Actual composition of gas mixture in curcuit of diving respiratory apparatus with closed breathing curcuit and electronic control: experimental study

OBJECTIVE. Based on the measurement results, to assess adequacy of the breathing gas mixture, formed in the breathing circuit of a diving respiratory apparatus with the closed breathing circuit and electronic control.

MATERIALS AND METHODS. 11 measurements of the actual composition of the breathing gas mixture in the breathing circuit of a diving respiratory apparatus with the closed breathing circuit and electronic control were conducted during diving descents in the hyperbaric chamber. The percentage of oxygen, helium and carbon dioxide in the inhaled breathing gas mixture was measured at the maximum planned depth of a diving descent as well as decompression stops at a depth of 12 m and 6 m, using Analox ATA Pro Trimix Analyzer and Dragger X-am 5600 devices. The results were compared to calculated and allowable values.

RESULTS. There were no significant deviations in the percentage of oxygen, helium and carbon dioxide in the breathing gas mixture from calculated and allowable values. Differences of the actual values of oxygen from the calculated ones did not exceed 8,1 %, and in deep-water diving descents the difference was no more than 4,9 %. Differences of the actual helium values from the calculated ones did not exceed 10,4 %. Carbon dioxide concentration in the breathing gas mixture, equated with the dive depth, on inhalation within the measurement period did not exceed 1 %.

DISCUSSION. Differences of the actual values from the calculated ones, recorded as a result of measurements, can be explained by the design feature of a modern diving respiratory apparatus with the closed breathing circuit and electronic control, where the formation of the breathing gas mixture is a dynamic process.

CONCLUSION. The results obtained suggest lack of preconditions for the development of specific diving diseases, arising as a result of forming inadequate breathing gas mixture in the breathing circuit of the apparatus.

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