Cold-Related Injuries #3

FUEL AND WATER REQUIREMENTS TO STAY WARM

How much food/fuel and water do we need on a daily basis, not only live, but to be able to maximize our performance?  Dehydration may not rapidly lead to death but, it will definitely decrease and impair normal physical and mental abilities.  So, to be at our best we have to stay well hydrated and well fed - fuel to burn.

NUTRITIONAL REQUIREMENTS = average of 2500 CALORIES/DAY

Carbohydrate = 4cal/gram 60%
    (200 - 400 grams/day = 1200 -1600 cal/day)
Fat   = 9cal/gram  10%
    (20 - 60 grams/days = 180 - 540 cal/day)
Protein = 4cal/gram  30%
    (30 - 55 grams/day  = 120 - 220 cal/day)

Number of calories required varies with activity:
Normal daily activity:  2000 - 2500 calories/day.
Winter outdoor sports:  3000 - 4000 calories/day
High altitude mountaineering:  4000 - 6000 calories/day.

HYDRATION REQUIREMENTS = average of 2 LITERS/DAY

Normal water losses per day:  
Insensible loss:   nl temp.    hot temp.     heavy exercise
Skin  =      350ml          350ml           350ml
Respiration  =      350ml          250ml           650ml
Sweating  =     100ml         1400ml         5000ml
Urination  =    1400ml         1200ml          500ml
Defecation  =      100ml         100ml           100ml
TOTALS        2300ml      3300ml        6600ml

Water requirements will vary with activity, sweat output, and altitude.
Exertional sweat loss is 1 - 3 liters/hour for up to 4 hours without replacement.
        (can lose up to 3 liters per hour for 4 hours = 12 liters or 3 gallons = 24 pounds)
Altitude has a very low vapor pressure = will lose 1 cup/hour via respirations.
            (or 24 cups/24 hours = 6 quarts or liters)                                                     
        
LIFE AT ALTITUDE:
O - 8000 feet  = normal elevations for humans to live within.
8000 - 14000 feet = upper limits of sustainable life.
14000 - 18000 feet (½ atmosphere) = high altitude, can visit.
18000 - 28000 feet very high altitude, constant negative deficit, the death zone.

More detailed information in the Jan/Feb 2004 issue of the Wilderness Medicine Newsletter.

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