Project 456746

Asthma impacts 3.4 million Canadians. Asthma is characterized by reversible airflow obstruction, wheezing, dyspnea, and disability due to bronchoconstriction and lower airway inflammation. Asthma has no cure. Although, bronchodilator and anti-inflammatory treatments often control asthma symptoms, asthma symptoms are not completely prevented in 90% of Canadians with asthma. A major sign of poor asthma control is nocturnal asthma. A modifiable risk factor for nocturnal asthma is obstructive sleep apnea (OSA), which occurs due to the pharyngeal collapse during sleep. The prevalence of OSA is 4-5 times higher in patients with asthma than the general population. OSA is associated with 2-7 times greater risk of asthma exacerbations, and treating OSA with continuous positive airway pressure (CPAP) improves quality of life in patients with asthma. However, the mechanisms by which OSA worsens asthma and CPAP improves asthma control are not well understood. We hypothesize that pharyngeal airway collapse in OSA cause a strong suction force in the thorax to resume inspiration, which also pulls more fluid to the lungs and narrows airways in asthma. On the other hand, treatment of OSA with CPAP prevents fluid accumulation in the thorax and improves overnight airway narrowing in patients with asthma. This study can lead to novel treatments for patients with asthma and OSA by preventing fluid accumulation in the thorax. These treatments can be as practical as exercise, wearing compression stockings during the day, taking diuretics, or elevating the head during sleep