The rat: a laboratory model for studies of the diving response.
J Appl Physiol. 2010 Jan 21;
Authors: Panneton WM, Gan Q, Juric R
Underwater submersion in mammals induces an apnea, a parasympathetically-mediated bradycardia, and a sympathetically-mediated peripheral vasoconstriction. These effects are collectively termed the diving response, potentially the most powerful autonomic reflex known. Although these physiological responses are directed by neurons in the brain, the study of the neural control of the diving response has been hampered since: a) it is difficult to study the brains of animals while they are underwater, b) feral marine mammals are usually large and have brains of variable size, and c) there are but few references on the brains of naturally-diving species. Similar responses are elicited in anesthetized rodents after stimulating their nasal mucosa, but this nasopharyngeal reflex has not been compared directly to natural-diving behavior in the rat. In the present study, we compared…

(Source: Aviation, Space, and Environmental Medicine)

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Marked pericardial inhomogeneity of specific ventilation at total lung capacity and beyond.
Respir Physiol Neurobiol. 2009 Oct 31;169(1):44-9
Authors: Sun Y, Butler JP, Lindholm P, Walvick RP, Loring SH, Gereige J, Ferrigno M, Albert MS
We measured regional ventilation at 1l above functional residual capacity (FRC+1L) and total lung capacity (TLC) in three normal subjects and four elite breath-hold divers, and above TLC after glossopharyngeal insufflation (TLC+GI) in the divers. Hyperpolarized (3)He MRI was used to map the local ventilation per unit volume over the entire lung. At TLC and above, there was markedly increased regional ventilation of the lungs in the pericardial region compared with the relatively uniform ventilation throughout the rest of the lung. The distribution of fractional ventilation regionally was relatively uniform at FRC+1L, with a small non-gravitational cephalocaudal gradient of specific ventilation in the supine posture. Our observations at high lung volu…

Decompression sickness in breath-hold divers: A review.
J Sports Sci. 2009 Dec 3;:1-16
Authors: Lemaitre F, Fahlman A, Gardette B, Kohshi K
Although it has been generally assumed that the risk of decompression sickness is virtually zero during a single breath-hold dive in humans, repeated dives may result in a cumulative increase in the tissue and blood nitrogen tension. Many species of marine mammals perform extensive foraging bouts with deep and long dives interspersed by a short surface interval, and some human divers regularly perform repeated dives to 30-40 m or a single dive to more than 200 m, all of which may result in nitrogen concentrations that elicit symptoms of decompression sickness. Neurological problems have been reported in humans after single or repeated dives and recent necropsy reports in stranded marine mammals were suggestive of decompression sickness-like symptoms. Modelling attempts have suggested that marine mammals may live permanently with elevated nitrogen concentrations …

Linér MH, Andersson JPA. Hypoxic syncope in a competitive breath-hold diver with elevation of the brain damage marker S100B. Aviat Space Environ Med 2009; 80:1066-8.
Introduction: Competitive breath-hold divers can accomplish previously unbelievable performances; e.g., the current world record for apnea during rest (“static apnea”) is 11 min 35 s. However, whether such performances are associated with a risk for hypoxic brain damage has not been established. Case Report: A breath-hold diver's competitive performance resulted in a loss of consciousness, after which he was subjected to a medical examination by the event physician. Blood samples were collected for analysis of the brain damage marker S100B in serum. The S100B in serum was 0.100 μg · L−1 in the blood sample collected 15 min after the loss of consciousness. At 1 and 5 d after the incident it was 0.097 μg · L−1 and 0.045 μg · L−1, respectively. Discussion: The elevated level of S10…

Authors: Breskovic T, Ivancev V, Banic I, Jordan J, Dujic Z Apnea divers are exposed to repeated massive arterial oxygen desaturation, which could perturb chemoreflexes. An earlier study suggested that peripheral chemoreflex regulation of sympathetic vasomotor tone and ventilation may have recovered 4 or more weeks into the off season. Therefore, we tested the hypothesis that peripheral chemoreflex regulation of ventilation and sympathetic vasomotor tone is present during the training season. We determined ventilation, heart rate, blood pressure, cardiac stroke volume, and muscle sympathetic nerve activity (MSNA) during isocapnic hypoxia in 10 breath hold divers and 11 matched control subjects. The study was carried out at the end of the season of intense apnea trainings. Baseline MSNA...

