Treatment Protocols

Oxygen, when breathed under increased pressure, is a potent drug. Besides the beneficial effects discussed above, hyperbaric oxygen can produce noticeable toxic effects if administered indiscriminately. Safe time dose limits have been established for hyperbaric oxygen exposure, and these profiles form the basis for today's treatment protocols. It is only quite recently that disease-specific hyperoxic dosing has been introduced.

Emergency cases, such as carbon monoxide poisoning or cerebral arterial gas embolism may only require one or two treatments. In those cases for which angiogenesis is the primary goal, as many as 20 to 40 treatments may be necessary. The precise number of treatments will often depend upon the clinical response of each patient. Transcutaneous oximetry can provide more exacting dose schedules, thereby improving cost effectiveness.

With the exception of decompression sickness and cerebral arterial gas embolism, periods of exposure last approximately two hours. Treatments may be given once, twice or occasionally three times daily, and can be provided in both inpatient and outpatient settings.

Therapeutic Tables (Treatment Tables)

These tables are used in HBO therapy. Duration and depth calculated, bearing in mind CNS and pulmonary oxygen toxicity and the inadvisability of giving the inside attendant DCI. All Hyperbaric Medicine Units have their own, although some are common to all, e.g. Table 62 (USN 6). At Descend the attendant breathes oxygen during all ascents. Each treatment table (except RN61 and RN62) IS IDENTIFIED BY A SERIES OF NUMBERS e.g. 18:120:36

18 denotes the treatment depth in metres of sea water (msw)
120 denotes the time in minutes from commencing the descent to commencing the ascent
36 denotes the time in minutes needed to ascend to the surface.

The Treatment Tables currently in use are:

How often are HBO Treatments Given?

Once started treatments are usually given on a daily basis.

How are Treatments Given?

Patients are placed into a hyperbaric chamber. The chamber allows patients to sit or recline during treatments. Visual observation from inside and outside the unit is available through viewports or windows.

Communication is maintained to the chamber via an intercom link.

Patients are allowed to read books or magazines, relax, listen to music, or even sleep while being treated.

Medical personnel may accompany patients during the treatment.

A typical patient treatment schedule would be 90 minutes of oxygen at the prescribed pressure, but the length of treatment, depth (or amount of pressure), and the number and frequency of treatments vary according to the condition of the patient being treated. Usually, four to 24 hours will be allowed between treatments.

What Can Be Taken Into The Chamber?

Air is used as the compression medium for the chamber, so there is some latitude in patient amenities. Surgical dressings need not be removed for treatment to proceed. Petroleum-based ointments may need to be covered with gauze.

Because 100 percent oxygen is in use during the treatment, however, safety precautions must be observed for the patient's protection. Certain items, therefore, cannot be taken into the chamber. Among them are lighters or matches, cigarettes, nylons, wigs or hairpieces, petroleum jelly, ointments, hearing aids, watches, makeup, lipstick or lip balm, hairspray, hair oil or relaxers, synthetic fabrics, or hard contact lenses.

Because the vasoconstricting effect of nicotine interferes with neovascular proliferation, patients are not aloud to smoke during the entire course of HBO therapy. Smokers also have a higher CO level than nonsmokers, and thus fail to receive the full benefit of oxygenation, even when not in the hyperbaric chamber.

Current Indications for Hyperbaric Therapy

The following is based on the recommendations of the Undersea and Hyperbaric Medical Society Committee report of 1991.

Accepted Indications

• Decompression illness
• Cerebral Arterial Gas Embolism
• Carbon Monoxide poisoning
• Clostridial myonecrosis
• Osteoradionecrosis
• Chronic Refractory Osteomyelitis

Experimentally Supported Indications*

• Thermal burns
• Problem wounds (esp. diabetic)
• Other myonecroses (e.g. Fourniers gangrene)
• Comprised flaps and grafts
• Macular oedema
• Cyanide poisoning
• Soft tissue Radionecrosis
• Brain Injuries
• Xerstomia

*For these conditions, there is increasing experimental and some clinical evidence of efficacy which as yet falls short of universal acceptance as being indications for HBO.

Possible Side Effects

As with any treatment, side effects are possible. They are, however minimal. The most common is barotrauma to the ears and sinuses caused by pressure changes.

Patients are taught autoinflationary techniques techniques to promote adequate clearing of the ears during treatment. Decongestants may be helpful. This problem is temporary and resolves when HBO treatment is completed.

