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

Abstract

Duffin and McAvoy's (1988) modification of the Read (1967) CO2 rebreathing (CO2RB) method is widely used to study chemical control of breathing (ChemoCB). We used a CO2RB laboratory to challenge undergraduate science majors (to investigate the ChemoCB). We collated and analyzed 8 years of data to study the reproducibility of the laboratory and compared the results to the literature. Students (aged 19–21 yrs; IRB approval) performed the technique using a rebreathing bag containing 95% O2 to suppress peripheral chemoreceptor activity. Ventilation was measured following hyperventilation to deplete tissue CO2 stores, which also enhances detection of the central chemoreflex threshold (CCT). Data were analyzed by 3 investigators. Of 37 data sets, 7 were rejected due to technical issues. CO2 sensitivity and CCT were 4.69±3.12 L/min/mmHg (mean±SD) and 43.5±3.9 mmHg respectively. The CCT was normally distributed, whereas sensitivity was skewed to the left. Values agree well with those reported by Duffin & McAvoy (1988). We conclude CO2RB is a robust method for undergraduate investigation of the principles of chemical control of breathing. Funded by Queen's University, NSERC and CIHR.