Comparison of Pharyngeal Oxygen Delivery by Different Oxygen Masks

The intent of this study is to determine the difference in pharyngeal oxygen concentration in patients who have a natural airway (not intubated) using commonly available oxygen delivery systems. The investigators will test the hypothesis that oxygen concentration during the period of inspiration (FiO2) in the pharynx is dependent on oxygen delivery system design, even at high flow (15 liters/minute) oxygen delivery. Specific measurements include oxygen concentration at subjects' lips and pharynx when breathing 100% oxygen and room air via a simple mask, non-rebreather mask, OxyMaskTM, and anesthesia mask with headstrap and Jacson Rees circuit. A mean difference of 10% pharyngeal FiO2 between any of the masks will be considered clinically important. The expected standard deviation of the within-subject FiO2 is 3.5%. With a significance criterion of 0.05, 10 subjects would provide more than 90% power to detect a mean difference of 10%.