Laboratory Session 9: Cardiovascular Function During Acute Hypoxia

Name: ______1

Laboratory Session 9: Cardiovascular Function During Acute Hypoxia Background The Exercise Science Program at UNM owns a hypo- and hyper-barometric chamber, which is located next to Carlisle Gym. This facility has been used in research, and is also a great teaching aid to expose students to the stress of higher altitude (simulated by decreasing pressure inside the chamber).

During acute exposure to increasing altitude (lower pressure), the body’s alveolar partial pressure of oxygen (PAO2) decreases in a near linear manner with the lower pressure. This causes a slight reduction in PaO2 and the saturation of hemoglobin (though well preserved for low to moderate altitude due to the oxy-hemoglobin dissociation curve), so that there is less oxygen content of arterial blood. To compensate, there is an increase in ventilation and heart rate. The mild hyperventilation raises PAO2 and PaO2 slightly (though PAO2 is still lower than if at a lower altitude), and the increased heart rate functions to raise cardiac output so that blood oxygen delivery remains similar to normoxia (normal oxygen content of inspired air).

Purpose The purpose of this laboratory is to expose students to hypobaric hypoxia (hypoxia induced by lowering atmospheric pressure). During exposure to altitudes of 5,000 (baseline), 7,000, 10,000, 13,000 and 16,000 ft, data will be recorded from each student for heart rate, SaO2 (arterial oxy- hemoglobin saturation) and ventilation rate.

Methods Participation in this lab is voluntary, and students who volunteer and are healthy with no symptoms of airway congestion, common cold, or history of claustrophobia, will enter the chamber. Air will be suctioned from the chamber at a rate equivalent to an altitude change of 1,000 ft/min.

Prior to the development of hypobaric hypoxia, measures of heart rate, SaO2 and ventilation rate will be made on each student. The same measures will be made at each of 7,000, 10,000, 13,000, and 16,000 ft.

Data Processing Get a copy of the data from Dr. Robergs (will be made as an Excel file and attached to the Assignments web page for Lab 8). Use the formula mode to calculate the mean and standard deviation data for all variables and conditions.

Perform 1-way ANOVA statistics on the change in each variable for the 5 altitude conditions. Dr. Robergs will show you how to do this in lecture.

Results Graph the meanSD data for each variable, and use symbols to show means that are significantly different.

Discussion Comment on how the oxy-hemoglobin dissociation curve minimizes reductions in PaO2 during hypoxia. How does acute altitude exposure alter VO2max? Why? What does a sustained hyperventilation do to blood acid-base balance? What would be good and bad for living at higher altitude and its impact on exercise performance? Name: ______2

References

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