Adaptations To Altitude Flashcards
Why is altitude a hypoxic environment?
Low barometric pressure (hypobaric environment)
What kinds of things occur when going higher in altitude
Psychomotor effects due to lack of o2 to brain
Loss of consciousness
What barometric pressure are aircrafts at and what’s the result of this
Barometric pressure of a higher altitude than sea level
Therefore lower po2 levels
What is another way of saying barometric pressure
Atmospheric (mix of all gases)
What is typical mmhg po2 at altitude compared to 100 normally
42
Why is low po2 at altitude affecting gas exchange
Lack of a diffusion gradient between alveoli, blood and tissues
Does minute ventilation increase when in altitude due to low po2
Yes
Increase TV and ventilation rate
What is the acute response to hypoxia called
Hypoxic ventilatory response (ie via peripheral chemoreceptors)
What happens to increase hyper ventilation at altitude
Detection of lower po2 eg 60 mmhg
Detection via glomus cells in carotid peripheral chemoreceptors
Impulse sent down X to drg and vrg to increase hyperventilating
What happens due to the hyperventilation of the peripheral chemoreceptors
Increased respiratory alkalosis as less co2 can react with water
This increased ph is detected / low co2 detected and causes hypo ventilation = not enough oxygen at altitude
Which acute response is there for acid base homeostasis due to hyperventilation at altitude
Renal compensation
How does renal compensation deal with resp alkalosis due to hyperventilation
Reduce HCO reabsorption to reduce ph (HCO is alkali)
Also stop A cell action which excrete H
What is reduced co2 called causing alkalosis
Hypocapnia
How does diamox drug also work to reduce ph for alkalosis due to hyperventilation
It is a CA inhibitor
Stops H2co3 changing to co2 and water
Increase H levels so reduces ph
How does saturation of Hb change in altitude
Saturated until around 2000 when po2 is too low due to hypobaric pressure
Causes dissociation
Which substance is produced if someone is at high altitudes to increase dissociation
2,3 dpg
How is % saturation worked out
Amount of o2 bound / unbound x 100
Why is 2,3 dpg an issue
Stops oxygen binding to Hb at alveoli exchange
What are the 2 long term responses to living in high altitude
Increase haematocrit (rbc)
Increase capillaries
How is there an increase in haematocrit short term
Increased resp loss of h20 due to ventilation causing evaporation
= concentration of haematocrit higher
How is haematocrit higher LT
Increased haematopoiesis from bone marrow
And increased erythropoiesis
What is capillary increase in altitude to cause higher a-v difference called a
Angiogenesis
What does acclimatisation mean
Adjusting to environment
What is the physical impact of hypoxia at high altitude
Acute mountain sickness
What types of things cause AMS
Rate of altitude and height and length of time at altitude
Which 2 things does ams lead to if you don’t descend
HAPE - pulmonary Edema
HACE - cns edema
What pathology does pulmonary Edema have
Hypoxic pulmonary vasoconstriction of arterioles increases hydrostatic pressure in capillaries and causes damage
This causes permeability of capillaries causing Edema (interstitial fluid)
Which 2 drugs are given for pulmonary and cerebral Edema
Nifedipine
Dexamethosome
Cerebral hypoxia leads to what symptoms
Impaired brain functions
What is vasogenic Edema caused by cerebral hypoxia in HACE
Fluid crosses the blood brain barrier causing impairment
Apart from vasogenic Edema which other thing does cerebral hypoxia cause
Cytotoxic Edema
Fluid is released from cells in the cns and causes impairment