If the patient has ear pain or is unable to clear his or her ears the insertion of myringotomy tubes may be necessary before the treatment continues.

Other side effects are more rare.

Oxygen toxicity can cause CNS and pulmonary effects. Seizures occur rarely during treatment and are self-limiting.
Seizures will cease when the patient is removed from breathing the pure oxygen.

Factors such as history of seizures, high temperature, acidosis and low blood sugar are taken into account before treatment is begun.

Pulmonary oxygen toxicity may occur in patients who require supplemental oxygen between treatments. This is very rarely seen with the limited number of treatments currently used.

Some patients may suffer claustrophobia. This is managed by maintaining communication, use of relaxation techniques and mild sedation, if necessary. Rarely, patients develop temporary changes in eyesight; these are minor and occur only in those individuals who have large numbers of treatments.

Patients with cataracts may experience accelerated maturation of the cataract, but the treatments do not cause cataract formation.

Contra Indications of Hyperbaric Oxygen Therapy

Asthma
Small airway hyper-reactivity may result in air trapping and pulmonary barotrauma on ascent. A decision to treat such patients should not be undertaken lightly, particularly in light of evidence that the administration some brochodilators may increase the incidence of cerebral arterial gas embolism through pulmonary vasodilatation.

Congenial spherocytosis
Such patients have fragile red cells and treatment may result in massive haemolysis.

Cisplatinum
There is some evidence that this drug retards wound healing when combined with HBO.

Disulphiram (Antabuse)
There is evidence to suggest that this drug blocks the production of suproxide dismutase and this may severely effect the body's defences against oxygen free radicals. Experimental evidence suggest that a single exposure to HBO is safe but that subsequent treatments may be unwise.

Doxurubicin
(Adriamycin). This chemotherapeutic agent becomes increasingly toxic under pressure and animal studies suggest at least a one week break between last dose and first treatment in the chamber.

Emphysema with CO2 retention
Caution should be exercised in giving high pressures + concentrations of oxygen to patients who may be existing on the hypoxic drive to ventilation. Such patients may become apnoeic in the chamber and require IPPV. In addition, gas trapping and subsequent lung rupture are associated with bullous disease.

High Fevers
High fevers (> 38.5 deg.C) tend to lower the seizure threshold due to O2 toxicity and may result in delaying of relatively routing therapy. If patients are to be treated then attempt should be made to lower their core temperature with antipyretics and physical measures.

History of middle ear surgery or disorders
These patients may be unable to clear their ears. Or risk further injury with vigorous attempts to do so. An ENT consult for possible placement of grommets is usually wise.

History of seizures
HBO therapy may lower the seizure threshold and some workers advocate increasing the baseline medication for such patients.

Optic Neuritis
There have been reports in patients with a history of optic neuritis of failing sight and even blindness after HBO therapy. This complain would seem to be extremely rare but of tragic consequence.

Pneumothorax
A pocket of trapped gas in the pleura will decrease in volume on compression and re-expand on surfacing during a cycle of HBO therapy. During oxygen breathing at depth nitrogen will be absorbed from the space and replaced with oxygen. These fluxes of gases and absolute changes in volume may result further lung damage and or arterial gas embolisation. If there is a communication between lung and pneumothorax with a tension component, then a potentially dangerous situation exists as the patient is brought to the surface. As Boyles Law predicts, a 1.8 litre pneumothorax at 20 msw is potentially a 6 litre pneumothorax at sea level - certainly a life threatening situation. For this reason it is mandatory to place a chest tube to relieve a pneumothorax before contemplating HBO therapy. Particular care must be taken with patients who give a history of chest trauma or thoracic surgery.

Pregnancy
The fears that either retrolental fibroplasia or closure of the ductuc arteriosus may result in the foetus whose mother undergoes HBO appear to be groundless from considerable Russian experience. However, this unit continues to exercise caution in limiting treatment of pregnant women to emergency situations.

Upper Respiratory Tract Infections
These are relative contra-indications due to the difficulty such patients may have in clearing their ears and sinuses. Elective treatment may be best postponed for a few days in such cases.

Viral Infections
Many workers in the past have expressed concern that viral infections may be considerably worsened after HBO. There have been no studies to give convincing evidence of this and no reported activation of herpetic lesions associated with HBO.