Airway resistance at maximum inhalation as a marker of asthma and airway hyperresponsivenessReport as inadecuate




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Respiratory Research

, 12:96

First Online: 01 December 2011Received: 07 September 2010Accepted: 15 July 2011

Abstract

BackgroundAsthmatics exhibit reduced airway dilation at maximal inspiration, likely due to structural differences in airway walls and-or functional differences in airway smooth muscle, factors that may also increase airway responsiveness to bronchoconstricting stimuli. The goal of this study was to test the hypothesis that the minimal airway resistance achievable during a maximal inspiration Rmin is abnormally elevated in subjects with airway hyperresponsiveness.

MethodsThe Rmin was measured in 34 nonasthmatic and 35 asthmatic subjects using forced oscillations at 8 Hz. Rmin and spirometric indices were measured before and after bronchodilation albuterol and bronchoconstriction methacholine. A preliminary study of 84 healthy subjects first established height dependence of baseline Rmin values.

ResultsAsthmatics had a higher baseline Rmin % predicted than nonasthmatic subjects 134 ± 33 vs. 109 ± 19 % predicted, p = 0.0004. Sensitivity-specificity analysis using receiver operating characteristic curves indicated that baseline Rmin was able to identify subjects with airway hyperresponsiveness PC20 < 16 mg-mL better than most spirometric indices Area under curve = 0.85, 0.78, and 0.87 for Rmin % predicted, FEV1 % predicted, and FEF25-75 % predicted, respectively. Also, 80% of the subjects with baseline Rmin < 100% predicted did not have airway hyperresponsiveness while 100% of subjects with Rmin > 145% predicted had hyperresponsive airways, regardless of clinical classification as asthmatic or nonasthmatic.

ConclusionsThese findings suggest that baseline Rmin, a measurement that is easier to perform than spirometry, performs as well as or better than standard spirometric indices in distinguishing subjects with airway hyperresponsiveness from those without hyperresponsive airways. The relationship of baseline Rmin to asthma and airway hyperresponsiveness likely reflects a causal relation between conditions that stiffen airway walls and hyperresponsiveness. In conjunction with symptom history, Rmin could provide a clinically useful tool for assessing asthma and monitoring response to treatment.

List of abbreviationsAUCarea under the curve

Rminminimal airway resistance achievable during a deep inspiration

Rrsrespiratory system resistance

Electronic supplementary materialThe online version of this article doi:10.1186-1465-9921-12-96 contains supplementary material, which is available to authorized users.

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Author: Nancy T Mendonça - Jennifer Kenyon - Adam S LaPrad - Sohera N Syeda - George T O-Connor - Kenneth R Lutchen

Source: https://link.springer.com/







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