Preparation for Board Examination
Decompression Accidents: Management

Compiled and maintained
by Ernest S Campbell, MD

---

Early Treatment

• Recognition *Symptoms usually appear 15 minutes to 12 hours after surfacing*

• Blotchy rash
• Paralysis or weakness
• Coughing spasms
• Staggering or instability
• Unconsciousness

• Tired feeling
• Itching
• Pain, arms, legs or trunk
• Dizziness
• Numbness, tingling or paralysis
• Chest compression or shortness of breath

• Immediate oxygen breathing, continue even if person improves markedly
• Stabilize patient the same way as for Air Embolism
• Urgent recompression after stabilization in trauma facility
• Early recompression treatment for all forms of decompression sickness

Medical Management of DCS and AGE

• Provide 100% oxygen through a tight-fitting mask. This helps to off-gas inert gases. The oxygen will wash nitrogen out of the lungs and set up an increased diffusion gradient to increase nitrogen off-loading from the body. Resuscitation equipment should be available on all dive boats and in all dive facilities. Divers should refuse to dive if this equipment is not readily available.
• Give copious fluids as needed to maintain good urinary output. Fluids should be administered at a rate greater than 0.5ml/kg/hr--usually 1 L qhr or 1 L q4hr, titrated against the hematocrit, which should be maintained at less than 50%. The hemoconcentration associated with decompression sickness is the result of increased vascular permeability mediated by endothelial damage and kinin release. The fluids can be given orally if the diver is conscious--if not, give fluids by intravenous, if available. Avoid using hypotonic fluids, such as D5W, using 0.9% saline instead. Insert a urinary catheter if there is spinal cord DCS.
• Intubation, aggressive resuscitation and chest tube thoracostomy should be performed, if indicated.
• Give steroids if there is neurological DCS; dexamethasone 10 to 20 mg IV initially, followed by 4 mg every 6 hours; diazepam (5 to 10 mg) controls the dizziness, instability and visual disturbances associated with labyrinthine (vestibular) damage to the inner ear.
• Seizure activity is treated with a loading dose of Dilantin. Seizures result from damage incurred from cerebral bubbles formed from DCS or air embolism (resulting from pulmonary barotrauma); they can also result from oxygen toxicity associated with the treatment schedule. Dilantin (phenytoin) is given IV at 50 mg/min for 10 minutes for the first 500 mg and then 100 mg every 30 minutes thereafter. Blood levels of Dilantin should be monitored to maintain a therapeutic concentration of 10 to 20 mcg/mL. Levels over 25 mcg/mL are toxic.
• Some people provide aspirin, 600 mg, for its anti-platelet effects; this modality is debatable because of the possibility of associated spinal cord hemorrhage. Lidocaine has been shown to be protective in animal models but has not been studied adequately in humans. Standard cardiac doses could be used as a guide.

Attempting to treat the diver by returning him/her to the water, (known as in-water recompression), is hazardous not only to the diver, but to the caregivers who have to be re-subjected to pressure. This should not be attempted unless special arrangements have been made to do so. For example, in Australia, because of the great distances and time lags involved in reaching a recompression chamber, dive operators have a system of surplus air and oxygen tanks ready for in-water recompression.

See Edmonds 'In-Water Recompression',
Other links

Transportation. Ascending to an altitude greater than 1000 feet should be avoided. Sea level aircraft that are acceptable for transportation include the military C9, the Cessna Citation and the Lear Jet. Commercial aircraft fly at 5000 to 8000 feet cabin pressure. The "ABCs" initiated at the dive site should be continued while in transport.

Treatment in the chamber. The treatment of choice for decompression illness, whether DCS or AGE, is recompression in a multiplace, hands-on chamber. It should have the capability of locking personnel and equipment in or out with trained attendants available for critical care monitoring.

Multiplace chambers. These units (Fig. 1) can accommodate between 2 to 18 patients, depending upon configuration and size. They incorporate a minimum pressure capability of 6 atmospheres absolute. Patients are accompanied by hyperbaric staff members, who may enter and exit the chamber during therapy via an adjacent access lock or compartment. The multiplace chamber is compressed on air and patients are provided with oxygen via an individualized internal delivery system. A dedicated compressor package and high volume receivers provide the chamber's air supply.

