[abstract] EXCURSIONS TO THE SURFACE FROM AIR SATURATION AT 45, 55 AND 65 FSWG.

Abstract

Military, commercial and research saturation diving operations require the occasional use of emergency decompression procedures. Frequently, this involves brief surface intervals (SI) prior to recouping missed decompression in a hyperbaric chamber. This practice is currently necessary in U.S. Navy submarine rescue operations. Although theoretical calculations exist which allow SI from air saturation at depths to 65 fsw, human studies are lacking. To test the safety and feasibility of these procedures, 9 U.S. Navy divers (12 by the time of presentation) were exposed to a 30 min SI after 48 hrs at 45 fsw, a 17 min SI after 24 hrs at 55 fsw and a 7 min SI after 24 hrs at 65 fsw. All 3 excursions were performed on a single dive, final decompression occurring 20 hrs after the last excursion and requiring 32 hrs. Subjects are monitored closely for signs and symptoms of decompression sickness (DCS) and venous gas embolii (VGE). Results are in table. The lack of both symptoms and VGE in the 65 fsw excursion suggests that prolongation is possible. This does not appear to be true for the other excursions. An effect of the early excursions on the late cannot be ruled out. VGE grades were low and correlation with symptoms was not apparent. No DCS was noted on the final decompression. We conclude that surface excursions from air saturation, as performed in this study, are safe and feasible for use in emergency decompression procedures. (NMRDC Work Unit No. M0099PN001.8013) [table] SURFACE EXCURSION FROM (FSWG): 45, 55, 65; EXCURSION DURATION (MIN): 30, 17, 7; TOTAL NUMBER OF SUBJECTS; NUMBER OF SUBJECTS WITH: -ITCHING: 3, 7, 0; -DCS TYPE I SYMPTOMS: 1, 1, 0; -DCS TYPE II SYMPTOMS: 0, 1, 0; NUMBER OF SUBJECTS WITH VGE: - AT REST 2, 0, 0; -WITH MOVEMENT: 3, 2, 1; [end table]