Sensitivity of aerosol bolus behavior to methacholine-induced bronchoconstriction.
OBJECTIVE
Airway narrowing causes alterations in the shape of an exhaled aerosol bolus that can serve as indexes of airway changes during bronchoprovocation. We compared the sensitivities of aerosol bolus behavior and specific airway conductance (SGaw) during bronchoprovocation in normal subjects.


METHODS
Fifteen normal, nonsmoking subjects were studied. Doubling methacholine (MCh) concentrations were delivered during tidal breathing. After each dose, SGaw was determined followed by inhalation of narrow pulses of 1-microm particles introduced into 1-L breaths. Inhaled and exhaled particle concentrations were measured with light scattering photometry. Using plots of concentration vs volume, the exhaled bolus was compared with the inhaled bolus for measurements of volumetric change in mode location (modal shift), particle deposition, and dispersion. To determine baseline intrasubject variability, sham studies using buffer solution were performed on five subjects.


RESULTS
MCh caused a proximal modal shift, and increased dispersion and deposition of the exhaled bolus. At most doses, a greater percentage of subjects showed significant change (p<0.05) from baseline for modal shift and deposition than for SGaw. Aerosol bolus behavior displayed less intrasubject variability than did SGaw during sham studies.


CONCLUSIONS
Aerosol bolus behavior is at least as sensitive as SGaw in detecting MCh-induced airway constriction in normal subjects and exhibits less intrasubject variability.
Hardy
K G
KG
Division of Pulmonary and Critical Care Medicine, John L. McClellan Veterans Administration Medical Center and the University of Arkansas for Medical Sciences, Little Rock 72205, USA.
Gann
L P
LP
Tennal
K B
KB
Walls
R
R
Hiller
F C
FC
Anderson
P J
PJ
D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects*; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D012016:Reference Values; D012129:Respiratory Function Tests / Q000379:methods*; D012680:Sensitivity and Specificity
D000336:Aerosols; D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride