Breath-Hold Diving in Terrestrial Mammals

Lin, Yixin

doi:10.1249/00003677-198201000-00009

Cited by 56 publications

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“…HR is reduced during apnea in exercising humans (4, 7, 26, 27, 33), and the extent of the apnea-induced HR response varies substantially from individual to individual (24,26). We selected 2 groups from among the 86 subjects tested in preliminary experiments: those in the L group showed strong apnea-induced bradycardia during dynamic exercise, whereas those in the S group showed a mild bradycardic response.…”

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“…mean arterial pressure; femoral blood flow; breath hold LARGE CARDIOVASCULAR RESPONSES occur during breath-hold diving in both animals and humans (10,12,14,19,28,36). The response is characterized by bradycardia and vasoconstriction related to the so-called "diving reflex" (1,8,10,20,24,36), and it has been proposed that the function of these changes is primarily to preserve an adequate O 2 supply to vital organs (1,4,15,18,19,24). Some diving animals, such as seals, show remarkable bradycardia during voluntary diving (36).…”

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“…Some diving animals, such as seals, show remarkable bradycardia during voluntary diving (36). In humans, the bradycardic response seen during apnea or diving is smaller than in diving animals and varies a great deal from individual to individual (5,21,24,31,32).Acute apnea-induced bradycardia is observed in humans during exercise on land (3,4,6,7,22,25,26,27,30,33). Bjertnaes et al (7) reported that during exercise, the decrease in cardiac output (CO) induced by apnea was nearly paralleled by a reduction in heart rate (HR).…”

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“…In some people, apnea induces marked bradycardia, during which HR is reduced to levels below the resting level, even during moderate exercise (24). Bjertnaes et al (7) suggested that, for these people, the strong bradycardia could lead to a large reduction in CO.…”

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Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

Nishiyasu

Tsukamoto

Kawai

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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Nishiyasu T, Tsukamoto R, Kawai K, Hayashi K, Koga S, Ichinose M. Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise. Am J Physiol Heart Circ Physiol 302: H864 -H871, 2012. First published December 9, 2011; doi:10.1152/ajpheart.00413.2011.-Our aim was to test the hypothesis that apnea-induced hemodynamic responses during dynamic exercise in humans differ between those who show strong bradycardia and those who show only mild bradycardia. After apneainduced changes in heart rate (HR) were evaluated during dynamic exercise, 23 healthy subjects were selected and divided into a large response group (L group; n ϭ 11) and a small response group (S group; n ϭ 12). While subjects performed a two-legged dynamic knee extension exercise at a work load that increased HR by 30 beats/min, apnea-induced changes in HR, cardiac output (CO), mean arterial pressure (MAP), arterial O2 saturation (SaO 2 ), forearm blood flow (FBF), and leg blood flow (LBF) were measured. During apnea, HR in the L group (54 Ϯ 2 beats/min) was lower than in the S group (92 Ϯ 3 beats/min, P Ͻ 0.05). CO, SaO 2 , FBF, LBF, forearm vascular conductance (FVC), leg vascular conductance (LVC), and total vascular conductance (TVC) were all reduced, and MAP was increased in both groups, although the changes in CO, TVC, LBF, LVC, and MAP were larger in the L group than in the S group (P Ͻ 0.05). Moreover, there were significant positive linear relationships between the reduction in HR and the reductions in TVC, LVC, and FVC. We conclude that individuals who show greater apnea-induced bradycardia during exercise also show greater vasoconstriction in both active and inactive muscle regions. mean arterial pressure; femoral blood flow; breath hold LARGE CARDIOVASCULAR RESPONSES occur during breath-hold diving in both animals and humans (10,12,14,19,28,36). The response is characterized by bradycardia and vasoconstriction related to the so-called "diving reflex" (1,8,10,20,24,36), and it has been proposed that the function of these changes is primarily to preserve an adequate O 2 supply to vital organs (1,4,15,18,19,24). Some diving animals, such as seals, show remarkable bradycardia during voluntary diving (36). In humans, the bradycardic response seen during apnea or diving is smaller than in diving animals and varies a great deal from individual to individual (5,21,24,31,32).Acute apnea-induced bradycardia is observed in humans during exercise on land (3,4,6,7,22,25,26,27,30,33). Bjertnaes et al. (7) reported that during exercise, the decrease in cardiac output (CO) induced by apnea was nearly paralleled by a reduction in heart rate (HR). In addition, Lindholm et al. (27) reported that the extent of the bradycardia induced by apnea during exercise had a significant negative relationship with the reduction in arterial blood O 2 saturation (Sa O 2 ) and suggested that the reduction in CO during apnea could conserve O 2 in arterial blood during apnea in exercisin...

