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  • 1.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cardiovascular and hematological responses to voluntary apnea in humans2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with cardiovascular and hematological responses to voluntary apnea in

    humans, with a special focus on O2 usage and storage. Humans, and many other air‐breathing

    animals, respond to apnea (breath holding) with a collection of interacting cardiovascular

    reflexes, which are collectively called the diving response. In humans, the main characteristics of

    the diving response are a reduction in heart rate (bradycardia), decreased cardiac output,

    peripheral vasoconstriction and increased arterial blood pressure. Another response during

    apnea in mammals, more recently also observed in man, is a transient increase in hemoglobin

    concentration across a series of apneas, probably due a reduction in spleen size. There may also

    be long‐term effects on erythropoiesis in the apneic diver, as suggested by high hemoglobin

    levels observed in divers. The focus of the included studies are the short transient diving

    response (I), the more slowly occurring transient hematological changes to apnea, most likely

    related to a reduction in spleen size (II), and the possible effects of repeated apnea on serum

    erythropoietin concentration (III).

    I) The aim was to study the effects of body immersion on the O2‐conserving effect of the

    human diving response. The results showed that, regardless of body immersion, apnea with face

    immersion causes a stronger cardiovascular diving response compared to during apnea alone,

    leading to a smaller reduction in arterial oxygen saturation levels. Thus the diving response is

    triggered and conserves O2 even during whole‐body immersion, which has previously only been

    observed during apnea without whole‐body immersion.

    II) The aim was to study hematological responses to voluntary repeated maximal‐duration

    apneas in divers and non‐divers. Increases in hemoglobin concentration were found across a

    series of 3 apneas in elite breath‐hold divers, elite cross‐country skiers and untrained subjects.

    However a larger increase in hemoglobin was found in divers compared to non‐divers, which

    suggests a possible training effect of their extensive apnea‐specific training. In contrast, physical

    endurance training does not appear to affect the hematological response to apnea.

    III) The aim was to study the effects of serial voluntary apnea on the serum erythropoietin

    concentration. In a comparison between elite breath‐hold divers and subjects untrained in apnea,

    divers were found to have a 5% higher resting hemoglobin concentration. An average maximum

    increase in erythropoietin of 24 % was found in untrained subjects after 15 maximal duration

    apneas, preceded by 1 min of hyperventilation. This suggests a possible erythropoietic effect of

    apnea‐induced hypoxia, which may connect the increased resting hemoglobin found in divers to

    their apnea‐specific training.

    It was concluded from these studies that man responds to apnea with a series of different

    adjustments in order to limit O2 usage and increase O2 storage: The classical diving response is

    effectively restricting O2‐consumption also during full immersion, the spleen related hemoglobin

    increase occurs in both divers and non‐divers with different levels of physiological training, but

    is more prominent in divers, and finally, the observed high levels of hemoglobin concentration in

    divers may be related to enhanced erythropoiesis during dive training.

  • 2.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The function of the human diving response in the immersed diver2003In: Annual Meeting of the European Underwater and Baromedical Society, Copenhagen, Denmark, 2003Conference paper (Other scientific)
    Abstract [en]

    Background: Much previous research has used apneic face immersion as a model for studying the diving response and its oxygen-conserving effect, however there are few direct comparisons to apneic face immersion with the body immersed. Therefore, it is not settled if the oxygen conserving effect revealed in the dry-body model persists in the immersed diver. In this study we compared the diving response and its effect on arterial oxygen saturation between apnea in horizontal dry-body and immersed-body conditions. Methods: Twelve individually determined near-maximal apneas of the same duration were completed by 17 healthy untrained subjects at rest. Three apneas in each of four categories were performed: dry-body apnea (DA), dry-body, face-immersion apnea (DFIA), immersed-body apnea (IA), and immersed-body, face-immersion apnea (IFIA), in a weighted order. For the face and body immersions, mean water temperature (± SD) was 23.1 ±0.12oC and mean air temperature was 23.3 ±0.32oC. Heart rate and arterial haemoglobin saturation were recorded non-invasively with a pulse oximeter. Results: The diving response was similar for both the dry-body and the immersed body-categories. In all 4 categories the heart rate was reduced. The heart rate reduction in DFIA and IFIA categories was more pronounced than in the DA and IA categories. Heart rate reduction during DA and DFIA was 10% (±1.6) and 18% (±2.8) respectively (P<0.01), while heart rate reduction during IA and IFIA was 9% (±2.6) and 18% (±3.1) respectively (P<0.01). In both the DFIA and IFIA categories there was less desaturation compared to the DA and IA categories (DA vs. DFIA P<0.001, IA vs. IFIA P<0.05). Conclusion: Face immersion enhances the apneic diving response both in the dry- and immersed-body conditions, and is associated with a less pronounced arterial oxygen desaturation. We conclude that the immersed diver may benefit from an oxygen conserving diving response. This study also shows that the dry-body model can be useful for studying the diving response.

