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PHOTO CREDIT
we have conducted several thousand echocardiograms and
documented various degrees of bubbles. We shared our findings
with the tested divers, and they often modified their dive profiles
(by decreasing bottom time, adding decompression time or
using more oxygen) to keep their postdive bubble grades and
their risk of DCS low. We also conducted basic anthropometric
measurements, lung-function tests and evaluations of
participants’ fitness. A number of divers have provided
blood samples for studies of microparticles and markers of
inflammation and cell injuries. These studies continue, and
data are still being examined. Some preliminary findings were
presented in the Journal of Applied Physiology.
Oxygen Toxicity and Erectile Dysfunction
Drugs
PDE-5 inhibitors are a group of drugs that includes Cialis and
Viagra and are used for the treatment of erectile dysfunction
(ED) as well as some other indications such as enlarged
prostate. PDE-5 inhibitors achieve their desired effects by
dilating arteries and increasing blood flow. Most of that
effect is limited to targeted areas, but circulation in the brain
may also be affected to a lesser degree. Theoretically, this
could increase the risk of oxygen toxicity. Indeed, DAN was
called by a diver who suffered seizure activity during a dive
while he was using a drug for ED. This started a discussion
among researchers, and eventually a study was initiated by
Dr. Ivan Demchenko and coworkers at Duke University. This
experimental study showed that animals treated with PDE-5
take less time to develop oxygen seizures when exposed to
hyperbaric oxygen. The lesson learned for divers is to not
combine PDE-5 drugs with high partial pressure of oxygen.
Various preparations of PDE-5 stay in the blood for various
lengths of time, and divers using these drugs should be aware
of the half-life times of the specific drug they use.
Effects of Pseudoephedrine (PSE) on
Oxygen Toxicity
PSE is an active component in many over-the-counter (OTC)
drugs used to combat congestion from common colds or
allergies. Among the most well known of these drugs is Sudafed,
which is widely used among divers. There were concerns that
it may not be safe to use Sudafed while diving with nitrox or
other hyperoxic gases, but these concerns were never addressed
in experimental studies. DAN sponsored a study by Dr. Dean
Jay of the University of South Florida. The study used an animal
model and showed that normal doses of PSE should not increase
the risk of oxygen toxicity, but very high doses (which could
be inadvertently achieved by divers using multiple OTC drugs
containing PSE at the same time) could increase the risk. The
study also confirmed the notion that some individuals at some
times may be more vulnerable to oxygen toxicity than the
average diver. To learn more about oxygen toxicity, see Expert
Opinions on Page 44.
Effects of Predive Checklist Use on
Diving Mishaps
In the summer of 2012 DAN conducted a study on the effect of
predive-checklist use on the incidence of diving mishaps. The
study was conducted in four different locations with the help
of DAN summer interns. More than 1,000 divers volunteered
for the study. Findings indicate that the incidence of mishaps
(such as out-of-air emergencies, buoyancy problems, buddy
separation, exceeding planned depths or time) was reduced
in divers who received predive checklists before diving in
comparison with divers who were not given checklists but who
could have used their own. While most training agencies teach
the use of predive checklists, it appears that many divers do not
use them in unsupervised diving. We hope the demonstration
of efficacy this study provides will help support a campaign for
an improved culture of safety in diving that includes the use of
predive checklists. Checklists are effective tools for preventing
human errors and reducing injuries and fatalities; to read more
about this study, see Safety 101 on Page 54.
Studies in 2013
Several new lines of research will be explored this year.
The first will be the prevalence of increased muscular mass
of the left heart (known as left ventricular hypertrophy or
LVH) in divers and its correlation with the incidence of
heart-rhythm abnormalities during diving. This study will
use echocardiography to establish LVH and continuous
electrocardiogram (Holter monitoring) during diving to
monitor for arrhythmias.
DAN is also working on studies that will address physical
fitness for diving in greater detail; both the requirements and
the methods of evaluation will be reviewed.
Another study will address the possible effects of scuba and
breath-hold diving on brain function in divers who did not
exhibit obvious signs of injury. For this study, we will use a
digital pen and a clock-drawing test — a test with a long history
in clinical medicine. In combination with a digital pen, this test
becomes a very sensitive and valuable tool in the early detection
of diseases such as Alzheimer disease. It is sensitive enough to
detect minor and transitory changes in executive brain functions
that could be occurring after some extreme dives.
Through this research, DAN continues its ongoing mission of
promoting dive safety and helping divers in need. AD
Cooperation
DAN’s core mission is to improve dive safety. We continually
enhance the caliber and capacity of our medical services
and research through collaborations with leading institutions
and research groups. In recent years these include:
Duke University, University of Pennsylvania, University
of California at San Diego, University of Split (Croatia),
University of South Florida and the Watson Clinic.