CO₂ rebreathing: an undergraduate laboratory to study the chemical control of breathing

Abstract

The Read CO2 rebreathing method (Read DJ. A clinical method for assessing the ventilatory response to carbon dioxide. Australas Ann Med 16: 20-32, 1967) provides a simple and reproducible approach for studying the chemical control of breathing. It has been widely used since the modifications made by Duffin and coworkers. Our use of a rebreathing laboratory to challenge undergraduate science students to investigate the control of breathing provided 8 yr of student-generated data for comparison with the literature. Students (age: 19-22 yr, Research Ethics Board approval) rebreathed from a bag containing 5% CO2 and 95% O2 (to suppress the peripheral chemoreflex to hypoxia). Rebreathing was performed, and ventilation measured, after hyperventilation to deplete tissue CO2 stores and enable the detection of the central chemoreflex threshold. We analyzed 43 data sets, of which 10 were rejected for technical reasons. The mean threshold and ventilatory sensitivity to CO2 were 43.3 ± 3.8 mmHg and 4.60 ± 3.04 l·min(-1)·mmHg(-1) (means ± SD), respectively. Threshold values were normally distributed, whereas sensitivity was skewed to the left. Both mean values agreed well with those in the literature. We conclude that the modified rebreathing protocol is a robust method for undergraduate investigation of the chemical control of breathing.

Central respiratory chemosensitivity and cerebrovascular CO2reactivity: a rebreathing demonstration illustrating integrative human physiology

“…In the health science education setting, the hyperoxic rebreathing test is relatively simple to set up and perform and is a safe test to quantify both respiratory and cerebrovascular responses to increases in CO 2 in healthy or clinical populations. This test has been previous adopted for an educational demonstration, which focused only on the control of breathing (12). The hyperoxic rebreathing test also has theoretical utility, where advanced students of physiology or medicine require an understanding of fundamental principles of respiratory, cardiovascular, and cerebrovascular control but also an understanding of the integration between multiple organ systems in health and disease.…”

“…In a recent issue of this journal, Domnik et al (12) illustrated the utility of the rebreathing test as a laboratory demonstration for the central chemoreflex control of breathing. Domnik et al performed the "Duffin" modified rebreathing test on 33 healthy young participants, described the test, and illustrated the plotting and quantification of the ventilatory recruitment threshold and the ventilatory response to CO 2 .…”