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Respiratory system > hypoxia > Flashcards

hypoxia Flashcards

1
Q

hypoxia

A

specific env and ste of conditions

specifically PO2 in the env

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2
Q

hypoxaemia

A

describes the blood env

PaO2

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3
Q

Ischemia

A

tissue receiving inadequate oxygen eg forearm ischemia

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4
Q

Factors that cause hypoxic stress on the body

A

altitude
exercise - but physiological response is efficient so not experienced- more O2 is supplied
disease - COPD

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5
Q

what is the O2 cascade

A

describes the decreasing O2 tension from inspired air to respiring cells ]
ambient air - highest PO2
reduction in upper airway - humidification
biggest loss in alveoli - mixing - have tio ventilate
small loss in arteries for bronchiole drainage
big loss in tissues - O2 diffusion
vol perfusion matching
cardiac output
thickness of membrane

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6
Q

factors affecting the O2 cascade

A

o2 therapy increase start PO2
breathing inhaled air decrease start
hyperventilation - reduce affect of mixing - faster
hypoventilation exacerbate mixing
diffusioin affect reduce PO2 in post alv cap
exercise reduce PO2 in tissue - diffusion, increase PCO2

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7
Q

PCO2 and PO2 in O2 cascade

A

changes are not same
O2 - sigmoid shape
CO2 - linear change

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8
Q

Oxygen cascade on Everest

A

lower starting PO2

gradient less to work with

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9
Q

Fick’s law

A 
of diffusion 
flow rate proportional to pressure grad 
Vgas = area/thickness * diffusibility * PP grad 
structural disease reduce area
fluid in alveoli - increase thickness
hypoxic gas reduce PP grad 
hyperoxic gas increase PP grad
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10
Q

Gas transport change at altitude

A

boiling point inversely proportional to altitude
need pressurised suit at high altitude - allow breathe and stop body fluids evaporating
hypoxia - less O2 in the air
thermal stress: -7degrees for 1000m, wind chill
solar radiation- sun and reflection
hydration - water lost humidifying inspired air - hypoxia induced diuresis - breathe dry air
hypoxia induced confusion and miscoordination

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11
Q

Oxygen dissociation curve

A

how much O2 bidn is dependant on PP

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12
Q

Type 1 resp failure

A 
failure of pul gas exchange 
V/Q inequality
hypoxic 
O2 into blood impaired
CO2 out - fine because it is more diffusible 
PaO2<8KPa 
PaCO2 - low/normal 
hypoventilation 
diffusion abnormality 
pul oedema 
pneumonia 
atelectasis - collapse or closure of the lung - worse GE
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13
Q

Type 2 resp failure

A 
hypercapnic resp failure 
getting gas there problem
V/Q problem 
PaO2<8KPa - low but not really the problem - O2 down greater conc grad so fine 
PaCO2 >6.7KPa 
increased CO2 production 
decreased VCO2 elimination 
decreased CNS drive 
increased work of breathing 
pul fibrosis 
neuromuscular disease 
increased physiological dead space
obesity
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14
Q

good Physiological response to high altitude

A 
low atm O2 
reduced PAO2 
reduced PaO2 
activation peripheral chemoreceptors - carotid bodies 
increase sympathetic outflow 
increase vent 
reduce PaCO2 
increase PH 
alkalosis detected by carotid body 
increase HCO3 excretion 
ODC normalises 
increased O2 unloading
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15
Q

good ‘side effects’ of physiological response to attitude

A

increased symp outflow =
increased HR and Flow
increased O2 loading

increased vent =
increased PAO2
increased O2 loading

decreased PaO2 = 
increased erythropoietin 
increased erythropoiesis 
increased O2 loading 
increased ox loading
increase oxidsative enzymes
small increase in 2,3-DPG in RBC 
right shift ODC 
increase O2 unloading 
increase O2 utilisation
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16
Q

bad ‘side effects’ of physiological response to altitude

A

reduced PaCO2 =
loss of central drive to breathe
reduced vent
reduced O2 loading

increased pH =
left shift ODC
decrease O2 unloading

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17
Q

Prophylaxis of altitude treatment

A

acclimation - from artificial exposure to the environment
acetazolamide - carbonic anhydrase inhibitor, accelerate the slow renal compensation to hypoxia induced ventilation - reduce initial alkolytic response

