The effect of CO2 on peripheral airways.
In each of ten healthy young subjects breathing different concentrations of CO2 in O2, four alveolar CO2-tension levels were obtained, ranging from about 20 mmHg when hyperventilating in O2 to 50 mmHg. Maximum expiratory flows at 60% total lung capacity were measured at each level and corrected for the influence of the expired gas on the flow. The corrected maximum flow decreased significantly when the alveolar CO2 tension was below 30-35 mmHg, while there was only slight or no influence of CO2 on the maximal flow when the tension was above 35 mmHg. The decrease is taken as evidence of a constrictor effect on peripheral bronchi of hypocapnia.
D000328:Adult; D000403:Airway Resistance / Q000187:drug effects; D001980:Bronchi / Q000187:drug effects*; D002245:Carbon Dioxide / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008448:Maximal Expiratory Flow Rate; D008449:Maximal Expiratory Flow-Volume Curves; D010313:Partial Pressure; D012115:Residual Volume; D012119:Respiration / Q000187:drug effects*; D014109:Total Lung Capacity; D014797:Vital Capacity
D002245:Carbon Dioxide