Study design
ARTERIAL STIFFNESS, BLIND, ASTHMA
Following signing informed consent, reporting medical history, and filling out the Asthma Control Questionnaire (ACQ) [The subsequent study consisted of three experimental days where the participant received either: 1) mannitol airway challenge, 2) methacholine airway challenge, or 3) saline airway challenge (i.e. placebo). The order of challenges was computer-randomized independently from allocation and the subjects were blinded to the type of airway challenge administered. Because of potential bronchoconstriction, it was not possible to fully blind the researchers obtaining post-challenge data. However, vascular and inflammatory data were analyzed blind to the intervention. Each visit occurred at a minimum of one week apart to allow for recovery and to minimize potential carry-over effects between challenges. All participants were asked to withhold caffeinated drinks, food, alcohol, and exercise for a minimum of 12 hours prior to each study visit. While no changes were made to individual medication plans, all participants withheld short-acting beta-agonists for eight hours and long-acting controller medication for 48 hours prior to each test day [Each test visit started with the participant resting in the supine position for 10 minutes in a dimly lit room. Baseline brachial blood pressure was measured in duplicate, and a stable baseline was established when the variance between systolic blood pressure measurements was less than five percent. Arterial stiffness and vascular function were then evaluated. Serum was collected for systemic inflammatory measurements. Following baseline measurements, participants completed one of the three bronchial challenges. For consistency, independent of the airway response to the given intervention, each participant received 400°g salbutamol inhalation powder at the end of each intervention, within five minutes of challenge termination. Follow-up testing occurred within one hour after each bronchial challenge, and all measurements were repeated in the same order as at baseline.