Advantages include constant patient attendance and evaluation (particularly useful in treating evolving diseases such as decompression sickness), and multiple patients treated per session; disadvantages include high capitalization and staffing costs, large space requirements and risk of decompression sickness in the attending staff.

Duoplace chambers include the Reneau (Proteus) and the Sigma II with pressurization capabilities to 6 ATA and 3 ATA respectively. The chambers are compressed with air, and the patient breathes oxygen by an individualized internal delivery system. Advantages include constant patient attendance, with access limited to the head and neck; disadvantages include relatively high capitalization cost for single patient treatments and risk of decompression sickness in the attending staff.

The multiplace chamber is not always possible, however, and the monoplace chamber is sometimes the only alternative. Hart and coworkers, as well as Kindwall and colleagues have developed protocols with the monoplace chamber, utilizing Navy Treatment Table 6  which can be used with air breaks.

Monoplace chambers. These units, first introduced in the 1960s are designed for single occupancy. They are constructed of acrylic, have a pressure capability of 3 atmospheres absolute and are compressed with 100% oxygen. Recent technical innovations have allowed critically-ill patients to undergo therapy in the monoplace chamber. The high flow oxygen requirement is supplied via the hospital's existing liquid oxygen system.

Advantages of this chamber include that it provides the most cost efficient delivery of hyperbaric oxygen (capitalization and operating costs), and that it presents essentially no risk of decompression sickness to the attending staff. Disadvantages include relative patient isolation and increased fire hazard.

Treatment goals in all instances are to reduce bubble size and surface area while providing hyperbaric oxygenation (HBO). HBO reduces edema, blocks WBC adherence, protects and preserves the microcirculation, corrects hypoxia (100% oxygen under pressure produces 7 volume % in the plasma), blocks reperfusion injury, and facilitates the removal of dissolved gas from the lungs through perfusion.

Outcome. The most recent DAN (Divers Alert Network) report (1994 data) suggests that complete resolution of symptoms occurred in only 56% of cases while 28% of divers had neurologic sequelae and 17% continued to experience pain. Travel after treatment of DCS should be delayed for at least 48 hours; 72 hours for arterial gas embolism. Recurrence of symptoms has occurred with flying more than one week after the initial event. Diving should not be resumed if there is any residual neurological damage.

Treatment. Decompression sickness is treated with recompression in a chamber to 60 FSW or deeper associated with hyperbaric oxygen breathing. In the US, this therapy is usually guided by a Navy Treatment Table. These tables are very effective, especially when recompression is begun promptly.

The purpose of the therapy called for in the Navy Treatment Tables is two-fold: to promote inert gas elimination and to help cause a decrease in bubble size. The treatment outlined by the tables also provides oxygen to the damaged tissues, treats platelet and clotting damage and allows excretion of harmful metabolites. The oxygen reduces CNS edema and provides a high oxygen gradient (2000 mm Hg) for the ischemic tissues.

Specifics: Recompression treatment of decompression sickness. First, it is important to take the time for a careful clinical exam, because true Type I DCS without other manifestations is very rare, and diagnostic tests are of little value.

The initial therapy for Type I and Type II DCS is treatment in a chamber with Navy Treatment Table 6. Table 6 indicates recompression to 60 feet for 285 minutes, with intermittent oxygen breathing periods and slow "ascent to the surface." (The diving tables indicate increases in pressure with the word "descent" and decreases with "ascent." They also give their pressure values in depth-equivalents.) The periods of oxygen breathing are broken up into intervals to prevent O₂ toxicity. If O₂ seizures occur, turn off the O₂ for 15 minutes and continue the treatment.

In the case of poor response to standard Navy Treatment Tables 6A or 6, Treatment Table 6 can be extended for additional oxygen breathing periods at 60 or 30 feet. If you are following Treatment Table 6A and there is no resolution or the patient is getting worse on ascent, try Treatment Table 4, which indicates staying at 165 feet for 2 hours--then go to Table 6 at 60 feet with extensions, if necessary.

Treatment Table 7 is used for worsening or unresolved DCS or AGE. It is a long, involved and dangerous treatment and should not be used unless adequate support is available. If all else fails, call Divers Alert Network (DAN) at (919) 684-8111, rather than creating your own treatment table.

