Hyperbaric oxygen therapy involves breathing pure oxygen under increased pressure. When a patient inhales 100% oxygen, molecules of hemoglobin continue to saturate completely, but plasma dissolves extra oxygen. One molecule of hemoglobin is capable of absorbing four molecules of oxygen under usual conditions. This pattern cannot be outnumbered due to the chemical structure of hemoglobin. However, according to Henry’s law, the more pressure applied to the gas above the liquid, the greater amount of the gas will dissolve in a given type of liquid. By increasing the pressure, more oxygen dissolves in the plasma. Thus, hyperoxygenation is thought to occur.
In their review, Gill and Bell (2004) describe the biophysical basis of hyperoxygenation:
When breathing normobaric air, arterial oxygen tension is approximately 100mmHg, and tissue oxygen tension is approximately 55mmHg. However, 100% oxygen at 3 ATA (atmosphere absolute) can increase arterial oxygen tensions to 2000mmHg, and tissue oxygen tensions to around 500mmHg, allowing delivery of 60ml oxygen per liter of blood (compared to 3ml/l at atmospheric pressure), which is sufficient to support resting tissues without a contribution from hemoglobin. (p. 386)
The authors claim, since oxygen dissolves in a liquid, that its molecules supply tissues with oxygen in places that red blood cells cannot reach. Moreover, in cases when oxygen is also transported by hemoglobin (like carbon monoxide poisoning), hyperbaric oxygenation provides tissues with extra oxygen adequately.
Hyperbaric oxygen is administered in a specially designed chamber or through an endotracheal tube (Latham, Hare, & Neumeister, 2012; Gill & Bell, 2004; Tibbles & Edelsberg, 1996). Duration of a single treatment varies from 45 minutes to 5 or more hours depending on the underlying pathology. Treatments may repeat for a number of times. Tibbles and Edelsberg (1996), in their substantial review, note that most protocols for wound healing last on average from 20 to 30 treatments. Careful monitoring is essential during the procedure.
Hyperbaric oxygenation has numerous therapeutic implications for treatment of carbon monoxide poisoning as well as decompression sickness and arterial gas embolism management. It also aids in severe anemia due to blood loss, thermal burns, wound healing, and radiation injury recovery, compartment syndrome and acute traumatic ischemic injury, refractory osteomyelitis and soft tissue infections, including necrotizing fasciitis, and gas gangrene (Latham et al., 2012; Gill & Bell, 2004; Tibbles & Edelsberg, 1996). It should be noted that most reviews agree on the fact that hyperbaric oxygen is extremely helpful in complicated wound healing such as diabetic foot ulcers (Lipsky & Berendt, 2010). Hyperbaric oxygenation is also the primary treatment for such conditions as arterial gas embolism, decompression sickness, and severe carbon monoxide poisoning.
At the same time, hyperbaric oxygen treatment carries potential complications. The most common complications result from oxygen toxicity. Hyperbaric oxygenation increases free radicals and other toxic products. Although hyperbaric oxygenation is a relatively safe intervention (Gill & Bell, 2004), toxic particles carry potential negative effects. Some complications from hyperbaric oxygenation include reversible myopia, seizures, middle ear and pulmonary barotraumas, chest, ear, or tooth pains, and coughing (Latham et al, 2012; Gill & Bell, 2004). Historically, concerns that oxygen stimulates malignancy precluded its use among patients, albeit recent studies have proved this belief false (Gill & Bell, 2004).
Contraindications to hyperbaric oxygenation are minor. Different authors agree the only absolute contraindication to hyperbaric oxygen therapy is untreated tension pneumothorax. However, some other conditions, such as claustrophobia, asthma, high fever, and upper respiratory infections, should be taken into consideration before beginning treatment (Latham et al., 2012).
In conclusion, it should be noted that hyperbaric oxygen lacked scientific support in the past. However, nowadays it is the primary option for treatment of various challenging conditions. In spite of its high costs and varying evidence for curing some diseases, hyperbaric oxygenation is often a life-saving intervention.