This study was conducted to determine whether ventilatory parameters would change in breath-hold divers (BHDs) after they performed the glossopharyngeal technique for lung insufflation. Fifteen elite BHDs, 16 non-expert BHDs and 15 control subjects participated in this cross-sectional study. Volumes and expiratory flow rates were measured twice, before and after the glossopharyngeal technique performed at rest. Before the technique, greater forced vital capacity (FVC) and forced expiratory volume in 1_s (FEV1) and lower FEV1/FVC were noted in the elite and non-expert BHDs compared with controls. No difference was noted regarding the other pulmonary parameters. After the technique, increases were noted in FVC, FEV1 and maximal voluntary ventilation in the elite BHDs (P_<&n...

In conclusion, direct measurements of ABP during apnea diving showed no or only mild increases in ABP. However, our results cannot be extended over environmental conditions different from those of the present study. (Source: Journal of Applied Physiology)

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The deepest dive: how far down can a free diver go?
New Yorker. 2009 Aug 24;:24-30
Authors: Wilkinson A

PMID: 19694091 [PubMed - indexed for MEDLINE]

Description from YouTube.com

A SPOT-Freedive foi convidada a deslocar-se aos Açores para leccionar cursos 2* e 3* aqui estão os resultados....Mergulhos entre os 25/30m

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Description from YouTube.com

A SPOT-Freedive foi convidada a deslocar-se aos Açores para leccionar cursos 2* e 3* aqui estão os resultados....Mergulhos entre os 25/30m

...

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Surgical removal of right-to-left cardiac shunt in the American alligator (Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving.
J Exp Biol. 2009 Nov;212(Pt 21):3553-63
Authors: Eme J, Gwalthney J, Blank JM, Owerkowicz T, Barron G, Hicks JW
Crocodilians have complete anatomical separation between the ventricles, similar to birds and mammals, but retain the dual aortic arch system found in all non-avian reptiles. This cardiac anatomy allows surgical modification that prevents right-to-left (R-L) cardiac shunt. A R-L shunt is a bypass of the pulmonary circulation and recirculation of oxygen-poor blood back to the systemic circulation and has often been observed during the frequent apnoeic periods of non-avian reptiles, particularly during diving in aquatic species. We eliminated R-L shunt in American alligators (Alligator mississippiensis) by surgically occluding the left aorta (LAo; arising from right ventricle) upstream and …

Peripheral chemoreflex regulation of sympathetic vasomotor tone in apnea divers.
Clin Auton Res. 2009 Oct 10;
Authors: Breskovic T, Valic Z, Lipp A, Heusser K, Ivancev V, Tank J, Dzamonja G, Jordan J, Shoemaker JK, Eterovic D, Dujic Z
OBJECTIVES: Involuntary apnea episodes in obstructive sleep apnea patients result in selective potentiation of peripheral chemoreceptor regulation of sympathetic vasomotor tone. Breath-hold diving is associated with repeated 'voluntary' apnea episodes and massive arterial oxygen desaturation, which could also perturb chemoreflex function. METHODS: We measured ventilation, heart rate, blood pressure, cardiac stroke volume, and muscle sympathetic nerve activity (MSNA) during isocapnic hypoxia in 11 breath-hold divers and eleven matched control subjects. The study was carried out at least 1 month after intense apnea training. RESULTS: Baseline MSNA frequency was 30 +/- 4 bursts/min in control subjects and 31 +/- 7 bursts/min in divers (ns). During hypoxia MSNA frequency a…

Lemaitre, F, Seifert, L, Polin, D, Juge, J, Tourny-Chollet, C, and Chollet, D. Apnea training effects on swimming coordination. J Strength Cond Res 23(6): 1909-1914, 2009-Triathletes and elite breath-hold divers show an adaptive response to hypoxia induced by repeated epochs of breath holding. We hypothesized that hypoxic training could also improve swimming coordination. Before and after a 3-month breath-hold training program, 4 male swimmers performed a maximal incremental test on bicycle and a 50-m front crawl race at maximal speed without breathing so that interarm coordination could be assessed. Swim velocity, stroke rate (SR), stroke length (SL), and the arm stroke phases were calculated from video analysis. Arm coordination was quantified in terms of an index of coordination (IdC) b...

