US NAVY DIVE MANUAL CHAPTER 14 SURFACE-SUPPLIED MIXED GAS DIVING PROCEDURES

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US NAVY DIVE MANUAL CHAPTER 14 SURFACE-SUPPLIED MIXED GAS DIVING PROCEDURES
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US NAVY DIVE MANUAL CHAPTER 14 SURFACE SUPPLIED MIXED GAS DIVING PROCEDURES
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US NAVY DIVE MANUAL CHAPTER 14 SURFACE-SUPPLIED MIXED GAS DIVING PROCEDURES
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  1. 14-2.1
    Depth and Exposure Limits, normal operational limit
    Surface-supplied mixed gas diving is 300 fsw for 30 minutes.
  2. 14-2.1
    Wait time between mixed gas dives:
    • Following a no-decompression dive - 12 hours 
    • Following a decompression dive - 18 hours.

    One day break after four consecutive days of diving.
  3. 14-2.2
    Ascent to Altitude
    • Following a no-decompression dive - 12 hours
    • Following a decompression dive - 24 hours.
  4. 14-2.4
    Gas Mixtures
    • Bottom Mixture - may vary from 90% to 60% helium depending on the diver’s depth.
    • 50% Helium 50% Oxygen - used from 90 to 40 fsw . Oxygen may range from 49 to 51 percent.
    • 100% Oxygen -  used at the 30 and 20 fsw water stops during in water decompression and at 50, 40 and 30 fsw in the chamber. 
    • Air  - used as an emergency backup gas and for air breaks.
  5. 14-2.5
    Emergency Gas Supply
    Shall be the same as the bottom mixture unless the bottom mixture contains less than 16 percent oxygen, in which case the mixture may range from 15 to 17 percent oxygen.
  6. 14-3.1
    Selecting the Bottom Mix.
    • Minimum oxygen percentage allowed:
    • 14 percent for depths to 200 fsw
    • 10 percent for depths in excess of 200 fsw.

    • Never exceeds an oxygen partial pressure of 1.3 ata 
    • Diving with a mixture near maximum oxygen percentage offers a decompression advantage
  7. 14-3.5
    Special Procedures for Descent with Less than 16 Percent Oxygen.
    • 1. Place the diver on air on the surface.
    • 2. Make the appropriate predive checks.
    • 3. Have the diver descend to 20 fsw.
    • 4. At 20 fsw, shift the diver to the bottom mix and ventilate the diver for 20 seconds.
    • 5. Confirm the diver is on bottom mix, then perform a final leak check. The diver is allowed 5 minutes to descend to 20 fsw, shift to the bottom mixture and perform equipment checks.
    • 6. Have the diver begin descent.
    • 7. Start bottom time. 
    • If the diver spends 5 minutes or less performing above procedures, bottom time starts when the diver leaves 20 fsw. 
    • If the diver spends more than 5 minutes performing above procedures, bottom time starts at the 5 minute mark.
    • 8. If it is necessary to bring the diver back to the surface from 20 fsw to correct a problem: 
    • Shift the diver from the bottom mixture back to air. 
    • Ventilate the diver.
    • Confirm the diver is on air. 
    • Have the diver begin ascent.
    • When the diver reenters the water, the 5 minute grace period begins again. No adjustment of bottom time is required for the previous exposure at 20 fsw.
  8. 14-3.6
    Aborting Dive During Descent
    • 1. If it is necessary to bring the diver back to the surface from depths of 100 fsw and shallower: 
    • *Ensure the diver is in a no-decompression status. 
    • *If the bottom mixture is 16% oxygen or greater, ascend directly to the surface at 30 fsw/min.
    • *If the bottom mixture is less than 16% oxygen, ascend to 20 fsw at 30 fsw/min.
    • *Shift the diver from the bottom mixture back to air.
    • *Ventilate the diver.
    • *Confirm the diver is on air.
    • *Complete ascent to the surface on air.
    • *If desired, another dive may be performed following a dive aborted 100 fsw and shallower. 
    • 2. If it is necessary to abort a dive deeper than 100 fsw: 
    • Follow the normal decompression schedule to the surface.
    • Repetitive diving is not allowed following a dive aborted deeper than 100 fsw.
  9. 14-3.7
    Procedures for Shifting to 50/50 at 90 fsw
    • 1. Shift the console to 50/50 when the diver reaches 90 fsw.
    • 2. If there is a decompression stop at 90 fsw, ventilate each diver for 20 seconds at 90 fsw.
    • 3. Confirm the divers are on 50/50.
    • 4. If there is no decompression stop at 90 fsw, delay ventilation until arrival at the next shallower stop.

