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Fahlman A, Burggren W, Milsom WK. The role of cognition as a factor regulating the diving responses of animals, including humans. J Exp Biol 2024; 227:jeb246472. [PMID: 39177084 DOI: 10.1242/jeb.246472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2024]
Abstract
The dive response involves three main components - breath holding, reduced heart rate and increased peripheral vasoconstriction - and is ubiquitous during forced dives in air-breathing vertebrates; however, numerous studies in free-diving animals have shown that the heart rate response to diving varies considerably in a manner that suggests cognitive control. Furthermore, studies on free-diving animals and controlled experiments in trained animals both indicate that the dive response can be conditioned, such that the reduction in heart rate begins before submergence and the extent of the reduction is set early in the dive. In addition, numerous species also experience an increase in heart rate and blood flow during ascent at the end of a dive, a phenomenon commonly called 'ascent tachycardia'. Collectively, these data suggest that although the dive response is under autonomic control, many species can vary its magnitude depending on the length and type of the planned dive - an indication of a role for cognition in the overall physiological responses associated with diving. Here, we provide examples of the conditioned cardiac responses - including anticipatory changes in heart rate - in several diving species and propose potential underlying mechanisms. We also discuss how the anticipatory cardiovascular responses not only improve diving capacity, but also prevent diving-related problems, such as decompression sickness or barotrauma, through a mechanism described by the selective gas exchange hypothesis.
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Affiliation(s)
- Andreas Fahlman
- Fundación Oceanogràfic, Gran Vıa Marques del Turia 19, 46005 Valencia, Spain
- Global Diving Research, 11540 San Lucar de Barrameda, Spain
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden
| | - Warren Burggren
- Developmental Integrative Biology Group, School of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX 76203, USA
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Le-Bert CR, Mitchell GS, Reznikov LR. Cardiopulmonary adaptations of a diving marine mammal, the bottlenose dolphin: Physiology during anesthesia. Physiol Rep 2024; 12:e16183. [PMID: 39245795 PMCID: PMC11381195 DOI: 10.14814/phy2.16183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 07/29/2024] [Accepted: 07/31/2024] [Indexed: 09/10/2024] Open
Abstract
Diving marine mammals are a diverse group of semi- to completely aquatic species. Some species are targets of conservation and rehabilitation efforts; other populations are permanently housed under human care and may contribute to clinical and biomedical investigations. Veterinary medical care for species under human care, at times, may necessitate the use of general anesthesia for diagnostic and surgical indications. However, the unique physiologic and anatomic adaptations of one representative diving marine mammal, the bottlenose dolphin, present several challenges in providing ventilatory and cardiovascular support to maintain adequate organ perfusion under general anesthesia. The goal of this review is to highlight the unique cardiopulmonary adaptations of the completely aquatic bottlenose dolphin (Tursiops truncatus), and to identify knowledge gaps in our understanding of how those adaptations influence their physiology and pose potential challenges for sedation and anesthesia of these mammals.
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Affiliation(s)
- Carolina R Le-Bert
- Department of Physiology & Aging, College of Medicine, University of Florida, Gainesville, Florida, USA
- U.S. Navy Marine Mammal Program, Naval Information Warfare Center Pacific, San Diego, California, USA
| | - Gordon S Mitchell
- Department of Physical Therapy, College of Public Human and Health Professionals, University of Florida, Gainesville, Florida, USA
| | - Leah R Reznikov
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA
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Burggren W, Fahlman A, Milsom W. Breathing patterns and associated cardiovascular changes in intermittently breathing animals: (Partially) correcting a semantic quagmire. Exp Physiol 2024; 109:1051-1065. [PMID: 38502538 PMCID: PMC11215480 DOI: 10.1113/ep091784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 02/29/2024] [Indexed: 03/21/2024]
Abstract
Many animal species do not breathe in a continuous, rhythmic fashion, but rather display a variety of breathing patterns characterized by prolonged periods between breaths (inter-breath intervals), during which the heart continues to beat. Examples of intermittent breathing abound across the animal kingdom, from crustaceans to cetaceans. With respect to human physiology, intermittent breathing-also termed 'periodic' or 'episodic' breathing-is associated with a variety of pathologies. Cardiovascular phenomena associated with intermittent breathing in diving species have been termed 'diving bradycardia', 'submersion bradycardia', 'immersion bradycardia', 'ventilation tachycardia', 'respiratory sinus arrhythmia' and so forth. An examination across the literature of terminology applied to these physiological phenomena indicates, unfortunately, no attempt at standardization. This might be viewed as an esoteric semantic problem except for the fact that many of the terms variously used by different authors carry with them implicit or explicit suggestions of underlying physiological mechanisms and even human-associated pathologies. In this article, we review several phenomena associated with diving and intermittent breathing, indicate the semantic issues arising from the use of each term, and make recommendations for best practice when applying specific terms to particular cardiorespiratory patterns. Ultimately, we emphasize that the biology-not the semantics-is what is important, but also stress that confusion surrounding underlying mechanisms can be avoided by more careful attention to terms describing physiological changes during intermittent breathing and diving.
