The reflex effects of intralaryngeal carbon dioxide on the pattern of breathing

摘要

1. The reflex effects on the pattern of breathing and total lung resistance of introducing 30, 10 and 5% CO2 in air into the larynx have been studied in anaesthetized and decerebrate cats breathing through a tracheostomy tube.2. Flowing 30% CO2 into the larynx caused a two-phased response. First, respiratory frequency and tidal volume decreased, with a consequent fall in minute ventilation. After two to ten breaths, frequency remained slow, but tidal volume increased beyond the control level, so that minute ventilation was restored to control levels.3. Flowing 5 or 10% CO2 into the larynx caused slowing of breathing with small and inconsistent changes in tidal volume. Minute ventilation was significantly diminished.4. Off effects, on re-introducing air into the larynx, after 2 and 10 min of CO2 exposure, suggested that the reflex response diminishes with increased duration of exposure to CO2.5. None of the concentrations of intralaryngeal CO2 changed total lung resistance or compliance.6. CO2 mixtures in the larynx generally caused no change in blood pressure or pulse rate of the cats.7. The reflex effects of intralaryngeal CO2 were abolished by denervating the larynx.8. Hypoxic mixtures introduced into the larynx did not change breathing.