Rockswold SB et al. Effects of hyperbaric oxygenation therapy on cerebral metabolism and intracranial pressure in severely brain injured patients. J Neurosurg 2001 Mar;94(3):403-11.

Please note that HDOT has been substituted for HBO in this summary of the summary.

A prospective randomized trial has already shown that hyperbaric oxygenation therapy (HDOT) reduces the mortality of severely brain-injured patients by 50%. In this study the effects of HDOT on cerebral blood flow (CBF), cerebral metabolism, and intracranial pressure (ICP), have been measured in an attempt to determine the optimum frequency of treatment. 100% at 1.5 atm absolute was delivered to 37 patients for 60 minutes every 24 hours (maximum of seven treatments/patient). The increased cerebral metabolic rate of oxygen (CMRO2) and decreased cerebrospinal fluid (CSF) lactate levels after treatment indicate that HDOT may improve aerobic metabolism in severely brain-injured patients. This is the first study to demonstrate a prolonged effect of HDOT treatment on CBF and cerebral metabolism. On the basis of their data the authors suggest that shorter, more frequent exposure to HDOT may be better.

Comments:

• The authors have not acknowledged that Sukoff and Ragatz actually showed this nearly 20 years ago. Ref: Sukoff MH and Ragatz RE Hyperbaric oxygenation for the treatment of Acute cerebral edema. Neurosurgery 1982;10: 29-38).
• One hour of a higher dosage of oxygen in 24 hours is not enough. A total of at least 16 hours in 24 has been given at 2 atm abs in the resuscitation of a patient after cardiac surgery. Ref. Yacoub MH, Zeitlin GL. Hyperbaric oxygen in the treatment of the Postoperative low-cardiac-output syndrome. Lancet 1965; i: 581-83.
• Giving more oxygen (HDOT) in the presence of a lack of oxygen is likely to improve the CMRO2, that is the brain's use of oxygen. Ref. No reference is needed here ...........
• The presence of lactate indicates that there is not enough oxygen for (normal) aerobic (air related) metabolism and giving some more (HDOT) allows more normal (aerobic) metabolism. Ref. No reference is needed here either...

Dr P.B. James MB ChB DIH PhD FFOM
Wolfson Hyperbaric Medicine Unit
University of Dundee.