The concentration of the protein S100B in serum is used as a brain damage marker in various conditions. We wanted to investigate whether a voluntary, prolonged apnea in trained breath-hold divers resulted in an increase of S100B in serum. Nine trained breath-hold divers performed a protocol mimicking the procedures they use during breath-hold training and competition, including extensive preapneic hyperventilation and glossopharyngeal insufflation, in order to perform a maximum-duration apnea, i.e., 'static apnea' (average: 335 s, range: 281–403 s). Arterial blood samples were collected and cardiovascular variables recorded. Arterial partial pressures of O2 and CO2 (PaO2 and PaCO2) were 128 Torr and 20 Torr, respectively, at the start of apnea. The degree of asphyxia at the end of apnea was considerable, with PaO2 and PaCO2 reaching 28 Torr and 45 Torr, respectively. The concentration of S100B in serum transiently increased from 0.066 µg/l at the start of apnea to 0.083 µg/l after the apn…

We report a case with a breath-hold diver who inadvertently experienced a packing blackout. During the incident, an electrocardiogram (ECG) and blood pressure were recorded, and blood samples for determinations of biomarkers of cardiac muscle perturbation (creatine kinase-MB isoenzyme (CK-MB), cardiac troponin-T (TnT), and myoglobin) were collected. The ECG revealed short periods of asystole during the period of 'packing blackout', simultaneous with pronounced reductions in systolic, diastolic, and pulse pressures. Serum myoglobin concentration was elevated 40 and 150 min after the incident, whereas there were no changes in CK-MB or TnT. The ultimate cause of syncope in this diver probably was a decrease in cerebral perfusion following glossopharyngeal insufflation. The asystolic periods r...

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Behaviour and kinematics of continuous ram filtration in bowhead whales (Balaena mysticetus).
Proc Biol Sci. 2009 Aug 19;
Authors: Simon M, Johnson M, Tyack P, Madsen PT
Balaenid whales perform long breath-hold foraging dives despite a high drag from their ram filtration of zooplankton. To maximize the volume of prey acquired in a dive with limited oxygen supplies, balaenids must either filter feed only occasionally when prey density is particularly high, or they must swim at slow speeds while filtering to reduce drag and oxygen consumption. Using digital tags with three-axis accelerometers, we studied bowhead whales feeding off West Greenland and present here, to our knowledge, the first detailed data on the kinematics and swimming behaviour of a balaenid whale filter feeding at depth. Bowhead whales employ a continuous fluking gait throughout the bottom phase of foraging dives, moving at very slow speeds (less than 1 m s(-1)), allowing them to filter feed continuously at depth. Des…

Cardiovascular changes during maximal breath-holding in elite divers.
Clin Auton Res. 2009 Aug 5;
Authors: Guaraldi P, Serra M, Barletta G, Pierangeli G, Terlizzi R, Calandra-Buonaura G, Cialoni D, Cortelli P
During maximal breath-holding six healthy elite breath-hold divers, after an initial 'easy-going' phase in which cardiovascular changes resembled the so-called 'diving response', exhibited a sudden and severe rise in blood pressure during the 'struggle' phase of the maneuver. These changes may represent the first tangible expression of a defense reaction, which overrides the classic diving reflex, aiming to reduce the hypoxic damage and to break the apnea before the loss of consciousness.
PMID: 19655193 [PubMed - as supplied by publisher]

Last week's story started our travel to several Japanese villages to live and dive with the AmaSan breath-hold divers, the SeaWomen. It continues here. The SeaWomen told me their stories. 'I started when I was eight years old,' one told me. 'I gathered kelp and seaweed on the beach. As I got better and older, I could go further in the waters, and bring more food.' None had any knowledge of Ama... (Source: The Fitness Fixer)

Conclusion: These results confirm that elite divers present a potentiation of the well-known apnoea response in both SA and DA conditions. This response is associated with higher brain perfusion which may partly explain the high levels of world apnoea records. (Source: Acta Physiologica)