Measurement of intraindividual airway tone heterogeneity and its importance in asthma.
While airways have some degree of baseline tone, the level and variability of this tone is not known. It is also unclear whether there is a difference in airway tone or in the variability of airway tone between asthmatic and healthy individuals. This study examined airway tone and intraindividual airway tone heterogeneity (variance of airway tone) in vivo in 19 individuals with asthma compared with 9 healthy adults. All participants underwent spirometry, body plethysmography, and high-resolution computed tomography at baseline and after maximum bronchodilation with albuterol. Airway tone was defined as the percent difference in airway diameter after albuterol at total lung capacity compared with baseline. The amount of airway tone in each airway varied both within and between subjects. The average airway tone did not differ significantly between the two groups (P = 0.09), but the intraindividual airway tone heterogeneity did (P = 0.016). Intraindividual airway tone heterogeneity was strongly correlated with airway tone (r = 0.78, P < 0.0001). Also, it was negatively correlated with the magnitude of the distension of the airways from functional residual capacity to total lung capacity at both baseline (r = -0.49, P = 0.03) and after maximum bronchodilation (r = -0.51, P = 0.02) in the asthma, but not the healthy group. However, we did not find any relationship between intraindividual airway tone heterogeneity and conventional lung function outcomes. Intraindividual airway tone heterogeneity appears to be an important characteristic of airway pathophysiology in asthma.
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland; Department of Medicine, Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland; Department of Environmental Health Sciences, Division of Physiology, Johns Hopkins University, Baltimore, Maryland; Department of Radiology, Johns Hopkins University, Baltimore, Maryland; and rbrown@jhsph.edu.
Robert H
RH
Brown
Department of Medicine, Divisions of Allergy and Clinical Immunology and Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland.
Alkis
A
Togias
D000328:Adult; D000420:Albuterol / Q000494:pharmacology; D001249:Asthma / Q000188:drug therapy / Q000473:pathology*; D001993:Bronchodilator Agents / Q000494:pharmacology; D005260:Female; D005652:Functional Residual Capacity / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000473:pathology*; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D013147:Spirometry / Q000379:methods; D014109:Total Lung Capacity / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
D001993:Bronchodilator Agents; D000420:Albuterol
airways; bronchodilation; distensibility