THE REPRODUCIBILITY OF THE RESPONSE OF THE HUMAN NEWBORN TO CO2 MEASURED BY REBREATHING AND STEADY-STATE METHODS

1. The ventilatory response (VR) of the full-term newborn to CO2 was studied during quiet sleep using rebreathing and steady-state methods. 2. Rebreathing responses were obtained under normoxic (fractional inspired oxygen F-i,F-O2 = 0.21) and hyperoxic (F-i,F-O2 = 0.4) conditions. Ten infants were tested three to five times using each of the two rebreathing protocols and the results averaged. 3. Overall, there was no significant difference between either the mean variability (coefficient of variation) or slope of the VR measured under normoxic and hyperoxic conditions. 4. Four infants were studied using a steady-state technique. There was marked test-to-test variability in VRs measured by this method.