Decompression vs. decomposition : distribution, amount, and gas composition of bubbles in stranded marine mammals

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Physiology 3 (2012): 177, doi:10.3389/fphys.2012.00177.Gas embolic lesions linked to military sonar have been described in stranded cetaceans including beaked whales. These descriptions suggest that gas bubbles in marine mammal tissues may be more common than previously thought. In this study we have analyzed gas amount (by gas score) and gas composition within different decomposition codes using a standardized methodology. This broad study has allowed us to explore species-specific variability in bubble prevalence, amount, distribution, and composition, as well as masking of bubble content by putrefaction gases. Bubbles detected within the cardiovascular system and other tissues related to both pre- and port-mortem processes are a common finding on necropsy of stranded cetaceans. To minimize masking by putrefaction gases, necropsy, and gas sampling must be performed as soon as possible. Before 24 h post mortem is recommended but preferably within 12 h post mortem. At necropsy, amount of bubbles (gas score) in decomposition code 2 in stranded cetaceans was found to be more important than merely presence vs. absence of bubbles from a pathological point of view. Deep divers presented higher abundance of gas bubbles, mainly composed of 70% nitrogen and 30% CO2, suggesting a higher predisposition of these species to suffer from decompression-related gas embolism.This work was supported by the Spanish Ministry of Science and Innovation with two research projects: (AGL 2005-07947) and (CGL 2009/12663), as well as the Government of Canary Islands (DG Medio Natural). The Spanish Ministry of Education contributed with personal financial support (the University Professor Formation fellowship). The Woods Hole Oceanographic Institution Marine Mammal Centre and Wick and Sloan Simmons provided funding for the latest stage of this work

Deadly diving? Physiological and behavioural management of decompression stress in diving mammals

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proceedings of the Royal Society B Biological Sciences 279 (2012): 1041-1050, doi:10.1098/rspb.2011.2088.Decompression sickness (DCS; ‘the bends’) is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N2) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N2 tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N2 loading to management of the N2 load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.This paper and the workshop it stemmed from were funded by the Woods Hole Oceanographic Institution Marine Mammal Centre

Bubbles quantified in vivo by ultrasound relates to amount of gas detected post-mortem in rabbits decompressed from high pressure

The pathophysiological mechanism of decompression sickness is not fully understood but there is evidence that it can be caused by intravascular and autochthonous bubbles. Doppler ultrasound at a given circulatory location is used to detect and quantify the presence of intravascular gas bubbles as an indicator of decompression stress. In this manuscript we studied the relationship between presence and quantity of gas bubbles by echosonography of the pulmonary artery of anaesthetized, air-breathing New Zealand White rabbits that were compressed and decompressed. Mortality rate, presence, quantity, and distribution of gas bubbles elsewhere in the body was examined postmortem. We found a strong positive relationship between high ultrasound bubble grades in the pulmonary artery, sudden death, and high amount of intra and extra vascular gas bubbles widespread throughout the entire organism. In contrast, animals with lower bubble grades survived for one hour after decompression until sacrificed, and showed no gas bubbles during dissection

Costridium perfringens septicemia in a long-beaked common dolphin Delphinus capensis : an etiology of gas bubble accumulation in cetaceans

Author Posting. © Inter-Research, 2014. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Diseases of Aquatic Organisms 111 (2014): 183-190, doi:10.3354/dao02783.An adult female long-beaked common dolphin Delphinus capensis live-stranded in La Jolla, California, USA, on July 30, 2012 and subsequently died on the beach. Computed tomography and magnetic resonance imaging revealed gas bubble accumulation in the vasculature, organ parenchyma, mandibular fat pads, and subdermal sheath as well as a gas-filled cavity within the liver, mild caudal abdominal effusion, and fluid in the uterus. Gross examination confirmed these findings and also identified mild ulcerations on the palate, ventral skin, and flukes, uterine necrosis, and multifocal parenchymal cavitations in the brain. Histological review demonstrated necrosis and round clear spaces interpreted as gas bubbles with associated bacterial rods within the brain, liver, spleen, and lymph nodes. Anaerobic cultures of the lung, spleen, liver, bone marrow, and abdominal fluid yielded Clostridium perfringens, which was further identified as type A via a multiplex PCR assay. The gas composition of sampled bubbles was typical of putrefaction gases, which is consistent with the by-products of C. perfringens, a gas-producing bacterium. Gas bubble formation in marine mammals due to barotrauma, and peri- or postmortem off-gassing of supersaturated tissues and blood has been previously described. This case study concluded that a systemic infection of C. perfringens likely resulted in production of gas and toxins, causing tissue necrosis.Aspects of this study were funded by NOAA Prescott Grant no. NA - 11NMF4390085 and NMFS Office of Protected Resources, Marine Mammal Health and Stranding Response Program

