Diver Treatment on the Fly: A Closer Look at Portable Hyperberic Chambers

By Andrew R. Mrozinski, RRT, DMT, CHT

Recently, there has been increased discussion concerning the importance of early recompression in effective treatment of decompression illness resulting from today's provocative technical diving exposures

Generally, the availability and proximity of recompression facilities to the dive site is essential in determining the advisability, safety, and conservatism of planned dives.

Early (immediate) recompression after a dive accident even if only minimal, may reverse life threatening symptoms and prevent offending nitrogen bubbles or "seeds of decompression sickness", from reaction with body tissues. This reaction initiates a series of localized responses, including tissue swelling, release of certain cellular chemical components and other immune and complement system reactions which result in worsening of symptoms that become more refractory to treatment.

If the planned diving activities suggest that early recompression will not be logistically/geographically available or that initial decompression problems might be life threatening due to the extreme exposure nature of dive planned, on site recompression capabilities may be advisable. On-site recompression capabilities may be advisable. On-site recompression, although an invaluable modality, is no simple endeavor. The costs of proper equipment and training usually require an organized group approach to the task. Legal issues of providing hyperbaric medical treatment may also need to be addressed on some dive operations, especially of conducted at domestic U.S. sites.

The objectives of the project must first be established. Currently, there are portable chambers available capable of variable levels of care ranging from initial hyperbaric oxygen first aid to definitive complete treatment of the injured diver.

The training capabilities of the care givers must also be well defined and practical. Most manufacturers offer hands on training with their units and more advanced training; sanctioned by the Undersea and Hyperbaric Medical Society (UHMS) and other organizations are also available. Such training should be augmented by at least a basic first responder or EMT level of understanding of emergency patient care to be effective. The following is brief review of some of the commercially available portable chambers, from simple too more advanced designs.

Remember, to fulfill the definition of hyperbaric oxygen therapy, the unit must be capable of providing 100 percent oxygen to the patient while the patient's entire body is exposed to elevated atmospheric pressure.

Usually the chamber fills with air while the patient breathes 100 percent oxygen. The treatment should never provide for air breathing only as symptoms would return and worsen after treatment.

Additionally, the transfer under pressure pf the stricken diver by air or land may be regulated by applicable laws. This depends on the pressure vessels manufacturers certification. The plan to treat on site, or during transport, must be established. The plan may call for an initial treatment on site, then transfer on surface oxygen, depending on regulations, or patient condition. Transfer under pressure also involves additional risks from movement/trauma of pressurized vessel during transport. Gas supply requirements of the vessel need to be appropriate for the projected duration of use. Recirculation or scrubbing (cleansing) of chamber air and patient therapy gas (oxygen) is an ideal but expensive way to conserve a gas supply. Most units are scuba cylinders filled with air to provide a gas supply for compression and are attachable to the unit for transport.

The Chamberlite 15, from MRG International, is probably the simplest and one of the lightest units on the market. It is capable of providing 100 percent oxygen at 2 to 2.4 ata pressure with special adapters. This unit is constructed of foldable polyurethane, has ten viewing ports and weighs less than forty pounds thus making it highly portable by standard stretcher or two person carry. It is priced at $20,000US and is considered a first aid rather than definitive treatment chamber by its manufacturer. It seals by use of a specially designed zipper rather than removable end plates as the next unit uses.

Another unit is the Hyperlite chamber, a foldable unit that is made of Para-Armid fiber (Kevlar) and is capable of a full standard treatment depth of 2.82 ata pressure. This unit has similar gas supply equipment as described above with a slightly more sophisticated control mechanism. The unit can accommodate on site treatment using accepted U.S. Navy Treatment tables. This is a heavier duty unit weighing in at 165 lbs. complete and is pricier at about $40,000US. This unit has been favorably tested by Lloyds Register (UK) and has provisional engineering structure approval in the US. The Hyperlite is manufactured in the United Kingdom by SOS Limited.

The Hyperbaric BackPack is a new design from Italy's GSE. It is a 30-inch interior diameter, 7-foot long chamber, which weighs in at 92 pounds. The door frame and door are made of aluminum. The body consists of a double bag of translucent composite polyester, which allows light in to the diver. The inner bag forms the seal, and the outer bag of courser weave, gives it overall strength. The BackPack folds down to about one-foot thick when collapsed. It has two view ports, with four additional ones an option. It is specified for 6 ata (165 fsw) which is the maximum treatment depth specified in the US Navy tables. The chamber, however, has been successfully tested to 60 atmospheres. The 30 inch basic unit is priced at $15,000US. A 40 inch is also available at 24,500US. Other options include pressure locks for entrance and exit of medical personnel and for passing food and drink to the diver. J.B. Hughes and Associates represent the unit in the US.

Marine Dynamics has been making decompressing chambers since 1965 and offers a 42-inch double-lock chamber that contains two compartments in an all-steel welded tank. Of interest to the cost conscious tech divers, this unit alone among those researched, can be rented. It has two 26 I.D. doors, o-rings seals, two sound powered phones, three 8-inch I.D. acrylic view ports, and is rated to 7.8 atmospheres, 100 psi. The doors are self-sealing and self adjusting. Priced at an attractive $13,000US the unit has the drawback of weighing 3,500 pounds.

The final unit is called a paracel and resembles a smaller portable stainless steel version of the standard hospital chamber. This unit actually has capabilities that exceed what most hospital chambers can achieve. It has full structural integrity and is certified to 6.5 ata (180 fsw) pressure. This unit conforms to the size and weight limitations required for transport in many fixed wing and twin jet helicopters and it has an optional entry lock allowing transfer of medical personnel in and out while maintaining treatment lock chamber pressure. This unit has considerable commercial diving and hospital clinical application due to its sophisticated design. This two person chamber allows for care of the critically ill, intensive care, ventilator patient which is not usually possible in a single occupant chamber where hands on care is not possible. This unit is much more expensive, but can perform up to the capabilities of even the most experienced/expert hyperbaric staff and may be practical for commercial, clinical, and regional sport diving operations. Manufactured in Australia by International Innovations Limited and is available in the US though Oxycare Inc.

In conclusion there are many camber designs available throughout the world, but these designs describe the range of features, capabilities and cost that are offered. Currently, the standard of care does not require on site recompression for diving injuries.

However, as we venture further from medical facilities, deeper into the depths and into more exotic gas mixtures we may find a benefit to immediate, access to onsite recompression as part of the dive plan.

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