Apnea Diving: Long-Term Neurocognitive Sequelae of Repeated Hypoxemia

University of Queensland, St. Lucia, Brisbane, Australia.
The Clinical Neuropsychologist (Impact Factor: 1.72). 03/2006; 20(1):160-76. DOI: 10.1080/13854040590947407
Source: PubMed


This article examines the neurocognitive sequelae of repeated exposure to hypoxemia in apnea (breath-hold) divers. A brief review of the literature on the physiological and neurological adaptations involved in the "human diving reflex" is presented. The results from a neuropsychological investigation of N = 21 elite apnea divers are evaluated. Standard neuropsychological tests, with known sensitivity to mild brain insults, included speed of visuo-motor responding, speed of language comprehension, response inhibition, and visual and verbal attention and recall tasks. Results indicated that the breath-hold divers performed tasks within the average range compared to norms on all tests, suggesting that 1-20 years of repeated exposure to hypoxemia including multiple adverse neurological events did not impact on performance on standard neuropsychological tasks. The results are discussed in relation to implications for clinical conditions such as sleep apnea, respiratory disorders, altitude sickness, and recreational apnea activities.

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Available from: Ken Mcfarland, Sep 05, 2014
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    • "Furthermore, the results suggest that apnea does not affect the heart supporting that diving might be of interest to those seeking enhanced aerobic capacity. Yet, the plasma levels of NSE indicate that hypoxia affected the nervous system (Schoerkhuber et al., 1999; Ridgway & McFarland, 2006; Andersson et al., 2009b; Liner & Andersson, 2009), which may be problematic in regard to advocate diving including glossopharyngeal insufflation as a mean to increase red blood cell mass. Repetitive apnea may reduce the chemoreceptor responsiveness to CO 2 , and this may limit the ventilatory response to exercise . "
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    ABSTRACT: Free diving is associated with extreme hypoxia. This study evaluated the combined effect of maximal static breath holding and underwater swimming on plasma biomarkers of tissue hypoxemia: erythropoietin, neuron-specific enolase and S100B, C-reactive protein, pro-atrial natriuretic peptide, and troponin T. Venous blood samples were obtained from 17 competing free divers before and 3 h after sessions of static apnea and underwater swimming. The heart was evaluated by echocardiography. Static apnea for 293 ± 78 s (mean ± SD) and subsequent 88 ± 21 m underwater swimming increased plasma erythropoietin from 10.6 ± 3.4 to 12.4 ± 4.1 mIU/L (P = 0.013) and neuron-specific enolase from 14.5 ± 5.3 to 24.6 ± 6.4 ng/mL (P = 0.017); C-reactive protein decreased from 0.84 ± 1.0 to 0.71 ± 0.67 mmol/L (P = 0.013). In contrast, plasma concentrations of S100B (P = 0.394), pro-atrial natriuretic peptide (P = 0.549), and troponin T (P = 0.125) remained unchanged and, as assessed by echocardiography, the heart was not affected. In competitive free divers, bouts of static and dynamic apnea increase plasma erythropoietin and neuron-specific enolase, suggesting that renal and neural tissue, rather than the heart, is affected by the hypoxia developed during apnea and underwater swimming.
    Full-text · Article · Sep 2014 · Scandinavian Journal of Medicine and Science in Sports
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    • "Depth disciplines are dependent on advanced training and use of specific equalization techniques to avoid squeeze when the lung is compressed below RV, and factors such as the capacity for " blood shift " (Ferrigno et al., 1987) and the ability to use free-fall (Table 2) in order to conserve energy will affect the depth reached (Schagatay, 2011). For depth, also the neuropsychological tolerance to nitrogen narcosis (Ridgway and McFarland, 2006) will be increasingly important, and with depths increasing beyond 100 m there is also an increasing risk of developing decompression sickness on ascent (Schagatay, 2011) and a negative effect of a large lung air supply may become evident; divers may eventually have to allow lung collapse to reach further (Fitz-Clarke, 2007). Not only physiological features and individual results determine who participates in the world championship in a young sport like apnea. "
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    ABSTRACT: Humans share with e.g. seals the ability to contract the spleen and increase circulating hematocrit, which may improve apneic performance by enhancing gas storage. Seals have large spleens and while human spleen size is small in comparison, it shows great individual variation. Unlike many marine mammals, human divers rely to a great extent on lung oxygen stores, but the impact of lung volume on competitive apnea performance has never been determined. We studied if spleen- and lung size correlated with performance in elite apnea divers. Volunteers were 14 male apnea world championship participants, with a mean(SE) of 5.8(1.2) years of previous apnea training. Spleen volume was calculated from spleen length, width and thickness measured via ultrasound during rest, and vital capacity via spirometry. Accumulated competition scores from dives of maximal depth, time and distance were compared to anthropometric measurements and training data. Mean dive performance was 75(4) m for constant weight depth, 5 min 53(39) s for static apnea and 139(13) m for dynamic apnea distance. Subjects’ mean height was 184(2) cm, weight 82(3) kg, vital capacity (VC) 7.3(0.3) L and spleen volume 336(32) ml. Spleen volume did not correlate with subject height or weight, but was positively correlated with competition score (r=0.57; P<0.05). Total competition score was also positively correlated with VC (r=0.54; P<0.05). The three highest scoring divers had the greatest spleen volumes, averaging 538(53) ml, while the three lowest scoring divers had a volume of 270(71) ml (P<0.01). VC was also greater in the high-scorers, at 7.9(0.36) L as compared to 6.7(0.19) L in the low-scorers (P<0.01). Spleen volume was reduced to half after 2 min of apnea in the highest scoring divers, and the estimated resting apnea time gain from the difference between high and low scorers was 15 s for spleen volume and 60 s for VC. We conclude that both spleen- and lung volume predict apnea performance in elite divers.
    Full-text · Article · Jun 2012 · Frontiers in Physiology
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    ABSTRACT: The spleen acts as a storage site for red blood cells, and contraction of the spleen is for many mammals a way of coping with situations where increased blood oxygen storage is beneficia l. This ability h as a lso recently been found in humans, where most individuals respond with an increase in circulating erythrocytes in response to environmenta l or physiologica l stress, th e majority of which can be a ttributed to the spleen. The initiation of th is response, however, is unclear, as is the variability of the response's development among individuals. Th is thesis identif ies th at there is a strong correla tion between spleen contraction and circulating hemoglobin (Paper I), th a t release of these erythrocytes from the spleen is more pronounced in those trained in breath-hold diving th an in elite cross-country skiers and untra ined persons (Paper II), and th a t the response develops even in oxygen-poor environments such as at h igh a ltitude (Paper III) . Th is is due to the hypoxic stimulus th at exists such environments, wh ich acts as an initia tor of the response (Paper IV), a lthough even high levels of carbon dioxide are important (Paper V). The size of world ch ampionship apnea divers' spleens is a lso predictive of the ir apneic performance, showing th a t spleen contraction is an important factor in natural diving ability (Paper VI). In conclusion, the contractile response of the spleen, a long with the previously described "diving response" helps humans to better endure low-oxygen situations, but despite the ir common function these responses are not initia ted and do not develop in the same manner (Paper VII).
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