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7 Cards in this Set
- Front
- Back
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What is the ventilation/ perfusion ratio? How does it change within the lung?
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Ratio of ventilation of blood for a single alveolus or the entire lung.
The normal V/Q ratio for the whole lung is 0.8 The apex of the lung has a much higher V/Q and the base of the lung has a much lower V/Q due to the effects of gravity. |
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When is the V/Q 0? What is the consequence? When is the V/Q infinity? What is the consequence?
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V/Q=0 in a shunt. This occurs hwen the airway is blocked. The lung is perfused, but not ventilated, resulting in a lower arterial PO2.
V/Q=infinity in a pulmonary embolism. The ventilation is normal, but the perfusion is zero. This is alveolar dead space. |
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What is the alveolar-arterial O2 gradient? Why does this exist?
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A-a gradient is the difference between alveolar and arterial O2 tension. Normally is 10-15 mmHg.
This occurs because a normal percentage of blood shunts and does not get oxygenated in the lungs. |
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When would the A-a gradient increase pathologically?
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Left to right cardiac shunts.
Pulmonary fibrosis Asthma Chronic bronchitis Pneumonia Atelectasis |
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How do obstructive present physiologically?
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Impaired expiration causes a dilated alveolus and decreased gas exchange.
results from asthma, bronchitis, COPD |
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How do restrictive disorders cause physiological problems?
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Plug blocks inspiration and prevents the full expansion of the lungs.
Results from atelectasis, pneumothorax |
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How do vascular and infectious disorders cause physiological problems?
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Excess interstitial fluid prevents adequate gas exchange.
Occurs in pulmonary edema, pneumonia, pleural effusion. |