Even after "successful" treatment, some people experience relapse of symptoms. Recurrences are treated with Treatment Table 5 or Treatment Table 6 once or twice-daily until no further improvement is observed by the medical director of the facility. Recent evidence indicates that persistent neurologic defects may be lessened by repetitive treatments on Navy Treatment Tables 5, 6 or even with 100% oxygen at 30 FSW for 90 minutes bid. Flying should be avoided for a period of 72 hours after treatment for DCS or AGE.

Equipment which might be needed in the altered pressure environment includes ventilators, bubble traps and pumps for use with intravenous catheters, endotracheal tube cuffs which inflate with water, and if chest tubes are required, the patient must be vented during descent using #18 gauge 1 1/2 " needle.

Treatment of Arterial Gas Embolism

Treatment. Management is generally similar to that of DCS--recompression and HBO are indicated in all cases as quickly as possible.

Specifics: Recompression treatment of gas embolism. In contrast to the treatment of decompression sickness, one should not delay for diagnostic work-up or extensive clinical evaluation. Instead, the first question is whether to use Treatment Table 6A or 6. If there is a delay greater than 4 hours, Treatment Table 6 should be used initially and then proceed to 6A depending on the clinical response. Treatment Table 6A allows for rapid compression to 165 feet and is used for major air embolisms. If such a chamber is not available, then one should use a 3 ATA chamber.

For those patients not responding to Navy Table 6, other choices are available: US Navy Table Treatment 4 or the Comex Table, which prescribes 30 minutes breathing 50/50 O₂/N2 mix at 100 feet. Unproven treatment schedules should be avoided, but extensions to the tables are not experimental and should be used as necessary.

Special Considerations (Difficult circumstances)

1. Diver at 165 feet (50 meters) not responding to 6A, or getting worse on decompression:

a. Continue on USN 4 (165 ft air+oxygen) for 2h at 165 feet to 60 ft. and then on extended 6. (Unproven).

b. Duke oxy-nitrogen saturation (Lancet, 7/22/1978)

c. 50 % oxygen by mask while at 165 ft.
 
 

2. Patient at 60 ft. (18 m.) not responding to maximum oxygen or deteriorating on decompression.

a. Continue on air (with additional oxygen sessions) at 60 ft. and decompress on saturation table. (USN 7)

b. Compress to 100 ft. (30 m.) on 50% oxygen, Comex Table CX 30.

c. 100 ft and onto the Duke regimen.
 

Other Considerations

USN 5 (for 'pain only') is no longer recommended in commercial diving. This is due to the overlooking of serious symptoms. This is replaced by USN 6 in many schedules.

Cases from oxy-nitrogen bounce diving should be treated as though from compressed air. Cases from oxy-nitrogen saturation diving should be treated as oxy-helium saturation.

Residual manifestations- Table 6 daily, or CX 12 or pO2 1.7 bar. Continue for as long as there is subjective improvement, with a maximum of ten sessions.

Treatment of Tri-mix or oxy-helium decompression illness

Never use compressed air tables

1. Bounce diving, onset at surface: Table 6 using oxy-helium in place of air. Continue down to depth of significant relief with chamber pO2 0.4 bar. If a blow up, consider recompression to 3 bar greater than depth of the dive. Use oxygen rich oxy-helium (pO2 1.5 to 2.5 bar) mixtures by mask intermittently at depth for 2 hours. Decompress without an initial upward excursion but on a saturation table.

2. Bounce diving - onset during decompression: Immediate compression to depth of relief or full depth of the dive, if necessary. Otherwise treat as in 1. above.

3. After downward excursion in saturation diving - Compress to depth of relief, possibly depth of excursion but not less than three bar. Remain at treatment depth at least 2 hours, or 24 hours if needed. Use saturation decompression with no upward excursion.

4. Onset during saturation decompression - Compress slowly to depth of relief but by not more than 2 bar (for pain) or 3 bar (for serious) deeper than depth of onset. Remain 2 hours to 6 hours wit up to 6 intermittent periods of breathing oxygen rich mixtures for 20 minutes each.

The condition of the patient should determine the rate of decompression.

References:

Decompression Problems
Decompression Sickness: Definition and Early Management
Decompression Sickness: Part I
(Treatment Tables)
Decompression Sickness: Part II
(Treatment Tables)
Diving Accident Management
First Aid for Diving Accidents Requiring Immediate Transport

Translate...FrenchGermanItalianPortugueseSpanish