Air Decompression EP's Flashcards
Bottom Time in Excess Of The Table
- Contact NEDU for advice on how to decompress.
If NEDU cannot be contacted:
- Use the Thalmann Algorithm Dive Planner to compute decompression.
- Read down to Deeper depths in the Air Decompression Table until a depth is found that has a schedule that is equal to or longer than the bottom time.
Loss of Oxygen Supply in the Water.
Diver cannot be shifted to oxygen.
- continue air breathing, consider any time spent on air as dead time.
- if the problem can be corrected, vent divers and resume decompression.
- if the problem cannot be corrected and a chamber is available initiate surface decompression.
- if there is no chamber, continue in-water decompression on air.
Loss of Oxygen Supply in the Water
Oxygen supply lost during the 30 foot stop after divers have been shifted to oxygen.
- Shift the divers back to air.
- if corrected quickly, vent divers and resume decompression at point of interruption.
- if the problem cannot be corrected, initiate surface decompression. Compute the number of chamber periods by multiplying the remaining O2 time by 1.1, divide the total by 30, round up to the next half period.
- if there is no chamber, multiply the remaining 30 foot stop time by the air/o2 ratio at 30 feet. to compute the air/o2 ratio, divide the scheduled air stop time by the Oxygen stop time on the table.
- take the full 20 foot air stop as prescribed in the air decompression table.
Loss of Oxygen Supply in the Water
Oxygen supply lost during the 20 foot stop after divers have been shifted to oxygen.
- Shift the divers back to air.
- if the problem can be corrected quickly, ventilate divers and resume decompression at point of interruption.
- if the problem cannot be corrected, initiate surface decompression. Compute the number of chamber periods by multiplying the remaining O2 time by 1.1, divide the total by 30, round up to the next half period.
- if there is no chamber, multiply the remaining 20 foot stop time by the air/o2 ratio at 20 feet. to compute the air/o2 ratio, divide the scheduled air stop time by the Oxygen stop time on the table.
Contamination of Oxygen Supply with Air
- Align the ORCA properly.
- Re-ventilate each diver with oxygen for 20 seconds.
- Restart oxygen time. Consider any time on contaminated oxygen as dead time.
CNS Oxygen Toxicity Symptoms
In water non-convulsive and chamber is available.
- Initiate Surface Decompression.
- Shift the console to air during travel to the surface.
- Compute the number of chamber periods by multiplying the remaining O2 time by 1.1, divide by 30, round up the next half period.
CNS Oxygen Toxicity Symptoms
In water non-convulsive at 30 foot stop.
chamber is not available.
- Up 10 feet and shift to air during travel to 20 feet.
- ventilate both divers, affected first.
- complete decompression on air at 20 feet. compute the 20 foot stop time by multiplying the missed 30 foot oxygen stop time by the air/o2 ratio at 30 feet. add the result to the 20 air stop time listed on the table.
CNS Oxygen Toxicity Symptoms
In water non-convulsive at 20 foot stop.
chamber not available.
- Shift both divers to air.
- ventilate both divers, affected first.
- compute the 20 foot stop time by multiplying the remaining 20 foot oxygen time by the air/o2 ratio for the 20 foot stop.
Oxygen Convulsion in water.
Chamber is available.
- Shift both divers to air.
- Have the unaffected diver ventilate himself and then ventilate the stricken diver.
- If only one diver is in the water, launch standby immediately and have him ventilate the stricken diver.
- Hold the divers at depth until the tonic-clonic phase of the convulsion has subsided. Generally 1-2 minutes.
- At the end of the tonic-clonic phase, have the dive partner or standby diver ascertain whether the diver is breathing.
- If the diver is breathing, hold him at depth until he is stable, then surface decompress.
- Compute the number of chamber oxygen periods required by multiplying the remaining oxygen time at the stops by 1.1, dividing the total by 30 min, then round the result up to the next highest half period.
Oxygen Convulsion in water
At 30 foot stop, chamber is not available.
- Shift both divers to air.
- Have the unaffected diver ventilate himself and then ventilate the stricken diver.
- If only one diver is in the water, launch standby immediately and have him ventilate the stricken diver.
- Hold the divers at depth until the tonic-clonic phase of the convulsion has subsided. Generally 1-2 minutes.
- At the end of the tonic-clonic phase, have the dive partner or standby diver ascertain whether the diver is breathing.
- If he is breathing. Continue decompression in water on air. Compute the remaining stop time at 30 feet by multiplying the remaining oxygen stop time by the air/o2 ratio at 30 feet.
- take the full 20 foot air stop time.
Oxygen Convulsion in water
At 20 foot stop, chamber is not available.
- Shift both divers to air.
