A Feasibility Study of SenseGuard to Assess Airway Responsiveness During Methacholine Challenge Test (MCT)

Inclusion Criteria: * Male or female, aged ≥18. * Eligible for MCT procedure. The contradictions to MCT are listed as exclusion criteria. * Provision of a signed and dated informed consent form. * Subject who receives one of the following medications, that decrease bronchial hyperresponsiveness, is required for a washout period, before conducting the MCT: inhaled bronchodilators, oral albuterol , inhaled and oral glucocorticoids, leukotriene modifying agents, theophylline, cromolyn, and anti-histamines due to their anticholinergic effect. Exclusion Criteria: * Subjects who have known contradictions to MCT, including: * Tolerate inhalation of the challenge agents * Low baseline FEV1: Airflow limitations in FEV1 less than 60% predicted or 1.5L (baseline FEV1 of \< 1.5 L or \< 60% predicted). * Spirometry quality: inability to consistently reproduce quality spirometry * Cardiovascular problems: recent myocardial infarction within past three months, uncontrolled hypertension, known aortic aneurysm * Recent ophthalmologic surgery or patients at risk for intracranial pressure elevation. * Pregnancy and nursing mothers: Methacholine is a pregnancy category C drug and it is not known whether it is excreted in breast milk or is associated with fetal abnormalities. Women subjects will be asked to sign a statement, as part of the Informe Consent Form, that they are not pregnant or nursing mothers). * Inability to provide informed consent. * Known allergic reactions to materials used in the components of the SG, i.e., polyethylene or silicon, or gold, nickel, copper or alloys containing any of the above.