  • 3.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Pettersson, Sofia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High hemoglobin levels in divers may be a result of apnea induced EPO-production2005In: FASEB JOURNAL, 2005, p. A211-A212Conference paper (Refereed)
    Abstract [en]

    Oxygen storage capacity is important for apneic duration and affects performance in endurance sports. We studied if hemoglobin concentration (Hb) was different in divers compared to endurance athletes and untrained subjects and if any differences could be connected to training-induced erythropoietin (EPO) -production. We first compared Hb in 3 groups of subjects: 13 elite apneic divers (35±4 years), 13 elite cross-country skiers (20±1 years) and 23 untrained subjects (29±1 years) with similar weight and height. After 20 min of horizontal rest blood samples were drawn and analysed for Hb using standard methods. In a second experiment, we compared EPO levels before and after a series of 15 maximal apneas in air in 9 previously untrained volunteers (302 years). Apneas were spaced by 2 minutes, the last minute with hyperventilation to produce durations long enough to induce hypoxia. Values were also compared to the EPO levels of a control day without apneas. The apneic divers had higher Hb than untrained subjects (P<0.05) and skiers (P<0.01). After apnea training in untrained subjects EPO levels increased in all subjects, with a mean peak value after 3 h, where the increase was 135 % of the pre apnea value (P<0.05). No increase was observed during the same time period of the control day. We concluded that higher Hb levels in apneic divers may be a result of enhanced EPO-production due to the apnea training.

  • 4.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hemoglobin levels in elite divers, elite skiers and untrained humans2004Conference paper (Other academic)
  • 5.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Milling, U
    Lemon, H
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Erythropoietin production as a result of repeated apneas2004Conference paper (Refereed)
    Abstract [en]

    Background: It has been known for decades that high altitude hypoxia will lead to increased erythropoiesis. Hypoxia in mainly the kidney results in an increased production of erythropoietin (EPO) stimulating erythropoiesis. High altitude natives display a higher haemoglobin concentration than sea level residents, which in turn increase their haemoglobin concentration as part of the adaptation to altitude. Another group of humans exposed to hypoxia is apneic divers, which may endure transient acute hypoxia, spaced by periods of normal breathing. We recently found higher haemoglobin levels in elite apneic divers, compared to groups of elite skiers and untrained subjects, suggesting that apnea training may induce erythropoiesis in humans. It is well known that diving mammals display high haemoglobin concentrations, and the beneficial effects are obvious: A larger oxygen store before diving prolongs the aerobic dive limit, and a higher haemoglobin concentration may speed up recovery after apneas and act as a buffer against acidosis during the dive. Although our group comparisons reveal a higher haemoglobin concentration in divers, it cannot be determined whether this is a training effect or genetically determined i.e. if individuals with higher concentrations of haemoglobin are more prone to take up apneic diving. Methods: To investigate if apnea training can induce EPO production, 5 previously untrained volunteers (3 men and 2 women, mean ageSD 28 5.5 years) performed 15 maximal apneas in a horizontal position in air. The apneas were grouped in 3 series of 5 apneas and spaced by 2 minutes of which 1 minute was spent slightly hyperventilating, to produce apneas sufficiently long to induce hypoxia. Series were spaced by 10 minutes resting periods. To determine EPO levels, venous blood samples were taken before apneas and directly after the last apnea series, followed by samples 1, 2, 3 and 5 hours after the apneas. Results: Mean baseline EPO before the apneas was 10.2 U/L. In all subjects EPO levels increased during the 5 hours period after the apneas. The time for EPO-peak values were different among individuals. The mean peak value occurred after 3 h, where the mean increase was 12 % of the pre apnea reference value. Conclusion: The results suggest that apnea induced intermittent hypoxia could lead to increased erythropoiesis. The evaluation of these findings in a larger group of subjects, including measurements of the individual circadian variations in EPO production, is in progress.