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Affiliation(s)
- Warren Burggren
- Developmental Integrative Biology Group, Department of Biological SciencesUniversity of North TexasDentonTexasUSA
| | - Andreas Fahlman
- Fundación OceanogràficValenciaSpain
- Kolmården Wildlife ParkKolmårdenSweden
- IFMLinkoping UniversityLinkopingSweden
| | - William Milsom
- Department of ZoologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
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Fahlman A. Cardiorespiratory adaptations in small cetaceans and marine mammals. Exp Physiol 2024; 109:324-334. [PMID: 37968859 PMCID: PMC10988691 DOI: 10.1113/ep091095] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 10/25/2023] [Indexed: 11/17/2023]
Abstract
The dive response, or the 'master switch of life', is probably the most studied physiological trait in marine mammals and is thought to conserve the available O2 for the heart and brain. Although generally thought to be an autonomic reflex, several studies indicate that the cardiovascular changes during diving are anticipatory and can be conditioned. The respiratory adaptations, where the aquatic breathing pattern resembles intermittent breathing in land mammals, with expiratory flow exceeding 160 litres s-1 has been measured in cetaceans, and where exposure to extreme pressures results in alveolar collapse (atelectasis) and recruitment upon ascent. Cardiorespiratory coupling, where breathing results in changes in heart rate, has been proposed to improve gas exchange. Cardiorespiratory coupling has also been reported in marine mammals, and in the bottlenose dolphin, where it alters both heart rate and stroke volume. When accounting for this respiratory dependence on cardiac function, several studies have reported an absence of a diving-related bradycardia except during dives that exceed the duration that is fuelled by aerobic metabolism. This review summarizes what is known about the respiratory physiology in marine mammals, with a special focus on cetaceans. The cardiorespiratory coupling is reviewed, and the selective gas exchange hypothesis is summarized, which provides a testable mechanism for how breath-hold diving vertebrates may actively prevent uptake of N2 during routine dives, and how stress results in failure of this mechanism, which results in diving-related gas emboli.
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Affiliation(s)
- Andreas Fahlman
- Global Diving Research SLValenciaSpain
- Fundación Oceanogràfic de la Comunidad ValencianaValenciaSpain
- Kolmården Wildlife ParkKolmårdenSweden
- IFMLinköping UniversityLinköpingSweden
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Fahlman A, Mcknight JC, Blawas AM, West N, Torrente AG, Aoki K. Cardiorespiratory coupling in the bottlenose dolphin ( Tursiops truncatus). Front Physiol 2023; 14:1234432. [PMID: 37811493 PMCID: PMC10558176 DOI: 10.3389/fphys.2023.1234432] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 09/11/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction: The bottlenose dolphin (Tursiops truncatus) is an intermittent breather, where the breath begins with an exhalation followed by inhalation and an extended inter-breath interval ranging from 10 to 40 s. Breathing has been shown to alter both the instantaneous heart rate (if H) and stroke volume (iSV) in the bottlenose dolphin, with a transitory ventilatory tachycardia following the breath, and an exponential decrease to a stable if H around 40 beats • min-1 during the inter-breath period. As the total breath duration in the dolphin is around 1 s, it is not possible to assess the contribution of exhalation and inhalation to these changes in cardiac function during normal breathing. Methods: In the current study, we evaluated the if H response by separating expiration and inspiration of a breath, which allowed us to distinguish their respective contribution to the changes in if H. We studied 3 individual male bottlenose dolphins trained to hold their breath between the different respiratory phases (expiration and inhalation). Results: Our data show that inspiration causes an increase in if H, while expiration appears to result in a decrease in if H. Discussion: These data provide improved understanding of the cardiorespiratory coupling in dolphins, and show how both exhalation and inhalation alters if H.
