NEW NO-DECOMPRESSION TABLES BASED ON NO-DECOMPRESSION LIMITS DETERMINED BY DOPPLER ULTRASONIC BUBBLE DETECTION Karl E. Huggins Assistant in Research University of Michigan Michigan Sea Grant Publications Office 2200 Bonisteel Blvd. Ann Arbor, Michigan 48109 Single copies free Bulk orders $.40 ea. copy

ABSTRACT Studies done by Spencer in 1976 produced new no-decompression limits designed to eliminate venous bubbles. This paper has used those limits as the basis for a full set of no-decompression tables. The resulting tables are more conservative than the Navy tables but have more potential for multi-level diving. DISCLAIMER These tables have been developed mathematically and have not been subjected to testing to validate them. They are more conservative than the Navy's tables and if used in the same manner as the Navy's tables will give less allowed bottom time. The use of these tables, or any others, for multi-level diving should be discouraged until testing has validated an acceptable technique. This research was sponsored by Michigan Sea Grant under grant NA79AA-D-00093 from the Office of Sea Grant, NOAA, U.S. Department of Commerce and funds from the State of Michigan. The work was conducted at the Underwater Technology Laboratory, University of Michigan; Lee Somers, Ph.D., Director.

1 INTRODUCTION Recently there has been growing concern in the diving community that the Navy nodecompression tables may not be as safe for the sport diver as they should be. Studies have shown that there is bubble formation in divers who have been exposed to dives within the Navy's limits (Spencer 1976). Using these findings new no-decompression limits were calculated to prevent the formation of bubbles. This paper carries this development one step further by developing a set of no-decompression tables based on these new limits. BACKGROUND The concern over the Navy tables exsists even though the incidence of decompression sickness experienced by Navy divers using the tables is less than 0.04% (Bassett 1979). The problem with this statistic is that its sample is made up of Navy divers, not sport divers. Most of the Navy's no-decompression dives are conducted in depths shallower than 60 feet, and the tables are not pushed to their limits. Sport divers, on the other hand, quite frequently push the tables to their limits and dive to depths in excess of 100 feet. Another problem that occurred recently, in using the Navy tables, is that divers developed multi-level methods to extend their bottom time by reading the tables sideways. In theory some of tese multi-level methods are feasible (Graver 1976), but the Navy tables were not developed for such manipulations. Calculations have shown that tissue pressures produced by this type of diving are pushed to and sometimes over the limits set by the Navy (Huggins 1980). The worst problem in the sport diving community is that reporting of decompression sickness tends to be neglected in all but the most serious cases. In a study (Spencer 1976) using a Doppler ultrasonic bubble detector, it was shown that venous gas bubbles were produced after exposing subjects to dives within the Navy's nodecompression limits. Although there is some controversy on the effects that these bubbles may have on the body, it seems a good idea to try to prevent their formation. As a result of this study, new no-decompression limits were developed for the prevention of bubble formation (Table 1). TABLE 1. NO-DECOMPRESSION LIMITS Depth Navy's Spencer's Depth Navy's Spencer's 30' none 225 min 80' 40 min 30 min 35' 310 min 165 min 90' 30 min 25 min 40' 200 min 135 min 100' 25 min 20 min 50' 100 min 75 min 110' 20 min 15 min 60' 60 min 50 min 120' 15 min 10 min 70' 50 min 40 min 130' 10 min 5 min The objective of this project was to develop a set of no-decompression tables that would be based on these new limits and could theoretically be used safely for multi-level diving.

