Us Navy Dive Manual Chapter 19 Rev 6 Change A

Front 1

CNS O2 toxicity is not likely to occur at partial pressures below _____

Back 1

1.3 ATA

Front 2

What are the causes of CNS O2 Toxicity?

Back 2

- Increased ppo2 with depth change
- Increased exposure time
- Stress from strenuous exercise
- CO2 build up
- Cold stress
- Systemic diseases that increase O2 consumption such as adrenal or thyroid disorders. Divers with these conditions should be excluded from oxygen diving

Front 3

What is the clearest warning sign of CNS O2 Tox?

What is the treatment for nonconvulsive symptoms?

Back 3

-Twitching

-Stricken diver and buddy make a controlled ascent to surface and inflate life preserver if necessary.
-Buddy should watch stricken diver closely for worsening symptoms
-Abort the dive

Front 4

CNS O2 toxicity: Treatment of underwater convulsion?

Back 4

1. Assume postion behind diver, weightbelt should be left in place unless ditching is absolutely neccessary for ascent. Weight belt will prevent face down position.
2. Leave mouthpiece in, do not attempt to replace it if it's not. Switch the mouthpiece to SURFACE position
3. Grasp the victim around his chest using the best method to gain positive control
4. Make a controlled ascent to the surface while applying slight pressure to chest to assist in exhalation
5. If needed use the victims BC for additional buoyancy
7. Upon surfacing inflate the victims BC
8. Remove the victim's mouthpiece and ensure the mouthpiece is in the surface position to reduce the chance of rig flood out and additional weight
9. Signal for emergency pick up
10.Commence mouth to mouth if needed
11. If an upward excursion occurred during the actual convulsion transport to chamber for evaluation of diving related illness.

Front 5

What is the off-effect?

Back 5

A hazard associated with CNS O2 toxicity, may occur several minutes after the diver comes off gas or experiences a reduction of PPO2. The off-effect is manifested by the onset or worsening of CNS O2 tox

Front 6

where should you position yourself when dealing with a convulsing diver

Back 6

behind the diver

Front 7

What are the causes of hypoxia with the MK 25 UBA and when is the diver at the greatest risk of getting hypoxia? Why?

Back 7

The primary reason is inadequate/incorrect purge of the UBA. The risk is greatest on the surface as the diver consumes oxygen, the oxygen fraction in the breathing loop will begin to decrease, as will the gas volume in the breathing bag. If there is sufficient nitrogen in the breathing loop to prevent the bag from being emptied no oxygen will be added and the oxygen fraction may drop to 10% or lower.

Front 8

What are the MK 25 UBA purge procedures?

Back 8

Procedures designed to remove as much of the inert gas (nitrogen) from a divers lungs as possible prior to the start of a dive. They ensure the oxygen in the breathing loop is sufficiently high to prevent the occurance of hypoxia. Procedures are located in the MK 25 O&M manual.

Front 9

What are the symptoms of hypoxia?

Back 9

- Confusion
- Loss of coordination
- Dizziness
- Convulsion
- Unconciousness

Front 10

How do you treat hypoxia?

Back 10

-Add O2 to the UBA and abort the dive
-If unconsciousness occurs the buddy should add O2 to the rig and bring the diver to the surface at a moderate rate, remove the mouthpiece and have him breathe air. Monitor ABC's and administer 100% O2, dive buddy shall ensure mouthpiece is in surface mode
-If it is clear that hypoxia was the cause and the diver recovers with normal neurological function do not treat for AGE.

Front 11

What are the main causes of hypercapnia with the MK 25 UBA?
What are the symptoms of hypercapnia?

Back 11

Inadequate ventilation (breathing volume) by the diver or failure of the CO2 absorbant canister.
- Increased Sweating
- Increased rate and depth of breathing (labored)
- Confusion
- Convulsions
- Headache
- Inability to concentrate
- Loss of consciousness
- Drowsiness

Front 12

How do you treat hypercapnia?

Back 12

- Increase ventilation if skip breathing is cause
- Decrease exertion level
- Abort the dive. Return to surface to breathe air
- During ascent maintain a vertical position and activate the bypass valve to add fresh oxygen. If the symptoms are a result of a flood out this will decrease the risk of chemical injury to the diver
-Handle an unconscious diver the same as you would with managing an underwater convulsion

Front 13

What are some ways to prevent hypercapnia?

Back 13

- Use only approved carbon dioxide absorbent
- Follow the prescribed canister filling procedure
- Dip test the UBA before the dive, check for leaks
- Do not exceed canister duratuion limits for water temp
- Ensure one way valves are installed correctly
- Swim at comfortable pace and do not skip breathe

Front 14

How are chemical injuries best prevented.

