Allometric scaling of decompression sickness risk in terrestrial mammals; cardiac output explains risk of decompression sickness

Fahlman, Andreas

doi:10.1038/srep40918

Cited by 14 publications

(22 citation statements)

References 30 publications

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“…The reduction of brain oxygen supply and the increase of carbon dioxide in the blood consequent to prolonged breath-holding dives may lead to severe brain injury and eventually drowning induced by black-out, at least in animal models (Toklu et al, 2006;Fahlman, 2017) and humans (Modell, 2010;Dujic and Breskovic, 2012). The complex physiological conditions that take place during Table 1).…”

Section: Discussionmentioning

confidence: 99%

Dynamics of blood circulation during diving in the bottlenose dolphin (Tursiops truncatus). The role of the retia mirabilia

Bonato

Bagnoli

Centelleghe

et al. 2019

Journal of Experimental Biology

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The retia mirabilia are vascular nets composed of small vessels dispersed among numerous veins, allowing blood storage, regulation of flow and pressure damping effects. Here, we investigated their potential role during the diving phase of the bottlenose dolphin (Tursiops truncatus). To this effect, the whole vertebral retia mirabilia of a series of dolphins were removed during post-mortem analysis and examined to assess vessel diameters, and estimate vascular volume and flow rate. We formulated a new hemodynamic model to help clarify vascular dynamics throughout the diving phase, based on the total blood volume of a bottlenose dolphin, and using data available about the perfusion of the main organs and body systems. We computed the minimum blood perfusion necessary to the internal organs, and the stroke volume and cardiac output during the surface state. We then simulated breath-holding conditions and perfusion of the internal organs under the diving-induced bradycardia and reduction of stroke volume and cardiac output, using 10 beats min −1 as the limit for the heart rate for an extended dive of over 3 min. Within these simulated conditions, the retia mirabilia play a vital role as reservoirs of oxygenated blood that permit functional performances and survival of the heart and brain. Our theoretical model, based on the actual blood capacity of the retia mirabilia and available data on organ perfusion, considers the dynamic trend of vasoconstriction during the diving phase and may represent a baseline for future studies on the diving physiology of dolphins and especially for the blood supply to their brain.

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Section: Discussionmentioning

confidence: 99%

Dynamics of blood circulation during diving in the bottlenose dolphin (Tursiops truncatus). The role of the retia mirabilia

Bonato

Bagnoli

Centelleghe

et al. 2019

Journal of Experimental Biology

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“…These responses would elevate transfer of N 2 from the lungs and increase absorption in the tissues. Thus, with prolonged entrapment in the fishing nets at depth, enough N 2 may be stored in the tissues for GE to be formed during rapid ascent to the surface (Fahlman, 2017;Fahlman et al, 2017a;García-Párraga et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…As the ambient pressure is reduced upon ascent, the high levels of N 2 in the blood and tissues begin to come out of solution, leading to supersaturation in the blood. If the ascent is too rapid, the supersaturation may cause bubbles to form in the blood and tissues (Fahlman, 2017). In breath-hold diving vertebrates, N 2 uptake and removal through the lung is more complex, as increased ambient pressure causes a pulmonary shunt that correlates with dive depth as the pressure compresses the gas exchange surface (Berkson, 1967;Fahlman et al, 2017b;Kooyman and Sinnett, 1982).…”

Section: Introductionmentioning

confidence: 99%

Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

García-Párraga

Lorenzo

Wang

et al. 2018

Journal of Experimental Biology

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To provide new insight into the pathophysiological mechanisms underlying gas emboli (GE) in bycaught loggerhead sea turtles (Caretta caretta), we investigated the vasoactive characteristics of the pulmonary and systemic arteries, and the lung parenchyma (LP). Tissues were opportunistically excised from recently dead animals for in vitro studies of vasoactive responses to four different neurotransmitters: acetylcholine (ACh; parasympathetic), serotonin (5HT), adrenaline (Adr; sympathetic) and histamine. The significant amount of smooth muscle in the LP contracted in response to ACh, Adr and histamine. The intrapulmonary and systemic arteries contracted under both parasympathetic and sympathetic stimulation and when exposed to 5HT. However, proximal extrapulmonary arterial (PEPA) sections contracted in response to ACh and 5HT, whereas Adr caused relaxation. In sea turtles, the relaxation in the pulmonary artery was particularly pronounced at the level of the pulmonary artery sphincter (PASp), where the vessel wall was highly muscular. For comparison, we also studied tissue response in freshwater sliders turtles (Trachemys scripta elegans). Both PEPA and LP from freshwater sliders contracted in response to 5HT, ACh and also Adr. We propose that in sea turtles, the dive response (parasympathetic tone) constricts the PEPA, LP and PASp, causing a pulmonary shunt and limiting gas uptake at depth, which reduces the risk of GE during long and deep dives. Elevated sympathetic tone caused by forced submersion during entanglement with fishing gear increases the pulmonary blood flow causing an increase in N 2 uptake, potentially leading to the formation of blood and tissue GE at the surface. These findings provide potential physiological and anatomical explanations on how these animals have evolved a cardiac shunt pattern that regulates gas exchange during deep and prolonged diving.

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“…We did not find evidence of this, but our sample size was small. Various factors, such as prior dives, activity level, or previous fishery interactions may influence gas bubble formation in marine turtles and confound interpretation of results, especially when sample sizes are limited, as is often the case due to many logistical challenges associated with fisheries-based studies 23 . Table 3.…”

Section: Allmentioning

confidence: 99%

On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean

Parga¹,

Crespo-Picazo

Monteiro³

et al. 2020

Sci Rep

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Decompression sickness (DCS) was first diagnosed in marine turtles in 2014. After capture in net fisheries, animals typically start showing clinical evidence of DCS hours after being hauled on-board, often dying if untreated. these turtles are normally immediately released without any understanding of subsequent clinical problems or outcome. The objectives of this study were to describe early occurrence and severity of gaseous embolism (GE) and DCS in marine turtles after incidental capture in trawl gear, and to provide estimates of on-board and post-release mortality. Twenty-eight marine turtles were examined on-board fishing vessels. All 20 turtles assessed by ultrasound and/or post-mortem examination developed GE, independent of season, depth and duration of trawl and ascent speed. Gas emboli were obvious by ultrasound within 15 minutes after surfacing and worsened over the course of 2 hours. Blood data were consistent with extreme lactic acidosis, reduced glomerular filtration, and stress. Twelve of 28 (43%) animals died on-board, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days. This is the first empirically-based estimate of on-board and post-release mortality of bycaught marine turtles that has until now been unaccounted for in trawl fisheries not equipped with turtle excluder devices.

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Allometric scaling of decompression sickness risk in terrestrial mammals; cardiac output explains risk of decompression sickness

Cited by 14 publications

References 30 publications

Dynamics of blood circulation during diving in the bottlenose dolphin (Tursiops truncatus). The role of the retia mirabilia

Dynamics of blood circulation during diving in the bottlenose dolphin (Tursiops truncatus). The role of the retia mirabilia

Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean

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