  • 6.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Increased erythropoietin concentration after repeated apneas in humans2008In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 102, no 5, p. 609-613Article in journal (Refereed)
    Abstract [en]

    Hypoxia-induced increases in red blood cell production have been found in both altitudeadapted populations and acclimatized lowlanders. This process is mediated by erythropoietin (EPO) released mainly by the hypoxic kidney. We have previously observed high hemoglobin concentrations in elite breath-hold divers and our aim was to investigate whether apnea-induced hypoxia could increase EPO concentration. Ten healthy volunteers performed 15 voluntary maximal duration apneas, divided into three seriesof five apneas, each series separated by 10 min of rest. Apneas within series were separated by 2 min and preceded by 1 min of hyperventilation to increase apnea duration and arterial oxygen desaturation. When EPO concentration after serial apneas was compared to baseline values, an average maximum increase of 24% was found (P<0.01). No changes in EPO concentration were observed during a control day without apnea, eliminating possible effects of a diurnal rhythm or blood loss. We therefore conclude that serial apneas increase circulating EPO concentration in humans.

  • 7.
    de Bruijn, Robert
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Oxygen-conserving effect of the diving response in the immersed human2009In: Diving and hyperbaric medicine, ISSN 1833-3516, Vol. 39, no 4, p. 193-199Article in journal (Refereed)
    Abstract [en]

    Research involving the human diving response has often simulated diving by apneic face immersion. However, no comparisons of cardiovascular responses and their oxygen- conserving function have been made between simulated diving and apneic face immersion when the body is constantly immersed as during diving. We compared the diving response and its effects on arterial oxygen saturation during apneas in horizontal dry body and immersed body positions. Both air and water temperatures were 23ºC. Twelve near-maximal apneas of the same duration were completed by 17 subjects. Four series of 3 apneas each were conducted: dry body apnea (DA), dry body, face-immersion apnea (DFIA), immersed body apnea (IA), and immersed body, face-immersion apnea (IFIA). Heart rate, skin capillary blood flow, arterial blood pressure, arterial hemoglobin saturation, lung volume and end-tidal PACO2 and PAO2 were recorded non-invasively and responses during apneas were compared among series. Cardiovascular responses showed similar patterns in all series. Face immersion led to a greater reduction in heart rate during apnea, regardless of body immersion. Both DFIA and DA resulted in a transient skin vasoconstriction, more pronounced during DFIA (p<0.001). During body immersion skin vasoconstriction was constant, and neither IA nor IFIA reduced blood flow further. Less arterial desaturation occurred after both FIA series, suggesting an oxygen-conserving effect of the more powerful diving response associated with face immersion in both body positions. We conclude that a similar oxygen-conserving diving response is triggered by apnea and face immersion during full-body immersion in cool water, as in the dry body model.

  • 8. Richardson, M
    et al.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, J
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The incidence of hematocrit increase during apnea in non divers: European Underwater and Baromedical Society (EUBS) meeting Copenhagen, Denmark2003Conference paper (Other academic)
  • 9.
    Richardson, Matt
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hypoxia augments apnea-induced increase in hematocrit and hemoglobin concentration2009In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 105, no 1, p. 63-68Article in journal (Refereed)
    Abstract [en]

