Research Projects

High-Fat Diet and Risk of Decompression Illness

dietObesity has been long considered a risk factor for decompression sickness (DCS). It has been based on findings in animal studies and epidemiological data in military diving. There was no data to confirm the same effects of obesity on incidence of DCS in recreational diving; however, there were some studies indicating a positive correlation between body mass index (BMI) and likelihood of venous gas emboli (circulating gas bubbles) after dive.

In a recent paper, Kaczerska D, et al. The influence of high-fat diets on the occurrence of decompression stress after air dives. UHM 2013;40(6):487-497, intended to test possible effects of high fat intake on risk of DCS.

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A Look at Crowdsourcing for Research Funding

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Crowdsourcing is a means to raise funds through public contributions in a manner which allows a large number of small contributions to make a difference. Originally started in technology areas where considerable upfront capital was required to make the project viable, SciFund and Experiment.com have taken this into the research arena to allow small research projects to gain support. As those in research know, it is notoriously difficult to raise funds for small research projects and crowdsourcing provides that opportunity. As an example of how well it can work, Experiment has raised $600,000 over the last 4 years.

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Scuba diving and Pregnancy: Is Another Study Justified?

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The possible effects of scuba diving on pregnancy have been a concern since the sport began. The main concern is that decompression may cause occurrence of free gas that could hurt the fetus. Indeed, it was shown in sheep that circulating bubbles do occur in maternal and fetal circulation, even when the mother does not display signs of decompression sickness. As such, the general advisement issued is not to dive while pregnant.

Unfortunately, most women become aware of their condition weeks or months after conception and some after they have already dived. This raises concerns about possible damage to their fetus and women often seek counseling after the fact. In an era of evidence-based medicine, it does not suffice to offer good wishes. However, the evidence about safety of diving while pregnant or damaging effects on outcome of pregnancy is not available.

In the past  several survey-based studies queried about exposure and outcome, but most came up short of conclusions, because, wisely, most women stop diving when they learn they are pregnant. Thus, there are few reported cases of pregnancy exposed to diving and the exposures are limited to a small number of dives. This further limits the ability to detect a possible small increase in frequency of adverse outcomes above the baseline rates. Thus, it seems that another survey is justified if it could provide a sufficient sample size to achieve reliable conclusions.

Dr. David Baud, MD, PhD, specialist in obstetrics, gynecology and materno-fetal medicine from Lausanne, Switzerland, proposed an international survey that could reach enough women who had inadvertently dived in pregnancy to yield sufficient data to detect even small increases in rates of possible adverse events.  The study is supported by International DAN organizations: DAN Europe, DAN America, DAN Southern Africa and hopefully by others. Researchers from these organizations are co-investigators on the study, but most the important support will be that of female divers from all over the world.

If you are a female diver, regardless if you are currently pregnant or not, please click and complete the survey. The survey is available in English and in several other languages. It is anonymous and it takes up to 10 minutes to complete it.

For more information about pregnancy and diving read:

Scuba diving and pregnancy: Can we determine safe limits?

The Risks of Diving While Pregnant

Post written by: Petar Denoble, MD, D.Sc.

Trip Report: Left ventricular hypertrophy and risk of cardiac death in divers

We’ve just recently returned from the first field trip for the left ventricular hypertrophy and risk of cardiac death in divers study in Bonaire (August  31-September 7). For the first time, we field tested the study logistics and the protocol. The dive trip was organized by Down Under Surf & Scuba in Raleigh, N.C. Out of 36 subjects in the group, 25 were qualified participants over 40 years of age and actively participated in the study. Most of the baseline testing was completed prior to the trip in four sessions: two at DAN Headquarters and two at the dive shop. Five new subjects joined us from other parts of the country and were pre-screened upon arrival to Bonaire.

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The Buddy Dive Resort was our central study location. They were very accommodating and allowed us to use their main classroom as a lab. The classroom was at the waterfront where most divers enter and exit water or board the boat for the boat dives.

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 The plan was to get every participant scanned by echo twice after a full day of diving and once in the morning after a night’s rest. We took take a resting electrocardiogram (ECG) to monitor heart rate variability after a full day of diving on select dive days. All divers carried the Holter Monitor during at least one dive and were asked to record the depth and time of all their dives.

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The compliance was nearly perfect. In fact, the only delays were related to travel time back from some remote dive sites. We completed a total of:

  • 100 echo scans
  • 50 resting ECGs
  • 24 underwater Holters
  • Nearly 500 recorded dives

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The research team included cardiologist Dr. Douglas Ebersole, two professional echo cardiographers Brandy Emory of Lakeland Clinic and Lisa Caudill of Duke and myself. They did an excellent job maintaining the tight schedule and were well received by all of the participants. They even had time to join participants on some dives.

Scott Powell, the manager of Down Under Surf & Scuba and Rochelle Wright, a DAN Member Services specialist, managed all of the logistical challenges so we were able to complete our study. We’re very thankful for their support as well as the overwhelming support from the participants. We appreciate your participation and thank you for helping us to work toward improving diver safety.

Photography and Post by: Petar Denoble, MD, D.Sc.

Microparticles and DCS

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Two studies presented by Steven Thom, one with divers and the other with isolated cells, indicate a role of inert gas under pressure in nitric oxide dependent oxidative stress response which results with microparticles (MP) and inflammation. Microparticles are linked to intravascular bubbles and the cell study seems to indicate that MPs come first and bubbles after (chicken or the egg). The human study provided less obvious answers. While this represents significant progress in elucidating cellular mechanisms involved in decompression sickness, it is far from a straight forward answer. DAN contributed to this study in collaboration with University of Split, Croatia. Sixteen divers volunteered in four dives each and provided blood samples before and after their dives. DAN specialists monitored their heart rate during the dive using an underwater ecg monitor and the presence of venous gas emboli postdive using echocardiography. Additional blood samples have been collected during field studies at Innerspace, a technical diving event in Grand Cayman. Analysis of this data is pending.

The full paper “Microparticle production, neutrophil activation, and intravascular bubbles following open-water SCUBA diving” is available online.

Post written by: Petar Denoble, MD, D.Sc.