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
