebuck-Campbell and Read, respectively. The results were analyzed by linear regression using the minute ventilation as the dependent variable and SaO2 (hypoxia) or PCO2 (hypercapnia) as the independent variables.
Results:
Seven subjects had very low or no response to hypoxia. The mean hypoxia slope was 0.7 +/- 0.6 L/min/% (+/- SD) and the hypercapnia slope was 3.0 +/- 1.4 L/min/mmHg. The intercepts were 176 +/- 278 for SaO2 and 3.0 +/- 7 for PCO2.
Conclusions:
A low respiratory response to hypoxia was found in Mexico City Healthy residents. The response to hypercapnia was similar in slope to other studies but had an intercept shifted to lower values. The Mexico City residents showed a behavior typical of patients with chronic hypoxemia or of dwellers at high altitudes.
More Related Videos
Related Concept Videos
Factors Affecting Respiration
Physiological Control of Respiration
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...
Chemical Factors Affecting Respiration Centers
CO2 has a potent influence on respiration and is strictly regulated. Under...
Hyperpnea and Hyperventilation
Acute Respiratory Failure-II
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:
Acute Respiratory Failure-III

