Typerreactivity of the airways to inhaled broncho-constrictor agents is widely used to diagnose asthma, both in clinical practice and in epidemiologic studies, as well as to study the mechanisms of asthma itself. Histamine-induced bronchoconstriction is known to produce mild arterial hypoxemia, but the mechanism of this effect has not been investigated, to our knowledge. Most previous studies on the effect of bronchial challenge on breathing patterns used either masks or mouthpieces, which can affect the breathing pattern. We therefore used the respiratory inductive plethysmograph to measure ventilation and breathing pattern, without mouthpiece, noseclip, or mask, and related these measurements to the arterial hypoxemia observed during bronchial challenge. my canadian pharmacy.com
Material and Methods
We studied ten male asthmatic patients aged 17 to 61 years (mean age, 36 years), all of whom had an increase in FEV, of at least 20 percent following the inhalation of a 02-agonist. All were in a stable clinical state at the time of study, having had no exacerbation of asthma for at least six weeks. Their baseline FEV, values before histamine inhalation was 1.1 to 3.8 L (mean, 2.4 L) and before methacholine inhalation 1.4 to 3.6 L (mean, 2.47 L). Five had positive skin reactions to extracts of grass pollens, Dermatophagcrides ptewnyssimus, and/or cat fur. All were being treated with regular inhaled (Vagonists, and three patients also received 5 to 10 mg of prednisolone daily by mouth. Three other patients were receiving oral theophylline, but therapy was discontinued for at least 24 h before the study. The β2-agonists by inhalation were also withheld for at least 8 h before each study. No patient was receiving sodium cromoglycate.
All patients were challenged by inhaling histamine on one day and inhaling methacholine on a subsequent day, using the method described by Cockcroft et al. The FEV, was measured using a dry spirometer. After initial FEV, measurements were made, the patient inhaled from a Wright nebulizer using a face mask.