    Gas shift time is included in the stop time
  10. 14-3.8
    Procedures for Shifting to 100 Percent Oxygen at 30 fsw
    • 1. Shift the console to 100% oxygen when the diver reaches 30 fsw.
    • 2. Ventilate each diver for 20 seconds.
    • 3. Verify the diver’s voice change.

    Time at the 30-fsw stop begins when the divers are confirmed to be on oxygen.
  11. 14-3.9
    Air Breaks at 30 and 20 fsw
    • When an air break is required, shift the console to air for 5 minutes then back to 100% oxygen.
    • Ventilation of the divers is not required.
    • If the total oxygen stop time is 35 minutes or less, an air break is not required at 30 minutes
  12. 14-3.11
    Surface Decompression on Oxygen (SurDO2).
    Time limit
    The interval from leaving 40-fsw in the water to arriving at 50-fsw in the chamber cannot exceed 5 minutes without incurring a penalty
  13. 14-3.11
    Surface Decompression on Oxygen, oxygen periods
    • The first period consists of 15 minutes on oxygen at 50 fsw followed by 15 minutes on oxygen at 40 fsw.
    • Periods 2, 3, and 4 are spent at 40 fsw.
    • Periods 5, 6, 7 and 8 are spent at 30 fsw. 
    • Ascent time is included in the oxygen/air time.
    • Ascent from 40 to 30 fsw, if required, should take place during the air break.
  14. 14-3.11
    Surface Decompression on Oxygen, shifting from in water decompression to Sur D O2
    • Once in the chamber, the diver should receive the full number of chamber oxygen periods prescribed by the tables.
    • Unlike in air diving, no credit is allowed for time already spent on oxygen in the water.
  15. 14-3.12.1
    Early Arrival at the First Stop.
    1. Begin timing the first stop when the required travel time has been completed.
  16. 14-3.12.2
    Delays in Arriving at the First Stop, Delay less than 1 minute
    1. Delays in arrival at the first stop of less than 1 minute may be ignored.
  17. 14-3.12.2 Delays in Arriving at the First Stop, Delay greater than 1 minute.
    • Round up the delay time to the next whole minute and add it to the bottom time.
    • Recompute the decompression schedule.
    • If no change in schedule is required, continue on the planned decompression.
    • If a change in schedule is required and the new schedule calls for a decompression stop deeper than the diver’s current depth, perform any missed deeper stops at the diver’s current depth.
    • Do not go deeper
  18. 14-3.12.3
    Delays in Leaving a Stop or Arrival at the Next Stop, Deeper than 90 fsw, Greater than 1 minute.
    • Add the delay to the bottom time and recalculate the required decompression.
    • If a new schedule is required, pick up the new schedule at the present stop or subsequent stop if the delay occurs between stops.
    • Ignore any missed stops or time deeper than the depth at which the delay occurred.
    • If a delay occurs between stops, restart subsequent stop time at completion of the delay.
  19. 14-3.12.3
    Delays in Leaving a Stop or Arrival at the Next Stop, between 90 to 70 fsw, Greater than 1 minute less than 5 minutes
    • Resume the normal decompression schedule at the completion of the delay.
    • If a delay occurs between stops, restart subsequent stop time at completion of the delay
  20. 14-3.12.3
    Delays in Leaving a Stop or Arrival at the Next Stop, between 90 to 70 fsw, Greater than 5 minutes
    • Shift the diver to air
    • At the completion of the delay, return the diver to 50/50% oxygen.
    • Add the time on air to the bottom time and recalculate the required decompression.
    • If a new schedule is required, pick up the new schedule at the present stop or subsequent stop if delay occurs between stops.
    • Ignore any missed stops or time deeper than the depth at which the delay occurred.
  21. 14-3.12.3
    Delays in Leaving the 30 fsw, greater than 1 minute.
    The delay leaving the 30-fsw stop shall be subtracted from the 20-fsw stop time.
  22. 14-3.12.3
    Delays in Leaving a Stop or Arrival at the Next Stop, between 70-30 fsw, greater than 1 minute
    • Resume the normal decompression schedule at the completion of the delay.
    • If a delay occurs between stops, restart subsequent stop time at completion of the delay
  23. 14-4.1
    Bottom Time in Excess of the Table.
    • 1. Decompress using the 120-minute schedule for the deepest depth attained.
    • 2. Shift to 100 percent oxygen at 40 fsw.
    • 3. Surface the diver after completing 30 minutes on oxygen at 40 fswn.
    • 4. Press the diver to 60 fsw in the chamber as fast as possible not to exceed 100 fsw/min.
    • 5. Treat the diver on an extended Treatment Table 6.
  24. 14-4.2
    Loss of Helium-Oxygen Supply on the Bottom.
    • 1. Shift the diver to EGS.
    • 2. Abort the dive.
    • 3. Remain on the EGS until at 90 fsw.
    • 4. At 90 fsw, shift the diver to 50/50  and complete decompression as planned.