2 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12 0:10 2:31 3:42 4:43 5:23 5:57 6:21 6:49 7:09 7 2:30 3:41 4:42 5:22 5:56 6:20 6:48 7:08 7 0:10 1:20 2:21 3:01 3:35 3:59 4: 27 4:47 5 B 1:19 2:20 3:00 3:34 3:58 4:26 4:46 5 I I 0:10 1:04 1:44 2:18 2:42 3:10 3:30 3 I | C 1:03 1:43 2:17 2:41 3:09 3:29 3 I I I 0:10 0:50 1:24 1:48 2:16 2:36 2 |I w D 0:49 1:23 1:47 2:15 2:35 2 ~I D I I 0:10 0:43 1:07 1:35 1:55 2 I 1 1: E 0:42 1:06 1:34 1:54 2 0:10 0:34 1:02 1:22 1 I I I 0:33 1:01 1:21 1 0:10 0:34 0:54 1 [ [ I [ [ [ G 0:33 0:53 1 0:10 0:30 0 I I I I I I I 0:29 00 I I I I I I I I I I I I I I I OT I ] [ J0:10 0: I I I I I I 0 I I I I I I I I j DEPTH NO DECOM. BOTTOM TIME AND REPETITIVE GROUP COD I I I I I I I I I I I I I I I I I I I (FT.) LIMITS A I I I I I I IH I J 20 - 10 25 40 60 85 110 135 170 215 27 30 225 5 15 25 40 50 65 75 95 110 13 35 165 5 15 20 30 40 50 60 70 85 10 40 135_5 10 20 25 35 40 45 55 60 7: 50 75__ 10 15 20 25 30 35 37 40 51 60 50__- 5 10 15 20 23 25 27 30 3. 70 40 5 10 13 15 17 20 23 25 2' 80 30 - 5 7 10. 13 15 17 20 90 25 5 7 10 -b 13 15 1_ 120 10 _ __ - _ -_ - _ 5 -7,> 7. 130 5 - - - - 5 5 7 35 165 5 15 20 30 40 50 60 70 85 10 40 135 5 10 20 25 35 40 45 55 60'7 50 75 - 10 15 20 25 30 35 37 40 5' 60 50 - 5 10 15 20 23 25 27 30 3. 70 40 - 5 10 13 15 17 20 23 25 2' 80 30 _ 5 7 -> 10 13 15 17 20 -~ 90 25 -_ - - 5 7 - - 10 t' 13 15 1' __100 20 - - - 5 7 o10 + + 110, 15 _ - - - 5. 7 -- 1( 120 10 _ _ _ _ _ 5. - 7 - 130 5 - - - - - 5 ______ ___ _ _ _ 5__ -_5

3 12:00 12I00 12'0012 100 12 1 2 A 12 8 7 6 5 4 4 3 3 3 3 2 2 8:01 8:18 84 7 5 41 34 8:00 8'17 8 26B 8:39 8:1 8:2B 28 18 16 14 11 9 8 7 6 6 5 5 5:39 5:56 6:05 5:2 46 38 5:553 53 3 11 9 4:22..::4 45 29 25 21 17 14 12 9 8 6 6 5 5 4:-22 4:39 4-:48 4:21 4:38 4:47 6 5 1 3.52 3 54 D 635 41 34 30 23 19 15 10 8 7 6 5 5 3:27 3:44 3:53 3:271 1 1 E 86 53 44 37 2822 17 12 9 8 7 5 2:47 3:04 3:13 2:46 3:03 312 F 111 66 53 43 32 24 19 14 11 9 7 6 6 2:14 2:31 2:40 2:13 230 2:39 G 140 0 62 49 36 27 22 17 12 10 8 7 6 1:46 2:03 2:12 1:45 2'02 2'11 10 0.24 033 L 175 96 73 57 40 30 24 19 14 11 9 8 7 1: N 22 1:39 1:48 1:21 1:8 17 219 113 86 65 45 34 26 21 16 12 10 8 7 101 1:17 126 1'00 1216 1325 1:6005J 279 132 103 75 51 38 29 23 18 13 11 9 8 0:42 0:58 1:07 45 47 50 0:41 0:57 3106K 369 154 122 88 57 43 32 26 20 15 12 10 8 0:24 0:40 0:49 — 0:23 0:39 048 L - 178 139 103 64 47 35 28 22 18 13 11 9 0:10 0:24 0:33 -- 0:23 0:32 M 207 0230:2 207 158 124 71 52 40 30 25 20 15 12 10 010 0:18.. 15 017 20 N 01 N - 225 165 135 75 53 41 31 26 21 16 13 11 I I 0:10 L N 175 205 225 135 155 165 100 120 135 60 70 75 * NEW* 45 47 50 33 35 40 NO-DECOMPRESSION TABLES 27 30 20 23 25 15 17 20 13 15 10

4 PROCEDURES & CALCULATION The basic problem was to develop the three tables that make up the no-decompression tables: the Repetitive Group table, the Surface Interval table, and the Residual Nitrogen Time table. Programs were developed for a Hewlett Packard HP-67 calculator that would produce these tables given: a. limits for the depths; 20, 30, 35, 40, 50, 60, 70, 80, 90, 100, 110, 120, and 130 feet; bo MQ values for six tissue groups; c. what percent of Mo corresponded to Group A on the tables; d. the increments between the groups, in percentage of M, The limits for the respective depths are already given by the new limits listed in Table 1. The Mo values were a little more difficult to obtain. The MO value for a tissue group is the pressure of nitrogen that the group can withstand at the surface. The six tissue groups used for these tables are the same that are used in the Navy's model. They are the 5 min., 10 min., 20 min., 40 min., 80 min., and 120 min. tissue groups. The new Mo values were found by calculating the tissue pressures produced by exposures to the new limits using the formula:?t = Po + (Pa - Po) (1 - e-.693t/T.5) where: Pt = Total pressure of nitrogen in the tissue group Po = Initial pressure of nitrogen in the tissue group Pa = Ambient partial pressure of nitrogen in the breathing medium t = Time exposed to pressure Pa T.5 = Tissue group, half-time The calculated tissue pressures are shown in Table 2 with the greatest pressure achieved by a single group underlined.

