TY - JOUR T1 - Airway resistance during the methacholine challenge test: Comparison between impulse oscillometry and plethysmographic technique JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p2132 AU - Egidio Beretta AU - Francesco Tana AU - Andrea Aliverti AU - Luca Novelli AU - Gabriele Simone Grasso AU - Giuseppe Miserocchi Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p2132.abstract N2 - Background: Plethysmographic airway resistance (Raw) does not allow identification of bronchoconstriction sites. Conversely, respiratory system resistance (Rrs) measured by impulse oscillometry (IOS) can distinguish between changes in peripheral and central airways mechanics (< 5Hz for peripheral and 5-20 Hz for central airways).We wish to compare Raw to Rrs in response to methacholine challange (MCh).Methods: 18 subjects underwent saline aerosol bolus (baseline) followed by increasing methacholine doses inhalation. At each dose, Raw and Rrs were measured respectively by body plethysmography and IOS. The measurements were repeated until reaching PD20 (estimated from FEV1) or the maximal dose (2400 μg). We considered subjects with PD20 < 800γ.Results: Raw increased in all subjects during MCh. In 67% of subjects (group 1) Rrs increased at 1Hz only, while in 33% (group 2) an increase in Rrs was found at all frequencies. In group 1, unlike in group 2, the goodness of the regression between Rrs and Raw (as from R2) was highest at 1Hz, waning progressively with increasing impulse frequency.View this table:Rrs vs RawConclusions: Measurements of Rrs in the range 1-20 Hz allow to identify different sites for MCh response. The significant correlation between Rrs at 1Hz and Raw in group 1 suggests that variation in Raw mostly reflects changes in small airways mechanics. In group 2 the significance of the regressions between Rrs at all frequencies and Raw suggests that changes in airways mechanics of various calipers impact on plethysmographic measurements. ER -