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13 Cards in this Set
- Front
- Back
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DDx of arterial hypoxemia
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V/Q mismatch
R to L shunt Hypoventilation Decreased diffusion Low inspired PO2 (high altitude) |
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Characteristics of V/Q mismatch
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Main cause in chronic lung disease.
Increased dead space. PaCo2 variable. *Responds to oxygen |
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Characteristics of R to L shunt
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Blood flow with no air supply.
Seen in ARDS, pneumonia, pulmonary edema. Poor response to oxygen. May need PEEP. |
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Characteristics of hypoventilation.
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Inversely related to PCO2.
Increased alveolar PCO2 displaces O2. A-a gradient in NORMAL. ** If normal A-a gradient then there is NO aspiration. |
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Characteristic with decreased diffusion.
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Seen in emphysema.
Improves with oxygen. |
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Characteristic of low inspired PO2
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A-a gradient is normal.
**Read alveolar air equation |
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A-a gradient
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Increased in all causes of hypoxemia except high altitude and hypoventilation.
Normal 5-15 in young patients. 150-(PaO2 + 1.25PaCO2) or PaCO2/0.8 |
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Oxygen transport
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DO2= Cardiac output (Q) x O2 content of arterial blood (CaO2)
**= CO x (1.34hg x SpO2) Primarily manipulated by cardiac output. |
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Oxyhemoglobin dissociation curve- shift to right
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Decreased affinity and release of oxygen to tissue.
Increased temp Increased H+ (acidosis) Increased 2,3 DPG **Therefore will need to maintian a higher PaO2 in these patients. |
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Oxyhemoglobin dissociation curve- shift to left
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Will have more affinity for oxygen and will not release it to tissue.
Decreased temp Alkalosis Decreased 2,3 DPG |
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Stuff about 2,3 DPG
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RBC contains it.
Formed during anerobic glycolis. Increased in: hypoxia, anemia, high PO4 Decreaed in: stored blood more than 1 week |
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Carbon monoxide poisoning and oxyhemoglobin dissociation curve.
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CO saturates hemoglobin.
Pulse ox is usually normal. Need to measure PaO2 and carboxyhemoglobin levels. Shift to far left. |
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Stuff about methemoglobin
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Iron in hg IS oxidized from ferrous to ferric form.
Cannot bind O2 or CO2. Increased by drugs- nitrates, nitrites, sulfonamides, lidocaine. 25%- peripheral and perioral cyanosis 35-40%- fatigue, dyspnea >60%- CNS depression, coma, death Pulse ox is not accurate. ***ABG- high PaO2 with low SpO2 Rx- oxygen, IV methylene blue |
