lecture 7 (respiratory) Flashcards
(29 cards)
what affects high altitude?
- barometric pressure
what occurs to partial pressure of oxygen as altitude increases?
- decreases
why is change needed to help inspiration?
- barometric pressure changes
- PO2 changes
what is the equation for inspired PO2?
inspired PO2 = (pressure - water vapour) x O2 fraction
what is the alveolar gas equation?
PAO2 = (inspired PO2) - (PCO2/respiratory exchange ratio)
what does a decrease in PO2 cause?
- increased respiration
- due to hypoxia
does heart rate increase or decrease?
- increases in response to hyperaemia
- increases O2 delivery to the periphery
what occurs at high altitude?
- lower inspired PO2
- ventilation increases
- PCO2 decreases
- pH increases
what happens in hypoxia (low oxygen)?
- low PO2 activates peripheral chemoreceptors
- increases ventilation
- increases PO2
- decrease in PCO2 and increase in pH
- low PCO2 inactivates central chemoreceptors
- ventilation decreases
- PCO2 rises and initiates slow deep breath
- oxygen demand not met so process begins again
- need climatisation process
what happens within the body?
- CO2 can freely diffuse from CSF to blood
- changes in blood changes pH of CSF pH
what does the acclimatisation process do?
- normalise pH and CSF pH
- allows central chemoreceptors to work to increase ventilation
what allows this process to occur?
- choroid plexus
what physiological adaptations occur due to high altitude?
- short term = increases in 2,3 DPG (releases oxygen at lower pressures)
- long term = increased haematocrit, increased capillary numbers
what is the initial response leading to increased haematocrit?
- initial decrease in plasma volume
- increased rbc content
- increased urination
- increased respiratory loss of H2O as increased ventilation rate and dry air
- increased haematocrit
what is the long term response leading to increased haematocrit?
- increased haemopoiesis (formation of blood cellular components)
- decrease O2 tension in kidney
- kidney releases erythropoietin
- increased haematocrit
why do capillary numbers increase to adapt long term to high altitude?
- allows angiogenesis (formation of new blood vessels)
- improves diffusion of oxygen by shortening distance between cell and capillary
- increases SA for gas exchange at alveoli and tissue
- more mitochondria and cellular respiratory enzymes formed
what are the symptoms of acute mountain sickness?
- headache
- weight loss
- nausea
- malaise (discomfort)
- lack of energy
- disturbed sleeping
- occasional vomitting
- different brain function (doing things you wouldn’t usually)
what is the treatment for acute mountain sickness?
- descent
- oxgen
- acetazolamide (causes acidosis)
- dexamethasone
what is a Gamow bag?
- bag can climb inside of and inflate
- increases barometric pressure (same as descending mountain)
what are the symptoms of high altitude pulmonary oedema?
- breathlessness
- noticeable lying down
- crackles during breathing
- pink frothy sputum
what is high altitude pulmonary oedema due to?
- uneven vasoconstriction
- increased BP, HR
- leakage of rbc into alveolar spaces
- causes structural changes to liquid barrier (effects diffusion)
why is the sputum pink and frothy?
- due to escaping of rbc
what is the cause of the pink sputum?
- little flexibility
- stretched pores
- disruption to membranes
what is high altitude cerebral oedema?
- develop with AMS
- due to higher pressures in brain affecting BBB (structural changes)
