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20 Cards in this Set
- Front
- Back
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What is the definition of respiratory failure?
What are two main causes? What are three main types? |
Failure of O2 - CO2 homeostasis
pump failure (poor ventilation) membrane failure (poor gas exchange) hypoxemic hypercapnic mixed |
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What are the four most common causes of left axis deviation?
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LBB
LVH - two most common L anterior fasiscular block right side MI |
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What is a normal V/Q ratio
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1
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V/Q ratio < 1 suggests ?
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shunt, atelectasis, filled alveoli
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V/Q ratio > 1 suggests
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dead space
ventilated areas without perfusion |
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What are 3 clinical situations that could cause LOW V/Q?
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filled alveoli
atelectasis true R to L shunt |
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Hypoxemia with normal A-a gradient, likely causes?
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hypoventilation, as from opiate overdose
high altitude |
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Hypoxemia with abnormal A-a gradient, likely causes?
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V/Q mismatch (as in PE)
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What are five mechanisms of hypoxemic respiratory failure?
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Decreased partial pressure of O2 (altitude)
Impaired diffusion Shunt Hyopventilation V/Q mismatch |
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In early ILD, hypoxemia is only seen in what condition?
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During exertion or exercise
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What is the normal physiologic response to high V/Q mismatch?
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increasing minute ventilation
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No perfusion: this is what condition and what V/Q status?
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deadspace
high V/Q because Q is small PE or COPD (bullous dz, airtrapping) |
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No ventilation: this is what condition and what V/Q status?
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shunt - blood bypassing lung partially or fully
low V/Q because V is small atelectasis, pneumonia or CHF (filled alveoli) are like shunt also |
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What is the normal value of the A-a gradient?
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8-12
or age/4 + 4 |
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What is the value of normal alveolar oxygen tension?
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100
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What is the formula for alveolar oxygen tension?
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- (BP - water vapor) FiO2 -- PaCo2/0.8
thus - (760 - 47) 0.21 -- [40 / 0.8] = 100 mg |
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What is A-a gradient used to determine?
Normal A-a gradient suggests ? High A-a gradient suggests ? |
In cases of hypoxemia, it helps to determine if the problem is due to HYPOVENTILATION / OXYGEN , or if it is functional.
Normal: hypoventilation High: functional (V/Q mismatch, shunt, diffusion) |
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What are the three variables that determine oxygen delivery to tissues?
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Hb concentration
O2 saturation cardiac output |
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What is a metabolic sign that not enough oxygen is being delivered to tissues?
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lactic acidosis
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What is more important in assessing oxygen delivery to tissues, O2 saturation or blood gas measure of oxygen?
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O2 sat
Note that in the formula, PaO2 is always negligible and is often dropped from calculation: -([Hb] * %O2sat * 1.34) + (PaO2 * 0.003) |