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Affiliation(s)
- A. Fahlman
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia 19, Valencia, Spain
- Kolmården Wildlife Park, Kolmården, Sweden
- Global Diving Research SL, Valencia, Spain
| | | | - A. M. Blawas
- Duke University Marine Laboratory, Nicholas School of the Environment Duke University, Beaufort, NC, United States
| | - N. West
- Dolphin Quest, Kahala Resort, Waikoloa, HI, United States
| | - A. G. Torrente
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - K. Aoki
- Department of Marine Bioscience, Atmosphere and OceanResearch Institute, The University of Tokyo, Chiba, Japan
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Blawas AM, Nowacek DP, Rocho-Levine J, Robeck TR, Fahlman A. Scaling of heart rate with breathing frequency and body mass in cetaceans. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200223. [PMID: 34121456 PMCID: PMC8200651 DOI: 10.1098/rstb.2020.0223] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/16/2021] [Indexed: 01/23/2023] Open
Abstract
Plasticity in the cardiac function of a marine mammal facilitates rapid adjustments to the contrasting metabolic demands of breathing at the surface and diving during an extended apnea. By matching their heart rate (fH) to their immediate physiological needs, a marine mammal can improve its metabolic efficiency and maximize the proportion of time spent underwater. Respiratory sinus arrhythmia (RSA) is a known modulation of fH that is driven by respiration and has been suggested to increase cardiorespiratory efficiency. To investigate the presence of RSA in cetaceans and the relationship between fH, breathing rate (fR) and body mass (Mb), we measured simultaneous fH and fR in five cetacean species in human care. We found that a higher fR was associated with a higher mean instantaneous fH (ifH) and minimum ifH of the RSA. By contrast, fH scaled inversely with Mb such that larger animals had lower mean and minimum ifHs of the RSA. There was a significant allometric relationship between maximum ifH of the RSA and Mb, but not fR, which may indicate that this parameter is set by physical laws and not adjusted dynamically with physiological needs. RSA was significantly affected by fR and was greatly reduced with small increases in fR. Ultimately, these data show that surface fHs of cetaceans are complex and the fH patterns we observed are controlled by several factors. We suggest the importance of considering RSA when interpreting fH measurements and particularly how fR may drive fH changes that are important for efficient gas exchange. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.
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Affiliation(s)
- Ashley M. Blawas
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC 28516, USA
| | - Douglas P. Nowacek
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC 28516, USA
- Pratt School of Engineering, Duke University, Durham, NC 27708, USA
| | | | | | - Andreas Fahlman
- Fundación Oceanogràfic de la Comunitat Valenciana, Valencia, Spain 46005
- Global Diving Research, Inc., Ottawa, Canada, K2 J 5E8
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Aoki K, Watanabe Y, Inamori D, Funasaka N, Sakamoto KQ. Towards non-invasive heart rate monitoring in free-ranging cetaceans: a unipolar suction cup tag measured the heart rate of trained Risso's dolphins. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200225. [PMID: 34176321 DOI: 10.1098/rstb.2020.0225] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Heart rate monitoring in free-ranging cetaceans to understand their behavioural ecology and diving physiology is challenging. Here, we developed a simple, non-invasive method to monitor the heart rate of cetaceans in the field using an electrocardiogram-measuring device and a single suction cup equipped with an electrode. The unipolar suction cup was placed on the left lateral body surface behind the pectoral fin of Risso's dolphins (Grampus griseus) and a false killer whale (Pseudorca crassidens) in captivity; their heart rate was successfully monitored. We observed large heart rate oscillations corresponding to respiration in the motionless whales during surfacing (a false killer whale, mean 47 bpm, range 20-75 bpm; Risso's dolphins, mean ± s.d. 61 ± 15 bpm, range 28-120 bpm, n = 4 individuals), which was consistent with the sinus arrhythmia pattern (eupneic tachycardia and apneic bradycardia) observed in other cetaceans. Immediately after respiration, the heart rate rapidly increased to approximately twice that observed prior to the breath. Heart rate then gradually decreased at around 20-50 s and remained relatively constant until the next breath. Furthermore, we successfully monitored the heart rate of a free-swimming Risso's dolphin. The all-in-one suction cup device is feasible for field use without restraining animals and is helpful in further understanding the diving physiology of free-ranging cetaceans. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.
