Ventilatory response to intermittent inspired carbon dioxide

¹ Department of Environmental Medicine, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland

The hypothesis that cyclic variation of CO₂ tension of the arterial blood (Pa_COCO2) about its mean produces an additional stimulus to ventilation was tested in the dog. Oscillations of alveolar carbon dioxide tension were produced by the intermittent administration of 20% CO₂ for 1 breath every 7–12 breaths. The increment in ventilation per mm Hg rise in mean Pa_COCO2 during the intermittent administration of 20% CO₂ was compared to that during continuous administration of 3% CO₂ in nine adult dogs anesthesized with sodium pentobarbital. Thirteen experiments with oscillating CO₂ and eighteen with steady CO₂ were performed. In all except one animal the increase in ventilation per mm Hg change in mean Pa_COCO2 was greater during intermittent CO₂ than during steady CO₂. In three experiments intermittent administration of CO₂ caused a ventilatory response sufficient to lower the mean Pa_COCO2 below control values. The increment in total ventilation per mm Hg rise in arterial carbon dioxide tension for steady CO₂ breathing was 0.58 liters/min per mm Hg and for intermittent CO₂ was 2.00 liters/min per mm Hg. These findings support the concept that chemoreceptors are stimulated by oscillations of Pa_COCO2 as well as by the mean level of Pa_COCO2. The oscillatory stimulus appears not to be related to the amplitude of the oscillation or to the peak Pco₂ attained, but rather to the rate of increase of arterial Pco₂.

Submitted on October 17, 1963

This article has been cited by other articles:

				A. R. Dowell, C. E. Buckley III, R. Cohen, R. E. Whalen, and H. O. Sieker Cheyne-Stokes Respiration: A Review of Clinical Manifestations and Critique of Physiological Mechanisms Arch Intern Med, April 1, 1971; 127(4): 712 - 726. [Abstract] [PDF]