Apneotéka

This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive. However, a remarkable, and so far poorly understood, variation in individual disposition for such problems exists. Mortality connected with breath-hold diving is primarily concentrated to less well-trained recreational divers and competitive spearfishermen who fall victim to hypoxia. Particularly vulnerable are probably also individuals with preexisting cardiac problems and possibly, essentially healthy divers who may have suffered severe alternobaric vertigo as a complication to inadequate pressure equilibration of the middle ears. The specific topics discussed include the diving response and its expression by the cardiovascular system, which exhibits hypertension, bradycardia, oxygen conservation, arrhythmias, and contraction of the spleen. The respiratory system is challenged by compression of the lungs with barotrauma of descent, intrapulmonary hemorrhage, edema, and the effects of glossopharyngeal insufflation and exsufflation. Various mechanisms associated with hypoxia and loss of consciousness are discussed, including hyperventilation, ascent blackout, fasting, and excessive postexercise O(2) consumption. The potential for high nitrogen pressure in the lungs to cause decompression sickness and N(2) narcosis is also illuminated.

Implications: Breath-holding time is significantly prolonged in hyperbaric air than it is in hyperbaric oxygen. The mechanism involves the anesthetic effect of nitrogen suppressing the suffocating feeling during breath-holding.

The diving response is known as “diving bradycardia” and prolonged breath-holding time (BHT) (1). Diving bradycardia is induced by apnea and cold water face immersion. Paco2 and Pao2 and psychological factors could affect BHT (2). Increasing Paco2 and decreasing Pao2 drive respiratory stimulation through respiratory centers. BHT can be increased by training through unconscious hyperventilation before breath-holding and psychological adaptation (3). However, the effect of high atmospheric pressure on BHT has not yet been investigated. This study was performed to determine whether and how hyperbaric air could influence BHT in comparison with hyperbaric oxygen.

In pursuit of Irving and Scholander: a review of oxygen store management in seals and penguins.
J Exp Biol. 2011 Oct 15;214(Pt 20):3325-39
Authors: Ponganis PJ, Meir JU, Williams CL
Abstract
Since the introduction of the aerobic dive limit (ADL) 30 years ago, the concept that most dives of marine mammals and sea birds are aerobic in nature has dominated the interpretation of their diving behavior and foraging ecology. Although there have been many measurements of body oxygen stores, there have been few investigations of the actual depletion of those stores during dives. Yet, it is the pattern, rate and magnitude of depletion of O(2) stores that underlie the ADL. Therefore, in order to assess strategies of O(2) store management, we review (a) the magnitude of O(2) stores, (b) past studies of O(2) store depletion and (c) our recent investigations of O(2) store utilization during sleep apnea and dives of elephant seals (Mirounga angustirostris) and during dives of emperor penguins (Aptenodytes forster…

Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?
J Comp Physiol B. 2011 Sep 21;
Authors: Noren SR, Williams TM, Ramirez K, Boehm J, Glenn M, Cornell L
Abstract
Odontocetes have an exceptional range in body mass spanning 10(3) kg across species. Because, size influences oxygen utilization and carbon dioxide production rates in mammals, this lineage likely displays an extraordinary variation in oxygen store management compared to other marine mammal groups. To examine this, we measured changes in the partial pressures of respiratory gases ([Formula: see text], [Formula: see text]), pH, and lactate in the blood during voluntary, quiescent, submerged breath holds in Pacific white-sided dolphins (Lagenorhynchus obliquidens), bottlenose dolphins (Tursiops truncatus), and a killer whale (Orcinus orca) representing a mass range of 96-3,850 kg. These measurements provided an empirical determination of the effect of body si…

