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33 Cards in this Set
- Front
- Back
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What is hypoxia ? |
hypoxia = decr delivery of O2 to tissue or inability of tissue to use O2 for ATP synth |
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What is anoxia? |
a complete lack of O2 in the tissue |
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what is stagnant hypoxia? how does it affect PaO2 and arterial [O2]? what are some causes? |
- O2 delivery to issue is reduced due to decr blood flow - PaO2 = normal - arterial [O2] = normal - caused by heart failure or vascular diseases that compromise organs' perfusion |
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what is anemic hypoxia? how does it affect PaO2 and arterial [O2]? what are some causes? |
= there is a reduced O2 capacity in the blood - caused by all factors leading to anemia (reduced Hb in blood) or compromised Hb ability to bind O2 (CO poisoning) - PaO2 = normal - arterial [O2] = reduced |
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what is histotoxic anemia? how does it affect PaO2 and arterial [O2]? what are some causes? |
= toxins block the use of O2 in the tissues - both PaO2 and a[O2] are normal - caused by cyanide, H2S, and other poisons |
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what is arterial hypoxia? how does it affect PaO2 and a[O2]? |
arterial hypoxia = hypoxemia = reduced arterial O2 saturation - PaO2 = reduced **only form with reduced PaO2** |
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what are the different types of hypoxemia? |
- low inspired PO2 (low PIO2) - diffusion limitation - hypoventilation - (alveolar ventilation)/perfusion mismatch - right to left (venous) shunt |
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how does low inspired PO2 -> hypoxemia? what else does it cause? what the most common cause? |
low PIO2 -> decrease in P(A)O2 -> decr PaO2 -> stim carotid body chemoreceptor -> increase alveolar ventilation -> decrease in PaCO2 and P(A)O2 - from high altitude |
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how does diffusion limitation -> hypoxemia? |
diffusion limitation (a widened AaDO2) means less O2 goes to artery than should have - not common - in cases of severe lung damage, infections, pulmonary edema |
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What is cyanosis? peripheral vs central? what is it dependent on? |
bluish tint in nail beds (peripheral cyanosis), or in the tongue and gums (central cyanosis) **cant have central without peripheral cyanosis - happens due to having 5% (5g/100mL) deoxyhemoglobin in blood - also dependent on the O2 extraction from blood by the tissues |
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in what patients is cyanosis more/less prevalent? |
- anemic patients are less likely due to less Hb -> harder to get to the 5g/100ml blood of deoxyhemoglobin (5g is a larger fraction of the total Hb) - Polycythemic patients are more likely (have more RBC and Hb -> 5g is a smaller fraction of the total Hb |
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when does central cyanosis occur? Why? |
when O2 saturation in arterial blood is low - best seen in organs with high perfusion - O2 saturation in capillaries = O2 saturation in arterial blood at high perfusion |
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When does peripheral cyanosis occur? why? |
reduced perfusion (long capillary refill time) - increases the O2 extraction of capillary blood -> cyanosis even with fully oxgenated arterial blood |
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why does P(A)O2 not equal PaO2 in normal ventilation? |
- the shunts (left to right) - V/Q mismatch (only affects the O2 though) |
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What does global alveolar hypoventialtion lead to? |
- decreased P(A)O2 -> hypOxemia (decr PaO2) - increased P(A)CO2 -> hypERcapnia (incr PaCO2) |
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how does increasing PIO2 affect a person with hypOventilation? |
- aleiviate hypoxemia - increase PaCO2 most likely **due to stimulation of chemoreceptors by low PO2 does not happen -> no more stimulation of breathing** |
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what is the perfusion distribution in the lung of an upright individual? Why? |
- low at top - high at bottom **due to gravity effect on blood** |
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what is the ventilation distribution in the lungs of an upright individual? Why? |
- low at top - high at bottom **the weight of the lung -> the bottom pulls on the top -> stretch -> decr compliance -> low ventilation** **think of dangling a slinky the rings are further apart at the top** |
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how is V/Q distributed throughout the lung? Why? |
- top V/Q is higher - bottom V/Q lower **ventilation increases as going down at slower rate than perfusion** |
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what does a high V/Q lead to? |
- higher O2 - low CO2 |
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what does a low V/Q lead to? |
- low O2 - high CO2 |
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how does regioanl V/Q mismatch affect gas exchange? Why? |
reduces the efficiancy - |
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how does V/Q mismatch affect pulmonary CO2 exchange? Why? |
creates an aADCO2 just like O2, but much smaller (ignorable) - due to steep CO2 binding curve -> change in CO2 content of arterial blood (from mixing venous blood) -> small change in PCO2 - PaCO2 is a strong stimulus for breathing -> small increase -> enhance ventilation until PaCO2 normal |
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what does hypoxic vasoconstriction do? |
low PO2 of alveolar region -> contracts arteries -> decrease in perfusion -> blood goes to normoxic and/or blood is diverted to hyperoxic alveolar regions - V/Q increases |
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what does hypocapnic bronchoconstriction do? |
- low P(A)CO2 from hyperventilated region -> bronchoconstriction -> divert air to hypoventilated regions -> decrease in V/Q mismatch |
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what are the 2 extremes of V/Q mismatch? |
- complete obstruction of airway -> no ventilation -> V/Q = 0 - complete block of blood flow -> no perfusion -> infinite high V/Q |
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what causes a decrease in V/Q? |
hypoventilated -> V/Q less than 1 in alveolar regions -> mixing of deoxy and oxy blood (from norm ventilated regions) **right to left shunt is max at V/Q = 0** aka **venous shunt** |
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What causes an increase in V/Q? |
hyperventilated -> V/Q greater than one **Alveolar dead space ventilation is the max (alveoli is ventilated but not perfused with blood)** |
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how does the binding curves of O2 and CO2 compare? why is it important? |
CO2 curve is steep -> increase in CO2 content -> small increase in PCO2 **the small increase -> not being affected by mismatch V/Q** O2 curve is flat -> small increase in O2 content -> large increase in PO2 **the large increase -> being more affect by mismatch V/Q |
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how do you know if hypoxia is due to diffusion problems? |
if CO diffusion is < normal = diffusion problems if CO diffusion = normal = V/Q mismatch |
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how do you determine if hypoxia is caused by hypoventilation? |
PaCO2 is above normal |
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how do you determine if hypoxia is caused by decrease in PIO2 (high altitude)? |
PaCO2 will be lower |
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how do you determine if hypoxia is caused by increase in left to right shunt? |
When on 100% O2 if their PaO2 < 400mmHg - PaCO2 > 400mmHg = V/Q mismatch or diffusion problem **PaO2 on 100% O2 should = 600mmHg** |
