Human Injury Criteria for Underwater Blasts

Abstract

Underwater blasts propagate further and injure more readily than equivalent air blasts. Development of effective personal protection and countermeasures, however, requires knowledge of the currently unknown human tolerance to underwater blast. Current guidelines for prevention of underwater blast injury are not based on any organized injury risk assessment, human data or experimental data. The goal of this study was to derive injury risk assessments for underwater blast using well-characterized human underwater blast exposures in the open literature. The human injury dataset was compiled using 34 case reports on underwater blast exposure to 475 personnel, dating as early as 1916. Using severity ratings, computational reconstructions of the blasts, and survival information from a final set of 262 human exposures, injury risk models were developed for both injury severity and risk of fatality as functions of blast impulse and blast peak overpressure. Based on these human data, we found that the 50% risk of fatality from underwater blast occurred at 302±16 kPa-ms impulse. Conservatively, there is a 20% risk of pulmonary injury at a kilometer from a 20 kg charge. From a clinical point of view, this new injury risk model emphasizes the large distances possible for potential pulmonary and gut injuries in water compared with air. This risk value is the first impulse-based fatality risk calculated from human data. The large-scale inconsistency between the blast exposures in the case reports and the guidelines available in the literature prior to this study further underscored the need for this new guideline derived from the unique dataset of actual injuries in this study.

An Experimental Model for the Study of Underwater Pressure Waves on the Central Nervous System in Rodents: A Feasibility Study

“…A 50% risk of fatality from underwater blast at 302±16 kPa-ms impulse was derived from 262 human exposures, including a 20% risk of pulmonary injury at one kilometer from a 20 kg charge. 13 We detected EEG changes at pressure levels by which mild organ hemorrhage occurred, warranting further investigations to determine neurological effects of underwater blast.…”

“…12 Both peak pressure and impulse may be necessary to accurately predict injury risk, similar to the use of both peak pressure and overpressure duration to predict injury risk in air blast. 13 For this study, we selected peak pressures based on our earlier studies of air pressure wave effects on swine brains. Air pressure waves of 237 kPa gave pronounced effects on EEG for 5-15 s, and changes for up to 2 min.…”

“…A US Navy 500 psi (3447 kPa) guideline, which was intended to provide a peak pressure at which injuries were likely to occur, was based on unconfirmed assertions that later propagated throughout the literature. 12,13 While no universal standard for underwater blast safety currently exists, the guideline developed by Richmond et al seems to be the most commonly applied today. 14 Underwater blast differs from blast in air.…”

“…12 Similar to air blast, the gas-containing organs are the most affected in underwater blast. 13 There is limited experience on how underwater blast waves influence the brain. Underwater blast may cause disorientation and balance impairments to a diver, which could lead to inability to protect the airway and cause drowning.…”

Marine Mammal Lung Dynamics when Exposed to Underwater Explosion Impulse

“…Risk models for humans are developed, for both injury severity and risk of fatality, as functions of blast impulse and peak overpressure that remain based on exposure datasets found in open literature, rather than actual blast exposure data (Lance et al, 2015). The current US Navy underwater risk guidelines remain based on the untested assumptions by Greaves et al (1943) that (1) there is a general pressure threshold for air-backed tissue damage in humans from an underwater shock wave, and (2) this threshold is equal to the minimum shock overpressure value where a free-field UNDEX will exhibit bubble jetting and venting at the surface.…”