Preliminary observations on the effect of hypoxic and hyperbaric stress on pulmonary gas exchange in breath-hold divers.
Diving Hyperb Med. 2011 Jun;41(2):97-100
Authors: Garbella E, Piarulli A, Fornai E, Pingitore A, Prediletto R
Abstract
AIM: To evaluate pulmonary alveolar-capillary membrane integrity and ventilation/perfusion mismatch after breath-hold diving.
METHODS: Pulmonary diffusing capacity to carbon monoxide (DLCO) and nitric oxide (DLNO), haemoglobin (Hb) and haematocrit (Hct) were measured in six elite divers before and at 2, 10 and 25 minutes after a maximal breath-hold dive to a depth of 10 metres' sea water.
RESULTS: Compared to pre-dive, DLCO showed a slight increase at 2 minutes in five subjects and a tendency to decrease at 25 minutes (P 0.001) in all subjects. DLNO showed an increase at 10 minutes in three divers and a slight decrease at 25 minutes in five subjects. There was a small but significant (P 0.001) increase in Hb and Hct at 2 minutes, possibly affecting the DLCO m…

Hemoptysis and pneumomediastinum after breath-hold diving in shallow water: a case report.
Undersea Hyperb Med. 2011 May-Jun;38(3):213-6
Authors: Henckes A, Arvieux J, Cochard G, Jézéquel P, Arvieux CC
We report the case of a healthy 21-year-old woman who performed iterative breath-hold dives in relatively cold water, not exceeding depths of 5 meters but with 'empty lungs.' At the end of a dive, after experiencing an intense involuntary diaphragmatic contraction underwater, she presented hemoptysis followed by chest pain and cough. Chest radiography and computed tomography were performed 24 hours later, confirming the diagnosis of pneumomediastinum. The clinical course was benign: However, chest pain and effort dyspnea lasted for a few weeks. The pathophysiology of this accident may be explained by a combination of mechanisms involved in several clinical entities, namely pulmonary edema of immersion, pulmonary barotrauma and spontaneous pneumomediastinum.
PMID: 21721355 [PubMed - in process]

Cardiovascular changes during underwater static and dynamic breath-hold dives in trained divers.
J Appl Physiol. 2011 Jun 30;
Authors: Breskovic T, Uglesic L, Zubin P, Kuch B, Kraljevic J, Zanchi J, Ljubkovic M, Sieber A, Dujic Z
Limited information exists concerning arterial blood pressure (BP) changes in underwater breath-hold diving. Simulated chamber dives to 50 meters of freshwater (mfw) reported very high levels of invasive BP in two divers during static apnea (SA), while recent study, using noninvasive subaquatic sphygmomanometer, reported unchanged or mildly increased values at 10 m SA dive. In this study we investigated underwater BP changes during not only SA but, for the first time, during dynamic apnea (DA) and shortened (SHT) DA in 16 trained breath-hold divers. Measurements included BP (subaquatic sphygmomanometer), ECG and pulse oxymetry (arterial oxygen saturation, SpO(2) and heart rate, HR). BP was measured during dry conditions, at surface fully immersed (SA), and at 2 mfw (DA and …

Cardiovascular adjustments in breath-hold diving: comparison between divers and non-divers in simulated dynamic apnoea.
Eur J Appl Physiol. 2011 May 24;
Authors: Tocco F, Crisafulli A, Melis F, Porru C, Pittau G, Milia R, Concu A
The diving response is the sequence of cardiovascular, respiratory and metabolic adjustments produced by apnoea and further strengthened by cooling of the facial area and/or hypoxia. This study aimed at comparing the cardiovascular response to diving of trained divers with that of a control group. In this order, 14 trained divers were compared with 14 non-divers. By means of impedance cardiography and continuous monitoring of arterial pressure, hemodynamic data were collected during three different experimental sessions. Each session included a cycle-ergometer exercise against a workload of 0.5 W kg(-1) of body mass, pedalling in a steady-state condition. During exercise, each subject randomly accomplished 40 s of breath-hold exercise with face immersion (test A) or in a…

Conclusions: The identification of hypertension and fish oil in particular as risk factors raise questions about the role of cardiac diastolic function in the setting of water-immersion cardiac preload, as well as the hematologic effects of fish oil. Mechanistic studies of these risk factors in a directly observed prospective cohort are indicated. (Source: The American Journal of Emergency Medicine)MedWorm Message: Find out how you can get your message posted here and on over 100,000 other medical web pages in just a couple of days, plus support MedWorm at the same time.

