Nitrogen and bolus closing volumes: differences after histamine-induced bronchoconstriction.
Studies in normal subjects have shown that there is little difference in the size of the closing volume when measured by either the nitrogen methods or a bolus method. In this study we have examined the changes in closing volume following histamine-induced bronchoconstriction. In five normal subjects histamine resulted in a reduction in the vital capacity, an increase in the residual volume, and an increase in the airway resistance. The size of the closing volume measured by a bolus method increased after induced bronchoconstriction (0.52 +/- 0.15 1 to 0.74 +/- 0.17 1). With the nitrogen method the closing volume became smaller (0.51 +/- 0.19 1 to 0.17 +/- 0.17 1). Similar differences between the two methods are demonstrated in patients with asthma. The suggested explanation for these differences lies in the different methods used to establish a concentration gradient of gas in the lung. If there is "air trapping" the nitrogen method may fail to establish a concentration gradient.
D000328:Adult; D000336:Aerosols; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology; D001980:Bronchi / Q000187:drug effects*; D003250:Constriction; D005260:Female; D005459:Fluorides; D005652:Functional Residual Capacity; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods*; D008297:Male; D009584:Nitrogen; D012115:Residual Volume; D013455:Sulfur; D014797:Vital Capacity
D000336:Aerosols; D013455:Sulfur; D006632:Histamine; D009584:Nitrogen; D005459:Fluorides