Comparison of changes in lung function measured by plethymography and IOS after bronchoprovocation.
OBJECTIVE
Lung function tests are essential for the diagnosis and management of bronchial asthma. Impulse oscillation (IOS) system is an alternative way to measure lung mechanics for some patients. We investigated the relative sensitivities of IOS, body plethysmography and spirometry in detecting allergen- and methacholine-induced bronchoconstriction.


METHODS
Twenty-two subjects had single allergen inhalation and 8 subjects had 3 methacholine challenges. The tests were stopped when FEV1 fell by 20%. Lung function was measured using IOS (R5, R20, R5-R20, X5, AX, fres), plethysmography (sRaw, sGaw, FRC, lung volumes) and spirometry (FEV1, FVC, PEF, FEF50%) during inhalation challenges, and expressed as percent change from pre-challenge baseline.


RESULTS
All subjects were non-smoking adults with mild allergic asthma. Following allergen challenges, the most sensitive IOS index was R5-R20 and the most sensitive plethysmography and spirometry measurements were sRaw, sGaw and FEF50%. Following methacholine challenge the most sensitive IOS index was AX, the most sensitive plethysmography measurement was sRaw. Overall, IOS (R5-R20, AX, X5Hz) proved to be more sensitive than plethysmography and spirometry measurements following allergen-induced and methacholine-induced bronchoconstriction.


CONCLUSIONS
Our result shows that IOS is more sensitive than other lung function tests following allergen and methacholine challenge. In addition, IOS can act as an alternative measurement technique of airway resistance and obstruction in patients where manoeuvres involved in plethysmography and spirometry prove difficult to perform.
Cardiorespiratory Research Laboratory, Department of Medicine, McMaster University, 1200 Main St West, Hamilton, ON L8N 3Z5, Canada.
Nizar
N
Naji
Elaine
E
Keung
James
J
Kane
Rick M
RM
Watson
Kieran J
KJ
Killian
Gail M
GM
Gauvreau
D000328:Adult; D000403:Airway Resistance / Q000502:physiology; D000485:Allergens; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods*; D016085:Bronchoconstrictor Agents; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D009991:Oscillometry / Q000379:methods; D010993:Plethysmography, Whole Body / Q000379:methods; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000379:methods; D055815:Young Adult
D000485:Allergens; D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride