Selected contribution: airway caliber in healthy and asthmatic subjects: effects of bronchial challenge and deep inspirations.
In 9 healthy and 14 asthmatic subjects before and after a standard bronchial challenge and a modified [deep inspiration (DI), inhibited] bronchial challenge and after albuterol, we tracked airway caliber by synthesizing a method to measure airway resistance (Raw; i.e., lung resistance at 8 Hz) in real time. We determined the minimum Raw achievable during a DI to total lung capacity and the subsequent dynamics of Raw after exhalation and resumption of tidal breathing. Results showed that even after a bronchial challenge healthy subjects can dilate airways maximally, and the dilation caused by a single DI takes several breaths to return to baseline. In contrast, at baseline, asthmatic subjects cannot maximally dilate their airways, and this worsens considerably postconstriction. Moreover, after a DI, the dilation that does occur in airway caliber in asthmatic subjects constricts back to baseline much faster (often after a single breath). After albuterol, asthmatic subjects could dilate airways much closer to levels of those of healthy subjects. These data suggest that the asthmatic smooth muscle resides in a stiffer biological state compared with the stimulated healthy smooth muscle, and inhibiting a DI in healthy subjects cannot mimic this.
Jensen
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A
Respiratory and Physiological Systems Identification Laboratory, Biomedical Engineering, Boston University, Boston, Massachusetts 02115, USA.
Atileh
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H
Suki
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Ingenito
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EP
Lutchen
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KR
D000328:Adult; D000403:Airway Resistance; D000420:Albuterol; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D001980:Bronchi / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction; D001993:Bronchodilator Agents; D003199:Computer Systems; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity; D008297:Male; D012016:Reference Values; D012143:Respiratory Physiological Phenomena
D001993:Bronchodilator Agents; D000420:Albuterol