Term
| What is the equation for determining O2 content of blood? |
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Definition
| O2 content = (Hgb x 1.34) x % saturation + (PO2 x 0.0031) |
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Term
| What is the numerical definition of arterial hypoxemia and respiratory failure? |
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Definition
Arterial hypoxemia is defined as a PaO2 < 70 mm Hg
Respiratory failure is defined as a PaO2 < 50 mm Hg |
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Term
| What is the equation for determining oxygen delivery to a tissue? |
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Definition
| oxygen delivery = oxygen content x cardiac output (usually 5) x 10 |
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Term
| What is the normal amount of delivered oxygen that is consumed by tissue? How high can it go to compensate for anemia, hypoxemia, low cardiac output, etc.? |
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Definition
At rest, only about 25 to 30% of delivered oxygen is consumed by the tissues at rest
Tissue oxygen extraction can reach 40-45% of the amount delivered to compensate for situations of low O2 |
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Term
| At rest, how much oxygen do the cells of the body consume? What is the normal oxygen delivery at rest? |
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Definition
| Cells of the body consume 250 ml/min at rest; Normal oxygen delivery at rest is more than 700 ml O2/min |
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Term
| What is the purpose of the Fick equation? What is the equation? |
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Definition
To determine the cardiac output in research and clinical medicine
CO = O2 consumption / (A-V) O2 Content Difference |
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Term
| What is the normal (A-a) DO2 difference on room air? |
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Definition
20 mm Hg
Anything < 20 is considered normal |
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Term
| What is the purpose of determining (A-a) DO2? |
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Definition
| This calculation is used to determine the presence and severity of a gas exchange abnormality |
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Term
| What is the equation for the inspired partial pressure of oxygen? |
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Definition
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Term
| Diffusion abnormalities are caused by diseases that reduce what? |
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Definition
| The cross sectional area of the alveolar-capillary bed |
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Term
| In patients with moderate to severe diffusion abnormality, do the red blood cells become completely saturated with oxygen? |
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Definition
| Yes; normally, diffusion of oxygen from the alveolus into the red blood cell is complete when the red cell travels one-third of the distance through the capillary; so, there is some buffer here if the diffusion of oxygen into the red cell takes longer |
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Term
| When would a patient with moderate to severe diffusion defects suffer from hypoxemia? |
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Definition
During exercise, with an increased CO decreases the pulmonary capillary transit time
This can be seen in a widened (A-a)DO2 |
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Term
| What is the major cause of hypoxemia? |
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Definition
| Regional mismatches between ventilation and perfusion; decreases in ventilation without matching decreases in perfusion to the hypoventilated areas |
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Term
| What are the five listed possible causes of hypoxemia? |
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Definition
| Altitude, alveolar hypoventilation, diffusion abnormalities, ventilation-perfusion imbalance, and intrapulmonary shunt |
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Term
| Will an increase in FiO2 using supplemental oxygen correct hypoxemia due to shunting? |
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Definition
| No, because the blood entering the well ventilated alveoli is already maximally saturated with oxygen when breathing room air |
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Term
| How will decreased cardiac output affect arterial hypoxemia? |
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Definition
| It will increase arterial hypoxemia due to low mixed venous oxygen content |
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