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A1 A hyperbaric stretcher is a folding portable pressure vessel suitable for the pressurisation and transport under pressure of a person requiring hyperbaric oxygen therapy (HBO). It is rigid when inflated, but when not in use, can be packed away for easy portability.

Q2 What is the purpose of a Hyperbaric Stretcher?

A2 The presence of a hyperbaric stretcher at an accident or emergency site enables a casualty requiring hyperbaric oxygen therapy (HBO) to be treated as soon as the first symptoms of the requirement become apparent. The importance of immediate treatment of diving accidents cannot be over-emphasised. Delay in treatment greatly reduces the likelihood of full resolution.

Due to the lightness and portability of a hyperbaric stretcher, it is almost always possible to have a unit on site, irrespective of the whereabouts of the incident, whereas to have a larger therapeutic chamber available on site is often logistically not possible.

Note: 1 bar = 10 msw = 33 fsw. At sea level the pressure is 1 atmosphere absolute (ATA) which is just over 1 bar (1.3% over). Chamber/stretcher pressures in hyperbarics are usually measured in metres (or feet) seawater and are assumed to be above 1 atmosphere, ie the depth of seawater. Remember that with a hyperbaric stretcher, you may not be at sea level and therefore it is more correct to consider absolute pressures when referring to therapies.

Q3 To what pressure does a hyperbaric stretcher need to be capable of operating?

A3 A hyperbaric stretcher should be capable of operating to a pressure of at least 1.8 bars above ambient pressure. Above 3 bars absolute pressure (2 bars above atmospheric pressure at sea level), pure oxygen becomes toxic very quickly. Furthermore, at 3 bars absolute pressure or above, one cannot remove the patient from the hyperbaric stretcher in an emergency, without life threatening consequences.

Q4 Are higher pressures never required in the treatment of diving accidents?

A4 Initial treatment therapies for diving accidents are normally conducted at 2.8 bars absolute. If resolution does not take place, then the patient may be subjected to higher pressures when transferred into a therapy chamber where full hands-on medical care is available.

Q5 Why does the Hyperlite have a maximum working pressure of 21msw (69 fsw)?

A5 When the Hyperlite is to be used in reduced atmospheres, such as in an aircraft or at altitude, then the differential pressure between the inside and outside of the hyperbaric stretcher may exceed 1.8 bars. This has been allowed for in the design of the hyperbaric stretcher.

Q6 Some chambers have a flange attachment so that they may be mated to a therapy chamber? Does the Hyperlite stretcher have such a flange?

A6 The Hyperlite was designed with a diameter (585 mm 23 in) small enough to enable it to fit through the door of almost any therapy chamber. A lock-on flange therefore is not required on the unit.

Q7 What tests have been carried out to prove the Hyperlite’s durability?

A7 The hyperbaric stretcher has been subjected to the following tests:

1. Hydrostatic Burst Tests:
The hyperbaric stretcher fails on average at 14.7 bars, 147 msw, 483 fsw), giving a safety factor in excess of 6:1.

2. Drop Test:
The hyperbaric stretcher was weighted with an internal litter and 90 kg. (200 lb.) of bagged water and dropped at an angle of 45 degrees on to a rough concrete surface from 3 feet (90cms) above the ground. No damage or pressure loss took place.

3. Cyclic Test:
The hyperbaric stretcher was cycled 17,000 times from atmospheric to maximum working pressure. It did not fail.

4. Folding Tests, Hot and Cold Storage and Inflation Tests, Solar Radiation and Salt Fog Resistance and Vibration Tests have been satisfactorily tested by the Defence Research Agency, Alverstoke UK for the Ministry of Defence UK, and/or by the Wyle Laboratories in Huntsville AL on behalf of the US Navy and US Air Force, who are accepting the Hyperlite as being suitable for military application.

Q8 To what Quality Standard are Hyperlite's built?

A8 All Hyperlite's are built to the BS EN ISO 9001 Quality Standard, covering both design and manufacture. This is the highest international standard attainable.

Q9 Is the Hyperlite supplied with a warranty?

A9 The Hyperlite is supplied with a full one-year warranty covering materials and workmanship. Each hyperbaric stretcher is built either to Lloyd's Register Rules and Regulations and/or to the ASME PVHO-1 Standard. It is a requirement that training be given to Hyperlite Operators. Use by unqualified personnel may invalidate the Warranty

Q10 How is the Hyperlite tested prior to delivery?

