The effects of carbon dioxide on pulmonary mechanics in hyperventilating, normal volunteers.
Transpulmonary pressure, air flow, and end-tidal carbon dioxide levels were measured in normal human volunteers during hypocapnic, eucapnic, and hypercapnic hyperventilation. Respiratory rate and tidal volumes were well matched at a minute ventilation of 52 L. on three inspired gas mixtures: 21 per cent oxygen and 79 per cent nitrogen; 5 per cent carbon dioxide, 21 per cent oxygen and 74 per cent nitrogen; and 12 per cent carbon dioxide, 21 per cent oxygen and 67 per cent nitrogen. Respiratory rate, tidal volume, lung compliance, resistance, and resistive work per liter were calculated with a digital computer. In 13 experiments in 7 normal volunteers, no net bronchoconstriction or bronchodilatation was observed when eucapnic hyperventilation was compared to hypocapnic or hypercapnic hyperventilation. During hyperventilation of this degree, a change in bronchomotor tone owing to alteration in arterial or alveolar PCO2 either does not occur or else is masked by other reflexes or mechanical factors acting on the bronchi.
D000328:Adult; D000403:Airway Resistance; D001696:Biomechanical Phenomena; D002245:Carbon Dioxide; D002986:Clinical Trials as Topic; D003201:Computers; D006801:Humans; D006935:Hypercapnia; D006985:Hyperventilation / Q000503:physiopathology*; D008168:Lung / Q000502:physiology*; D008170:Lung Compliance; D008297:Male; D008954:Models, Biological; D012123:Pulmonary Ventilation; D012119:Respiration; D013990:Tidal Volume
D002245:Carbon Dioxide