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Obesity and Scuba Diving
Questions are often asked about diving while overweight, body mass index and percent of body fat. There is no question that the risks are increased for divers who are overweight (BMI greater than 30kg/m2). There are several reasons why adiposity is important in considering whether or not a person is 'fit to dive'.
Decompression
Illness risk increase
Cardiovascular
Disease (Hypertension) risk increase
Diabetes
risk increase (blood sugar fluctuations)
Decreased
pulmonary function (hypoxia, CO2 retention)
Decreased
physical fitness
Increased DCS
Decreased ability for Self rescue
Decreased Buddy rescue ability
Increased risk of panic in stressful situations
There is a considerable body of work relating an increased incidence of DCS to increased percentage of body fat. Higher DCS rates have been noted in the older diver, due in part, to the gradual increase in skin fold thickness (% body fat) and possibly to the increased incidence of cardiovascular disease, commonly noted in the obese.
Michael Powell, PhD
describes the effects of diving in
the obese as follows: "From the standpoint of
decompression, when one dives, nitrogen dissolves in
all tissues of the body in proportion to the gas solubility and the
blood
flow to the tissue. As far as joint pain DCS is concerned (“the
bends”),
this arises primarily in tissues that contain water. However, nitrogen
is very soluble in adipose (fat) tissue and, in
overweight people, the fraction of this tissue in the
body is high. In some cases, nitrogen loads can rise in adipose tissue
and bubble formation can be extensive. While one would not develop pain
DCS from this, these gas bubbles would be dumped into the venous system
where they are carried to the heart and lungs. If the gas bubble loads
to these organs is high, the lung capillaries become blocked, blood
pressures
rise in the pulmonary artery, and bubbles can pass through the lung
vasculature
(or a PFO, patent foramen ovale in the heart) and embolize the brain.
We
end up with a vein-to-artery "stroke" and neurological DCS."
Undersea
Biomed Res 1984 Dec;11(4):395-406
Health risk factors for the development of
decompression
sickness among U.S. Navy divers.
Dembert ML, Jekel JF, Mooney LW
185 U.S. Navy divers who did experience decompression sickness either before or after examination had significantly higher measures of skin fold thickness and weight when compared to those who remained free of decompression sickness. These findings suggest that obesity may be a contributory factor to the occurrence of decompression sickness.
Aviat
Space Environ Med 1984 May;55(5):391-5
Weight/height indices and percent body fat among U.S.
Navy divers.
Dembert ML, Jekel JF, Mooney LW
McCallum RI, Petrie A
Dysbaric osteonecrosis. Etiological and pathogenetic concepts.
Chryssanthou CP
Dysbaric osteonecrosis appears to be independent of decompression sickness. The 2 conditions, however, may share etiologic and pathogenetic factors. The incidence of osteonecrosis is influenced by the number of hyperbaric exposures, extent of pressure, decompression profile and possibly by the rate of compression and degree of obesity.
Circulating venous bubbles in recreational diving: relationships with age, weight, maximal oxygen uptake and body fat percentage.
Carturan D, Boussuges A, Burnet H, Fondarai J, Vanuxem P, Gardette B
Faculte des Sciences du Sport, Luminy, Marseille, France
Decompression sickness (DCS) is recognized as a multifactorial phenomenon depending on several individual factors, such as age, adiposity, and level of fitness. The detection of circulating venous bubbles is considered as a useful index for the safety of a decompression, because of the relationship between bubbles and DCS probability. The variables investigated were: age, weight, maximal oxygen uptake (VO2max) and percentage of body fat (%BF). The effects of age, weight and VO2max are more significant than the effect of %BF.
Aviat
Space Environ Med 1997 Aug;68(8):695-8
Relationship between age and susceptibility to
altitude
decompression sickness.
Sulaiman ZM, Pilmanis AA, O'Connor RB
Armstrong Laboratory, Crew Technology Division, Brooks
AFB, TX 78235-5104, USA.
In some areas of the world where medical fitness is more stringently regulated than the US, a high BMI (body mass index) would deter one from diving. Complicating conditions of adiposity include diabetes mellitus, dyslipidemia or hypertension and their associations with coronary artery disease. The BMI is important to divers due to the fact that people with high BMI are more prone to coronary artery disease and an untoward coronary event while diving. A BMI above 30 kg/m2 is thought to be excessively risky for diving. Of course, measured %BF can sometimes show that the diver is quite large and muscular and this needs to be taken into consideration. Figure your BMI by going to this web site:
http://www.nhlbisupport.com/bmi/bmicalc.htm
Appetite Suppressants
Medications given for appetite suppression also have
a risk for diving in that most have psychotropic effects and can cause
elevated blood pressures. The possible ill effects of nitrogen added to
the drugs are not known.
The overweight person
as also at increased risk for
diabetes. Unknown and untreated diabetics are at risk for wide swings
in
blood sugar levels, often brought on by stressful situations such as
diving
and cold water. Low blood sugar (hypoglycemia) is a risk factor for
divers,
known to cause drowning and gas embolism on ascent.
Increased DCS
Decreased ability for Self rescue
Decreased Buddy rescue ability
Increased risk of panic in stressful situations
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Ernest Campbell, MD, FACS All Rights Reserved.
