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13 Cards in this Set

  • Front
  • Back
DDx of arterial hypoxemia
V/Q mismatch
R to L shunt
Decreased diffusion
Low inspired PO2 (high altitude)
Characteristics of V/Q mismatch
Main cause in chronic lung disease.
Increased dead space.
PaCo2 variable.
*Responds to oxygen
Characteristics of R to L shunt
Blood flow with no air supply.
Seen in ARDS, pneumonia, pulmonary edema.
Poor response to oxygen.
May need PEEP.
Characteristics of hypoventilation.
Inversely related to PCO2.
Increased alveolar PCO2 displaces O2.
A-a gradient in NORMAL.
** If normal A-a gradient then there is NO aspiration.
Characteristic with decreased diffusion.
Seen in emphysema.
Improves with oxygen.
Characteristic of low inspired PO2
A-a gradient is normal.
**Read alveolar air equation
A-a gradient
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
Oxygen transport
DO2= Cardiac output (Q) x O2 content of arterial blood (CaO2)
**= CO x (1.34hg x SpO2)
Primarily manipulated by cardiac output.
Oxyhemoglobin dissociation curve- shift to right
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.
Oxyhemoglobin dissociation curve- shift to left
Will have more affinity for oxygen and will not release it to tissue.

Decreased temp
Decreased 2,3 DPG
Stuff about 2,3 DPG
RBC contains it.
Formed during anerobic glycolis.
Increased in:
hypoxia, anemia, high PO4
Decreaed in:
stored blood more than 1 week
Carbon monoxide poisoning and oxyhemoglobin dissociation curve.
CO saturates hemoglobin.
Pulse ox is usually normal.
Need to measure PaO2 and carboxyhemoglobin levels.
Shift to far left.
Stuff about methemoglobin
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