Difference between dosimeter and tidal breathing methacholine challenge - Contributions of dose and deep inspiration bronchoprotection
ABSTRACT Two bronchoprovocation methods are widely used. Compared to the tidal breathing method, the dosimeter method delivers approximately half the dose and involves five deep inhalations. Both the lower dose and the bronchoprotective deep inhalations contribute to the lesser airway response of the dosimeter.
To determine the relative role of dose and deep inspiration in the difference between the two methods.
Subjects with asthma (n = 24) underwent three methacholine challenges: a dosimeter challenge, a 2-min tidal breathing challenge (twice the dose), and a modified 2-min tidal breathing challenge (twice the dose plus five deep inhalations).
The dosimeter method produced a nonsignificantly lower response than the modified tidal breathing method (p = 0.14). Both deep inhalation methods produced significantly less response than did the standard tidal breathing method (p = 0.011). In the 12 subjects with the most mild airway hyperresponsiveness (AHR), the differences between the deep inhalation method and the tidal breathing method were greater (p = 0.007). By contrast, deep inhalations produced no effect in the 12 subjects with greater AHR; the two tidal breathing methods produced identical results, while the dosimeter produced less response than either (p = 0.033). Six current asthmatics with mild airway responsiveness (tidal breathing method) had negative dosimeter methacholine challenge results.
In subjects with moderate airway responsiveness, the difference between the methods is due to the difference in dose, whereas in subjects with mild AHR, deep inhalations had a large effect overwhelming the dose effect and producing false-negative methacholine challenge results in 25% of the subjects.
- SourceAvailable from: Nicola Scichilone[Show abstract] [Hide abstract]
ABSTRACT: ABSTRACT Inpatients with mild COPD, the effect of deep inspirations (DI) to reverse methacholine-induced bronchoconstriction is largely attenuated. In this study, we tested the hypothesis that the effectiveness of DI is reduced with increasing disease severity and that this is associated with a reduction in the ability of DI to distend,the airways. F ifteen subjects (GOLD stage I-II: 7; GOLD stage III-IV: 8) underwent methacholine bronchoprovocation in the absence of DI, followed by DI. Theeffectiveness of DIwas,assessed by their ability to improve IVC and FEV1. To evaluate airway distensibility, two sets of HRCT scans (at RV and at TLC) were obtained prior to the challenge. In addition, mean parenchymal density was calculated on the HRCTs. We found a strong correlation between,the response,to DI and baseline FEV1% predicted (r 2
Article: Bronchoprovocation testing.[Show abstract] [Hide abstract]
ABSTRACT: Bronchial hyperresponsiveness is a constant feature of asthma even when airflow obstruction is absent. Detecting nonspecific bronchial hyperresponsiveness is useful when the diagnosis of asthma has not been confirmed or when a patient describes symptoms of cough, chest tightness, and dyspnea that cannot be ascribed to other causes. Also, because wheezing is a symptom of other disorders, inhalation challenge tests can be useful in defining its cause when reversible airflow obstruction has not been documented. A number of easy and safe techniques are available to detect nonspecific bronchial hyperresponsiveness. The histamine and methacholine challenge have had the most widespread use in the clinical pulmonary function laboratory. The exercise and cold air challenges are limited by expense. The osmotic challenge may gain more acceptance as experience with this technique grows. These different agents have the advantage of simplicity, reproducibility, a low number of adverse effects, and a high degree of specificity and sensitivity. A limited number of asthmatics show bronchial hyperresponsiveness to specific agents such as chemical sensitizers in the workplace, aeroallergens, aspirin, nonsteroidal anti-inflammatory agents, and sulfiting agents. Bronchoprovocation testing with these agents is usually reserved for the hospital laboratory because severe or delayed reactions may occur. These tests, however, can be extremely useful in defining a population of sensitive asthmatics.Clinics in Chest Medicine 07/1989; 10(2):165-76. · 2.17 Impact Factor
- Journal of Allergy and Clinical Immunology 05/2006; 117(4):951-2. DOI:10.1016/j.jaci.2006.02.007 · 11.25 Impact Factor