SpO2 and ETCO2

Question 1

oximeter - definition

Answer 1

a measuring instrument that measures the oxygen in arterial blood

Question 2

Limitations of placing the Oximeter on the fingertip

Answer 2

Only shows how much O2 is in the blood at the fingertip

Question 3

How the sensor works

Answer 3

The sensor transmits 2 light beams to its receiving detector:

• Red light absorbed by de-oxyhaemoglobin (de-oxygenated RBC).
• Infra-red light absorbed by oxyhaemoglobin (oxygenated RBC).

The micro-computer in the unit determines which has the greater absorption and works out a percentage:

• High infra-red absorption = high oxygen saturation.
• High red absorption = low oxygenated saturation.

Question 4

Considerations

Answer 4

Hypothermia.
Hypovolaemia.
Probe movement.
Nail varnish - artificial nails.
Bright sunlight.
Blood.
Carbon monoxide.
Electrical interference.

Question 5

Capnography - definition

Answer 5

Capnography is the monitoring of the concentration or partial pressure of carbon dioxide in the respiratory gases.

Question 6

Internal respiration - definition

Answer 6

Gaseous exchange between the capillary and the cells. (O2 into the tissue cell - metabolism - CO2 into the capillary - blood flow back to the heart and lungs).

Question 7

External respiration - definition

Answer 7

Gaseous exchange between the alveoli and the capillary. (CO2 from capillary into the alveolus - O2 from the alveolus into the capillary).

Question 8

Respiratory Cycle

Answer 8

Ventilation = Blood - Lungs - Breath
Oxygenation = Lungs - Alveoli - Blood - Organs - Cells (then back to ventilation and round and round it goes)

Question 9

How the monitoring works

Answer 9

The etCO2, sensor measures the concentration of CO2 molecules, at the end of expiration, that absorb infrared light.

Question 10

kPa

Answer 10

Kilopascals

Question 11

Phases

Answer 11

End-Tidal CO2 is taken at D.

A->B = inspiration period.
B->C = breathing out.
C->D = breathing out plateaus but is still slightly increasing.
D->E(E is A as the phase restarts) = inspiration.
C______D
/ \ /
\A__B/ \E__B/

Question 12

Cardiac Arrest

Answer 12

CPR assessment attempt to maintain minimum of 1.33kPa

Question 13

Abnormal waveforms

Answer 13

Any waveform other than the normal waveform is considered abnormal and MUST be brought to the attention of the Lead Clinician.

Question 14

Remember…

Answer 14

etCO2 tells you about ventilation in the chest.

SpO2 tells you about oxygenation here.