The Bends Part 3

By Dennis Guichard with edits by Dr Frans Cronje

The very pinnacle of sub-sea and hyperbaric medicine rests with the hyperbaric physicians who practise it daily, treating chronic wounds and urgent maladies. There are no easy clinical tests that can confirm decompression sickness (DCS), and so it is often the incredible lifetime-gained talent and experience of the hyperbaric physicians whom we rely on to make a sound clinical judgement in prescribing an adequate course of treatment to ensure our well-being.

Dr Craig Springate is the attending physician at the Netcare St Augustine’s Hospital Hyperbaric Medicine and Wound Care Unit in Durban, South Africa, assisted by Hyperbaric Manager and Medic Chad Katz, his two most charming and good-humoured assistants, Sharon, and Debbie, as well as a host of amazing chamber attendants who freelance their time as demands require.

Fortunately, DCS seems to be rare, occurring at less than perhaps 2 cases per every 10,000 dives whilst cold water diving and deep technical decompression diving risks can be substantially higher at as many as 28 cases per 10,000 dives.

However, a concern worldwide is that mild cases may often not be reported, so the real picture of DCS risk and occurrence may be well understated.

DCS is related to the individual physiological response of any diver to any specific dive profile and resultant bubble loading. We are each quite bio-individual, so the risk is different and individualised for each of us. A dive profile that might be 'safe' to one diver might be 'risky' to another not just because of the profile itself but also because of our physiological state and variable predisposing risk factors on any given day.
 
Frequently we might even experience mild symptoms of DCS and brush them off, conveniently losing ourselves in denial, when the risk, however, is that mild symptoms can often progress into something more serious that can have residual impact.

Skin bends are a distinct manifestation of decompression sickness that can start with intense localised itching of the skin, followed by the development of its distinctive reddish blue mottling appearance. The condition can cause hypovolemic shock requiring extensive IV fluid administration (not unlike a burn wound), resulting from capillary leak syndrome, reduced blood flow, and impaired oxygen delivery to skin tissues, triggering inflammation secondary to the development of intravascular bubbles after provocative dive profiles.
 
Livedo Racemosa (skin bends) is almost always directly associated with the existence of a significant PFO/Patent Foramen Ovale (hole in the heart) in the patient diver, which can often be confirmed with contrast echocardiography by a qualified specialist. The condition has incorrectly long been considered a 'mild' form of decompression sickness. However, it is now more widely respected for the very serious condition it is that can often even be life-threatening.

The time from surfacing to the presentation of symptoms can often be a good rule-of-thumb indicator for the likely severity of the bend - the sooner the signs, the more likely the severity of the hit. There is a significant correlation between the severity of DCS and the resultant outcome for recovery often with persistent deficits after completion of treatment for neurological DCS.  

Primary first aid offered by dive leaders is critical in the treatment process through the administration of 100% oxygen at 15lt per minute flowrate via a non-rebreather face mask and the administration of fluids. It is also thus critical that all dive leaders are suitably trained and equipped in the recognition and treatment of DCS first aid and always call the DAN helpline (phone: +27 82 810 6010 in South Africa) to get reputable guidance on any suitable course of action.

There is a hypothesis that historically suggested that Aspirin might be protective against the progression of DCS by inhibiting platelet adhesion (clotting) on vascular microbubbles but the risks for worsening serious neurological manifestations through central nervous system bleeding in the brain or spinal cord, now widely rule out its administration unless prescribed as such by a hyperbaric physician.
 
In milder pain-only or joint cases of DCS, the success of treatment is generally measured by the resolution of symptoms in the chamber, so the administration of any form of analgesia (Aspirin, Paracetamol, etc.) may also interfere with the ability of the hyperbaric physician to assess healing. 
Steroids can sometimes be helpful in the clinical setting for reducing tissue oedema (fluid retention), ischaemia (insufficient blood supply and tissue oxygenation), and intravascular platelet aggregation but are generally not recommended to treat DCS.

Heparin can sometimes also likewise be prescribed by the hyperbaric physician as an anticoagulant for immobile or paralysed cases of severe neurological DCS.

Lidocaine can sometimes be helpful in severe cases of neurological decompression sickness because of its anti-inflammatory effect, although there is arguably insufficient clinical evidence to encourage its use. The hyperbaric physician can sometimes prescribe tenoxicam to resolve pain because of its anti-inflammatory benefits.

For 'mild' cases of pain-only joint or musculoskeletal decompression sickness, US Navy Treatment Table 5 can sometimes be specified by the hyperbaric physician in a twin-lock multi-place hyperbaric chamber. Table 5 is one of the shorter treatments lasting only 2-hours and 15-minutes; however, the risk with DCS is that what might initially present as 'mild' clinical symptoms can often progress into more serious neurological complications.

A quick Treatment Table 5 protocol may not always be sufficient to alleviate a need for ongoing repetitive chamber visits with decompression sickness that can sometimes persist in playing up with recuring sequela, so the default for hyperbaric physicians is often to opt for the more extended Treatment Table 6 instead, which lasts 4-hours and 45-minutes.

There is an endless suite of treatment tables available to any hyperbaric physician developed by the US Navy, British Royal Navy, COMEX, French Navy, Russian, German, and others. Specific tables get used depending on the clinical presentation of symptoms as well as in response to how patients recover during those treatments.
 
In South Africa, we have SAUHMA-accredited mono-place hyperbaric chambers available in Pretoria, Johannesburg, Cape Town, and Bloemfontein, with larger multi-place chambers in Durban and Port Elizabeth. The Simon's Town Naval Hyperbaric Facility, and the Institute for Aviation  Medicine in Pretoria, also have multi-place chambers available, although for military patients only.

There is often a risk that symptoms can wax and wane, so it can be challenging to establish a fixed endpoint of treatment, especially when a percentage of serious DCS cases can result in residual symptoms that might never completely heal. The successful outcome of treatment is often related to early recognition of signs and symptoms, the initial severity score of the bend, the initiation of adequate on-site first aid by the dive leader, and swift evacuation to a hyperbaric chamber facility following the DAN Helpline guidance.
 
The hyperbaric physician is a critical key in the swift treatment of decompression sickness, identifying what medication might best ensure the ultimate residual outcome, patient comfort during treatment, and which hyperbaric Treatment Table might best treat the disorder.

Dennis Guichard is a multi-agency qualified Scuba Instructor Trainer and a DAN ‘Master Dive Pro’ member. He is qualified as an offshore saturation medic and a Hyperbaric Technologist freelancing as a chamber operator and attendant at the Netcare St Augustine’s Hospital Hyperbaric Medicine and Wound Care Unit, Durban, South Africa.