Lesson 4: Bodies at Altitude Flashcards
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What did Dr. Phillip Ainslie say about the proportion of climbers to get mountain sickness?
50-60% suffer from AMS (acute mountain sickness)
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Who is Evangelista Torricelli?
He invented the mercury barometer to measure atmospheric/barometric pressure.
Why do humans need oxygen?
To provide fuel for a series of reaction that convert glucose/sugar to useable energy
What is hemoglobin?
- A protein found in red blood cells that facilitates the transport of oxygen.
- Consists of 4 protein molecules, each of which can carry an Oxygen molecule.
How much of the oxygen in our blood does hemoglobin transport in comparison to plasma?
Hemoglobin: 97%
Plasma: 3%
What is Oxygen saturation?
- The % of hemoglobin protein molecules that have oxygen attached to them.
- At sea level, even during strenuous activity, amount of O2 saturation is 100% (declines with altitude)
Recall: What is atmospheric pressure?
Pressure exerted by weight of air in the atmosphere.
In 1648, Blaise Pascal conducted an experiment to test…?
The hypothesis that atmospheric pressure decreased with altitude on the Puy-de-Dome Mountain in France.
Air at sea level and on mountain summits is comprised of ~ ___% N and ___% O2.
78% and 21%
Briefly describe the respiratory system?
Alveoli in lungs -> diffusion -> bloodstream to oxygenate other tissues -> CO2 exhaled through diffusion (concentration gradient)
What are the 2 properties that determine the rate at which )2 diffuses into blood?
- The surface area of the tissue across which diffusion occurs (SA of alveoli consistently high)
- The concentration gradient (oxygen diffusion depends mostly on this)
The concentration gradient of a gas, is determined by the difference in its partial pressure between locations. Describe partial pressure.
- The partial pressue of O2 in air is proportional to total atmospheric pressure, which is reduced at high altitudes.
- Partial pressure of O2 in the venous blood returning to, or entering, lungs is relatively similar at sea level and at higher altitudes
What does the smaller difference in the partial pressures of oxygen between the lungs and blood at higher altitudes mean?
- Means concentration gradient of oxygen between the lungs and blood is reduced at higher altitudes because there is a smaller difference in the partial pressures of oxygen.
- Decreased atmospheric pressure, therefore, reduces oxygen uptake
What is Hypoxia?
The condition when tissues are deprived of O2 at high altitudes where the rate of diffusion of O2 into blood is slower
What is the tidal volume?
- During normal respiration the amount of air that is moved in and out of the lungs in each breath.
- Average tidal volume of an adult is ~500 mL, but only 70% reaches the alveoli to deliver oxygen to the bloodstream
- 30 is called dead space
What are 2 ways to increase O2 intake?
- breathing deeper, increasing tidal volume
- hyperventilation, which increases air intake (not as effective)
- Dead space is fixed volume
Increases heart rate is a rapid response to low O2 conditions. How does it help?
- Increases heart rate increases the amount of blood pumped through the body in a given amount of time, and increases the amount of blood passing the alveoli in the lungs. Thus, more oxygen is circulates.
- Increases blood flow can compensate for lower amount of oxygen in blood
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Capacity to do work decline at higher elevations and may be suppressed even more in individuals who have breathing conditions such as asthma. Give an ex.
At the lookout atop Mount Evans in Colorado, at 4,300 m above sea level, capacity to work is reduced by almost 25%
What happens beyond 8000 m?
- This is referred to as the death zone
- Amount of O2 is considered insufficient for humans to acclimatise and survive
Low O2 levels also influence the autonomic nervous system which regulates…?
Body functions, such as the heart rate, digestion, respiratory rate, pupillary response, and urination.
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What are some early descriptions of Hypoxia?
- 1st accounts in Chinese txts in 1st century
- Marco Polo documented these ‘headache mountains’ at end of 13th century
- 1800s, ballooning
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Give examples of scientists that studied with ballooning.
- 2 scientists, James Glasher and Henry Tracey Coxwell, ascended >8000 m in <1hr (only 14 mountains with altitudes >8000 m)
- 1875, 3 scientists boarded Xenith (French balloon), ascended 8600 m in 1 hr. 2 died, 1 left partially deaf
How common is Acute Mountain Sickness (AMS)?
Most people are not affected <2500 m, but 1 in 4 people who travel >2500 m experience it.
What are symptoms of AMS?
Headache (most common), fatigue, loss of appetite nausea, dizziness, inability to sleep, and vomiting.
