EUBS 2017 has left us with more questions than answers, on the topic of post-dive bubbles.
Ballestra presented the preliminary results of an exploratory study of the effects of sonic vibrations on post-dive venous gas emboli detected by transthoracic echocardiography1. (more…)
Recompression treatment and hyperbaric oxygen (HBOT) are standard treatment for decompression illness. While it is generally accepted that sooner recompression is associated with better outcomes, the urgency of treatment may not be same for all cases. Looking for practical guidelines we regularly consult published case series. Three case series presented at EUBS 2017 may be used to illustrate problems with such approach. (more…)
Immersion pulmonary edema (IPE) continues to be a central focus of dive medicine researchers and clinicians. Late last week, at the 2017 EUBS Annual Meeting, four scientists presented five different studies on the subject.
It appears that IPE is significantly more common than previously reported. In a two year period (2014-16) one hyperbaric facility in Cozumel diagnosed 40 cases of IPE among recreational scuba divers1. On the other side of the world, there were 21 cases of IPE reported among French military rebreather divers in a six year period2. (more…)
Venous gas embolism (VGE), or bubbles, in divers postdive indicates that their decompression was too fast, their bodies became supersaturated and free gas emerged from solution in tissues. The occurrence of free gas is considered a necessary condition for decompression sickness (DCS), which can happen even without VGE. However, the presence of VGE increases the number and types of possible harms to the body and thus the probability of DCS.
A number of studies indicate variability in proneness to DCS among divers; however, the question of whether divers who have suffered DCS produce bubbles more readily in general has not been answered yet. To answer this question, researchers would need to identify “bubblers” and “nonbubblers” and observe the outcomes of their dives over some period of time, which would require a lot of resources and time.
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A popular article over last few days is one about crystalline salt that can uptake and store oxygen in high concentration. It was published in Chemical Science by Jonas Sundberg and coauthors from University of Southern Denmark.1 The article describes a synthetized crystalline containing cobalt combined with an organic compound, which has some properties of biological carriers of oxygen like iron-based hemoglobin in mammals or similar copper-based carriers in other animals.
The most significant property of this crystalline is that it binds oxygen reversibly – it can uptake oxygen and release it – and that this process may be controlled. Professor Christine McKenzie, the leader of the team that synthetized the crystalline, told the Science Daily2 that among other applications: “When the material is saturated with oxygen, it can be compared to an oxygen tank containing pure oxygen under pressure – the difference is that this material can hold three times as much oxygen. This could be valuable for lung patients who today must carry heavy oxygen tanks with them. But also divers may one day be able to leave the oxygen tanks at home and instead get oxygen from this material as it “filters” and concentrates oxygen from surrounding air or water. A few grains contain enough oxygen for one breath, and as the material can absorb oxygen from the water around the diver and supply the diver with it, the diver will not need to bring more than these few grains.”
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At the ONR-NAVSEA Undersea Medicine Program Review that took place this summer in Durham, North Carolina, two presentations pertained to monitoring Navy divers’ breathing gas for oil particulate contamination and carbon dioxide (CO2) levels.
Contamination of breathing gas may cause adverse health effects in divers. The type of injury depends on the contaminant. Impaired judgment and loss of consciousness, both of which may be deadly underwater, are among the most severe symptoms associated with CO2 and oil particulate contamination. The U.S. Navy bases their breathing air standards on CGA G-7.1 Grade D criteria, which lists a safety standard of 5 mg/m3 for oil mist and particulate and a maximum of 1,000 parts per million for CO2. So far, there is no convenient means of monitoring breathing gas for these contaminants outside of specialized laboratories.
Last April, a Canadian woman named Stacey Yepes experienced stroke symptoms, but by the time she made it to the hospital her symptoms were gone. Because her physicians could not find any signs of stroke, they believed that she was displaying symptoms of stress and released her home. A few days later, she had a similar attack and used her phone to tape herself during an episode in which she suffered from facial drooping and slurred speech. The video helped her doctors diagnose her with TIA (transient ischemic attack).
In many cases of diseases with transitory symptoms, physicians are unable to diagnose patients and opportunities for early treatments are missed. In the case of TIA, it is especially important to establish an early diagnosis and provide treatment to prevent the progression of symptoms and permanent loss of brain tissue. TIA can lead to blood clotting in the brain, but early administration of thrombolytic medication can prevent clotting and brain damage. Because of the transitory nature of TIA symptoms, some hospitals offer stroke telemedical consultations to enhance diagnosis of and establish early eligibility for thrombolytic medication. By using video connections, they establish a correct diagnosis in 96% of cases, as compared with only 83% of cases in which symptoms are only reported by phone.
Obesity 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.
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.
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.
The Dive Lab 