Hypoxia Flashcards
What is the difference between hypoxia and hypoxemia?
Hypoxia describes the environement, specifically in PO2 environement
Hypoxemia is for the blood environement-PaO2
Where can we measure PO2?
At sea levels around 21.3kPa, can measure in bronchi-around 20kPa. Alveoli, 13.3. Artery around 13.3.As pass by tissue around 5.3-then comes back to lungs around 5.3kPa
What is the O2 cascade?
Like a staircase-air outside has more oxygen and no more is ever taken in
It describes the decreasing oxygen tension from inspired air to respiratory cells
What law is important to the O2 cascade?
Ficks law-how thickness, surface area and the GRADIENT of O2 matter to intake-and if breather hyperoxic its better
Where is biggest proportion of air lost?
changing the gradient
Goes from 20kPa to 13.3
What does hyperventilation means?
It described how much youre breathing versus what you need
Why does, in exercise, oxygen and CO2 not go down/up at the same rate?
Because O2 dissociation is sigmoid while CO2 is linear
What can affect oxygen cascade?
aleveolar ventilation
V/Q mismatch-ventilation perfusion
Diffusion capacity
Cardiac output
How does being at the summet of evrest change the oxygen cascade ?
At the summet of Everest-less air in general outside so it starts much lower (around 5kPa). Barely any gradient to work with. Before going from 20 to 5. Now from 5 to lower On top of that exercise means youll have less oxygen left and more CO2
How long could a person survive on the Everest untrained?
Unconcisous in 1min, dead in 2 minutes. Ascent must be done slowly to allow body to acclimatise
What are the main challenged of high altitude/hypobaric hypoxia
Hypoxia, thermal stress, solar radiation, hydration (hypoxia induced diruses), danger (affected by altitidue)
What is the physiology of accommodation and acclimation in altitude?
Atm O2 down, PaO2 down, activation of peripheral chemoreceptors (O2 is peripheral)=>SNS outflow, HR and Q up-better O2 load
Ventilation Up so PAO2 up-better O2
But also increase of erythropoietin, so more RBC and O2 loading. Also more oxidative enzymes, increase in Mitochondria-both these cause increase 2.3DPG-help O2 unloading
BUT both of these cause PaCO2 to go down-central drive to breathe goes DOWN, so ventilation goes down-O2 down
Loss in CO2 increases pH, increasing shift of dissociation curve (towards left)-cause increases O2 unloading
Alkalosis detected-excretion by bicarbonate by kidney-try and normalise ODC-but that’s SLOW
What is the different between accommodation and acclimatisation
Accomodation-stimulated by artificial environement (like going gym tons). Acetazolamide drusg inhbit Cabonic anhydrase-less alkalosis response
What is chronic mountain sickness?
Acclimatised indivuduals spontaneouslt aquire mountains sickness (Monge disease)-failure of the help mechanism, and the compensatory mechanism over act
What are symptoms of Chronic mountain sickness?
As haematocrit goes up, blood is viscous and harder to pump-cyanosis, tiredness (supply problems)
What is acute mountain sickness?
Maladaptation to high altitude environmemt
What are the symptoms of Acute mountain sickness?
Like a hangover-nausea, vomit, irritable, dizziness, fatigue
Maybe causes by mild cebebreal odemeama-fluid accumulate in brain
Treatment-stop or go down
What are two common complications of acute mountain sickness?
High altitude cerebral oedema and high altitude pulmonary oedema
How does high altitude pulmonary odema develop?
Vasoconstriction (specific to lung) of vessels in response to hypoxia-increased pulmonary pressure, permeability-fluid leakage from capillaries accumulate once production exceeds maxium lymph drainage
Symtoms-all respiratory. Treat by going down, use drugs for vasodilation
How does ceberal oedema develop from acute mpuntain sickness?
Symtoms-confusion, ataxia (non coordination), hallucination
Vasodilation in responsse to hypoxeamia-more blood going to capillaries, fluid leakage to sealed box cranium
How does hyperventilation affect how long you can hold your breath?
Normally when holding breath, O2 down and CO2 up, until threshold which you breath
If yoi hyperventilate, higher O2 to play with and lower CO2-so can hold longer
What is respiratory failure?
3 types-fundamentally a failure of pulmonary gas exchange, generally V/Q problem
What is type 1 pulmonary failure?
Hypxic respiratory failure-PaO2<8kPa, PaCO2-normal low
Diffusion issue (like fluid in lungs)-CO2 can diffuse by but not oxygen. Infection, oedema, pneumonia
Not imminent failure
What is type 2 pulmonary failure?
Hypercapnic respiratory-PaO2<8, PaCO2>6.7. Failure to get CO2 out (elimination) or can be due to CO2 production. Can be due to less CNS drive, less capillaries. Problem either in making too much CO2 or cant be cleared out, or combination of both
