Symptoms and signs in the human include joint pain, skin rash, neurological dysfunction varying in severity from limb numbness to paralysis and hemiplegia, and, in some cases, cardiopulmonary collapse ( Melamed et al. Bubble nuclei will grow to macroscopic size only under conditions of supersaturation, which develop when the partial pressure of the inert gas in the tissues is higher than that in the ambient atmosphere ( Crum and Mao 1996). The accepted pathogenesis of DCS involves tissue injury resulting either directly or indirectly from the formation of inert gas bubbles during decompression ( Francis and Gorman 1993). B-mode ultrasound scanning of live-stranded dolphins demonstrated the presence of bubbles, which was later corroborated by computerized tomography and necropsy of the dead animals ( Dennison et al. Necropsy of these marine mammals revealed gas bubble-associated lesions and fat embolism in the blood vessels and parenchyma of vital organs, not unlike those described in human divers suffering from decompression sickness (DCS) ( Fernández et al. Recently, alarming numbers of mass stranding events have been reported in close association with the activity of mid-frequency (1–10 kHz) naval sonar systems ( Balcomb and Claridge 2001 Parsons et al. Mass strandings of cetaceans (whales and dolphins) have been recorded over many decades on the vulnerable north- and southeastern shores of the United States and in New Zealand and Australia, with most of the stranded animals showing no significant pathology ( Bogomolni et al. The study outcome has potential implications for human diving safety and may provide an explanation for the mass stranding of cetaceans purportedly associated with sonar activity. The results demonstrate induction of neurological damage by intense underwater sound during immersion, with a further deleterious effect when this was combined with decompression stress. Pathological SSEPs scores in animals immersed during the acoustic transmissions, but without changes in ambient pressure, were comparable to those observed in animals exposed to the dive profile. Significantly higher pathological SSEPs scores were noted for both underwater sound protocols. A significantly higher rate of decompression sickness was found among animals exposed to the 204-dB/8-kHz sound field. Recording of somatosensory evoked potentials (SSEPs) was employed under general anesthesia as an electrophysiological measure of neurologic insult. DCS severity was assessed using the rotating wheel method. Rats were subjected to immersion and simulated dives with and without simultaneous acoustic transmissions at pressure levels and frequencies of 204 dB/8 kHz and 183.3 dB/15 kHz. We examined the hypothesis that exposure to underwater sound may potentiate DCS. Necropsy showed bubble-associated lesions similar to those described in human decompression sickness (DCS). Mass stranding of cetaceans (whales and dolphins), in close association with the activity of naval sonar systems, has been reported on numerous occasions.
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