Oxygen measurements Flashcards
How many ml of O2 can 1g of Hb combine with?
1.34ml.
How many ml of O2 can 150g Hb combine with?
150 x 1.34= 201ml.
What is the equation for calculating O2 saturation?
O2 bound to Hb/ O2 capacity x100
What is SaO2?
Arterial oxygen saturation.
What is SpO2?
Peripheral oxygen saturation.
What is the definition of oxygen content?
The total volume of oxygen carried in a litre of blood.
What is the equation for oxygen content?
O2 content= (O2 carried by Hb) + (O2 in solution)
= ((1.34 xHb)x(SpO2/100)) + (0.225xPaO2)
What are some factors that affect oxygen content of arterial blood?
-partial pressure
-adequacy of ventilation and gas exchange
-Hb level and affinity of Hb to oxygen
What is hypoxaemia?
Lack of oxygen in blood (PaO2 below normal).
What is hypoxia?
Reduced oxygen supply to the tissues.
What is cyanosis?
Blue coloration of skin and mucus membranes- raised levels of deoxyHb caused by hypoxaemia.
What are the causes of hypoxaemia?
-hypoventilation
-diffusion limitation
-shunt (arterial blood not passed through ventilated areas of lung)
-V/Q mismatch
Why does respiratory failure occur?
When insufficient oxygen passes from the air in the alveoli into the blood.
What partial pressure of oxygen is defined as resp. failure?
<8kPa
What is type 1 respiratory failure?
This is a failure of oxygenation.
Low levels of O2 in blood (hypoxaemia) with normal or reduced arterial partial pressure of CO2.
