Abstract
Rational: Effective specific airway conductance (sGeff = 1/sReff) features a sensitive target parameter differentiating severity of AHR, performed by methacholine (MCH) challenge tests using a plethysmograph. sGeff is computed as ratio between the integral of the tidal flow/volume loop, and the integral of the resistive work of breathing (sWOB).
Aim: AHR assessed by sWOB in comparison to sGeff, FEV1 and MEF50, computing sensitivity and specificity (http://www.roccet.ca)
Method: From our database 348 subjects (141 males; 207 females; aged 14.7 to 88.4 ys) were selected, in order to differentiate asthmatic patients (121, 34.8%) from non-asthmatic subjects (227, 65.2%). MCH (5%) was administered as aerosol in 3 consecutive cumulative provocation levels (P1: 0.2 mg; P2: 1.0 mg; P3: 2.2 mg), using the Jaeger aerosol provocation system (APS), Provocation doses (PD) were calculated for each parameter specifically (PD150sWOB, PD40sGeff, PD20FEV1, PD20MEF50).
Results: Best sensitivity (s) and corresponding PD for MCH was found for PD150sWOB (s=85.9% at 1.26 mg), followed by PD40sGeff (s=79.7% at PD 0.64 mg), PD20FEV1 (s=70.9% at 1.42 mg), and PD20MEF50 (s=65.2% at 0.52 mg). Noteworthy, lowest PD were need for PD20MEF50, highest for PD20FEV1. Best response to MCH, and hence discrimination between mild, moderate or severe AHR, was detected by PD40sGeff (67.2%), followed by PD20MEF50 (51.4%), PD150sWOB (47.7%), and PD20FEV1 (25.8%)
Conclusions: sWOB feathers a highly sensitive, and discriminating parameter in the assessment of AHR. It offers insight into underlying mechanisms of lung physiology of MCH challenge tests.
- Copyright ©the authors 2016