- Have the unaffected diver ventilate himself and then ventilate the stricken diver.
- If only one diver is in the water, launch standby immediately and have him ventilate the stricken diver.
- Hold the divers at depth until the tonic-clonic phase of the convulsion has subsided. Generally 1-2 minutes.
- At the end of the tonic-clonic phase, have the dive partner or standby diver ascertain whether the diver is breathing.
- If he is breathing Continue decompression in water on air. Compute the remaining stop time at 20 feet by multiplying the remaining oxygen stop time by the air/o2 ratio at 20 feet.
CNS Oxygen Convulsion in water.
Cannot Ascertain whether the diver is breathing.
- Leave the unaffected diver at the stop to complete decompression.
- Surface the affected diver and standby at 30 feet/min.
- Standby should attempt to maintain an open airway on the stricken diver during ascent.
- On surface, the affected diver must receive necessary medical attention then be immediately recompressed and treated for AGE.
Surface interval greater than 5 minutes but less than 7 minutes.
- Increase the 50 foot stop time from 15 to 30 minutes.
2. Ascend to 40 feet during the air break
Surface interval greater than 7 minutes
- Continue compression to 60 feet.
- Treat the divers on a TT5 if the original schedule required 2 or fewer oxygen chamber periods.
- Treat the divers on a TT6 if the original schedule required 2.5 or more oxygen chamber periods.
“Safe Way Out” Procedure
- Compress the diver to the deepest depth he can attain initially, and begin oxygen breathing. Oxygen time starts when the diver initially goes on oxygen.
- If surface decompression was initiated while the diver was decompressing on oxygen in-water at 20 feet, attempt to gradually compress the diver to 20 feet.
- If surface decompression was initiated deeper than 20 feet, attempt to gradually compress the diver to 30 feet.
- Double the number of chamber periods indicated in the table and take these periods at the deepest depth the diver is able to obtain.
- Periods consist of 60 minutes on O2 with a 15-min air break.
- Surface the diver at 30 fsw/min upon completion of the oxygen periods and carefully observe on surface for the onset of decompression sickness.
Type I Decompression Sickness during the surface interval.
- Compress the diver to 50 FSW following normal SurD procedures. Delay Neuro until the diver reaches the 50 fsw stop and is on O2.
- If Type I symptoms resolve during the 15 minute 50-fsw stop, the surface interval was 5 minutes or less, and no neurological signs are found.
Increase the 50 fsw O2 time from 15 to 30 minutes.
Continue normal decompression for the schedule of the dive. Ascend from 50 to 40 fsw during the subsequent air break.
- If Type I symptoms do not resolve during the 15 minute 50 fsw stop or symptoms resolve but the surface interval was greater than 5 minutes.
Compress the diver to 60 FSW.
Treat on TT5 if the original schedule required 2 or fewer oxygen periods in the chamber.
Treat the diver on TT6 if the original schedule required 2.5 or more oxygen periods in the chamber.
Type II Decompression Sickness during the surface interval.
- Compress the diver to 60 feet on oxygen.
2. Treat the diver on a Treatment Table 6.
Decompression Sickness while decompressing at 50, 40 or 30 feet. during Surface Decompression.
- Treat as a recurrence of symptoms.
- Compress on oxygen to 60 feet.
- Complete three 20 minute periods on oxygen then reassess.
Loss of Oxygen Supply in the Chamber:
Temporary Loss.
- Return the diver to oxygen breathing.
2. Consider any time spent on air as dead time.
Loss of Oxygen Supply in the Chamber:
Permanent Loss. 50/50 is available.
- Multiply remaining O2 time by 2.
- Air breaks are not required.
- Consider any time on air as dead time.
Loss of Oxygen Supply in the Chamber:
Permanent Loss. Air Only at 50 foot stop.
- Ascend to 40 feet.
- Multiply remaining O2 time by the air/o2 ratio at 30 and 20 foot stops.
To calculate the air/o2 ratio. Add the 30 and 20 foot oxygen stops times together then , add the 30 and 20 foot air stops times together, divide the sum of the oxygen time by the sum of the air times.
- Allocate 10% of the time to the 40 foot stop, 20% of the time to the 30 foot stop and 70% of the time at the 20 foot stop.
Loss of Oxygen Supply in the Chamber:
Permanent Loss. Air Only at 40 foot stop.
- Multiply remaining O2 time by the air/o2 ratio at 30 and 20 foot stops.
- Allocate 10% of the time to the 40 foot stop, 20% of the time to the 30 foot stop and 70% of the time at the 20 foot stop.
Loss of Oxygen Supply in the Chamber:
Permanent Loss. Air Only at 30 foot stop.
- Multiply remaining O2 time by the air/o2 ratio at 30 and 20 foot stops.
