Term
| What happens in normal mismatching? |
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Definition
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The P(a)O2 is lower than the P(A)O2
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Term
| Describe the location of the 3 zones of the lung |
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Definition
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Zone 1: Top
Zone 2: Mid
Zone 3: Bottom
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Term
| What are the characteristics of Zone I? |
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Definition
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P(A) > P(a) > P(v)
Because gravity is pulling most of the blood towards the bottom of the lung, the alveolar pressure is greater than the arteriolar pressure.
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Term
| Characteristics of Zone II? |
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Definition
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P(a) > P(A) > Pv
Flow is determined by P(a) - P(A)
Blood flow may be decreased during exhalation and positive pressure mechanical ventilation
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Term
| Characteristics of Zone III |
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Definition
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P(a) > P(v) > P(A)
Pulmonary venous pressure is greater than alveolar pressure
Flow Q is determined by P(a) - P(v)
Capillaries are distended and have very low resistance
Blood flow is not affected by inspiration or exhalation
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Term
| How does Zone II differ from Zone III |
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Definition
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The determination of flow Q is different. Zone II is unique in that Q is calculated by P(a) - P(A). Zone III is P(a) - P(v).
Zone II flow is decreased by exhalation; whereas it is unaffected in Zone III.
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Term
| How does exercise affect the regional distribution to the lung? |
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Definition
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Because of recruitment of previously non-perfused vessels in the upper lung zones, blood flow to the upper parts of the lung will increase more than blood flow in the middle and lower zones.
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Term
| How do disease states affect regional distribution? |
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Definition
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Diseases that increase pulmonary venous pressure cause the distribution of blood flow to become more equally distributed due to recruitment and distension of vessels in zones I and II. At very high pulmonary venous pressures, more blood flow may be going to the upper lobes than the lower lobes.
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