    • 5. If the EGS becomes exhausted before 90 fsw, shift the diver to air, complete decompression to 90 fsw, shift the diver to 50/50, continue the decompression as planned.
  25. 14-4.3
    Loss of 50/50 During In-Water Decompression
    • 1. Shift the diver to air and continue the decompression as planned while trying to correct the problem.
    • 2. Shift to 50/50 once the problem is corrected. Time spent on air counts toward decompression.
    • 3. If the problem cannot be corrected:
    • -Continue the planned decompression on air.
    • -Shift the diver from air to oxygen upon arrival at the 50-fsw stop. 
    • -Breathe oxygen at 50 and 40 fsw for the decompression time, but do not to exceed 16 minutes at 50 fsw. If the 50-fsw stop exceeds 16 minutes, travel divers to 40 fsw and add remaining 50-fsw stop time to the 40-fsw stop time
  26. 14-4.4
    Loss of Oxygen Supply During In-Water Decompression
    • 1. Switch back to 50/50. If a switch to 50/50 is not possible, switch the diver to air.
    • 2. If the problem can be quickly remedied, reventilate the diver with oxygen and resume the schedule at the point of interruption. Consider any time on 50/50 or air as dead time.
    • 3. If the problem cannot be remedied, initiate surface decompression. Ignore any time already spent on oxygen..
    • 4. If the problem cannot be remedied and surface decompression is not feasible, complete the decompression on 50/50 oxygen or air.
    • For 50/50, double the remaining oxygen time at each water stop.
    • For air, triple the remaining oxygen time.
  27. 14-4.5
    Loss of Oxygen Supply in the Chamber During Surface Decompression.
    • Temporary Loss. Return the diver to oxygen breathing. Consider any time on air as dead time. 
    • Permanent Loss. Multiply the remaining oxygen time by three. If 50/50 is available, multiply the remaining oxygen time by two.
    • If the loss occurred at 50 or 40 fsw, allocate 10% at the 40-fsw stop, 20% to the 30-fsw stop, and 70% to the 20-fsw stop.
    • If the diver is at 50 fsw, ascend to 40 fsw to begin the stop time.
    • If the loss occurred at 30 fsw, allocate 30% at 30-fsw stop and 70% to the 20-fsw stop. Round the stop times to the nearest whole minute. Surface upon completion of the 20-fsw stop.
  28. 14-4.6
    Decompression Gas Supply Contamination.
    • 1. Find the source  Probable sources include: 
    • -An improper valve line-up on the console.
    • -Accidental opening of the EGS valve.
    • 2. When the problem is corrected: 
    • -Ventilate each diver for 20 seconds and confirm divers are on decompression gas. 
    • -Continue decompression as planned. Do not lengthen stop times to compensate for the time spent correcting the problem.
  29. 14-4.7
    CNS Oxygen Toxicity Symptoms (Nonconvulsive) at the 90-60 fsw Water Stops.
    • 1. Bring the divers up 10 feet and shift to air. Shift the console as the divers are traveling.
    • 2. Vent both divers upon arrival at the shallower stop. Ventilate the stricken diver first.
    • 3. Remain at the shallower stop until the missed time at the previous stop is made up.
    • 4. Resume the planned decompression breathing air.
    • 5. Upon arrival at the next shallower stop, return the divers to the 50/50. Ignore any missed time on the 50/50 mixture.
  30. 14-4.8
    Oxygen Convulsion at the 90-60 fsw Water Stop.
    • 1. Shift both divers to air.
    • 2. Have the unaffected diver ventilate himself first.
    • 3. If only one diver is in the water, launch the standby diver
    • 4. Hold the divers at depth until the convulsion has subsided. 
    • 5. Have the dive partner ascertain whether the diver is breathing.
    • 6. If the diver appears not to be breathing, have the dive partner attempt to reposition the head to open the airway.
    • 7. If the affected diver is breathing, have the dive partner tend the stricken diver and decompress both divers on air following the original schedule. Shift the divers to 50/50 upon arrival at 50 fsw. Surface decompress upon completion of the 40-fsw water stop.
    • 8. If it is not possible to verify that the affected diver is breathing, leave the unaffected diver at the stop to complete decompression, and surface the affected diver and the standby diver at 30 fsw/min. Shift the unaffected diver back to his 50/50 mixture for completion of decompression.
  31. 14-4.9
    CNS Toxicity Symptoms (Nonconvulsive) at 50- and 40-fsw Water Stops.
    • Bring the divers up 10 feet and shift to air. Shift the console as the divers are traveling.
    • Ventilate both divers upon arrival at the shallower stop. Ventilate the stricken diver first.
    • Remain on air at the shallower depth for double for air, triple for oxygen of the missed time from 50- and 40-fsw water stops, then surface decompress