- Allocate 30% of the time to the 30 foot stop and 70% of the time at the 20 foot stop.
CNS Oxygen Toxicity in the Chamber:
First symptom non-convulsive.
- Have the diver breathe chamber air.
- Wait 15 minutes after all symptoms have completely subsided.
- Resume oxygen breathing at the point of interruption.
CNS Oxygen Toxicity in the Chamber:
Second symptom or First convulsion.
- Remove the mask.
- 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.
- Resume oxygen breathing at the shallower depth at the point of interruption.
CNS Oxygen Toxicity in the Chamber:
Additional symptoms
- Complete decompression on chamber air.
- Compute the remaining chamber time on air.
- If the diver is at 40 feet, allocate 10% of the remaining time to the 40 fsw stop, 20% to the 30 fsw stop, and 70% to the 20 fsw stop.
- If the diver is at 30 feet, allocate 30% of the remaining time to the 30 fsw stop, and 70% to the 20 fsw stop.
Asymptomatic Omitted Decompression:
No decompression stop required.
- Observe on surface for one hour for signs and symptoms of decompression sickness or AGE.
- Conduct a neurological exam at the beginning, half, and end of the hour.
Asymptomatic Omitted Decompression:
Omitted decompression stops at 30 and 20 feet.
Surface interval less than 1 minute.
- Return the diver to depth of the missed stop.
- Increase that stop time by 1 minute.
- Resume decompression according to the original schedule.
Asymptomatic Omitted Decompression:
Omitted decompression stops at 30 and 20 feet.
Surface interval 1 to 7 minutes and a chamber is available.
- Initate Surface decompression procedure.
- If the diver was on oxygen at the time, compute the number of chamber periods by multiplying the remaining oxygen stop time at the stops by 1.1, divide by 30, then round the result up to the next half period.
- If the diver was on air compute the equivalent remaining oxygen time on air IAW Chapter 9.
- If the surface interval was greater then 5 minutes but less than 7 minutes add 15 minutes to the 50 foot oxygen time.
Asymptomatic Omitted Decompression:
Omitted decompression stops at 30 and 20 feet.
Surface interval greater than 7 minutes and a chamber is available.
- Treat the diver with Treatment Table 5 if the surface decompression schedule for that dive required two or fewer oxygen periods in the chamber.
- Treat on Treatment Table 6 if the surface decompression schedule for that dive required 2.5 or more oxygen periods in the chamber.
Asymptomatic Omitted Decompression:
Omitted decompression stops at 30 and 20 feet.
Surface interval greater than 1 minute and a chamber is not available.
- Return the diver to the depth of the omitted stop.
2. Complete in-water decompression by multiplying the 30 and / or 20 foot stop times by 1.5.
Asymptomatic Omitted Decompression:
Omitted decompression stops deeper than 30 feet.
Chamber is available.
- Treat on a Treatment Table 6.
- Treat on a Treatment Table 6A
if greater than 50 foot stop omitted.
Asymptomatic Omitted Decompression:
Omitted decompression stops deeper than 30 feet.
Chamber is not available.
- Return the diver to the depth of the omitted stop.
- Follow regular schedule to 30 feet.
- At 30 feet shift to 100% oxygen if available.
- Multiply 30 and 20 foot stop times by 1.5.
Decompression Sickness in Water:
Diver remaining in water on Oxygen.
- Launch Standby to assist. Decompress other diver according to original schedule.
- Descend 10 feet, If no significant relief, descend an additional 10 feet not to exceed 40 feet if on oxygen.
- Remain at treatment depth for 30 minutes.
- Decompress by multiplying stop times by 1.5.
- Begin Oxygen breathing at 40 feet.
- Continue on Oxygen for 1.5 times the 40, 30, and 20 foot stop times.
- Transport to the nearest Recompression Chamber.
Treat on a Treatment Table 5 if the diver is symptom free.
Treat on a Treatment Table 6 for residual symptoms.
Decompression Sickness in Water:
Diver remaining in water on Air.
- Launch Standby to assist. Decompress other diver according to original schedule.
- Descend 10 feet, If no significant relief, descend an additional 10 feet.
- Remain at treatment depth for 30 minutes.
- Decompress by multiplying stop times by 1.5.
- Transport to the nearest Recompression Chamber.
Treat on a Treatment Table 5 if the diver is symptom free.
Treat on a Treatment Table 6 for residual symptoms.
Decompression Sickness in Water:
Diver leaving the water Type I or Type II
- Surface and recompress immiediatly to 60 feet.
- Treat as Type II symptoms regardless.
- Observe for at least 6 hours. If any symptoms recur, treat as a recurrence of Type II symptoms.
