MK 16 diver surfaces with omitted decompression, no chamber on station — facilitator packet

Drill drill-001-ecuba-omitted-deco · intermediate · 45 min

Applies to: qual::inside-tender, qual::chamber-supervisor, qual::chamber-operator, qual::mk16-supervisor

Facilitator copy. Contains injects, the worked solution, and grading criteria. Do not hand this to the team being evaluated.

Objectives

• Correctly classify the omission by deepest stop omitted and surface interval.
• Apply the chamber-available-within-60-minutes branch of Table 15-7.
• Recognize when the situation converts from a decompression problem into a treatment problem.
• Manage the 1.3 ata ppO2 setpoint constraint when returning a diver to a shallow stop.

Setup

Mission

Hull inspection on a moored vessel. Two-diver MK 16 EC-UBA dive at 1.3 ata ppO2 setpoint, working depth 90 fsw.

Station

Small boat dive station. No recompression chamber on scene. The nearest certified chamber is a 35-minute drive from the pier, and you are 15 minutes from the pier.

Environment

Protected water, 58°F, slack current, good visibility.

Profile

Diver 1 and Diver 2 in the water at T+0. Planned bottom time 40 minutes at 90 fsw with a planned decompression obligation including a 30 fsw stop and a 20 fsw stop.

Personnel

• You: Diving Supervisor (MK 16 qualified)
• Diver 1 (the casualty in this drill), Diver 2
• Standby diver, two tenders, boat coxswain

Injects

T+0

Inject: Divers splash and descend. Dive proceeds normally through the bottom phase. Announce the bottom time as the team requests it.

Expected response:

• Supervisor keeps the timeline and calls the ascent to the first stop on schedule.
• Team confirms the decompression schedule before leaving the bottom.

T+44

Inject: During ascent, Diver 1 reports his primary display has gone blank and he is experiencing a rapid, uncontrolled ascent. Diver 1 arrives on the surface. His deepest omitted stop is the 30 fsw stop. He is conscious, alert, and reports no symptoms.

Expected response:

• Supervisor gets the diver out of the water and under direct observation.
• Supervisor establishes two facts immediately: the deepest stop omitted, and the surface interval clock started at the moment of surfacing.
• Supervisor recognizes deepest stop omitted is DEEPER than 20 fsw.
• Someone starts the surface interval clock out loud.

If the team stalls: If the team fixates on the UBA failure, ask: what is the diver's decompression status right now?

T+46

Inject: The team asks whether they should put the diver back in the water to finish his decompression.

Expected response:

• Supervisor states that for an omitted stop deeper than 20 fsw, use of a recompression chamber available within 60 minutes is mandatory.
• Team determines whether a chamber can be reached within 60 minutes: 15 minutes to the pier plus 35 minutes' drive is 50 minutes, so a chamber IS available within 60 minutes.
• Team therefore does NOT return the diver to the water.

This is the decision point the drill is built around. The team must actually do the arithmetic rather than assume "no chamber on scene" means "no chamber available."

T+50

Inject: Surface interval is now 6 minutes. Less than 30 minutes of decompression was missed. The diver remains asymptomatic. What treatment do you direct?

Expected response:

• Treatment Table 6, because the surface interval exceeds 5 minutes.
• Team notes that if the surface interval had been 0-5 minutes, it would have been Treatment Table 5 instead.
• Chamber and tenders are alerted; transport is initiated without delay.

If the team stalls: If the team says Table 5, ask them to state the surface interval and re-read the row.

T+55

Inject: Diver 1 now reports tingling in his left hand.

Expected response:

• The diver is no longer asymptomatic, so Table 15-7 (asymptomatic omitted decompression) no longer governs.
• This is now symptomatic and is managed as a diving casualty under the DCS/AGE treatment guidance.
• Undersea Medical Officer is contacted.

Table 15-7 is titled for the ASYMPTOMATIC diver. Teams routinely miss that the table stops applying the moment symptoms appear.

Worked solution

The correct answer is Treatment Table 6, initiated at the nearest chamber, with transport started immediately. The trap is the phrase "no chamber on station" - the standard is whether a chamber is available within 60 minutes, not whether one is on the boat.

1. Recover the diver and establish deepest stop omitted and surface interval.

Both values are inputs to the Table 15-7 lookup. Neither can be reconstructed later with confidence, so they must be captured at once.

Reference: USN Diving Manual Rev 7 Change A, para 15-12.6, Table 15-7

2. Classify the omission as deeper than 20 fsw.

The deepest stop omitted was 30 fsw. Para 15-12.6.2 states that when the deepest decompression stop omitted is deeper than 20 fsw, a more serious situation exists and use of a recompression chamber available within 60 minutes is mandatory.

Reference: USN Diving Manual Rev 7 Change A, para 15-12.6.2

3. Determine chamber availability against the 60-minute standard.

15 minutes to the pier plus a 35-minute drive is 50 minutes, which is inside 60. The chamber-available column of Table 15-7 governs.

Reference: USN Diving Manual Rev 7 Change A, Table 15-7

4. Select Treatment Table 6 on the surface-interval branch.

Less than 30 minutes of decompression was missed. Para 15-12.6.2 gives Treatment Table 5 when the surface interval is less than 5 minutes and Treatment Table 6 when it exceeds 5 minutes. The interval here is 6 minutes, so Treatment Table 6.

Reference: USN Diving Manual Rev 7 Change A, para 15-12.6.2, Table 15-7

5. Transport without delay and treat at the chamber.

The 60-minute figure is a limit, not a budget to spend. Time spent deliberating erodes the margin that made the chamber option valid.

6. On symptom onset, stop treating this as an asymptomatic omission.

Table 15-7 governs the initial management of the ASYMPTOMATIC EC-UBA diver. Once the diver reports tingling, he is a symptomatic diving casualty and is managed under the DCS/AGE treatment guidance, with the Undersea Medical Officer involved.

Reference: USN Diving Manual Rev 7 Change A, Table 15-7 title; Chapter 17

Common failure modes

• Reading 'no chamber on scene' as 'chamber not available' and putting the diver back in the water. The standard is 60 minutes, not on-station.
• Selecting Treatment Table 5 without checking the surface interval against the 5-minute threshold.
• Failing to start and announce the surface interval clock, making the table lookup unresolvable later.
• Continuing to apply Table 15-7 after the diver becomes symptomatic.
• Treating the UBA electronics failure as the emergency. The equipment failure caused the problem; the decompression obligation is the problem.

Evaluation

Debrief prompts

• What was the actual emergency, and when did it start?
• If the drive had been 50 minutes instead of 35, what changes? Walk the other column of Table 15-7.
• The diver was at a 1.3 ata ppO2 setpoint. If you had returned him to a stop shallower than 33 feet, what does Note 1 of Table 15-7 require?
• Who on your station could have made this call if you were the one in the water?

References

• USN Diving Manual Rev 7 Change A, para 15-12.6 through 15-12.6.3
• USN Diving Manual Rev 7 Change A, Table 15-7, Initial Management of Asymptomatic Omitted Decompression EC-UBA Diver
• USN Diving Manual Rev 7 Change A, Chapter 17, Diagnosis and Treatment of DCS and AGE