The focus of this proposal is an understanding of the mechanisms leading to sleep apnea by evaluating the structure and function of the upper airway using magnetic resonance imaging techniques. The proposed studies will elucidate the role of the motion of key structures of the upper airway in mediating airway closure. By examining state related changes in the upper airway and soft tissue structures surrounding the upper airway we can begin to understand the biomechanics of apneic events. The applicant will apply physiological imaging to the study of obstructive sleep apnea. The role of the soft tissue structures surrounding the upper airway and the way in which these structures mediate collapse of the airway will be specifically evaluated. I have collaborated in development of state-of-the-art, computer graphics-based analysis software to help us understand the interrelationships between the soft tissue structures and the airway. Currently we know that the airway of the apneic patient is smaller even in wakefulness, particularly in the lateral dimension. We do not know what leads to this narrowing. My own preliminary data point to the importance of thickening of the lateral walls of the pharynx. It is also important, moreover, to understand the motion of the upper airway structures during both respiration and sleep. The techniques that I plan to use will address the critical issues of which structures play the largest role in upper airway dimensional changes during respiration, with sleep and during airway closure (apnea). The approaches that I will employ include the use of techniques that I have developed to both permit and monitor sleep in the MRI as well as a number of magnetic resonance imaging techniques. These are: spin echo MRI for definition of the size of upper airway structures; magnetic resonance spectroscopy for measurement of the fat/water content of structures surrounding the airway; echoplanar (ultrafast) MRI for study of motion of structures; spatial modulation of magnetization (SPAMM) that permits study of regional wall motion. Improved understanding of the functional and mechanical airway abnormalities in patients with obstructive sleep apnea may lead to new treatment strategies for this disorder.
