Credits to:
Nicole Johnson & Mon Ha
students from Diana M. Fisher's Systems Dynamics class
Franklin High School
Portland Oregon
Mentor: Dr. Edward Gallaher
Research Pharmacologist
Oregon Health Sciences University
Purpose of the Model:
This model shows the effect of alcohol on the human body by tracing the ingestion, absorption and elimination processes through the body. With this model, it is possible to see the effects of a variety of factors on a human's blood alcohol concentration (BAC). These factors include body weight, alcohol type, and the quantity and rate of alcohol consumption.
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Vensim Version
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STELLA Version
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Excel Version
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A STELLA model representing the processing of alcohol by the body:
This graph represents a 117 pound person drinking 6 beers over 2 hours time:
a 150 pound person drinking 6 beers over 2 hours time
a 150 pound person drinking 6 beers in one hour
The Model Equations
Alcohol_into_Stomach(t) = Alcohol_into_Stomach(t - dt) + (Alcohol_Consumed_gm_per_min - Alcohol_Absorption) * dt
INIT Alcohol_into_Stomach = 0
Alcohol_Consumed_gm_per_min = DELAY(0,hours_of_drinking*60,drinks_per_hour*grams_alcohol_per_drink/60)
{After min_of_cont_drinking, 0 gm of alcohol is consumed}
Alcohol_Absorption = Alcohol_into_Stomach*Distribution_Rate
Alcohol_in_Body_gm(t) = Alcohol_in_Body_gm(t - dt) + (Alcohol_Absorption - Alcohol_Elimination_per_min) * dt
INIT Alcohol_in_Body_gm = 0
Alcohol_Absorption = Alcohol_into_Stomach*Distribution_Rate
Alcohol_Elimination_per_min = BAC_g_per_deciliter*vol_of_dist_in_deciliters*Vmax/(Michaelis_constant_km+BAC_g_per_deciliter)
alcohol_type = min(1,carbonation+concentrated) {affects the avg_absorption_halftime value}
avg_absorption_halftime = 10 {in minutes for beer or wine on a somewhat empty stomach. In general, depends on carbonation and concentration of alcohol as well as state of stomach (empty to full), typical range is 5 to 20 min}
BAC_g_per_deciliter = Alcohol_in_Body_gm/vol_of_dist_in_deciliters
Body_Weight_kg = Body_Weight_lbs/2.2 {2.2 lbs. per kg}
Body_Weight_lbs = 150
carbonation = 1 {set to 1 for beer}
concentrated = 0 {set to 0 for beer}
Distribution_Rate = LOGN(2)/(avg_absorption_halftime/alcohol_type)
{based on dN/dt = kN, absorption from stomach into bloodstream is exponential, distribution rate = k}
drinks_per_hour = 4
Elim_per_hour = Alcohol_Elimination_per_min*60
grams_alcohol_per_drink = 12
hours_of_drinking = 2
Maryland_Legal_Limit = 0.08
Michaelis_constant_km = 0.01
{is equal to the BAC when the alcohol elimination is running at half its maximum velocity}
relative_vol_of_dist = .75 {75% of a person's mass is liquid}
Vmax = .02/60 {maximum velocity of alcohol elimination reaction in gm per min. Can range from .01/60 to .035/60 depending on low to high tolerance to alcohol}
vol_of_dist_in_deciliters = Body_Weight_kg*relative_vol_of_dist*10