1	Standing guard over the flame of life Oxygen Monitoring in Acute Medicine
2	Life 2nd law of thermodynamics Entropy is time’s arrow
3	"C_nH_nO_n" C_nH_nO_n
4
5	Monitoring Oxygen As a Gas Inspired Tracheal Alveolar Oxygen analyser Calculated from FIO2 Calculated: Alveolar air equation End tidal oxygen analyser
6	Ideal Oxygen Analyser Rapid response Continuous Robust Low maintenance Do no harm
7	Oxygen Analysers Polarographic sensor Fuel cell Paramagnetic analyzer Robust Rapid response time Low maintenance
8	Paramagnetic Oxygen Analyser
9	Oxygram
10	Alveolar Air Equation P_AO₂ = F_IO₂ * (P_b- 47) - P_aCO₂ P_AO₂ = F_IO₂ * (P_b- 47) - P_aCO₂/R P_AO₂ = F_IO₂* (P_b- 47) - P_aCO₂/R(1-F_IO₂(1-R))
11
12
13	Ideal blood oxygen monitor Indicate oxygen tension Indicate oxygen supply Haemoglobin concentration Haemoglobin saturation Blood flow Rapid response Continuous Safe Non-invasive Robust Low maintenance Stable calibration Affordable
14	Monitoring blood oxygen Arterial tension Arterial saturation Blood gas analyser Trans cutaneous Calculated from tension Co-oximeter Pulse oximeter
15	Blood gas analyser Polarographic Measures tension Calculates saturation (functional) Problems invasive intermittent
16	Functional Saturation OxyHb (OxyHb+reducedHb) 7g OxyHb 1g reducedHb 2g metHb Functional Saturation = 7/(7+1) = 87%
17	Transcutaneous gas analyser Polarographic Measures tension persistent pulmonary hypertension diaphragmatic hernia Problems Delicate Heated Repositioning Recalibrating
18	Co oximeters Measures haemoglobin types by absorption of light To measure 4 types of Haemoglobin measure absorption at 4 different wavelengths OHb reducedHb COHb metHb
19	Fractional Saturation OHb (OHb+reducedHb+COHb +metHb) 7g OxyHb 1g reducedHb 2g MetHb Fractional Saturation = 7/(7+1+2) = 70%
20	Oximeters 1875 vonVierordt 1972 Takuo Aoyagi - "Pulse Oximetry" 1980's Nellcor 1988 pulse oximetry mandatory in Australia
21
22
23
24	Oximeter errors Signal artefact Light absorption artefact
25	Signal artefact Ambient light Poor perfusion Movement artefact If R = 1 pulse oximeter shows 85%
26	Light absorption artefact carboxyHb metHb
27
28
29	Light absorption artefact carboxyHb error showing low functional saturation error showing high fractional saturation metHb error toward 85%
30	Light absorption artefact carboxyHb reads low functional, high fractional metHb error toward 85% fetal Hb dyes nail polish bilirubin skin pigment
31	Monitoring oxygen Tissue Venous tension Venous saturation Cytochrome oximeters Blood gas analyser Optical fiber oximeter
32	Monitoring Oxygen