Aim 1 outcome: The assessment of the association between oxygen flow and transcutaneous PCO2 in order to determine ideal nasal cannula flow is accomplished by graphing the average transcutaneous PCO2 measurement obtained for each L/min flow. Each enrolled patient will have transcutaneous PCO2 recorded every five minutes and will remain on each flow of oxygen for thirty minutes. Then an average of the 6 transcutaneous PCO2 readings will be calculated for each flow rate. All recorded data averages will then be plotted on a graph for each individual patient. From this graph the flow at which minimal further change in PCO2 is obtained is the ideal flow for that patient.