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25 Cards in this Set
- Front
- Back
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What is the percentage of O2 ALWAYS |
21% |
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Percentage of N2 |
78% |
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What’s FIO2 |
Fraction of inspired oxygen |
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What’s PIO2 |
Pressure of inspired O2 |
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What happens tar high altitudes |
Pressure drops (we therefore breath in fewer molecules but the percentage of them is the same) |
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Why does PO2 drop as it enters the airways |
It is humidified |
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What’s the equation for PAO2 (alveolar =big A) |
PAO2= [(patm-ph20) x piO2] - (paco2/R) |
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What’s R |
The ration of co2 produced for every O2 |
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What is the average R |
0.8 (co2 per o2) |
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Why is there a drop between alveolar gas and arterial blood |
Small amount of blood which bypasses lungs (anatomical shunt) to dilute well oxygenated blood (this addition then means Pa02 lower than PA02 |
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What’s dissolved o2 content |
0.003mL 15ml/min |
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What favours O2 loading onto Hb |
High PaO2 |
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What is normal haemoglobin saturation |
95% |
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What’s CaO2 |
O2 content of arterial blood 203mL |
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What’s average cardiac output |
5L/min |
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Delivery of oxygen |
1000ml/min |
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Resting need for oxygen |
250mL/min |
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Causes of reduced O2 delivery |
Anaemia Interruption to Hb binding Hypoxaemia Insufficient CO |
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What could cause interruption to haemoglobin binding |
carbon monoxide (colourless, odourless, tasteless) 250 times greater affinity for Hb than O2 |
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What does CO and Hb together form |
Carboxyheamoglobin |
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Why is PaO2 of blood normal in Co poisoning |
Most O2 not carried in the blood |
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Symptoms of CO poisoning |
Nausea/ vomiting/ dizziness/ lethargy/ weakness/ confusion |
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Why is there a drop between arteries and tissues |
Diffusion at capillary beds here pressures equilibrate eg blood pressure with interstial compartments. Fall in pressure - 02 saturation drop |
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What are the 3 determinant of calculated PAO2 |
Percentage of inspired O2 Pressure of Co2 PAtm |
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When is pVO2 high |
Sepsis |