    • If surface decompression is not feasible, continue decompression in the water on either air or oxygen depending on the diver’s condition:
    • To continue on oxygen, ascend to 30 fsw (or remain at 30 fsw if already there). Take a 10 min period on air (Time on air does not count toward decompression). Then shift the diver to oxygen and complete decompression in the water according to the schedule. 
    • To continue on air, ascend to 30 fsw (or remain at 30 fsw if already there). Compute the remaining 30- and 20-fsw air stop times by tripling the oxygen time given in the original schedule. Surface upon completion of the 20-fsw stop.
    • Alternatively, the diver may complete the 30-fsw stop on air by tripling the oxygen stop time, then switch to oxygen upon arrival at 20 fsw. Remain at 20 fsw for the oxygen time indicated in the original schedule. Surface upon completion of the 20-fsw stop
  32. 14-4.10
    Oxygen Convulsion at the 50-40 fsw Water Stop
    • Shift both divers to air.
    • Have the unaffected diver ventilate himself first 
    • If the diver is breathing, hold him at his current depth until he is stable, then take one of the following actions:
    • If the diver missed any 50/50 or oxygen time at 50 fsw, hold the diver at depth until the total elapsed time on air is at least double the missed time for 50/50, triple the missed time for oxygen, add the 40-fsw water stop time to the 50-fsw chamber oxygen stop time.
    • If the diver did not miss any 50/50 or oxygen decompression time at 50 fsw, surface decompress. Add any missed 40 fsw stop time to the 50-fsw chamber  stop time.
    • If surface decompression is not feasible, complete decompression in the water on air. Compute the remaining stop times on air by doubling the 50/50, or tripling the oxygen time at each stop. 
    • If the diver is not breathing, surface the diver at 30 fsw/min while maintaining an open airway. Treat the diver for arterial gas embolism
  33. 14-4.11
    CNS Oxygen Toxicity Symptoms (Nonconvulsive) at 30- and 20-fsw Water Stops.
    • 1. If a recompression chamber is available on the dive station, initiate surface decompression. Shift the console to air during travel to the surface. Once in the chamber, take the full number of chamber oxygen periods.
    • 2. If a recompression chamber is not available on the dive station and the event occurs at 30 fsw, bring the divers up 10 fsw and shift to air to reduce the partial pressure of oxygen. Shift the console as the divers are traveling to 20 fsw. Ventilate the affected diver first. Complete the decompression on air in the water at 20 fsw. Compute the required air time at 20 fsw by tripling the sum of the missed oxygen time at 30 and 20 fsw.
    • 3.If a recompression chamber is not available on the dive station and the event occurs at 20 fsw, shift the console to air, ventilate both divers, affected diver first, and complete the decompression in the water at 20 fsw on air. Compute the required air time at 20 fsw by tripling the missed oxygen time at 20 fsw.
  34. 14-4.12
    Oxygen Convulsion at the 30- and 20-fsw Water Stop.
    • 1. Shift both divers to air, determine whether he is breathing
    • 2. If the diver is breathing, hold him at depth until he is stable, then surface decompress.
    • 3. If surface decompression is not feasible, ventilate both divers with air and complete decompression in the water on air. Compute the remaining stop times on air by tripling the remaining oxygen time at each stop. 
    • 4. If the diver is not breathing, surface the diver at 30 fsw/min while maintaining an open airway and treat the diver for arterial gas embolism
  35. 14-4.13
    Oxygen Toxicity Symptoms in the Chamber, first sign, non convulsion
    • 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.
  36. 14-4.13 Oxygen Toxicity Symptoms in the Chamber, second sign or convulsion
    • 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 on chamber air. Follow the guidance for permanent loss of chamber oxygen supply to compute the air decompression schedule
  37. 14-4.14
    Diver not be able to reach 50 fsw in the chamber because of difficulty equalizing
    • Compress the diver to the deepest depth he can attain initially. 
    • Begin oxygen breathing at that depth.
    • Once oxygen breathing has begun attempt to gradually compress the diver to 30 fsw or 20 fsw, which ever in water stop was scheduled next.
    • Double scheduled oxygen periods.
    • Interrupt oxygen breathing every 60 minutes with a 15-min air breaks.
    • Repetitive diving is not allowed following a dive in which the “safe way out” procedure is used
  38. Table 14‑2. 
    Management of Asymptomatic Omitted Decompression:
    20 or 30 fsw stop omitted
    Stops Required
    • SI Less than 1 min: 
    • Return to depth of stop. Increase stop time by 1 min. Resume decompression according to original schedule

