Final Exam - Extreme Environments Flashcards
What happens to the barometric pressure as we increase altitude?
Decreases
How high is the summit of mount everest?
What is the barometric pressure here?
Inspired O2 pressure?
- 8848 m
- Pb: 253 mmHg
- PiO2: 43 mmHg
If barometric pressure is low, how does this effect PaO2?
There is not much pressure to drive O2 into blood, creating a low PaO2
What happens initally as you increase altitude?
Hyperventilation to compensate for decreased barometric pressure
What chronic changes occur if you live at high altitude?
- Increased EPO leadind to increased Hct
- People born at high altitude have more surface area due to increased number of alveoli
What is the limiting factor to our performance?
- The heart (CO)
- We have 3x the lung surface are than we really need
Why do some people get altitude sickness and other do not?
Genetically predisposed
At a depth of 500 ft below sea level, what is the barometric pressure?
16 atmospheres
12,160 mmHg
What are the expected gas concentrations of O2 and N2 when diving with a total pressure of 5000 mmHg?
Nitrogen is very high because it constitutes 80% of inspired air
What is the main concern with ascending rapidly from a deep depth?
- The Bends
- Lots of nitrogen is dissolved in the blood at low depths
- When ascending rapidly, N2 comes back out of solution and forms air emboli
Pros and cons of using 100% oxygen while diving?
Pros: Less dissolved N2, prevents getting the bends
Cons: Expensive, flammable, can cause oxygen toxicity
A standatd hyperbaric chamber is usually at what pressure?
3 atm
Uses of hypobaric chamber?
- Decompression treatment
- Wound healing - pushes more O2 into the blood which the body can use to destroy infections and viruses (only really helpful with poor CV systems; diabetics)
What is the only way to increase blood oxygen?
- If Hb is fully saturated, the only way to increase O2 is increasing the dissolved portion
- This can happen with high pressures or increased FiO2
What are the 4 dangerous reactive species?
How is peroxynitrate formed?
What are it’s effects on the body?
- Superoxide and Nitric Oxide combine
- Can mutate DNA
Where are the reactive oxygen species used normally within the body?
Used in small amounts by macrophages and immune cells to destroy things
What enzymes regulate the reactive O2 species?
Superoxide dismutase - degrades superoxide
Peroxides - degrades hydrogen peroxides
Catalase - forms and degrades hydrogen peroxides
Acetylcysteines - scavenge reactive oxygen species (ROS)
What are acetylcysteines used for clinically?
N-acetylcysteine prevents the damage to the liver from acetaminophen overdose
How did polio cause respiratory failure?
Interupts the nerovous system communicating with skeletal muscles (diaphragm)
Why is the iron lung better that a PPV?
Represents normal breathing and is less traumatic
Which alveoli fill first during negative pressure and PPV?
- Negative pressure - alveoli near the chest walls fill first and pull open the deeper alveoli
- PPV - inner alveoli fill first and compress the alveoli closer to the chest wall
