Vocal Cord Responses During Hyperventilation in Normal Individuals and in Mild and Severe
The Investigators aim to: Study the effect of hyperventilation on the development of paradoxical vocal cord movement (PVCM) in healthy individuals and in patients with mild and severe asthma, Relate PVCM to airway symptoms and measurements of intra- and extra-thoracic airway hyperresponsiveness (ET-AHR), Evaluate the effects of inhaled anti-cholinergic agents on PVCM induced by hyperventilation. Hypotheses: In health PVCM will not occur in response to hyperventilation, In asthma PVCM will occur in response to hyperventilation, Airway symptoms and ET-AHR will develop in parallel with PVCM, Inhaled anticholinergic agents will prevent PVCM induced by hyperventilation.
• age >18 to 65 years old
• No history of chronic respiratory symptoms.
• The Investigators shall recruit a total of 16 patients with asthma - 8 patients with mild asthma (Group 2) and 8 patients with severe asthma (Group 3).
• Mild asthma will be defined as patients with forced expiratory volume in 1 second (FEV1) >80% predicted.
• Severe asthma will be defined as patients with FEV1 50-60% predicted.
• Asthmatics will also have a forced expiratory ratio (FER) less than the lower limit of normal, indicating obstruction.
• age 18-65 years
• A history of asthma defined as a bronchodilator response with increase in FEV1 >12% and 200mls or positive bronchoprovocation testing (methacholine).
• Asthmatics will have FEV1 >50% predicted.