Cardiovascular and cerebrovascular responses to progressive central hypovolemia in young smokers: a preliminary study.

The purpose of this study was to describe cardiovascular and cerebrovascular responses of smokers and nonsmokers to progressive central hypovolemia. Twenty subjects participated (equal male and female). We recorded the electrocardiogram, beat-to-beat arterial pressure (Finometer), cerebral blood velocity of the middle cerebral artery (transcranial Doppler), and end-tidal CO2. Lower body negative pressure (LBNP) was applied at 3 mm Hg · min(-1) for 20 minutes to an ending pressure of -60 mm Hg, and data were averaged in 2-minute bins. Arterial pressures were similar between groups at baseline, but heart rates tended to be higher, and stroke volumes and cerebral velocities tended to be lower in smokers at baseline and during LBNP (all p ≥ 0.17). Heart rates increased, and arterial pressures, stroke volumes, and cerebral velocities decreased during LBNP (all p ≤ 0.05), but responses were not different between smokers and nonsmokers. During the final stage of LBNP, systolic pressures and mean middle cerebral artery velocities were substantially lower in smokers than nonsmokers: these preliminary data may suggest clinical relevance of smoking status, but the magnitude of differences between groups were not distinguishable statistically. We therefore conclude that smokers and nonsmokers respond similarly to progressive central hypovolemia.