CHAPTER 9 — Air Decompression
Change A 9-25
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Permanent Loss. Multiply the remaining oxygen time by three to obtain the
equivalent chamber decompression time on air. If 50% helium 50% oxygen or
50% nitrogen 50% oxygen is available, multiply the remaining oxygen time
by two to obtain the equivalent chamber decompression time on 50/50.
Allocate 10% of the equivalent air or 50/50 time to the 40-fsw stop, 20% to the
30 fsw stop, and 70% to the 20 fsw stop. Round the stop times up to the next
whole minute. Surface upon completion of the 20 fsw stop.
Example. The oxygen supply to the chamber is lost at 10 minutes and 50/50 is not
available. The original surface decompression using oxygen schedule called for a
20-min. oxygen stop.
Solution. The remaining oxygen time is 10 minutes (20-10). The equivalent
chamber decompression time on air is 30 minutes (3 x 10). The 30 minutes of air
stop time should be allocated as follows: Three minutes at 40 fsw (30 x 0.1), 6
minutes at 30 fsw (30 x 0.2), and 21 minutes at 20 fsw (30 x 0.7).
9-10.1.3
CNS Oxygen Toxicity (40 fsw Chamber Stop). At the first sign of CNS toxicity,
the patient should be removed from oxygen and allowed to breathe chamber air.
Fifteen minutes after all symptoms have completely subsided, resume oxygen
breathing at the point of interruption. If symptoms of CNS oxygen toxicity
develop again or if the first symptom is a convulsion, take the following action:
1.
Remove the mask.
2.
After all symptoms have completely subsided, decompress 10 feet at a rate of
1 fsw/min. For a convulsion, begin travel when the patient is fully relaxed and
breathing normally.
3.
Resume oxygen breathing at the shallower depth at the point of interruption.
4.
If another oxygen symptom occurs, complete decompression time on air. Mul-
tiply the remaining oxygen time by three to obtain the equivalent chamber
decompression time on air. Allocate 30% of the equivalent air to the 30 fsw
stop and 70% to the 20 fsw stop. Surface upon completion of the 20 fsw stop.
9-10.1.3.1
Example. The diver has a third oxygen symptom after completing 28 minutes of
the required decompression. The diver is at 30 fsw based on the second oxygen
symptom protocol. The original surface decompression using oxygen schedule
called for a 38 min. oxygen stop.
9-10.1.3.2
Solution. The remaining oxygen time is 10 minutes (38-28). The equivalent
chamber decompression time on air is 30 minutes (3 x 10). The 30 minutes of air
stop time should be allocated as follows: Three minutes at 30 fsw (30 x 0.3) and
seven minutes at 20 fsw (30 x 0.7).
9-10.1.4
Repetitive Dives. There are no repetitive diving tables or surface interval tables
for surface decompression dives. If another surface decompression dive using
