Ventilatory response to inspired carbon dioxide in infants and adults

¹ Harriet Lane Home, Department of Pediatrics, and Department of Environmental Medicine, The Johns Hopkins University, Baltimore, Maryland

A rebreathing method was used to study the increase in ventilation with an increase in Pa_COCO2 in newborn infants and adults. The response curve of infants was shifted to the left of that of adults, which is consistent with their lower initial Pa_COCO2 and buffer base, and greater metabolism per kilogram of body weight. The rebreathing response curves of infants were also to the left of steady-state responses reported by others. It is postulated that nonchemical stimuli caused higher ventilation throughout the entire range of the CO₂ response curves in the infants studied by rebreathing without altering the sensitivity to increases in Pco₂. The change in ventilation per kilogram versus the change in Pa_COCO2, the slopes of the CO₂ response curves, were nearly the same in infants and adults studied by either method. This finding, when the comparison is made on the basis of body weight, suggests the sensitivity of the regulatory apparatus does not change with age, and the output of the effector apparatus, lungs and chest wall, is related to the mass of the individual.

Submitted on February 19, 1963

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