Hyperbaric oxygenation (HBO) as the method of increase in delivery of oxygen at critical patient (CP) is intuitively clear and it is proved. However, results of the metaanalysis numerous randomized clinical trials (RCT) of efficiency of the HBO in intensive therapy not always allow to include it in protocols of treatment. It is necessary to find explanations why efficiency of the HBO in separate clinical cases does not prove to be true in RCT.

Material and methods. Research is based on the new data on mechanisms of free-radical processes at pathology and results of studying of monitoring of parameters of heart rate variability (HRV) during the HBO. The analysis of a HRV is executed according to the international recommendations (1996) by means of our program, which has passed certification in Ukraine . Prospective observational clinical study is based on materials of supervision 607 patients with eczotoxicosis, a multiple sclerosis and other diseases. To these patients 3892 sessions of the HBO during which it has been received more than 25000 sample of cardiointerval for the analysis of a HRV have been executed.

Results of research are offered by us and discussed within last ten years in Ukrainian - Russian information space as journal publications, the part from which is submitted on the Internet ( <http://okontur.narod.ru/art/gbo> ). These results are expressed as the concept of strategy and tactics of the HBO, which includes the following sections. The new model of role free radical processes in mechanisms of infringements of delivery of oxygen at CP is created. This model was a basis of the clinical concept of ischemic shocks, which assumes various efficiency of the HBO depending on a therapeutic window of an ischemic shock. On a representative material, the hypothesis about variability of reactivity of an organism to a hyperoxia during the HBO is confirmed. This reactivity depends on various characteristics of clinical supervision. Various types of dynamics of parameters of a HRV during the HBO allow to estimate effect of one session of treatment and to predict clinical outcomes. Principles of selection of individual dozes of the HBO are developed according to dynamics of parameters of a HRV.

Conclusions . Results of the given research show probability of a high level of regular mistakes at studying efficiency of the HBO at CP by means of existing design of RCT. According to these explanations it is offered two approaches in improvement of efficiency of the HBO at CP.

1. A level of recommendations of the expert. Strategy of the HBO is a forecasting efficiency of the HBO at CP only during a therapeutic window at acute ischemic disorders. Duration of a therapeutic window depends on body of a target of an ischemia. The CP have high probability of toxic action of oxygen, therefore it is necessary to provide during each session of the HBO monitoring of parameters of a HRV in real time. Tactics of the HBO is a rule of selection of a doze of the HBO according to dynamics of a HRV in real time, which allows preventing toxic effects of a hyperoxia.

2. Changes of methodology RCT. The clinical epidemiology is a young and developing science, and planning RCT in intensive therapy demand perfection. We suggest adding known principles of planning RCT to new criteria of inclusion and exclusion, and the protocol of selection of an individual doze of the HBO according to parameters of a HRV in real time.