L20 - acute responses to altitude Flashcards
what is altitude
low PO2 in the air
-hypoxic
how to work out partial pressure of O2
frac conc of o2 in air X total pressure (baromteric - water vapour)
what level of PO2 does the carotid body respond
PO2 < 8kPa
- due to les HB saturation of O2
what receptors are stimulated during low PO2
peripheral chemoreceptors
- leading to hyper ventilation
fractional conc of O2 in the air
21%
what happens to BP when the
for every 5500m in the altitude, the PB half by half
why is it hard to predict the size of hypoventilation
hypoxia depresses respitatory centres
what happen to PCO2 at an altitude
becomes lower
- higher affinity for O2 by Hb
why is it a con for higher affinity for O2 by HB
the tissue already has low O2 due to hypoxia so there wont be enough O2 to meet the demand for other tissues
what is cheyne -stokes respiration
hyperventile > decrease CO2
- trigger apnea (breating stops)
- increase in CO2 and decrease In O2
- chemoreceptors detect this
- breaths hard
- cycle repeated to hyperventilate
eqn for PAO2
PIO2- (PAC02/R(0.8))
- 13kpa at sea level
what happen to the diffusion at a higher altitude
gets lower so the perfusion decreases
-O2 ocasade from air to the tissues decreases
what happens to the O2 casade when doing hyper ventilation
increases
what are cerebral vessel responsive to
arterial co2
- hyerpcapnia > vasocontriction
what happens to pulmonary vessel at a higher altitude
generalaised vaso con
-lower O2 delivery and O2 saturation so less cognitive function due to less O2 int he brain
what is acute momuntian sickness
heachache at an altitude
-
causes of acute mountian sickness
cerebral oedema > ilation of cerebral arterioles due to hypoxia
pulmonayr oedema > vasoconstriction so higher pul hypertension
- more diffsion distance
how does the body compensate for low PO2
pH is altered and restored due to the low Co2 alkalosis
- increased sensitivity of peripheral chemorRs
- increase in NT activity
how does the pH restored
the pH of CSF decreases so the HCO3- move out
- decreases reabsorption of HCO3 and H+ in the plasma
- this counteracts respiratory alkalosis and turn off the inhibtion of C and P chemoR
how does 2,3 -DPG help to adapt in higher altitudes
decrease O2 affinity by HB so more O2 are unloaded to the tissues
adaptation and chnages in chronic hypoxia
increased pordution of 2,3-DPG - new blood vessels -new RBCs -carotisd body sensitivity -conc of HB increases -HCT increases increases pulm diffusing capacity - increased efficiency of mitochondria
neg conseq of mountian sickness
compensatory responses fails
-Ve decreases
-icnreases in pulm pressure
too much HCT > higher R
wht happen to O2 when exercising at higher altitudes
V02max decrease by 10% every 1000m
-need higher ventilation
