Sympathetic and vascular effects of short-term passive smoke exposure in healthy nonsmokers

Background: The physiological effects of cigarette smoking have been widely studied; however, little is known about the effects of acute exposure to sidestream smoke (passive smoking). We examined the effects of sidestream smoke on muscle sympathetic nerve activity (MSNA) and forearm vascular resistance (FVR) at rest and during stressful stimuli, including the cold pressor test (CPT), sustained handgrip (SHG), and mental stress (MS). Methods and Results: In 17 healthy nonsmokers, blood pressure (BP), heart rate (HR), forearm blood flow (venous occlusion plethysmography), FVR, and MSNA (obtained through direct intraneural recordings) were measured before and during inhalation of sidestream smoke in one session (n=16) and before and during vehicle (air) inhalation in another session (n=17) on a separate day. The order of sessions was randomized between subjects. Responses to CPT, SHG, and MS were measured before and after inhalation of smoke or vehicle (ie, twice during each session). After 15 minutes' exposure to sidestream smoke, plasma nicotine and carboxyhemoglobin levels increased to 0.77±0.11 ng/mL and 0.36±0.04% (mean±SEM, P<.05), respectively. Sidestream smoke, but not vehicle inhalation, increased resting MSNA from 23±2 to 28±2 bursts/min (P<.05). FVR increased with passive smoking, but this increase was not significantly different from the change in FVR with vehicle. Plasma norepinephrine and epinephrine, BP, and HR were not changed significantly by sidestream smoke. The responses of MSNA, BP, HR, and FVR to the stressful stimuli were not potentiated by sidestream smoke, except for an increased BP response to the CPT (P<.05). Conclusions: Acute short-term passive (sidestream) smoke exposure elicits a modest increase in MSNA in healthy non- smokers but does not change HR, BP, or FVR.