Oxygen

Question 1

how much oxygen is dissolved in 100ml blood?

Answer 1

0.3ml

Question 2

how much oxygen is carried by haemoglobin in 100ml blood?

Answer 2

20.4ml

Question 3

what is the difference between SaO2 and SpO2?

Answer 3

SaO2 is oxygen saturation of arterial blood, measured by taking a blood sample.
SpO2 is oxygen saturation, measure by a pulse oximeter.

Question 4

What is PaO2?

Answer 4

this is the amount of oxygen dissolved in arterial blood plasma

Question 5

what is FiO2?

Answer 5

fraction of inspired oxygen that patient is inhaling

Question 6

All people with COPD are CO2 retainers. True/ False?

Answer 6

False. Only a third of people with COPD are CO2 retainers

Question 7

Type 1 Respiratory Failure features

Answer 7

Low O2

Normal CO2

Question 8

Type 2 Respiratory Failure Features

Answer 8

Low O2

High CO2

Question 9

What makes patients retain CO2?

Answer 9

V/Q mismatching
Areas of poor ventilation have vasoconstriction, give oxygen and this reverses, perfusion becomes good but ventilation is still poor. (Shunt). Chronically hypoxaemic patient has low Hb sats. CO2 occupies the empty binding sites on Hb. Giving high FiO2 pushes CO2 off the Hb, into the plasma

Question 10

Chronically hypoxaemic patients without CO2 retention can still become acidotic with too much O2. True/ False?

Answer 10

True
This is due to the Haldane Effect (oxygenation of blood in the lungs displaces CO2 from haemoglobin which increases the removal of CO2)