Effects of Nicotine-Free Hookah Smoking on Blood Flow to the Heart, Muscle and Skin

Inclusion Criteria: * 18 to 39 years of age * Habitual Hookah smoker defined as having smoked Hookah \>=12 times in the past 12 months * Have not smoked cigarettes within the past 12 months Exclusion Criteria: * Exhaled carbon monoxide level greater than 10 ppm\* as evidence of current or recent cigarette (excluded if smoked cigarette within 12 months) or Hookah smoking (excluded if smoked Hookah within past 72 hours) * History of cardiopulmonary disease * Use of any prescription medication with exception of oral contraceptive pills * History of psychiatric illness * History of neurologic disease * BMI ≥ 35 * Evidence of any of the above by physical examination, ECG or echocardiogram * Smoked cigarette in the past 12 months * History of illicit drug use * Pregnant * Any other condition(s) deemed by the physician investigators that put subjects at risk for participating in the study