Hyperbaric oxygen therapy means in a pressurized chamber patient is exposed to oxygen tensions exceeding the ambient barometric pressure(>760 mm Hg at sea level).
Until 20 th century hyperbaric treatment involved the use of air. clinical application of hyperbaric oxygen therapy (HBO) began in late 1950s,in parallel to increase understanding of blood gas analysis and gas exchange physiology.
PHYSIOLOGICAL EFFECT OF INCREASED GAS PRESSURE
Increased barometric pressure
Increased partial pressure of oxygen.
It shows four pharmacological effects
Increased oxygen content of blood.
Inhibition of endothelial leucocytic adhesions in injured tissue
Elevation of inert gas pressure
Elevation of absolute pressure during compression phase of deep diving.
Pressure reversal of anesthesia
Animal studies have shown that high pressure (50ATA) has a tendency to reverse general anesthesia.
Effect of hyper baric exposure on drug disposition
Major pharmacokinetic or pharmacodynamic differences wont be expected for most drugs up to the pressure used for most clinical purposes (6 ATA).
Indication of HBO therapy
Gas bubble disease
RATIONAL FOR TREATMENT OF SPECIFIC SYNDROMES
Shift of O-D curve to left
Binding with intracellular pigments.
Carboxy Hb level in blood
Role of HBO therapy – guidelines
H/o neurological impairment
Evidence of cardiac abnormalities
Carboxy Hb >25%
Pregnant woman who fulfills the above criteria
Half life of carboxy Hb is greatly reduced
Increased dissolved oxygen in plasma
GAS EMBOLISM AND DECOMPRESSION SICKNESS
Scuba divers during ascent from a dive while breathing compressed gas.
Iatrogenic causes like diagnostic arteriogram,heamodialysis,neurosurgical procedures, total hip replacement,arthroscopy.
In Open heart surgery with the advantage of reduction in transfusion requirements
During therapeutic lung lavage performed under GA with one lung ventilation.
MAINTENANCE OF O 2 TRANSPORT IN SEVERE ANAEMIA
Ability of hyperbaric oxygen to increase arterial content of oxygen in plasma to clinically useful level may allow support of tissue oxygen delivery even in absence of Hb temporarily pending the availability of definitive therapy in the form of cross matched blood
Multiplace chamber –
These chamber are compressed with air and patient breathes oxygen with a head tent.
Monitoring is relatively easy.
Expensive and large space needed.
Monoplace chamber –
Compressed with 100% oxygen.
Low cost and easy installation.
Monitoring and emergency care difficult
MULTI PLACE CHAMBER
HYPERBARIC TREATMENT SCHEDULE
Factors limiting dose and duration of HBO therapy
Oxygen toxicity, decompression obligation for nursing staff, difficulty in monitoring, patient boredom.
Gas embolism and Decompression sickness
U.S Navy Table 6
U.S Navy Table 6A
Duke therapeutic protocol
Whether a sufficient elevation in PaO 2 can be obtained.
Whether pt can equilibrate middle ear pressure.
Adequacy of control of seizure disorder.
Presence of pulmonary bullae or blebs.
Whether claustrophobia might occur during treatment.