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18
Q

Innate developments to prevent altitude sickness

A

barrel chest - larger TLC and capillarisation - more O2 in
increased haematocrit (vol % RBC in blood) - greater O2 carrying capacity - more O2 carried
larger heart to pump through vasoconstricted circulation - greater perfusion
increased mitochondrial density - greater oxygen utilisation at cellular level - more O2 used
because of exposure through childhood and genetics
not all expressed in all populations

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19
Q

Chronic mountain sickness

A

Monge’s disease
acclimatised people spontaneously acquire chronic mountain sickness
cause unknown

20
Q

pathophysiology of chronic mountain sickness

A

secondary polycythaemia - increase blood viscosity (haematocrit is increased)
sludge through cap beds- impede O2 delivery

21
Q

symptoms of c nmountain sickness

A

cyanosis

fatigue

22
Q

consequences of c mountain sickness

A

ischemic tissue damage
heart failure
eventual death

23
Q

treatment

A

no interventional treatment

forced to go down the hill

24
Q

causes of acute mountain sickness

A

maladaptation to high altitude env

recent ascent- onset in 24 hours - last a week

25
Q

pathophysiology of a mountain sickness

A

associated with mild cerebral oedema

fluid accumulate in the cranium

26
Q

symptoms of a mountain sickness

A 
nausea 
vomiting 
irritability
dizziness
insomnia 
fatigue
dyspnoea 
disappear after 48hours of increased kidney compensation
27
Q

consequences of a mountain sickness

A

development to high altitude pul oedema

development to high altitude cerebral oedema

28
Q

treatment of a mountain sickness

A 
monitor symptoms 
stop ascent 
analgesia - pain killer 
acetazolamide 
hyperbaric O2 therapy
29
Q

cause of High altitude pulmonary oedema

A

rapid ascent

inability to acclimatise

30
Q

pathophysiology of high alt oedema

A

vasoconstriction pul vessels -response to hypoxia
increased pul pressure
increased fluid leakage from caps
fluid accumulates - when exceed max lymph drainage

31
Q

symptom of high alt oedema

A

dyspnoea
dry cough
bloody sputum
crackling chest sounds

32
Q

consequences of high alt pul oedema

A

impaired GE and ventilatory mechanics

33
Q

treatment of high alt pul oedema

A 
descent 
hyperbariac O2 therapy 
nifedipine - Ca channel blocker - vasodilate pul cic
salmeterol - relax airway sm 
sildenafil - affect Bp
34
Q

cause of high altitude cerebral oedema

A

rapid ascent

inability to acclimatise

35
Q

pathophysiology of high alt cer oedema

A

vasodilation of vessels - hypoxia
more blood to cap - increased leakage
cranium in sealed box -cant expand
intracranial pressure increases

36
Q

symptoms of high alt cer oedema

A 
confusion 
ataxia - stumbling 
behaviourala change 
hallucinations 
disorientation - confusion - middle ear
37
Q

consequences of hugh alt cer oedema

A

irrational behaviour
irreversible neuro damage
coma
death

38
Q

treatment of high alt cer oedema

A

immediate decent
O2 therapy
hyperbaric O2 therapy
dexamethasone

39
Q

H0w can we hold our breath for along time

A

wet suit - protect form the cold external environment
hyperventilate with O2 - move the blackout and CO2 threshold
cold water over face - slows breathing and heart rate

40
Q

how do you calculate a persons total blood vol

A 
5l/70kg = 71ml/kg
71*weight = vol of blood
41
Q

how do you calculate the amount of Hb in the blood

A

multiply Hb conc in g/L against blood vol in L

42
Q

how do you calculate cardiac output from ESV and ejection fraction

A

ESV/(100-EF) = SV

SV - ESV

43
Q

stages of acclimatisation to high altitude

A 
low atmospheric O2 
reduced PAO2 
reduced PaO2 
hypoxia detected by carotid bodies 
increased vent 
increased PAO2 reduced PACO2 
increased PaO2 reduced PaCO2 
reduced [H+] increased pH 
pH imbalance detected by carotid bodies 
increased HCO3- excretion via the kidneys
increased H+ and reduced pH
44
Q

blood gases after 2 weeks at altitude

A

pH - unchanged- kidneys will have compensated by now
PCO2 - low - reduced because of increased ventilation
BE low
PO2 low

45
Q

maximum altitude for permanent human residence

A

5500m

46
Q

oxygen transport - partial pressure

A

age related decline in lung func

tissue use a lot of O2 - PP wise

Respiratory system (23 decks)

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