For a long time, the medical community did not support IWR, and there are indeed risks involved. However, documented IWR accident reports are incredibly rare. (If you find any, please share them with us.) While there is limited statistical data on the dangers of IWR, it is statistically safer than riding a motorcycle. This quiz aims to inform you of the risks so that you can make an educated choice.
Caution & Risk Mitigation
DCI can cause a patient to lose consciousness during a treatment dive. Furthermore, when breathing pure oxygen, the patient may suffer from convulsions due to central nervous system (CNS) oxygen toxicity. For these reasons, IWR is best conducted using a full-face mask under the guidance of a diving physician.
The onset of oxygen toxicity is often preceded by these warning signs:
- Visual disturbances; blurry vision or tunnel vision,
- Ringing in the ears (tinnitus)
- Nausea
- Muscle twitching, particularly around the mouth and hands
These warning signs require the patient to switch back to air and ascend immediately.
Note for the support diver: If you must bring up an unconscious or convulsing diver, the absolute priority is to keep their airway open during ascent to prevent a lung over-expansion injury. Additionally, keep your fingers on their regulator to reduce the chance of it dislodging.
Further Technical Challenges
- The oxygen tank has no regulator: If there is no regulator available for the oxygen tank, it is possible to breathe directly from a free-flowing tank. This takes practice; attempt it slowly and use common sense. If you are uncomfortable placing your mouth close to the metal valve, you can use a snorkel tube (with the mouthpiece removed) to direct the flow. The flow rate required to breathe from a continuous flow is roughly 50 liters per minute. Alternatively, you can open the valve only at the moment of inhalation. While this increases task loading, it conserves oxygen and buys extra time if your supply is limited. (Reference: Lake Victoria Uganda IWR training /India pool training / Zambia free flow breathing )
- Thermal management: The diver can get cold quickly. One solution is to run a nearby outboard engine and feed the warm cooling-water discharge through a hose directly into the diver's wetsuit.
- Hydration: The diver must hydrate. Juice pouches are easy to consume underwater, which is an excellent skill to practice. Offer the patient drinks regularly from the start of the treatment, even if they do not ask for them.
- Nutrition: During longer treatments, the diver will need sustenance. Bananas are easy to eat underwater and are worth practicing with.
- Communication: Pencils can be used to write on plastic yogurt cups or plastic cutting boards.
- Boredom: Long treatments can lead to boredom. You can send down laminated reading material or practice underwater yoga postures. Moderate movement is actually beneficial for off-gassing.
- Regulator retainer: A diver might lose their regulator during a convulsion. To prevent this, a regulator retainer can be tied to hold the regulator securely in the mouth. This is most effective if a gas switch-block is installed, because if a convulsion occurs, the patient must immediately switch from oxygen to standard air. Test your regulator retainer by putting it on and shaking your head vigorously to simulate a convulsion.
- In-water elimination: For those who have never defecated in the water, it is highly recommended lto practice the process so it does not cause excessive stress during an actual emergency treatment. If the water temperature allows, the wetsuit can be removed temporarily. If it is too cold to do so, the diver must use the suit and manage the cleanup afterward. Drysuit divers are advised to use adult diapers.
- a Neurological Examination before the IWR can show additional symptoms that otherwise would go unnoticed. After the IWR this examination can get repeated to take note of the differences.
The Divers Alert Network (DAN) specializes in assisting divers in distress. Their insurance plans offer peace of mind regarding the financial side of DCI treatments. However, even if you do not have insurance, you are always welcome to call them if you or your buddy exhibit symptoms of decompression sickness.
Benefits of IIWR
You can begin treatment almost immediately after experiencing the first symptoms of DCI.
- Autonomy: You maintain personal control over your treatment protocol.
- Low cost: Financial barriers are minimized.
- Preventative use: You can use it preventatively. For example, if you feel a minor itch and suspect it might be mild DCI, you can treat it immediately. Divers are often reluctant to report minor symptoms if they feel pressured into a lengthy, costly, and embarrassing chamber treatment. Because IWR is technically just another dive, you can finish the protocol and go home a few hours later.
The Training Scenario
In this quiz, we will prepare for the following scenario:
You are a group of four IIWR-trained dive buddies. After a dive, one of your buddies exhibits signs of decompression illness (DCI). Because there is no medical facility nearby, the patient and a safety buddy decide to descend to 4 meters for IIWR, where the patient begins breathing 100% oxygen for immediate relief. In the meantime, you contact DAN, and after careful consideration, the on-duty dive physician advises you to execute the Australian In-Water Recompression Table.
