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26 Cards in this Set
- Front
- Back
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Where is ventilation lowest |
Apex of lung |
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Where is ventilation highest |
At the base |
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Describe zone 1 |
Alveolar pressure greater than arterial and venous pressure causing cessation of blood flow (perfusion is absent) |
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What may cause zone 1 |
Acute haemorrhage |
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What’s zone 2 |
alveolar pressure is greater than Venous pressure and less than arterial pressure. Blood flow is intermittent eg systole Sporadic perfusion |
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Whats zone 3 |
Constant perfusion alveolar and venous pressure greater than alveolar pressure (flow unimpaired by alveolar pressure) |
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What does it mean if V/Q is greater than 1 |
The area is relatively under perfused |
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How does the pulmonary vasculature minimise V/Q mismatch in disease |
Hypoxic pulmonary vasoconstriction - directs blood flow away from poorly ventilated areas |
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What are the 5 mechanisms of hypoxaemia |
1)hypoventilation 2) reduced PIO2 3) diffusion limitations 4) mismatch 5) shunt |
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Define hypoxaemia |
Decreased arterial oxygen pressure causing reduction in delivery of O2 to tissues |
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What can cause hypoventilation |
- drug overdoses: narcotics/ depressants/ alcohol all impair the function of the respiratory control centre CNS Weakness |
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Give 2 causes of a diffusion limitation |
Decreased SA or increased thickness of membr |
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Eg of diffusion limitation |
Interstitial oedema/ inflammation/ scarring all increase the diffusion distance and slow diffusion |
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What happens to PA02 vs PaO2 in diffusion limitation |
PA02 normal pao2 low |
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What is the ratio in V/q mismatch |
Less than 1 |
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What is V/q mismatch |
When ventilation is substantially reduced in a given area - hypoxaemia |
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What is a pulmonary shunt |
When no ventilation occurs in a given area and hence there is the addition of poorly oxygenated venous blood to oxygenated blood |
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What can cause pulmonary shunt |
Lung consolidations eg pneumonia Arteriovenous malformations |
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What’s hypoxia |
Inadequate tissue oxygenation |
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4 types of hypoxia |
Hypoxaemia hypoxia Anaemic hypoxia Circulatory hypoxia Cytotoxic hypoxia |
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What’s minute ventilation |
Amount of air per minute breathed into the lung |
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What does VE stand for |
Minute ventilation |
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VE equation |
VE = TVxRR |
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How much is anatomical dead space |
30% 500ml |
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What is alveolar dead space |
Air that reaches the alveoli but can’t participate in gas evangelicals |
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What is hypercarbic respiratory failure |
Due to weakness/ increased dead space |