A10 In addition to quality control and visual inspections at all stages of manufacture, each Hyperlite is pressurised to 1.5 times the maximum working pressure for one hour. All testing may be witnessed by the purchaser's representative.

Q11 How is the Hyperlite protected from over-pressurization?

A11 The Hyperlite has an emergency blow-off valve set at 23 msw (75 fsw).

Q12 How do you ensure that the operator does not make wrong connections when assembling the Hyperlite?

A12 Each connection is different, either in size or type, so that no hose can be wrongly connected.

Q13 What material is used in the manufacture of the flexible tube to make it so strong and yet be so flexible?

A13 The Hyperlite flexible tube is made using para-aramid fiber. This is an extremely strong abrasion resistant material that is wound in a matrix of silicone rubber. The same fibers are used in the manufacture of bullet proof vests, conveyor belts, car tires, brake pads and other protective clothing.

Q14 Does the integrity of the Hyperlite tube suffer damage by folding?

A14 The tube is unlikely to suffer damage from repeated folding during its normal working life.

Q15 Does the Hyperlite tube suffer from being kept folded in the storage cases?

A15 No, silicone rubber will always resume its original shape, even after extended periods in the case. The manufacturer recommends however that the hyperbaric stretcher be removed every six months for a trial inflation.

Q16 Does the Hyperlite tube suffer from the effects of high or low temperature?

A16 The Hyperlite tube remains flexible and operational from -60C to 200C (-15F to 400F). The acrylic end domes should be kept below 40C (104F) in use. For patient comfort, the Hyperlite should ideally be kept below 29C (84F).

Q17 Can repairs be made to a damaged Hyperlite tube?

A17 The inner and outer silicone rubber walls of the tube are fully repairable, using the two part silicone rubber repair kit available from the manufacturers. Any damage to the fibres will need to be inspected by the manufacturer.

Q18 Can a patient be X-rayed inside the hyperbaric stretcher?

A18 By positioning the tube above the hyperbaric stretcher and the plate beneath the hyperbaric stretcher, any part of a patient can be X-rayed without loss of clarity. The intensity of dosage should not need to be increased.

Q19 Can the Hyperlite be used and carried at much lower pressures?

A19 It remains rigid and fully operational at pressures down to 3 msw (10 fsw).

Q20 Does the Hyperlite float?

A20 The Hyperlite will always remain buoyant when inflated, even with a large heavy casualty and all the services connected.

Q21 Could a patient suffer from claustrophobia in such a small unit?

A21 This is unlikely as the Hyperlite is supplied with two full diameter transparent domes giving the patient excellent vision from the unit.

Q22 How much air and oxygen is needed for a therapy?

A22 This will depend upon the pressures to which the Hyperlite will be are the responsibility of the operator and can easily be calculated.

Q23 Is patient monitoring possible inside the Hyperlite?

A23 Provided that the unit has been supplied with the correct penetrations and connections, full monitoring of the patient including ECG (EKG), EEG, BP, Pulse Oximetry, and IV sampling etc. are all possible.

Q24 What happens if the condition of the casualty deteriorates and a 'hands-on' situation becomes vital?

A24 This is a situation where the patient must be removed from the Hyperlite without delay. This can be done by fully opening the emergency vent in addition to the pressure exhaust valve. Even from maximum operating pressure, the patient can be de-pressurized in little over one minute.

Q25 If removal of a diving casualty from the Hyperlite becomes essential, will the return to ambient pressure bring back the 'bends'?

A25 Provided that the patient has been under pressure on oxygen for some time, it may well be that the nitrogen has already been flushed out of the system and the symptoms are unlikely to recur. The patient should however be re-pressurised as soon as possible.

Q26 Can the Hyperlite be carried on scheduled airlines or chartered aircraft?

A26 IATA regulations permit the carriage of the Hyperlite with a casualty in it aboard aircraft in emergency circumstances subject only to agreement with the Carrier. There are no formal restrictions concerning the carriage of air and oxygen cylinders for life support purposes in this situation.

Q27 Does the Hyperlite suffer from off-gassing?

A27 Other flexible chamber/stretcher manufacturers use polyurethanes (PU) for the pressure boundary of their units. The SOS Hyperlite is made with silicone rubber instead, which does NOT suffer from off gassing. (That is why it has so many medical applications). Off gassing is a very serious problem associated with PU’s and can last for a long period, especially if the PU is kept in a sealed container or restricted area.