Back 14

by prefoming a careful dip test during pre dive set up

preforming a leak check before leaving the surface

Front 15

What does the term chemical injury refer to and what are the causes?

Back 15

It refers to the introduction of a caustic solution from the carbon dioxide scrubber of the UBA into the upper airway of a diver caused by water coming into contact with the CO2 absorbant as a result of improper predives or an incorrect position of the mouthpiece assembly during a leak check or in water checks.

Front 16

What are the symptoms of a chemical injury (caustic cocktail)?

Back 16

Before actually inhaling the caustic solution the diver may experience rapid breathing or a headache which are caused by the CO2 buildup.
- Choking/gagging
- Foul taste
- Burning of mouth and throat

Front 17

Describe management of a chemical injury.

Back 17

- Immediatly assume an upright position
- Depress the manual bypass valve continuously
- Abort dive ascend to surface breathing through the nose to prevent overpressurization
- Should signs of system flooding occur during underwater purging, abort dive and return to open circuit or mixed gas UBA if possible
- Rinse mouth with fresh water several times but do not swallow. Do not rinse with weak acid solutions and do not induce vomitting.
- Obsreve for signs of AGE and treat as required and have px evaluated by a physian or corpsman. Respiratory distress may require hospitalization.

Front 18

What can be done to prevent chemical injury?

Back 18

- Careful predive dip test
- Pay special attention to mouthpiece rotary valve upon water entry and exit
- Dive buddies perform careful leak checks

Front 19

What is middle ear oxygen absorbtion syndrome and what is the cause?

Back 19

Negative pressure that develops in the middle ear following a long O2 dive. This is caused by gas with very high % of O2 entering the middle ear cavity during the course of an O2 dive. Following the dive the O2 is slowly absorbed by middle ear tissues reluting in negative pressure in the middle ear cavity. There may also be fluid present in the middle ear as a result of the differential pressure (serous otitis media).

Front 20

What are the symptoms, treatment, and prevention for middle ear oxygen syndrome?

Back 20

- Sense of pressure or mild discomfort in bolth ears
- Muffled hearing
- Moist crackling sensation in the ears
Treatment consists of performing a valsalva maneuver. This action will usually relive symptoms. Discomfort and hearing loss resolve quickly, but the middle ear fluid is absorbed more slowly.
Prvention is hard to avoid but to reduce the chances the diver should perform several valsalvas throughtout the day after a long O2 dive. This keeps the eustachian tubes open which equalizes the pressure

Front 21

What is the minimum equipment required for MK 25 UBA diving?

Back 21

-MK 25 MOD 2 UBA
-Approved life jacket
-Face mask
-Weight belt
-Dive knife
-Appropriate thermal protection
-Whistle
-Buddy lines (one per pair)
-Depth gauge (large face, accurate, one per diver)
-Compass (one per pair if on compass course)

Front 22

What is the pressure of the oxygen bottles and in what two ways may it become depleted? How can a diver maximize the duration of oxygen?

Back 22

3,000psi (207 bar) and it may be depleted by divers metabolic consumption or by the loss of gas from the UBA. The key factor to maximizing the duration of the oxygen supply is to swim at a relaxed comfortable pace.

Front 23

What is the average breathing gas consumption for MK 2?

Back 23

- Over bottom pressure= 50 psi(3.4 bar) Minimum
Gas consumption
- Normal: 15-17 psi per min
- Heavy work: Heavy work is NOT recommended

Front 24

CO2 absorbant canister duration is dependant on what three factors?

Back 24

- Water temperature
- Exercise rate
- Mesh size of NAVSEA-approved CO2 absorbent

Front 25

What are the approved CO2 Absorbants?

Back 25

- High performance Sodasorb, Regular
- Sofnolime 4-8 Mesh NI, L Grade
- Sofnolime 8-12 Mesh NI, D Grade
*ONLY FOR USE WITH URETHANE CANISTER*
- Diversorb Pro 5-8 Mesh

Front 26

State packing precautions in relation to the CO2 absorbant canisters.

Back 26

-Ensure it is completely filled
-Orient canister vertically and fill 1/3 of the way and tap sides with hand or rubber mallet. Repeat until you reach the fill line scribed into canister. This will prevent creating channels in absorbant material.
-Never mash the material which results in absobant material failure and creates dust which would then breathed into the lungs of the diver.

Front 27

What is a transit with excursion?
What are the limits?

Back 27

This calls for a maximum diving depth of 20' or shallower for the majority of dive but allows for a single excursion to depths as great as 50'. The total time of the dive cannot exceed :240, including the excursion.
21'-40' single excursion for up to :15 minutes
41'-50' single excursion for up to :05 minutes
The diver must have returned to 20' by the end of the allowable time for the excursion

Front 28

What are the single-depth exposure limits?

