Oxygen

Question 1

SaO2

Answer 1

O2 saturation of arterial blood
Invasive - needle inserted into radial artery
Sample taken from an ABG

Question 2

SpO2

Answer 2

O2 saturation detected by pulse oximeter
measured with finger probe

Target sats:
94-98% = normal
88-92% = type 2 resp failure

Question 3

FiO2

Answer 3

Fraction of inspired oxygen

How much oxygen you are giving to a patient (%)

Question 4

Nasal Cannula

Answer 4

low O2 requirements
Flow rate = 2-6L/min
FiO2 = uncontrolled
Depends on nasal breathing

Question 5

Simple face mask

Hudson face mask

Answer 5

Cheap
Simple
Low O2 requirements 
Flow rate = 5-10L/min 
FiO2 = variable

Question 6

Venturi mask

Answer 6

Fixed performance
FiO2 = specific
Used if patient is at risk of type II resp failure

Question 7

Reservoir bag mask

Answer 7

Non rebreather
Critical illness
Flow rate = 15L/min
FiO2 = 85%

Question 8

Type 1 resp failure

Answer 8

Low levels of O2 - something blocking the transfer of O2

Normal levels of CO2

Question 9

Type 2 resp failure

Answer 9

Low levels of O2
High levels of CO2 (CO2 retention)
Problem with ventilation of lung tissue - blood flow restricted to affected area so there is abnormal V/Q.
Giving O2 overcomes the perfusion problem but perfuses areas where gas exchange is not effective resulting in deoxygenated blood being pumped round the pulmonary circulation which collects lots of CO2

Question 10

Why do patients retain CO2

Answer 10

V/Q mismatch
Haldane effect
Hypoxic drive