This study is using FDA approved drugs (remifentanil, oxygen and carbon dioxide) in an investigational manner and the study is also developing a diagnostic test that is currently investigational. Investigational means that the FDA has not approved the use of the drugs in this manner or the diagnostic test being developed.~Opioid-Induced Respiratory Depression (OIRD) is recognized as potentially life threatening and the cause of substantial morbidity (poor health) and mortality (death). Respiratory depression is when the amount of breathing you do in a minute falls below normal. Opioids are medications widely used to treat both acute (lasting hours to days) and chronic (lasting months) pain, both within and outside the hospital setting. Opioids have been used outside the prescribed circumstances resulting in misuse and abuse. Even within the controlled environment of acute hospital care it is difficult to identify those individuals at most risk of OIRD, as many do not possess physical characteristics, such as obesity or obstructive sleep apnea (stop breathing during sleep), which may predispose to OIRD. In the absence of the ability to easily identify at-risk individuals the Anesthesia Patient Safety Foundation have suggested that all patients receiving opioids must be considered at risk of OIRD and therefore require appropriate monitoring.~Even when fully awake, the normal response to breathing a gas mixture containing carbon dioxide (CO2) is to increase the amount of breathing. The effect is similar to breathing in and out of a paper bag. This is called the Hypercapnic Ventilatory Response (HCVR) and can be measured. Not everyone responds in an identical manner - there will be differences in the HCVR from one person to the next. But if an individual's baseline HCVR is measured, then the change from baseline can also be measured.~This study is being done to: (1) classify or rate an individual subject's ventilatory (breathing) response in terms of respiratory depression to a bolus of a potent opioid (similar to morphine, often referred to as a narcotic). The opioid used for this study is Remifentanil and is commonly used in the operating room. Remifentanil will be given under normoxic (breathing room air [21% Oxygen]) and hyperoxic (breathing 50% oxygen) conditions to (2) determine if the measurement of the specific respiratory parameters will predict the OIRD response.
Purpose of the Study: (1) To classify an individual subject's ventilatory response in terms of respiratory depression to a bolus of remifentanil under normoxic and hyperoxic conditions. (2) Measurement of specific respiratory parameters to predict the opioid-induced respiratory depression (OIRD) response.