lec 20 - high altitude Flashcards
what occurs in the air as altitude increases
boarmetric pressure drops (pressure of atmosphere on a specific point)
oxygen concen doesn’t change
partial pressure of oxygen decreases because of drop in barometric pressure
what is the oxygen cascade
how oxygen moves from the environment into our tissues for metabolic purposes
- oxygen moves from high to low pressure
- lungs –> blood –> muscle
what is the effect of altitude on the oxygen cascade
PO2 is lower at all steps is lower
less O2 available to tissues
starting point is lower
what is the relationship between PaO2 and SaO2
PaO2 = partial pressure of O2 in arterial blood
SaO2 = how much oxygen our blood can hold
lower PaO2 = lower SaO2
for a drop in PaO2 there is a smaller drop in SaO2
(body protecting against a drop in saturation)
what does the arterial oxygen content depend on
hemoglobin concen
saturation of hemoglobin wtih O2
PO2 of blood
what does a decrease in PaO2 trigger
increased ventilation to partially counteract the decline in PaO2
also leads to reductions in SaO2 and CaO2 (arterial oxygen content)
what happens to HR, SV, CO, a-VO2, and VO2 during sub maximal exercise at altitude compared to sub maximal exercise at base level
HR = increases
SV = stays the same (inherent value for the heart)
CO = increases (need to send more blood because there’s less O2 in each unit)
a-VO2 = goes down (less O2 per unit of blood)
VO2 = doesn’t change
what happens to HR, SV, CO, a-VO2, and VO2 during maximal exercise at altitude compared to maximal exercise at base level
max HR = same
max SV = same
max CO = same (max amount of blood we can send)
a-VO2 = down
VO2 max = down
how is the oxygen cost for metabolism and sub max exercise influenced by hypoxia
doesn’t change
- always has the same cost
(VO2 max changes and lowers below regular levels)
what is exercise harder at altitude
VO2 max drops off exponentially as altitude increases
VO2 max intersects the line of oxygen cost for submax exercise
the VO2 for the exercise could be very low but the VO2max is also very low at extreme altitudes
why does VO2max decline in hypoxia
CO and leg blood flow are still maximal
tissue oxygen extraction can’t compensate for reduced O2 transport
reach max blood flow sooner in exercise in hypoxia (only so much blood to send and it has less O2)
what is the rationale for living high and training low strategy
increase hemoglobin mass
volume of RBCs
potentially increase hemglobin concentration
what is acute mountain sickness (AMS)
symptoms = headache, dizziness, fatigue, nausea (lake louise score)
self limiting - won’t kill you
sign that you haven’t fully acclimatised
what are the risk factors for AMS
ascent rate and altitude attained
previous history is NOT a risk factor
when does AMS occur
above 2500m
within 24 hours