5 TABLE 2. TISSUE PRESSURE PRODUCED BY THE NEW LIMITS TISSUE PRESSURES (fswp) Limit 5 min. 10 min. 20 min. 40 min. 80 min. 120 min. 30' for 225 min. 49.77 49.77 49.76 49.29 46.40 43.31 35' for 165 min. 53.72 53.72 53.63 52.41 47.10 43.06 40' for 135 min. 57.67 57.67 57.38 54.62 47.86 43.18 50' for 75 min. 65.57 65.35 62.63 54.80 44.95 39.96 60' for 50 min. 73.42 71.99 65.09 53.54 42.73 39.96 70' for 40 min. 81.15 77.91 67.55 53.72 42.27 37.48 80' for 30 min. 88.28 81.37 66.93 51.69 40.54 36.13 90' for 25 min. 94.95 84.60 67.28 51.07 39.92 35.63 100' for 20 min. 100.13 85.32 65.57 49.21 38.64 34.69 110' for 15 min. 102.11 82.25 61.30 45.96 36.66 33.28 120' for 10 min. 97.17 73.47 53.84 41.15 33.94 31.39 130' for 5 min. 77.42 56.15 42.41 34.59 30.42 28.99 By rounding these values down to the nearest 0.5fswp we get the new M, values. These new values are shown in Table 3 along with the Navy M,values for comparison. TABLE 3. COMPARISON OF NEW Mo VALUES TO NAVY'S Tissue Group Navy New % of Navy's 5 min. 104 102 98% 10 min. 88 85 97% 20 min. 72 67.5 94% 40 min. 58 54.5 94% 80 min. 52 47.5 91% 120 min. 51 43 84% As it can be seen the new MQ values are more conservative than the Navy's. These M o values were then used in the calculations for the new tables. The only other value that is needed to be found is the percent of saturation corresponding to Group A on the tables. This value was found by determining what percent surface nitrogen partial pressure was of the Mo values for each tissue group. It was found that the highest percent occured in the 120 minute tissues where the value was 60.63%. This meant a percent greater than 60.63% was needed for the value of Group A. The value that was chosen was 63%. The percent increment between the groups was chosen to be 3%. This means that group B represents 66% of the Mo pressure in the tissue groups, Group M, represents 99%, and N is 100% of the Mo pressure. With these values the no-decompression tables (Pages 2 & 3)were produced. They are read in the same manner as the Navy no-decompression tables.

6 DISCUSSION These new tables achieve the goals that were set to produce a set of no-decompression tables based on Spencer's no bubble, no-decompression limits and which are safe for multilevel diving. In preliminary examination calculations show that the M values are not exceeded when multi-level diving is performed using these tables. It must be remembered that the mathematical confirmation of the multi-level diving technique does not mean that the tables should be used in this manner. Testing is required before any type of confirmation can be made on the safety of any multi-level diving technique. Even though the tables produced are quite a bit more conservative than the Navy tables, they do give the diver a reasonable amount of bottom time before the limits are reached. I believe that if these tables are used by the sport diving community, the chances of divers developing any type of decompression sickness (reported or unreported) will greatly diminish. REFERENCES Bassett, Bruce E., "Results of Validation Testing of Flying After Diving Schedules," in Boone, C. (ed.) PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON UNDERWATER EDUCATION, National Association of Underwater Instructors, Colton, Ca, 1979. Graver, Dennis, "A Decompression Table Procedure for Multi-Level Diving," in Fead, 1. (ed.), PROCEEDINGS OF THE EIGHT INTERNATIONAL CONFERENCE ON UNDERWATER EDUCATION, National Association of Underwater Instructors, Colton, Ca, 1976. Huggins, Karl E., MATHEMATICAL EVALUATION OF MULTI-LEVEL DIVING, University of Michigan, 1980 (unpublished). Spencer, M., "Decompression Limits for Compressed Air Determined by Ultrasonically Detected Blood Bubbles," JOURNAL OF APPLIED PHYSIOLOGY, 40 (2): 229-235, 1976.