Back 28

-25' for :240 (4 hours)
-30' for :80
-35' for :25
-40' for :15
-50' for :10
No excursions allowed when using single depth limits

Front 29

Are downward excursions allowed using single depth limits?
What is the procedure for handling an inadvertant excursions?

Back 29

NO
-If depth/time of excurssion exceeds the provided limits or if a previous excursion was taken abort the dive
-If the excursion was within the allowed excursion limits the dive may be continued at 20' but no additional excursions are allowed
-The dive may be treated as a single-depth dive by applying the max depth to the single-depth limits

Front 30

What is a off oxygen interval?

Back 30

The time a diver stops breathing O2 on one dive to the time a diver stars breathing O2 on the next dive

Front 31

What is a sucessive oxygen dive and what are the exposure limits?

Back 31

A dive that follows a previous O2 dive after a off O2 interval of less than 2 hours.
No adjustment is needed if the oxygen interval exceeds 2 hours. If less than 2 hours from previous exposure make the appropriate corrections. No more than 4 hours of oxygen time is permitted within 24 hours

Front 32

The mixed gas to oxygen rule states that if the previous dive used a mixed gas breathing mix having an oxygen partial pressure of ___ ata or greater the previous exposure must be treated as a closed circuit O2 dive and the off-oxygen interval is calculated from the time the diver discontinued the previous breathing mix from the closed circuit oxygen rig.

Back 32

1.0 ata

Front 33

Is oxygen diving at high elevations authorized?

Back 33

Yes, the exposure limits and procedures set forth may be used without adjustment for closed-curcuit oxygen diving at altitudes above sea level

Front 34

Is flying after diving permitted when diving the MK-25 UBA?

Back 34

Yes, flying after diving is permitted immediatly following oxygen diving unless the diving has been part of a multiple-UBA dive un which another breathing mixture was being used, if so follow the guidelines for ascent to altitude found in chapter 9 of the dive manual

Front 35

What is required if more time is required for real life combat operations than what is permitted?

Back 35

Contact NEDU and a DMO for an estimate of the increased risk of CNS O2 Toxicity

Front 36

When planning MK25 operational combat swimmer operations, what are the operating limitations that must be considered?

Back 36

-UBA O2 supply
-UBA canister duration
-O2 exposure limits
-Thermal factors

Front 37

What are the operational considerations for the MK-25?

Back 37

-5 personnel minimum
-Buddy diver required
-Chase boat required

Front 38

How can you maximize operational range in the MK25?

Back 38

-Turtleback technique (Surface swim, breathe air when feasable)
-Use tides and currents to your advantage
-Verify oxygen bottles are fully charged before dive.
-Minimize gas loss by avoiding leaks and unnecessary depth changes.
-Maintain comfortable and relaxed swim pace, .8knots
-Wear adequate thermal protection.

Front 39

When diving the MK25, what is the recommended objective swim speed?

Back 39

Swim at a relaxed, comfortable pace. Usually around .8 knots.

Front 40

What is the minimum personnel requirements for conducting training and exercise MK25 dives?

Back 40

-Diving Supervisor/Boat Coxswain
-Standby diver in SCUBA
-DMT or individual trained in diagnosis/emergency treatment of diving injuries
-MK25 dive pair.

Front 41

When are bubby lines required for MK25 diving?

Back 41

Buddy lines are required equipment for oxygen dives. The diving supervisor must carefully consider each situation and allow buddy lines to be disconnected only when their use will impede the performance of the mission.

Front 42

What is the Diving Medical Technician required to have on station?

Back 42

-AMBU bag, self inflating bag-mask ventilator
-Oro-pharyngeal airway, adaptable mask to be used
-First aid kit
-Portable O2 kit
-2 canteens of fresh water for tx of chemical injury

Front 43

How many phases are there in MK 25 diving supervisor checks, what are they?

Back 43

Phase one- Diving supervisor observes the divers setting up their rigs IAW the MK 25 O&M manual. Sign the predive checklist.
Phase two- Does the equipment check once divers have donned gear (hands on)

Front 44

During the purge procedure on the MK25, what common mistakes must be avoided?

Back 44

Exhaling back into the bag.
Under-inflation of the bag
Lack of room for bag to expand.
Breaking the seal of your mask.

Front 45

What are the disadvantages of diving the MK25?

Back 45

Increased hazard to diver (CNS O2 Tox)
Limited to shallow depths.
No voice comms.
Limited thermal protection.
Greater training requirements
Greater expense.