Decompressive Pathology in Cetaceans Based on an Experimental Pathological Model

Decompression sickness (DCS) is a widely known clinical syndrome in human medicine, mainly in divers, related to the formation of intravascular and extravascular gas bubbles. Gas embolism and decompression-like sickness have also been described in wild animals, such as cetaceans. It was hypothesized that adaptations to the marine environment protected them from DCS, but in 2003, decompression-like sickness was described for the first time in beaked whales, challenging this dogma. Since then, several episodes of mass strandings of beaked whales coincidental in time and space with naval maneuvers have been recorded and diagnosed with DCS. The diagnosis of human DCS is based on the presence of clinical symptoms and the detection of gas embolism by ultrasound, but in cetaceans, the diagnosis is limited to forensic investigations. For this reason, it is necessary to resort to experimental animal models to support the pathological diagnosis of DCS in cetaceans. The objective of this study is to validate the pathological results of cetaceans through an experimental rabbit model wherein a complete and detailed histopathological analysis was performed. Gross and histopathological results were very similar in the experimental animal model compared to stranded cetaceans with DCS, with the presence of gas embolism systemically distributed as well as emphysema and hemorrhages as primary lesions in different organs. The experimental data reinforces the pathological findings found in cetaceans with DCS as well as the hypothesis that individuality plays an essential role in DCS, as it has previously been proposed in animal models and human diving medicine

Decompression sickness (‘the bends’) in sea turtles

Author Posting. © Inter-Research, 2014. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Diseases of Aquatic Organisms 111 (2014): 191-205, doi:10.3354/dao02790.Decompression sickness (DCS), as clinically diagnosed by reversal of symptoms with recompression, has never been reported in aquatic breath-hold diving vertebrates despite the occurrence of tissue gas tensions sufficient for bubble formation and injury in terrestrial animals. Similarly to diving mammals, sea turtles manage gas exchange and decompression through anatomical, physiological, and behavioral adaptations. In the former group, DCS-like lesions have been observed on necropsies following behavioral disturbance such as high-powered acoustic sources (e.g. active sonar) and in bycaught animals. In sea turtles, in spite of abundant literature on diving physiology and bycatch interference, this is the first report of DCS-like symptoms and lesions. We diagnosed a clinico-pathological condition consistent with DCS in 29 gas-embolized loggerhead sea turtles Caretta caretta from a sample of 67. Fifty-nine were recovered alive and 8 had recently died following bycatch in trawls and gillnets of local fisheries from the east coast of Spain. Gas embolization and distribution in vital organs were evaluated through conventional radiography, computed tomography, and ultrasound. Additionally, positive response following repressurization was clinically observed in 2 live affected turtles. Gas embolism was also observed postmortem in carcasses and tissues as described in cetaceans and human divers. Compositional gas analysis of intravascular bubbles was consistent with DCS. Definitive diagnosis of DCS in sea turtles opens a new era for research in sea turtle diving physiology, conservation, and bycatch impact mitigation, as well as for comparative studies in other air-breathing marine vertebrates and human divers.This work was supported with funds from the Pfizer Foundation, the SUAT-VISAVET Center of Complutense University of Madrid, the Oceanográfic of the ‘Ciudad de las Artes y las Ciencias’ of Valencia, and by the research projects CGL 2009/12663, CGL2012-39681, and SolSub C200801000288