    Increased hemoglobin concentration (Hb) and hematocrit (Hct) attributable to spleen contraction raises blood gas storage capacity during apnea, but the mechanisms that trigger this response have not been clarified. We focused on the role of hypoxia in triggering these Hb and Hct elevations. After horizontal rest for 20 min, 10 volunteers performed 3 maximal apneas spaced by 2 min, each preceded by a deep inspiration of air. The series was repeated using the same apneic durations but after 1 min of 100% oxygen breathing and oxygen inspiration prior to apneas. Mean apneic durations were 150s, 171s, and 214s for apneas 1, 2, and 3, respectively. Relative to pre-apnea values, the mean post-apneic arterial oxygen saturation nadir was 84.7% after air and 98% after oxygen. A more pronounced elevation of both Hb and Hct occurred during the air trial: after apnea 1 with air, mean Hb had increased by 1.5% (P<0.01), but no clear increase was found after the first apnea in with oxygen. After the third apnea with air Hb had increased by 3.0% (P<0.01), and with oxygen by 2.0% (P<0.01). After the first apnea with air Hct had increased by 1.9% (P<0.01) and after 3 apneas by 3.0% (P<0.01), but Hct did not change significantly in the oxygen trial. In both trials, Hb and Hct were at pre-apneic levels 10 min after apneas. Diving bradycardia during apnea was the same in both trials. We concluded that hypoxia is essential in inducing spleen-related Hb and Hct increase during apnea.

  • 10.
    Richardson, Matthew
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Björklund, Glenn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Increase of hemoglobin concentration after maximal apneas in divers, skiers and untrained humans2005In: Canadian Journal of Applied Physiology, ISSN 1066-7814, Vol. 30, no 3, p. 276-281Article in journal (Refereed)
    Abstract [en]

    Apnea is physiologically stressful and can within a short time frame pose a threat to survival. To sustain prolonged apnea, oxygen use should be minimized and its storage maximized. Two mechanisms known to have this effect are the cardiovascular diving response, directing the available oxygen selectively to the heart and brain, and spleen contraction increasing the circulating erythrocyte volume and thereby gas storage capacity. Spleen contraction is also observed after maximal exercise, and is thought to enhance aerobic performance. While the cardiovascular diving response is known to be more pronounced after apnea training, spleen contraction has not been studied in conjunction with apnea training or other types of training. The aim of the present investigation is to study the hematological responses to apnea performed during rest by elite apneic divers, by elite cross-country skiers and by untrained subjects. After 20 min of rest, subjects performed 3 maximal apneas spaced by 2 min normal breathing intervals. Blood samples were drawn before, directly after, and 10 min after the apnea series and hemoglobin concentration was measured. All groups responded to maximal apneas with an increase in hemoglobin concentration, which had disappeared after 10 min of recovery. The increase in hemoglobin concentration was more pronounced in the apneic divers (4g/L) than in skiers (3g/L) and untrained subjects (2g/L; P < 0.05). All groups prolonged their apneic times through the series, but the increase was most evident for the divers versus both the skiers (P < 0.05) and untrained subjects (P < 0.01). The results suggest that these responses could be more pronounced as a result of apnea training.

  • 11.
    Richardson, Matthew
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Pettersson, Sofia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Reimers, J.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    CORRELATION BETWEEN SPLEEN SIZE AND HEMATOCRIT DURING APNEA IN HUMANS2006In: Proceedings of the Undersea and Hyperbaric Medical Society/Divers Alert Network 2006 June 20-21 Workshop. Durham, NC, 2006Conference paper (Other academic)
  • 12.
    Richardson, Matthew
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hypoxia - A trigger for spleen contraction?2005In: EUBS 2005, 2005Conference paper (Other scientific)
    Abstract [en]

    Several mechanisms involving oxygen conservation or increased blood gas storage capacity serve to facilitate prolonged diving in mammals. Two such mechanisms present in humans are the cardiovascular �diving response� and the blood boosting spleen contraction. Repeated diving may elicit these adaptive responses by similar or different mechanisms. Increased hematocrit (Hct) attributable to spleen contraction raises blood gas storage capacity during human apneic diving or simulated diving, but the underlying mechanisms have not been clarified. The time course for development of the Hct response is slower than for the cardiovascular diving response: The development of spleen contraction is progressive across 3 serial apneas, and recovery takes 8-9 minutes. Also, while the diving response is initiated by apnea and fortified by facial chilling, the stimulus eliciting Hct increase is related to apnea alone. Thus apnea itself or its consequences appear to be the main stimulus. In this study we focused on the role of hypoxia in triggering spleen induced elevations in Hct. After horizontal rest for 20 min, nine volunteers performed 3 maximal apneas spaced by 2 min of rest, preceeded by an inspiration of normal air. The series was repeated at a different day using the same apneic durations but after 60 s of 100% oxygen breathing and oxygen inspiration prior to apneas. Relative to pre-apnea values, the post apneic arterial oxygen saturation nadir averaged 84% after the air trial and 99% after the oxygen trial. The Hct rose in both protocols, but with about twice the magnitude after apneas with air. A relative increase of 2.7% was found after three apneas with air (p<0.01), and 1.4% increase after three apneas with oxygen (p<0.05). Values returned to pre-apneic levels within 10 minutes. We conclude that hypoxia may be an important modifying factor influencing the magnitude of hematocrit increase during apnea.

