A critical evaluation of the MefarTM dosimeter

Ward, RJ; Liakakos, P; Leonard, R.F.; Reid, David W.; Johns, DP; Walters, E. Haydn

doi:10.1034/j.1399-3003.1999.14b31.x

Cited by 3 publications

(1 citation statement)

References 14 publications

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“…These findings imply that the airway hyperresponsiveness degree is dependent on the particle size of the inhaled broncoconstrictor agent and, in this case, that small airways also do not show a similar severity of hyperresponsiveness compared to large airways. In our study, we used the MB3 Mefar Dosimeter, a largely used dosimeter, which at the recommended driving pressure of 180 kPa can assure an output with particle size within the respirable range (<5 μM) [ 26 ]. Accordingly, we may assume that in our asthmatic patients the aerosolized methacholine reached the lower airways by acting in this part of the tracheo-bronchial tree.…”

Section: Discussionmentioning

confidence: 99%

Small airway dysfunction is associated to excessive bronchoconstriction in asthmatic patients

et al. 2014

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BackgroundWe investigated whether a relationship between small airways dysfunction and bronchial hyperresponsiveness (BHR), expressed both in terms of ease of airway narrowing and of excessive bronchoconstriction, could be demonstrated in asthma.Methods63 (36 F; mean age 42 yr ± 14) stable, mild-to-moderate asthmatic patients (FEV1 92% pred ±14; FEV1/FVC 75% ± 8) underwent the methacholine challenge test (MCT). The degree of BHR was expressed as PD20 (in μg) and as ∆FVC%. Peripheral airway resistance was measured pre- and post-MCT by impulse oscillometry system (IOS) and expressed as R5-R20 (in kPa sL−1).ResultsAll patients showed BHR to methacholine (PD20 < 1600 μg) with a PD20 geometric (95% CI) mean value of 181(132–249) μg and a ∆FVC% mean value of 13.6% ± 5.1, ranging 2.5 to 29.5%. 30 out of 63 patients had R5-R20 > 0.03 kPa sL−1 (>upper normal limit) and showed ∆FVC%, but not PD20 values significantly different from the 33 patients who had R5-R20 ≤ 0.03 kPa sL−1 (15.8% ± 4.6 vs 11.5% ± 4.8, p < 0.01 and 156(96–254) μg vs 207 (134–322) μg, p = 0.382). In addition, ∆FVC% values were significantly related to the corresponding pre- (r = 0.451, p < 0.001) and post-MCT (r = 0.376, p < 0.01) R5-R20 values.ConclusionsOur results show that in asthmatic patients, small airway dysfunction, as assessed by IOS, is strictly associated to BHR, expressed as excessive bronchoconstriction, but not as ease of airway narrowing.

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Section: Discussionmentioning

confidence: 99%

Small airway dysfunction is associated to excessive bronchoconstriction in asthmatic patients

et al. 2014

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Normally suppressing CD40 coregulatory signals delivered by airway macrophages to TH2 lymphocytes are defective in patients with atopic asthma

Tang

Ward

Reid

et al. 2001

Journal of Allergy and Clinical Immunology

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European Community Respiratory Health Survey calibration project of dosimeter driving pressures

Ward¹,

Ward²,

Johns³

et al. 2002

Eur Respir J

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Two potential sources of systematic variation in output from Mefar dosimeters, the system used in the European Community Respiratory Health Survey (ECRHS) study have been evaluated: individual nebulizer characteristics and dosimeter driving pressure.Output variation from 366 new nebulizers produced in two batches for the second ECRHS were evaluated, using a solute tracer method, at a fixed driving pressure. The relationship between dosimeter driving pressure was then characterized and betweencentre variation in dosimeter driving pressure was evaluated in an Internet-based survey.A systematic difference between nebulizers manufactured in the two batches was identified. Batch one had a mean ¡ SD output of 7.0 ¡ 0.8 mg?s -1 and batch two, 6.3¡0.7 mg?s -1 (pv0.005). There was a wide range of driving pressures generated by Mefar dosimeters as set, ranging between 70-245 kPa, with most outside the quoted manufacturer9s specification of 180¡5%. Nebulizer output was confirmed as linearly related to dosimeter driving pressure (coefficient of determination (R 2 )=0.99, output=0.03776driving pressure-0.4151). The range in driving pressures observed was estimated as consistent with a variation of about one doubling in the provocative dose causing a 20% fall in forced expiratory volume in one second.Systematic variation has been identified that constitutes potentially significant confounders for between-centre comparisons of airway responsiveness in the European Community Respiratory Health Survey, with the dosimeter driving pressure representing the most serious issue. This work confirms the need for appropriate quality control of both nebulizer output and dosimeter driving pressure, in laboratories undertaking field measurements of airway responsiveness. In particular, appropriate data on driving pressures need to be collected and factored into between-centre comparisons.Comprehensive collection of such data to optimize quality control is practicable and has been instigated by the organizing committee for the European Community Respiratory Health Survey II.

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A critical evaluation of the MefarTM dosimeter

Cited by 3 publications

References 14 publications

Small airway dysfunction is associated to excessive bronchoconstriction in asthmatic patients

Small airway dysfunction is associated to excessive bronchoconstriction in asthmatic patients

Normally suppressing CD40 coregulatory signals delivered by airway macrophages to TH2 lymphocytes are defective in patients with atopic asthma

European Community Respiratory Health Survey calibration project of dosimeter driving pressures

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