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Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

Nishiyasu

Tsukamoto

Kawai

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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Life Under Water: Physiological Adaptations to Diving and Living at Sea

Castellini

2012

Comprehensive Physiology

111

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This review covers the field of diving physiology by following a chronological approach and focusing heavily on marine mammals. Because the study of modern diving physiology can be traced almost entirely to the work of Laurence Irving in the 1930s, this particular field of physiology is different than most in that it did not derive from multiple laboratories working at many locations or on different aspects of a similar problem. Because most of the physiology principles still used today were first formulated by Irving, it is important to the study of this field that the sequence of thought is examined as a progression of theory. The review covers the field in roughly decadal blocks and traces ideas as they were first suggested, tested, modified and in some cases, abandoned. Because diving physiology has also been extremely dependent on new technologies used in the development of diving recorders, a chronological approach fits well with advances in electronics and mechanical innovation. There are many species that dive underwater as part of their natural behavior, but it is mainly the marine mammals (seals, sea lions, and whales) that demonstrate both long duration and dives to great depth. There have been many studies on other diving species including birds, snakes, small aquatic mammals, and humans. This work examines these other diving species as appropriate and a listing of reviews and relevant literature on these groups is included at the end. © 2012 American Physiological Society. Compr Physiol 2:1889‐1919, 2012.

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Breath‐Hold Diving

Fitz‐Clarke

2018

Comprehensive Physiology

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Breath-hold diving is practiced by recreational divers, seafood divers, military divers, and competitive athletes. It involves highly integrated physiology and extreme responses. This article reviews human breath-hold diving physiology beginning with an historical overview followed by a summary of foundational research and a survey of some contemporary issues. Immersion and cardiovascular adjustments promote a blood shift into the heart and chest vasculature. Autonomic responses include diving bradycardia, peripheral vasoconstriction, and splenic contraction, which help conserve oxygen. Competitive divers use a technique of lung hyperinflation that raises initial volume and airway pressure to facilitate longer apnea times and greater depths. Gas compression at depth leads to sequential alveolar collapse. Airway pressure decreases with depth and becomes negative relative to ambient due to limited chest compliance at low lung volumes, raising the risk of pulmonary injury called "squeeze," characterized by postdive coughing, wheezing, and hemoptysis. Hypoxia and hypercapnia influence the terminal breakpoint beyond which voluntary apnea cannot be sustained. Ascent blackout due to hypoxia is a danger during long breath-holds, and has become common amongst high-level competitors who can suppress their urge to breathe. Decompression sickness due to nitrogen accumulation causing bubble formation can occur after multiple repetitive dives, or after single deep dives during depth record attempts. Humans experience responses similar to those seen in diving mammals, but to a lesser degree. The deepest sled-assisted breath-hold dive was to 214 m. Factors that might determine ultimate human depth capabilities are discussed. © 2018 American Physiological Society. Compr Physiol 8:585-630, 2018.

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Breath-Hold Diving in Terrestrial Mammals

Cited by 56 publications

References 0 publications

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

Life Under Water: Physiological Adaptations to Diving and Living at Sea

Breath‐Hold Diving

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