Research protocols and related problems

* Randomizing studies

Should we be promoting the idea of a randomized study of HBO? This question has a matter of debate for over 20 years and, the answer depends on the characteristics of the evaluating team. For those already using HBO, it is inconceivable to deny one group of patients the benefit of HBO in combination with surgery and antibiotics. On the other hand, would a team unfamiliar with HBO be able to introduce this in the absence of any expertise using it? Many experimental and clinical issues that have arisen in recent times have lead to questioning the feasibility of such studies.

* Choosing a protocol

Actually the real problem is defining the best procedures for HBO. At present the pressure, duration and number of sessions are determined using few or no objective criteria. Although most teams use the procedures proposed in Hill's work on experimental gas gangrene in mice89, there are no actual clinical studies on this point. Nor are the criteria for ending HBO indisputably determined. So depending on the teams in charge of managing patients, the total duration of this treatment can vary from 5 days for those using HBO strictly for its anti-infectious activity, to 2 to 3 weeks for those who aim to provide the benefit of the wound healing as well.

For the moment, there appears to be no value in arguing for an ideal sequence for using the various modalities of therapy. HBO can be provided before or after initial surgery, depending on the availability of hyperbaric chambers and surgical theatres. However the general recommendation is that it should be started as soon as possible. Some actually operate patients inside the hyperbaric chambers4.

* Improving results

There are several ways of improving the use of HBO for treating soft-tissue anaerobic infections: (1) achieving consensus on the classification of anaerobic infections so that referrals are appropriate; (2) technical progress in measuring partial pressures of oxygen able to reach infected tissues, as this accounts for success or failure in using HBO; (3) evaluating bacterial clearance from the site of infection in response to treatment; and finally (4) controlled, multi-centre studies following strict methodology to allow objective assessment of therapeutic protocols, including the duration and frequency of HBO therapy.

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