Responsible Party/PI passed away. All subjects enrolled completed study prior to termination.

This is a pilot study on the acute effects of nicotine-free hookah (herbal/steam stones) smoking on the sympathetic neural control of the human cardiovascular system. Hookah smoking is known to transiently increase blood pressure and heart rate while decreasing heart rate variability suggesting - but not proving - sympathetic mediation. The contribution of nicotine to these effects is unknown. Here the investigators will directly measure the acute effects of nicotine-free Hookah smoking on sympathetic nerve activity with microneurography (intraneural microelectrodes) and quantify associated regional changes in vasomotor tone.

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