Acute alcohol ingestion and sympathetic neural responses during orthostatic stress in humans

Acute alcohol consumption has been reported to decrease mean arterial pressure (MAP) during orthostatic challenge, a response that may contribute to alcohol-mediated hypotension and eventually syncope. Muscle sympathetic nerve activity (MSNA) increases during orthostatic stress to help maintain MAP, yet the influence of alcohol on MSNA during orthostatic stress has not been determined. We hypothesized that alcohol ingestion would blunt arterial blood pressure and MSNA responses to progressive lower body negative pressure (LBNP). MAP, MSNA, and heart rate (HR) were recorded during progressive LBNP (-5, -10, -15, -20, -30, and -40 mmHg; 3 min/stage) in 30 subjects(age 24 ± 1 yrs). After an initial progressive LBNP protocol (pre-treatment), subjects were randomly assigned to consume alcohol (0.8g ethanol/kg body mass; n=15) or placebo (n=15) and then repeated the progressive LBNP protocol (post-treatment). Alcohol increased (drug × treatment, P ≤ 0.05) resting HR (59 ± 2 to 65 ± 2 beats/min) and MSNA (13 ± 3 to 19 ± 4 bursts/min) when compared to placebo. While alcohol increased MAP (83 ± 2 to 87 ± 2 mmHg), these increases were also observed with placebo (82 ± 2 to 88 ± 1 mmHg; treatment, P < 0.05; drug × treatment, P > 0.05). During progressive LBNP, a prominent decrease in MAP was observed after alcohol (drug × time × treatment, P < 0.05), but not placebo. There was also a significant attenuated response in forearm vascular resistance (FVR) during progressive LBNP (drug × time × treatment, P < 0.05). MSNA and HR increased during all LBNP protocols, but there were no differences between treatments or groups (drugs). In summary, acute alcohol ingestion induces an attenuation in blood pressure response during an orthostatic challenge, possibly due to the effect that alcohol has on impairing peripheral blood vessel constriction.

EXHAUST EMISSIONS OF LOW LEVEL BLEND ALCOHOL FUELS FROM TWO-STROKE AND FOUR-STROKE MARINE ENGINES

The U.S. Renewable Fuel Standard mandates that by 2022, 36 billion gallons of renewable fuels must be produced on a yearly basis. Ethanol production is capped at 15 billion gallons, meaning 21 billion gallons must come from different alternative fuel sources. A viable alternative to reach the remainder of this mandate is iso-butanol. Unlike ethanol, iso-butanol does not phase separate when mixed with water, meaning it can be transported using traditional pipeline methods. Iso-butanol also has a lower oxygen content by mass, meaning it can displace more petroleum while maintaining the same oxygen concentration in the fuel blend. This research focused on studying the effects of low level alcohol fuels on marine engine emissions to assess the possibility of using iso-butanol as a replacement for ethanol. Three marine engines were used in this study, representing a wide range of what is currently in service in the United States. Two four-stroke engine and one two-stroke engine powered boats were tested in the tributaries of the Chesapeake Bay, near Annapolis, Maryland over the course of two rounds of weeklong testing in May and September. The engines were tested using a standard test cycle and emissions were sampled using constant volume sampling techniques. Specific emissions for two-stroke and four-stroke engines were compared to the baseline indolene tests. Because of the nature of the field testing, limited engine parameters were recorded. Therefore, the engine parameters analyzed aside from emissions were the operating relative air-to-fuel ratio and engine speed. Emissions trends from the baseline test to each alcohol fuel for the four-stroke engines were consistent, when analyzing a single round of testing. The same trends were not consistent when comparing separate rounds because of uncontrolled weather conditions and because the four-stroke engines operate without fuel control feedback during full load conditions. Emissions trends from the baseline test to each alcohol fuel for the two-stroke engine were consistent for all rounds of testing. This is due to the fact the engine operates open-loop, and does not provide fueling compensation when fuel composition changes. Changes in emissions with respect to the baseline for iso-butanol were consistent with changes for ethanol. It was determined iso-butanol would make a viable replacement for ethanol.