    • SI 1–7 min: 
    • Use Surface Decompression Procedure

    • SI Greater than 7 min:
    • Treatment Table 5 if 2 or fewer periods
    • Treatment Table 6 if 3 or more periods
  39. Table 14‑2. 
    Management of Asymptomatic Omitted Decompression:
    40 or 50 fsw stop omitted
    Treatment Table 6
  40. Table 14‑2. 
    Management of Asymptomatic Omitted Decompression:
    60 fsw or deeper stop omitted
    • Stops Required: Less than 60 min missed, Treatment Table 6A
    • Stops Required: More than 60 min missed, Compress to depth of dive not to exceed 225 fsw. Use Treatment Table 8
    • For saturation systems: Compress to depth of dive. Saturate two hours. Use saturation decompression without an initial upward excursion
  41. 14-4.17
    Light Headed or Dizzy Diver on the Bottom.
    Initial Management.
    • Stop work and ventilate the rig
    • Check the oxygen content of the supply gas. 
    • If ventilation does not improve symptoms,  Shift banks to the standby BM supply and continue ventilation. 
    • If the entire gas supply is suspect, place the diver on the EGS and abort the dive.
  42. 14-4.19.1
    Decompression Sickness Deeper than 30 fsw.
    • Recompress the diver 10 fsw.
    • The diver may remain on 50/50 up to 100 fsw.
    • Remain at the stop for 1.5, If no stop time is indicated, use the next shallower stop time.
    • If symptoms resolve or stabilize decompress the diver to the 40-fsw water stop by multiplying each stop time by 1.5 or more as needed to control the symptoms.
    • Shift to 50/50 oxygen at 90 fsw.
    • Shift to 100 percent oxygen at 40 fsw and complete a 30 minute stop, then surface decompress and treat on Treatment Table 6.
  43. 14-4.19.2
    Decompression Sickness at 30 fsw and Shallower.
    • Recompress the diver 10 fsw.
    • Remain at the deeper stop for 30 minutes.
    • If symptoms resolve, surface decompress the diver at the end of the 30 minute period and treat on Treatment Table 6.
    • If symptoms do not resolve, but stabilize at an acceptable level, decompress the diver to the surface on oxygen by multiplying each intervening stop time by 1.5 or more as needed to control symptoms.
    • Treat on Treatment Table 6 upon reaching the surface.
  44. 14-6
    Diving at Altitude
    Wait time before initial dive after ascent to altitude
    The diver should wait 12 hours after arrival at altitude before making the first dive.

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