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Oxygen Physiology

Oxygen Physiology. We will cover. Oxygen Toxicity Pulmonary Oxygen Toxicity CNS Oxygen Toxicity Calculating & Tracking Oxygen Toxicity. Oxygen Toxicity. Pulmonary Toxicity ppO2 > 0.5 bar Inflammation of Lung Tissue Reduces area for gaseous exchange Difficulty breathing Dry cough Death

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Oxygen Physiology

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  1. Oxygen Physiology

  2. We will cover • Oxygen Toxicity • Pulmonary Oxygen Toxicity • CNS Oxygen Toxicity • Calculating & Tracking Oxygen Toxicity

  3. Oxygen Toxicity • Pulmonary Toxicity • ppO2 > 0.5 bar • Inflammation of Lung Tissue • Reduces area for gaseous exchange • Difficulty breathing • Dry cough • Death • Unlikely • Recompression • Tracking

  4. REPEX Maximum Daily OTU Chart Days in Mission Daily OTUs Period Total 1 850 850 2 700 1400 3 620 1860 4 525 2100 5 460 2300 6 420 2520 7 380 2660 8 350 2800 9 330 2970 10 310 3100 11 300 3300 12 300 3600 13 300 3900 Tracking Pulmonary Toxicity • Oxygen Tolerance Units (OTU) • REPEX Tables

  5. Table 1 Calculating OTUs • OTU Chart • Example: Ean33 Depth: 32m B.T: 40 minutes

  6. Table 2 Calculating OTUs Unlikely to reach maximum daily dose

  7. CNS Oxygen Toxicity • Sudden Onset • High ppO2 • Relatively short periods • Oxygen Free Radicals • Susceptibility Varies • Person to Person • Day to Day • CO2 levels • Activity Levels

  8. CNS Oxygen Toxicity • ConVENTID • Con – Convulsions • V – Visual disturbances • E – Ears eg. Tinnitus • N – Nausea • T – Twitching of muscles (Particularly facial) • I – Irritability • D – Dizziness • A Convulsion May Occur Without Warning

  9. Convulsions • Not in themselves lethal • Tonic Phase • Rigidity • Unconsciousness • Breathing Ceases • Clonic Phase • Spasm • Embolism • Breathing Resumes • Lift Diver

  10. Bottom Time at Depth x 100 NOAA Single Exposure Time for ppO2 at Specific Depth CNS% = CNS Tracking • NOAA ppO2 Time Limits Table • Recommended Limit – 80% • Dive: B.T. – 60 min. ppO2 – 1.2 bar

  11. NOAA ppO2 Time Limits Table • Dive: B.T. – 60 min ppO2 – 1.2 bar • Single Exposure Time for 1.2 bar = 210 min CNS% = (60 x 100)/210 = 28.57% ≈29% • No calculations if ppO2<0.5 bar

  12. CNS% Tracking Table • Speeds up calculation • Dive: B.T. – 60 min ppO2 – 1.2 bar CNS% = 0.48 x 60 = 28.8% ≈ 29%

  13. CNS% Tracking • Example 2 Dive: EAN 36 28 m 25 min ppO2 = FO2 x P = 0.36 x 3.8 = 1.368 ≈ 1.4 bar CNS% per min – 0.67 0.67 x 25 = 16.75 CNS% Reduced by 50% for each 90 min surface interval Only applies in 90 minute blocks Fully dessaturated after 12 h

  14. CNS Tracking – Surface Interval Example CNS% at end of dive – 29% S.I. – 3h 20 min (200 min) At the end of the dive CNS% = 29% After 90 minutes reduced by 50% = 14.5% After next 90 minutes reduced by 50% = 7% After next 20 minutes No decrease At the end of the surface interval CNS% = 7% Added to oxygen load of next dive within 12 h

  15. CFT Recommendations • Single Exposure Times • CNS% > 80% Minimum SI = 2h • Maximum Total Duration Times in 24h period • If >80% Minimum SI = 12h • Breathing normoxic air • Maximum CNS% - 80%

  16. Stage 1: ppO2 at 40m on EAN 28 = 1.4 Bar CNS% of 0.67% per minute CNS% = 0.67 x 10 = 6.7% • Stage 2: ppO2 at 15m on EAN 28 = 0.7 Bar CNS% of 0.18% per minute CNS% = 0.18 x 20 = 3.6% Multiple Profile Diving • Calculate for each depth stage • Example EAN 28, 10 min at 40m and 20 min at 15m • Total CNS% for the dive would be: 6.7 + 3.6 = 10.3%

  17. CNS Tracking - Example EAN 33, 29 metres, 25 min EAN 33, 24 metres, 12 min EAN 50, 14 metres, 2 min EAN 50, 4.5 metres, 8 min Stage 1: ppO2 0.33 x 3.9 = 1.287 bar CNS %/min 0.56 CNS% 0.56 x 25 = 14%

  18. CNS Tracking - Example Stage 2:EAN 33, 24m, 12 min ppO2 0.33 x 3.4 = 1.122 bar CNS%/min 0.43 CNS% 0.43 x 12 = 5.16% Stage 3:EAN 50, 14m, 2 min ppO2 0.50 x 2.4 = 1.2 bar CNS%/min 0.47 CNS% 0.47 x 2 = 0.94% Stage 4:EAN 50, 4.5m, 8 min ppO2 0.50 x 1.45 = 0.725 bar CNS%/min 0.18 CNS% 0.18 x 8 = 1.44%

  19. CNS Tracking - Example Total CNS% for the dive: 14 + 5.16 + 0.94 + 1.44 = 21.54%

  20. We have covered • Oxygen Toxicity • Pulmonary Oxygen Toxicity • CNS Oxygen Toxicity • Calculating & Tracking Oxygen Toxicity

  21. Questions?

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