HYPERBARIC OXYGEN THERAPY

Definition:

• Hyper" means increased and "baric" relates to pressure. Hyperbaric oxygen therapy (HBOT) thus refers to intermittent treatment of the entire body with 100-percent oxygen at greater than normal atmospheric pressures).

Mechanism of action:

• In the ambient atmosphere we normally breathe approximately 20 percent oxygen and 80 percent nitrogen. While undergoing HBOT, pressure is increased up to two times in 100% oxygen. In the Sechrist monoplace chambers utilized at our facilities, the entire body is totally immersed in 100-percent oxygen. There is no need to wear a mask or hood. This increased pressure, combined with an increase in oxygen to 100 percent, dissolves oxygen in the blood plasma and in all body cells, tissues and fluids at up to 10 times normal concentration—

high enough to sustain life with no blood at all (from 20% to 100% oxygen is a 5-fold increase.

A patient receives treatment in a state-of-the-art Sechrist Monoplace Hyperbaric Oxygen

Chamber.

Significant physiological mechanisms, which are activated as a result of hyperbaric oxygenation, explain the many therapeutic results of HBO

1. Hyperoxygenation:

• HBO physically dissolves extra oxygen into the blood plasma. The breathing of pure oxygen at three times normal pressure (3 A.T.A.) delivers 15 times as much physically dissolved oxygen to tissues as breathing room air. This promotes formation of new capillaries into wound areas, and sufficient oxygen tensions to meet the needs of ischemic tissues. Hyperoxygenation effects are useful in the treatment of anemias, ischemias and some poisonings.

2. Mechanical effect of increased pressure:

• Any free gas trapped in the body will decrease in volume as the pressure on it increases. With a threefold increase in pressure, a bubble trapped in the body is reduced by two-thirds. This reduction in gas volume has been successfully applied to air embolism and decompression sickness.

3. Mass action of gases (gas wash out):

• The flooding of the body with any one gas tends to "wash out" all others. This action occurs more rapidly under pressure than under ordinary conditions, and makes HBO an indicated treatment for carbon monoxide intoxication and acute cyanide poisoning.

4. Vasoconstriction:

• High pressure oxygen causes constriction of the blood vessels (without creating hypoxia) which decreases edema in injured tissues and secondarily decreases intracranial pressure. This effect is useful in burns, crush injuries and interstitial bleeding. It may also be effective in acute brain and spinal cord injuries.

5. Bacteriostasis:

• HBO inhibits the growth of a number of anaerobic as well as aerobic organisms. This effect also complements the improved action of host disease-fighting factors. It is useful in conditions where resistance factors are compromised such as dys-vascular conditions and disorders involving immunosuppression.

Mechanisms of action of HBOT, as they apply to wound healing

• 1) Greatly increases oxygen concentration in all body tissues, even with reduced or blocked blood flow;

• 2) Stimulates the growth of new blood vessels to locations with reduced circulation, improving blood flow to areas with arterial blockage;

• 3) Causes a rebound arterial dilation after HBOT, resulting in an increased blood vessel diameter greater than when therapy began, improving blood flow to compromised organs;

• 4) Stimulates an adaptive increase in superoxide dismutase (SOD), one of the body's principal, internally produced antioxidants and free radical scavengers; and,

• 5) Aids the treatment of infection by enhancing white blood cell action and potentiating germ-killing antibiotics.

Mechanism Clinical Application

Hyperoxygenation DCS/AGE CO poisoning Crush injury/compartment syndrome Compromised grafts and flaps Severe blood loss anemia

Decrease gas bubble size Air or gas embolism

Vasoconstriction † Crush injury/compartment syndromeThermal burns

Angiogenesis Problem wounds Compromised grafts and flapsDelayed radiation injury

Fibroblast proliferation/collagen synthesis

Problem woundsDelayed radiation injury

Leukocyte oxidative killing ‡ Necrotizing soft tissue infections Refractory osteomyelitisProblem wounds

Reduces intravascular leukocyte adherence

Crush injury/compartment syndrome

Reduces lipid peroxidation CO poisoningCrush injury/compartment syndrome

Toxin inhibition Clostridial myonecrosis

Antibiotic synergy Necrotizing soft tissue infectionsRefractory osteomyelitis

Uses of hyperbaric oxygen:

• Carbon monoxide poisoning • Decompression sickness (for example, a

diving injury) • Air or gas embolism • Bone infections (osteomyelitis) that have

not improved with other treatments • Burns • Certain types of brain or sinus infections • Gas gangrene • Necrotizing soft tissue infections • Radiation injury (for example, damage

from radiation therapy for cancer) • Skin grafts

CO poisoning

• (CO) poisoning, whether intentional or accidental, occurs when one inhales the colorless and odorless carbon monoxide gas. Despite improved awareness and sensory alarms, multiple deaths occur each year.

• CO binds to hemoglobin with 200 times the affinity of oxygen. CO also shifts the oxygen dissociation curve to the left (the Haldane effect), which decreases oxygen release to tissues. CO can also bind cytochrome oxidase aa3/C and myoglobin. Reperfusion injury can occur when free radicals and lipid peroxidation are produced.

• The treatment of CO poisoning with hyperbaric oxygen therapy (HBOT) is based upon the theory that oxygen competitively displaces CO from hemoglobin. While breathing room air, this process takes about 300 minutes. While on a 100% oxygen nonrebreather mask, this time is reduced to about 90 minutes; with HBOT, the time is shortened to 32 minutes. HBOT (but not normobaric oxygen) restores cytochrome oxidase aa3/C36 and helps to prevent lipid peroxidation.HBOT is also used to help prevent the delayed neurologic sequelae (DNS); treatment instituted sooner is more effective, Multiple papers describe controversial methods and conclusions about the use of HBOT for CO poisoning.