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Affiliation(s)
- Kagari Aoki
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan
| | - Yurie Watanabe
- Taiji Whale Museum and Aquarium, Wakayama 649-5171, Japan
| | - Daiki Inamori
- Taiji Whale Museum and Aquarium, Wakayama 649-5171, Japan
| | - Noriko Funasaka
- Taiji Whale Museum and Aquarium, Wakayama 649-5171, Japan.,Cetacean Research Center, Graduate School of Bioresources, Mie University, Mie 514-8507, Japan
| | - Kentaro Q Sakamoto
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan
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Fahlman A, Aoki K, Bale G, Brijs J, Chon KH, Drummond CK, Føre M, Manteca X, McDonald BI, McKnight JC, Sakamoto KQ, Suzuki I, Rivero MJ, Ropert-Coudert Y, Wisniewska DM. The New Era of Physio-Logging and Their Grand Challenges. Front Physiol 2021; 12:669158. [PMID: 33859577 PMCID: PMC8042203 DOI: 10.3389/fphys.2021.669158] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 02/26/2021] [Indexed: 12/20/2022] Open
Affiliation(s)
- Andreas Fahlman
- Fundación Oceanográfic de la Comunitat Valenciana, Valencia, Spain
| | - Kagari Aoki
- Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
| | - Gemma Bale
- Department of Physics and Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Jeroen Brijs
- Hawai'i Institute of Marine Biology, University of Hawai'i at Manoa, Manoa, HI, United States
| | - Ki H. Chon
- Biomedical Engineering, University of Connecticut, Storrs, CT, United States
| | - Colin K. Drummond
- Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - Martin Føre
- Department of Engineering Cybernetics, Norwegian University of Science and Technology, Trondheim, Norway
| | - Xavier Manteca
- Department of Animal and Food Science, Autonomous University of Barcelona, Barcelona, Spain
| | - Birgitte I. McDonald
- Moss Landing Marine Labs at San Jose State University, Moss Landing, CA, United States
| | - J. Chris McKnight
- Sea Mammal Research Unit, University of St. Andrews, Scotland, United Kingdom
| | - Kentaro Q. Sakamoto
- Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
| | - Ippei Suzuki
- Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Akkeshi, Japan
| | | | - Yan Ropert-Coudert
- Centre D'Etudes Biologiques de Chizé, La Rochelle Université, UMR7372, CNRS, France
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Blawas AM, Ware KE, Schmaltz E, Zheng L, Spruance J, Allen AS, West N, Devos N, Corcoran DL, Nowacek DP, Eward WC, Fahlman A, Somarelli JA. An integrated comparative physiology and molecular approach pinpoints mediators of breath-hold capacity in dolphins. Evol Med Public Health 2021; 9:420-430. [PMID: 35169481 PMCID: PMC8833867 DOI: 10.1093/emph/eoab036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 10/17/2021] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background and objectives
Ischemic events, such as ischemic heart disease and stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching tissues, leading to cell and tissue death, and eventual organ failure. While humans are relatively intolerant to ischemic events, other species, such as marine mammals, have evolved a unique tolerance to chronic ischemia/reperfusion during apneic diving. To identify possible molecular features of an increased tolerance for apnea, we examined changes in gene expression in breath-holding dolphins.
Methodology
Here, we capitalized on the adaptations possesed by bottlenose dolphins (Tursiops truncatus) for diving as a comparative model of ischemic stress and hypoxia tolerance to identify molecular features associated with breath holding. Given that signals in the blood may influence physiological changes during diving, we used RNA-Seq and enzyme assays to examine time-dependent changes in gene expression in the blood of breath-holding dolphins.
Results
We observed time-dependent upregulation of the arachidonate 5-lipoxygenase (ALOX5) gene and increased lipoxygenase activity during breath holding. ALOX5 has been shown to be activated during hypoxia in rodent models, and its metabolites, leukotrienes, induce vasoconstriction.
Conclusions and implications
The upregulation of ALOX5 mRNA occurred within the calculated aerobic dive limit of the species, suggesting that ALOX5 may play a role in the dolphin’s physiological response to diving, particularly in a pro-inflammatory response to ischemia and in promoting vasoconstriction. These observations pinpoint a potential molecular mechanism by which dolphins, and perhaps other marine mammals, respond to the prolonged breath holds associated with diving.
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Affiliation(s)
- Ashley M Blawas
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC, USA
| | - Kathryn E Ware
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Emma Schmaltz
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC, USA
| | - Larry Zheng
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC, USA
| | - Jacob Spruance
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Austin S Allen
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC, USA
| | | | - Nicolas Devos
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC, USA
| | - David L Corcoran
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC, USA
| | - Douglas P Nowacek
- Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC, USA
- Pratt School of Engineering, Duke University, Durham, NC, USA
| | - William C Eward
- Department of Orthopaedic Surgery, Duke University Medical Center, Durham, NC, USA
- Duke University Medical Center, Duke Cancer Institute, Durham, NC, USA
| | - Andreas Fahlman
- Global Diving Research, Inc., Ottawa, ON, Canada
- Research Department, Fundación Oceanogrāfic de la Comunitat Valenciana, Valencia, Spain
| | - Jason A Somarelli
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
- Duke University Medical Center, Duke Cancer Institute, Durham, NC, USA
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