Hyperbaric oxygen therapy (HBOT) involves breathing 100% oxygen in a treatment chamber where the pressure is increased to greater than normal atmospheric pressure; usually 2.5-2.8 ATA (2.5-2.8 × atmospheric pressure). It corresponds to diving to a depth of 15 msw (= meters of sea water; 2.5 ATA) or 18 msw (2.8 ATA).
Standard treatment is administered in 90 minute sessions 1-3 times a day on 5-7 days a week.
HBO therapy for decompression sickness Diving Medicine last 4 h 50 min - 6 h 10 min according to the USN6 table, or 2 h 15 min according to the USN5 table.
Mode of action
Physiological effects of the increased pressure
Reduction of the size of gas bubbles that are retained in the body and cause symptoms
Oxygen dissolves faster in the body fluids.
The effect of hyperbaric oxygen on tissues
Oxygen supply to the tissues is increased (oxygen dissolves in the plasma and its diffusion distance from the capillaries is increased by a factor of 3 to 4, and the partial pressure of oxygen in the tissues increases by a factor of 10 to 14).
Tissue swelling is reduced (vasoconstriction).
Healing of ischaemic wounds is accelerated (fibroblast activity is restored).
Capillary angiogenesis in ischaemic areas is increased (intermittent hypoxia/hyperoxia)
Activity of fibroblasts and osteoclasts as well as collagen synthesis are accelerated.
The effect of HBOT on infections
Growth of anaerobic bacteria is inhibited (e.g. Clostridium perfringens).
Production of toxins is inhibited (e.g. alpha and theta toxins, produced by Clostridium perfringens, that have a haemolytic effect and cause tissue necrosis).
Leucocyte antibacterial function in ischaemic tissues is improved (enhanced ”oxidative burst”)
The effect of some antimicrobial drugs (e.g. aminoglycosides, sulphonamides, ciprofloxacin) is enhanced.
HBOT may be beneficial when given < 6-8 hours after air embolism.
Empirical iIndications for HBOT
Severe, symptomatic carbon monoxide poisoning or smoke inhalation
Gas gangrene, necrotizing fasciitis and other necrotizing soft tissue infections (Fournier's gangrene, deep neck infections) Severe Infections of the Skin and Soft Tissues. HBOT is an adjunct to surgery and antimicrobial therapy.
HBOT promotes the healing and reduces the size of a diabetic foot ulcer more effectively than standard treatment.
HBOT is cost-effective in the treatment of a refractory diabetic foot ulcer compared to standard treatment alone.
The potential effect of HBOT can be estimated beforehand by transcutaneous oxygen measurement (TCOM) of the limb (while breathing in 100% oxygen at normal air pressure).
HBOT promotes healing of the mucous membranes in radiation proctitis, but but controlled evidence on the treatment benefits and the reduction of symptoms is lacking.
An international multi-centre study on the effect of HBOT in radiation cystitis is going on.
Indications where HBOT appears ineffective and should not be used
Ligament damage and stress injuries associated with exercise
Multiple sclerosis
Acute cerebral infarction and traumatic brain injury
Chronic tinnitus
Acute coronary syndrome
Autism
Contraindications
Absolute contraindication: untreated pneumothorax
Relative (can usually be treated)
Certain medications
Disulfiram (may increase the toxicity of oxygen)
Some cytostatic drugs: doxorubicin, cisplatin, bleomycin (both treatment effect and adverse effects increased)
Severe claustrophobia
Upper respiratory tract infection if associated with thick, obstructing secretions
Susceptibility to convulsions
History of a spontaneous pneumothorax
Emphysema and CO2 retention
Sequela to recent thoracic surgery
Congenital spherocytosis
Complications
Barotrauma in the air cavities (cf. diving; Diving Medicine)
Middle ear (tympanocentesis if the patient is unconscious or sedated)
Maxillary sinuses
Poor dental health or temporary fillings
Complications are usually associated with concurrent respiratory infection.
Oxygen toxicity
Convulsions
Occur in about 1.4 cases per 10 000 treatment sessions administered for 90 minutes at 2.5 ATA.
Drugs, respiratory acidosis, fever and sepsis predispose the patient to convulsions. Sedatives, ganglion blockers and hypothermia offer protection against convulsions.
Treatment consists of exposure to normal room air and diazepam if indicated
No late effects
Lung injury
Not a problem with modern treatment regimes
Transient myopia
May affect up to 30% of patients if the serial treatment continues for several months
Reversible without treatment
Accelerated maturation of a cataract
References
Jain KK. In: Textbook of Hyperbaric Medicine, 6th Edition. Cham: Springer International Publishing 2017.
Mathieu D, Marroni A, Kot J. Tenth European Consensus Conference on Hyperbaric Medicine: recommendations for accepted and non-accepted clinical indications and practice of hyperbaric oxygen treatment. Diving Hyperb Med 2017;47(1):24-32. [PubMed]
Game FL, Hinchliffe RJ, Apelqvist J ym. A systematic review of interventions to enhance the healing of chronic ulcers of the foot in diabetes. Diabetes Metab Res Rev 2012;28 Suppl 1():119-41. [PubMed]
Löndahl M, Katzman P, Nilsson A ym. Hyperbaric oxygen therapy facilitates healing of chronic foot ulcers in patients with diabetes. Diabetes Care 2010;33(5):998-1003. [PubMed]
Garcia-Covarrubias L, McSwain NE Jr, Van Meter K ym. Adjuvant hyperbaric oxygen therapy in the management of crush injury and traumatic ischemia: an evidence-based approach. Am Surg 2005;71(2):144-51. [PubMed]
Clarke RE, Tenorio LM, Hussey JR ym. Hyperbaric oxygen treatment of chronic refractory radiation proctitis: a randomized and controlled double-blind crossover trial with long-term follow-up. Int J Radiat Oncol Biol Phys 2008;72(1):134-143. [PubMed]
Glover M, Smerdon GR, Andreyev HJ ym. Hyperbaric oxygen for patients with chronic bowel dysfunction after pelvic radiotherapy (HOT2): a randomised, double-blind, sham-controlled phase 3 trial. Lancet Oncol 2016;17(2):224-233. [PubMed]
Ylikoski J, Mrena R, Makitie A ym. Hyperbaric oxygen therapy seems to enhance recovery from acute acoustic trauma. Acta Otolaryngol 2008;128(10):1110-5. [PubMed]
van der Veen EL, van Hulst RA, de Ru JA. Hyperbaric Oxygen Therapy in Acute Acoustic Trauma: A Rapid Systematic Review. Otolaryngol Head Neck Surg 2014;151(1):42-5. [PubMed]
Bartek JJr , Jakola AS, Skyrman S ym. Hyperbaric oxygen therapy in spontaneous brain abscess patients: a population-based comparative cohort study. Acta Neurochir (Wien) 2016;158(7):1259-67. [PubMed]