The Effects of the diving response on breath-hold divers
In contrast to the common findings cited above, elite divers
appear to have a significantly increased ability to hold their
breaths compared to average athletes. A study done by Heusser, K.
and his colleagues (2009) revealed that elite divers, during
voluntary apnea, have longer apnea time that is coupled with a five
old increase in sympathetic nerve activity. Vascular resistance
also increased markedly in elite divers explaining their ability to
hold their breaths for several minutes. Since the sympathetic
vasoconstrictor activity of these athletes is activated by
excessive chemoreflex, their vital organs are supplied with an
adequate oxygen supply. This finding is applicable during periodic
apnea of elite divers but is difficult to observe in
untrained athletes who undergo voluntary apnea.
Meanwhile, the quest to break the current world record in
breath-hold competition (10:12 min) at a depth of 214 meters has
been the main goal of competitive breath-hold divers (Lindholm, P.
and Lundgren, C., 2009). However, physiological reactions and
pathophysiological mechanisms need to be breached by each diver
attempting to prolong the minutes underwater and at deeper lengths.
For less-trained divers, they fall victims to decreased oxygen in
the brain called hypoxia (Hiebert, S. & Burch, E., 2003) as
well as pulmonary edema and hemorrhage in the alveolar sac after
diving (Leuenberger, U. et al, 2001). Divers who fall victims to
hypoxia underwater are in extreme danger of drowning once they lose
consciousness (Lindholm, P. and Lungdren, C., 2009). Other factors
related to increased risk of mortality while diving include having
an existing cardiac problem (Lindholm, P. et al, 2002); or divers
who have experienced earlier alternobaric vertigo (Lindholm, P. and
Lungdren, C., 2009). Researches have shown that the common effects
of diving response include bradycardia (Shiraishi, M. et al, 2002);
hypertension (Irgens, A. et al, 2007), arrhythmia (Kroenke, K. et
al, 2002) along with contraction of the spleen (Lindholm, P. and
Lungdren, C., 2009). The respiratory system also experiences a host
of problems once the diver prolongs his/her stay underwater. Some
examples include intrapulmonary hemorrhage (McCaul, C. et al,
2006), edema (Leuenberger, U. et al, 2001) and insufflation and
exsufflation of the glossopharynx (Lindholm, P. and Lungdren, C.,
2009). These divers are also at risk of blackout during ascent
(Shiraishi, M. et al, 2002), nitrogen narcosis (Irgens, A. et al,
2007) and decompression sickness.
While only immediate effects of the diving-response have been
recorded, there are some studies that have recognized the long-term
health effects of a career in diving (Ross, J. et al., 2007). For
example, aside from the common problems such as dysbaric bone
necrosis and decompression illness (Ross, J. et al, 2007)
associated with a long career in diving, studies have also noted
that these divers may experience musculoskeletal symptoms
(Pingitore, A. et al, (2007; Kroenke, K. et al. 2002); cognitive
dysfunction (Muth, C. et al, 2005); difficulties in concentration
(Taylor, C., et al, 2006) and forgetfulness (Kroenke, K. et al,
2002; Taylor, C., et al, 2006) along with hearing impairment.
However, it is imperative to acknowledge that diving animals are
more adapted to longer and deeper breath-hold diving (Mori, Y.,
1999). While the immediate physiologic effects such as bradycardia,
peripheral vasoconstriction, conservation of oxygen and a decrease
in CO or cardiac output are the same effects observed in diving
mammals, humans are still less adapted to longer breath-hold diving
(Ferrigno, M., et al, 1997). The main deterrents in humans are the
presence of arrhythmias and increase in blood pressure (Ferrigno,
M. et al, 1997).
In conclusion, the effects of the diving response on breath-hold
divers include various physiological impacts such as arrhythmia,
increased blood pressure and cardiac output, bradycardia and
conservation of oxygen with resulting anaerobic glycolysis.
However, the most dangerous effect of prolonged breath-hold diving
is hypoxia- which may result to loss of consciousness and
eventually drowning of inexperienced divers. While breath-hold
diving has elicited wide attention as an extreme sport, the desire
to breach current world records in terms of longevity under water
and depth submerged by breath-hold divers has always been present.
A number of researchers have acknowledged that the theoretical
limits have already been surpassed and apparently, the ability to
breach current records may lie on the amount of energy a
well-trained diver possess to achieve his goal of breaking world
records. If a diver can conserve more oxygen and produce more
energy without losing consciousness, this might significantly
improve his/her time to hold his breath underwater and at the same
time allow him to reach deeper into the water.