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Flashcards in SpO2 and ETCO2 Deck (14)
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1

oximeter - definition

a measuring instrument that measures the oxygen in arterial blood

2

Limitations of placing the Oximeter on the fingertip

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

3

How the sensor works

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.

4

Considerations

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

5

Capnography - definition

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

6

Internal respiration - definition

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).

7

External respiration - definition

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

8

Respiratory Cycle

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

9

How the monitoring works

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

10

kPa

Kilopascals

11

Phases

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/

12

Cardiac Arrest

CPR assessment attempt to maintain minimum of 1.33kPa

13

Abnormal waveforms

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

14

Remember...

etCO2 tells you about ventilation in the chest.

SpO2 tells you about oxygenation here.