Decompression Sickness and Air Embolism

• Decompression sickness (DCS) refers to symptoms caused by blocked blood supply, damage from direct mechanical effects, or later biochemical actions from suspected bubbles evolving from inert gas dissolved in blood or tissues when atmospheric pressure decreases too rapidly.24,25 DCS can occur after scuba diving, ascent with flying, or hypobaric or hyperbaric exposure.

DCS can be broken down into the following 3 types:

• Type I involves musculoskeletal, skin, and lymphatic tissue, and often has accompanying fatigue.

• Type II includes neurologic systems (either CNS or peripheral), cardiorespiratory, audiovestibular, and shock.

• Type III DCS describes a syndrome that presents with symptoms that progress to a spinal deficit that may be refractory to recompression.

• The bubbles causing DCS also can injure vessel endothelium, which leads to platelet aggregation, denatured lipoproteins, and activation of leukocytes, causing capillary leaks and proinflammatory events.

• Hyperbaric oxygen therapy (HBOT) is used to diminish the size of the bubbles, not simply through pressure, but also by using an oxygen gradient. According to Boyle’s law, the volume of the bubble becomes smaller as pressure increases. With a change in 1.8 ATA, this is only about 30%. The bubble causing DCS is thought to be composed of nitrogen. When a tissue compartment is at equilibrium and then ascends to a decreased atmospheric pressure, nitrogen seeps out of blood, tissue, or both, causing a bubble. During HBOT, the patient breathes 100% oxygen, creating oxygen-rich, nitrogen-poor blood. This creates a gradient of nitrogen between the blood and the bubble, causing nitrogen to efflux from the bubble into the bloodstream, which, in effect, makes the bubble smaller.

Other reported applications

• Diabetes mellitus related illness

such as diabetic foot diabetic retinopathy

diabetic nephropathy • Epidural abscesses • Certain kind of hearing loss• Radiation-induced hemorrhagic cystitis• Inflammatory .• treat a foot ulcer in someone with diabetes or very bad

circulation)

ADMINISTRATION OF HYPERBARIC OXYGEN

• When a patient is given 100% oxygen under pressure, hemoglobin is saturated, but the blood can be hyperoxygenated by dissolving oxygen within the plasma. The patient can be administered systemic oxygen via 2 basic chambers: Type A, multiplace; and Type B, monoplace. Both types can be used for routine wound care, treatment of most dive injuries, and treatment of patients who are ventilated or in critical care.

Multiplace chamber

Treat multiple patients at the same time, generally with a nurse or another inside observer who monitors the patients and assists with equipment manipulation or emergencies. Patients in a multiplace chamber breathe 100% oxygen via a mask or close-fitting plastic hood. Multiplace chambers can usually be pressurized to the equivalent of about 6 atmospheres of pressure Rectangular hyperbaric chamber

Interior of rectangular chamber

Cylindrical multiplace chamber

Monoplace chamber

• A monoplace chamber compresses one person at a time, usually in a reclining position. The gas used to pressurize the vessel is usually 100% oxygen. Some chambers have masks available to provide an alternate breathing gas (such as air). Employees tend to the patient from outside of the chamber and equipment remains outside the chamber; only certain intravenous lines and ventilation ducts penetrate through the hull. Newer Duoplace chambers can hold 2 people; their operation is similar to that of a monoplace chamber.

Monoplace chamber

Home treatment

An example of mild portable hyperbaric chamber. This 40" diameter chamber is one of the larger chambers available for home use.

These chambers are often used in a clinical settings, but are also used in homes.

Complications

• Barotrauma:

Pressure changes can cause a "squeeze" in the tissues surrounding trapped air inside the body, such as the lungs, behind the eardrum, inside paranasal sinuses, or trapped underneath dental fillings.

• oxygen toxicity:

Breathing high-pressure oxygen for long periods. • Blurred vision:

caused by swelling of the lens,usually resolves in two to four weeks.

• Rare complications:

Optic neuritis - cataract

Contraindications

Absolute Contraindications

Reason Contraindicated Necessary Conditions Prior to HBOT

Untreated pneumothorax

Gas emboliTension pneumothoraxPneumomediastinum

Thoracostomy

Bleomycin Interstitial pneumonitis No treatment for extended time from use of medication

Cisplatin Impaired wound healing No treatment for extended time from use of medication

Disulfiram Blocks superoxide dismutase, which is protective against oxygen toxicity

Discontinue medication

Doxorubicin Blocks superoxide dismutase, which is protective against oxygen toxicity

Discontinue medication

Sulfamylon Impaired wound healing Discontinue and remove medication

Relative Contraindications

Reason Contraindicated Necessary Conditions Prior to

HBOT

Asthma Air trapping upon ascent leading to pneumothorax

Must be well controlled with medications

Claustrophobia Anxiety Treatment with benzodiazepines

Congenital spherocytosis

Severe hemolysis None; HBOT for emergencies only

Chronic obstructive pulmonary disease (COPD)

Loss of hypoxic drive to breathe

Observation in chamber

Eustachian tube dysfunction

Barotrauma to tympanic membrane

Training, PE tubes

High fever Higher risk of seizures Provide antipyretic

Relative Contraindications

Reason Contraindicated Necessary Conditions Prior to

HBOT

Pacemakers or epidural pain pump

Malfunction or deformation of device under pressure

Ensure company has pressure-tested device and learn to what depth

Pregnancy Unknown effect on fetus (Previous studies from Russia suggest HBOT is safe.)

None, but HBOT may be used in emergencies

Seizures May have lower seizure threshold

Should be stable on medications; may be treated with benzodiazepines

Upper respiratory infection (URI)

Barotrauma Resolution of symptoms or decongestants