Hyperbaric oxygenation significantly shortens the elimination half-life of carboxyhaemoglobin.

Appraised by: Mike Bennett, Dept. of Diving and Hyperbaric Medicine, Prince of Wales Hospital

Sydney; Thursday, 10 December, 1998

Clinical Scenario: A patient with carbon monoxide poisoning.

Three-part Question: For patients with elevated levels of carboxyhaemoglobin, does administration of hyperbaric oxygen, compared to a normobaric regime, result in more rapid reduction in carboxyhaemoglobin?

Search Terms: hyperbaric oxygenation, carbon monoxide.

The Study:

Non-blinded randomised controlled crossover trial with intention-to-treat.

Healthy volunteer smokers exposed to a standard regime of five cigarettes in an hour to produce elevated COHb levels.

Control group (N =12 ;12 analysed): 40 minutes of oxygen via non-rebreathing mask at 15 liters/min.

Experimental group (N =12 ;12  analysed): 40 minutes of 100% oxygen at 1.58 ATA in a Gamow bag inflatable chamber.

The Evidence:

Comments:

1. No clinical outcomes, so the significance of these findings is not clear.

2. Further statistical evaluation suggests a shift from zero order to first order kinetics on application of hyperbaric oxygen.

3. This study addresses experimental, mild CO poisoning, unlike the clinical situation.

4. Two reports appear to be using the same data although slightly different t1/2s are published. Conclusions are identical.

Expiry date:   September 2004

References:

1.      Jay GD, McKindley DS. Alterations in pharmacokinetics of carboxyhaemoglobin produced by oxygen under pressure. Undersea and Hyperbaric Medicine 1997; 24:165-174.

2.      Jay GD, Tetz DJ, Hartigan CF, Lane LL, Aghababian RV. Portable hyperbaric oxygen therapy in the emergency department with the modified Gamow bag. Annals of Emergency Medicine 1995; 26:707-711.