  • 13.
    Richardson, Matthew
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schagatay, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hematological response pattern associated with maximal-duration apnea series in untrained subjects: Annual Meeting of the European Underwater and Baromedical Society, Copenhagen, Denmark.2003Conference paper (Other academic)
    Abstract [en]

    Background: In addition to the human cardiovascular ‘diving response’, i.e., bradycardia and peripheral vasoconstriction during apnea, recent studies have shown that spleen contraction also occurs during repeated apneas. This latter response may serve to expel erythrocytes into the circulation to promote gas transportation. However, prospective changes in blood parameters after repeated apneas have yet to be systematically described. As is the case with diving response parameters, some individuals may have stronger haematological changes from performing apneic series than others. These variations need to be considered in future studies of the function of the spleen and blood components during apnea. The present study was aimed to describe the haematological response pattern associated with repeated maximal apneas in healthy non-divers. Methods: After 20 min of rest, 46 healthy untrained subjects of both sexes performed three maximal apneas, spaced by two minutes rest and normal breathing. Blood samples were taken before, within 1 minute after, and 10 minutes after the apneic series and analyzed for changes in haemoglobin (Hb) concentration and hematocrit (Hct). Results: Pre-apnea Hb concentration (mean±SE) was normally distributed (147.1±1.6 g/L). An increase of 2.1±0.3% in the Hb value was seen immediately post-series, followed by a decrease from this value of 1.8±0.3% at 10 minutes post-series. Pre-apnea hematocrit (41.2±0.6 percent) showed a similar increase immediately post-series of 3.2±0.8% followed by a decrease of 1.6±0.4% from this value at 10 minutes post-series. Classifying subjects as strong responders (above 75th percentile) and weak responders (below 25th percentile) resulted in mean increases in Hb and Hct above pre-apneic values of 4.7±0.4% and 7.1±2.1%, respectively for strong responders, and -0.5±0.4 and 0.5±0.6, respectively for weak responders. Conclusion: Significant increases in Hb and Hct values occur immediately after a maximal apneic series, followed by a return towards baseline values after 10 minutes. These increases may be due to the spleen contraction as demonstrated in previous research. Furthermore, some subjects appear to respond more strongly than others, and pre-screening for these types of responders may be judicious in future testing. The mechanism(s) underlying the strength of these haematological responses warrants further investigation.

  • 14.
    Schagatay, Erika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Increase in hematocrit after short and long term apnea training2005In: Blue 2005. Human Behaviour and Limits in Underwater Environments. Abstract book: International Conference organised by: CNR Institute of Clinical Physiology, Pisa - Italy Apnea Academy - Italy University of Chieti - Italy. Pisa December 1-4 2005., Pisa: CNR Institute of Clinical Physiology , 2005, p. 57-58Conference paper (Refereed)
  • 15.
    Schagatay, Erika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Increases in diving response, hematocrit and asphyxia tolerance after apnea training2005Conference paper (Other scientific)
  • 16.
    Schagatay, Erika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Haughey, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Holmberg, Hans Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Naturlig bloddopning vid fysiologisk stress2004In: Svensk idrottsforskning, ISSN 1103-4629, Vol. 13, no 1, p. 18-21Article in journal (Other academic)
  • 17.
    Schagatay, Erika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Richardson, Matthew
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    de Bruijn, Robert
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, J.
    Cardiovascular and hematological adjustments to apneic diving in humans. -Is the 'spleen-response' part of the diving response?2006In: Breath-hold diving 2006: UHMS proceedings, Orlando, USA, June 20-24, 2006, p. 20-24Conference paper (Refereed)
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