Extreme human breath-hold diving

Department of Physiology, University Medical Centre, 1 Rue Michel Servet, 1211 Geneva 4, Switzerland.
Arbeitsphysiologie (Impact Factor: 2.3). 05/2001; 84(4):254-71. DOI: 10.1007/s004210000377
Source: PubMed

ABSTRACT In this paper, the respiratory, circulatory and metabolic adjustments to human extreme breath-hold diving are reviewed. A survey of the literature reveals that in extreme divers, adaptive mechanisms take place that allow prolongation of apnoea beyond the limits attained by non-diving subjects, and preservation of oxygen stores during the dives. The occurrence of a diving response, including peripheral vasoconstriction, increased arterial blood pressure, bradycardia and lowered cardiac output, is strongly implicated. Some peripheral regions may be excluded from perfusion, with consequent reliance on anaerobic metabolism. In addition, extreme breath-hold divers show a blunted ventilatory response to carbon dioxide breathing, possibly as a consequence of frequent exposure to high carbon dioxide partial pressures during the dives. These mechanisms allow the attainment of particularly low alveolar oxygen (< 30 mmHg) and high alveolar carbon dioxide (> 50 mmHg) partial pressures at the end of maximal dry breath-holds, and reduce oxygen consumption during the dive at the expense of increased anaerobic glycolysis (rate of blood lactate accumulation > 0.04 mM.s-1). The current absolute world record for depth in breath-hold diving is 150 m. Its further improvement depends upon how far the equilibrium between starting oxygen stores, the overall rate of energy expenditure, the fraction of energy provided by anaerobic metabolism and the diving speed can be pushed, with consciousness upon emersion. The ultimate limit to breath-hold diving records may indeed be imposed by an energetic constraint.

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    ABSTRACT: Apnea provokes a number of physiological responses especially with face immersion. We examine for the first time the cardio respiratory responses after sub-maximal apnea in ten swimmers. Apnea was performed during face immersion in cold water (10±1.050C) and with pre-determined duration of 40 seconds. The room temperature was maintained at 250C. The heart rate average value at rest was 80.95±17.75 (bpm) whereas after the apnea 64.35±14.56 and the difference is statistically significant (p<0.02). The systolic blood pressure at rest was 124±8.76 (mmHg) and after the apnea 138±6.33 (p<0.000). The oxygen consumption at rest was 375.6±118.51 (ml/min) whilst after the apnea 598.3±155.38 (p=0.009). The carbon dioxide production at rest was 377.7±208.31 (ml/min) and after the apnea 621.7±130.28 (p < 0.015). Results support the notion of the activation of the dive reflex after face immersion in the aforementioned physiological parameters.
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    ABSTRACT: The mental control of ventilation with all associated phenomena, from relaxation to modulation of emotions, from cardiovascular to metabolic adaptations, constitutes a psychophysiological condition characterizing voluntary breath-holding (BH). BH induces several autonomic responses, involving both autonomic cardiovascular and cutaneous pathways, whose characterization is the main aim of this study. Electrocardiogram and skin conductance (SC) recordings were collected from 14 elite divers during three conditions: free breathing (FB), normoxic phase of BH (NPBH) and hypoxic phase of BH (HPBH). Thus, we compared a set of features describing signal dynamics between the three experimental conditions: from heart rate variability (HRV) features (in time and frequency-domains and by using nonlinear methods) to rate and shape of spontaneous SC responses (SCRs). The main result of the study rises by applying a Factor Analysis to the subset of features significantly changed in the two BH phases. Indeed, the Factor Analysis allowed to uncover the structure of latent factors which modeled the autonomic response: a factor describing the autonomic balance (AB), one the information increase rate (IIR), and a latter the central nervous system driver (CNSD). The BH did not disrupt the FB factorial structure, and only few features moved among factors. Factor Analysis indicates that during BH (1) only the SC described the emotional output, (2) the sympathetic tone on heart did not change, (3) the dynamics of interbeats intervals showed an increase of long-range correlation that anticipates the HPBH, followed by a drop to a random behavior. In conclusion, data show that the autonomic control on heart rate and SC are differentially modulated during BH, which could be related to a more pronounced effect on emotional control induced by the mental training to BH.
    Frontiers in Neuroengineering 03/2012; 5:4. DOI:10.3389/fneng.2012.00004


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