Water depth at first stop, and total decompression time

4 Water depth at first stop, and total decompression time 

The separate decompression tables of the French Navy, the U.S. Navy, and the Japanese Department of Labor, which are all based on the Haldane-ratio principle (ref. 408-410), require total decompression times for the test dive which are much shorter than those required by other military and commercial tables (Table 8.1). The first stop during decompression with either the FN, USN, or Japan tables occurred at a 10-ft depth, and the mean bubble counts ( S.E.M.) within the 0.27-ml agarose samples just prior to termination of this first (and only) stop were 127.25 9.39, 111.88 17.64, and 98.75 10.72, respectively. Of these three Haldane-ratio-principle tables, the FN table required the shortest total decompression time and the Japan table the longest time, so that the mean bubble number at the 10-ft depth was inversely related to the total decompression time. (In these three cases, the total decompression time essentially represented the sum of the initial 

Bubble formation in agarose gels subjected to various decompression schedules3. (Slightly modified from ref. 56, copyright 1979 Undersea Medical Society, Inc.) 

The shortest total decompression time specified by any of the schedules (11.04 min) was that of the Yount et al. schedule (ref. 135,414) for the standard dive. Nonetheless, the final number of bubbles produced by this particular schedule, 98.63 5.91 per agarose sample (0.27 ml), was less than that produced by any of the three tables (FN, USN, Japan) based on the Haldane-ratio principle (Table 8.1). In particular, the final bubble count produced by the FN schedule was markedly higher (P 0.005), despite the fact that this schedule involved almost the same total decompression time, i.e., 12.00 min. The Yount et al. schedule has no stop during decompression, but instead initiates a slow and constant rate of decompression at about a 40-ft depth (ref. 135.414). The starting point for the slow decompression is, therefore, approximately 3.3 times deeper than with the tables (FN, USN, Japan) based on the 

As with the Yount et al. schedule, the Model 1, FL, and RNPL tables are based, at least in part, on diffusion theory (ref. 411). Accordingly, these latter three tables also require that slow decompression commence at a greater depth than that specified by the tables based on the Haldane-ratio principle (FN, USN, Japan) (see Fig. 8.1). The Model 1 schedule initiated slow decompression at the greatest depth (70 ft (Fig. 8.1)), with the result that the mean number of bubbles produced per 0.27-ml agarose sample (Table 8.1) was significantly less than the number produced by the FL schedule at the 10-ft stop (54.87 2.24 versus 74.13 6.96, 

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