Conclusions: Barotrauma was observed in breath-hold divers who increased their lung volumes by GI. The long-term effects of this barotrauma are uncertain and longitudinal studies are required to assess cumulative lung damage. (Source: Respirology)

Authors: Tamaki H, Kohshi K, Ishitake T, Wong RM A survey was conducted in the northern district of Yamaguchi, Japan to determine the relationship between neurological diving accidents and risk factors among commercial breath-hold divers (Ama). A questionnaire was distributed to 381 Ama divers who are members of the Ama diving union. We sought information on their dive practices (depth of single dive, single dive time, surface interval, length of dive shifts, lunch break) and the presence or absence of medical problems, such as hypertension, cardiac arrhythmia, diabetic mellitus and other issues. Of the 381 Ama divers, 173 responded (45%): 29 were Funado (assisted-descent using weights) and 144 Cachido (unassisted) divers. Twelve had experienced strokelike symptoms during or after repe...

Punctate reopening of the lung from subresidual volumes (sub-RV) is commonly observed in excised lung preparations, either degassed or collapsed to zero transpulmonary pressure, and in the course of reinflation of human lungs when the chest is open, secondary to traumatic or surgical pneumothoraxes. In the course of physiological studies on two elite breath-hold divers, who are able to achieve lung volumes well below traditional RV with glossopharyngeal exsufflation, we used MRI lung imaging with inhaled hyperpolarized 129Xe to visualize ventilatory patterns. We observed strikingly inhomogeneous inhalation patterns with small inhalation volumes from sub-RV, consistent with reopening of frankly closed airways. On the other hand, two age-matched and two older controls, inhaling from just abo...

Abstract: Breath hold divers are faced with two main physiological challenges: pressure induced compression and extended time without breathing, exposing them to extremes of hypoxia/hypercapnia. Current world records are 214m for depth and 11:35min for duration. Hypoxic loss of consciousness is frequently observed during competitions. The major physiological components of the diving response that occurs during breath holding are peripheral vasoconstriction, bradycardia, decreased cardiac output, increased cerebral and myocardial blood flow, increased blood pressure, splenic contraction and preserved O2 delivery to the brain and the heart. Sympathetic nervous activity is exceptionally engaged at the end of voluntary breath holds. We hypothesize that these adaptations to extended cessation o...

Authors: Breskovic T, Steinback CD, Salmanpour A, Shoemaker JK, Dujic Z We tested the hypothesis that breath-hold divers (BHD) attain higher level of sympathetic activation than controls due to the duration of breath-hold rather than a different recruitment strategy. In 6 control subjects and 8 BHD we measured muscle sympathetic neural activity (MSNA) prior to and during functional residual capacity (FRC) and total lung capacity (TLC) breath-holding. On a subset of subjects we applied a new technique for the detection of action potentials (APs) in multiunit MSNA. Compared with controls, BHD group had lower burst AP content (13±7 vs. 6±3AP/burst; P=0.05) and number of active clusters (5±1 vs. 3±1clusters/burst; P=0.05) at baseline. However, the overall sympathetic AP/unit-time was c...

We report on a Japanese male professional breath-hold diver (Ama) who developed neurological disorders during repetitive dives to 22 meters of sea water. Each diving duration and surface interval were 40-80 seconds and 20-30 seconds, respectively. He suffered from sensory numbness of the right cheek, hand and foot, and double vision after more than two hours of consecutive dives. Magnetic resonance images of his brain showed multiple cerebral infarcts, and one of the lesions was situated in the brainstem. There is a possibility that repetitive deep breath-hold dives with short surface intervals can induce fatal accidents for divers. PMID: 20369648 [PubMed - in process] (Source: Undersea and Hyperbaric Medicine)

We present a rare case of meningitis caused by Citrobacter koseri in an immunocompetent adult who had recently been freediving. Middle ear pressure changes from this recreational activity, and the subsequent inflammatory response, are likely to have provided this environmental organism access to the central nervous system, and thus the ability to cause clinically significant infection. (Source: Journal of Infection)

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...

Related Articles

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]