dive medicine

What is the Common Risk Faced by Recreation, Technical, and Breath Hold Divers?

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.

Pulmonary Edema - Water in Lungs

In the Cozumel study, an analysis of risk factors was attempted. For each case of IPE, there were two non-IPE recreational diving cases admitted to the same facility. Patients involved in the IPE cases in this series were found to be older than patients in the corresponding non-IPE cases. The non-IPE cases did more multi-day, repetitive, deeper and longer dives than IPE cases, and had a history of regular exercise more often. This could be interpreted as showing that IPE occurs more frequently in less fit divers, but more evidence is required to come to a definitive conclusion. Data from this study was presented in poster form, and we can only hope that this will be published as a full length paper at some point, with more details and data analysis.

Military divers involved in the French rebreather study were categorically both young and fit. The main factor that triggered the IPE in these cases was negative pressure breathing, which is present in back mounted rebreathers with lung centroid deeper than the breathing bag. In 30% of cases the situation was exaggerated by improper rebreather adjustment.

A third study report presented a case of pulmonary edema associated with Takotsubo syndrome in a 75-year old woman3. The woman had previously performed 100 dives. On the day of incident she performed a rapid ascent after 23 minutes at 84 feet. The reason for the ascent was not reported. Twenty minutes after surfacing, she started feeling the chest pain, pain in the bottom of the lungs, and difficulty breathing. Within an hour the patient reported further increased difficulty breathing was admitted to the emergency department. Initial evaluation with echocardiography revealed pulmonary edema, and further test found signs of pneumomediastinum with signs of acute coronary syndrome and dysfunction of the heart with characteristics of Takotsubo syndrome. The patient also underwent a coronarography which showed normal coronary arteries. Takotsubo syndrome is known as a stress induced cardiomyopathy and patients typically recover well, unless in case of aquatic activities, they drown. This patient probably decided to end the dive due to symptoms caused by this condition and associated pulmonary edema. During the ascent, she also experience a lung over-pressurization which resulted in the pneumomediastinum.

A fourth presentation showed that IPE may occur more often as the disabling condition preceding the drowning4. While at the surface in a vertical position, swimmers lungs are at a greater pressure than surface air, and they must breathe against negative pressure caused by their immersion. While this is occurring, their heart is additionally stressed due to a shift of blood from the extremities, to their chest cavity, also caused by immersion. It is expected that some water will seep into the lungs from the bloodstream in this situation, but in divers who are struggling due to panic or lack of buoyancy, this could develop into full pulmonary edema, flooding the alveoli completely and disabling a diver, who would then drown.

The final presentation on IPE covered risks involved in breath hold diving. While all activities that involve immersion in water have some risk of IPE, the risk involved in breath hold diving may be greater than previously understood. According to this presentation, 25% of elite breath hold divers have experienced IPE. The study used underwater echocardiography to study the mechanisms of IPE during breath hold diving, and preliminary reports indicate that IPE in breath hold diving is associated with hypoxia, pulmonary capillary congestion, and left ventricular dysfunction.

 

 

References
  1. Garcia-Magna E. Risk factors for scuba diving pulmonary edema in recreational divers. p. 78
  2. Gemp E et al. Immersion pulmonary edema with rebreather among French military divers from 2009 to 2015: role of hydrostatic imbalance. p 74.
  3. GArcia-Magna E. Takotsubo syndrome associated with scuba diving pulmonary edema (SDPE). p 79
  4. Castagna O, MacIver D. Is cardiogenic pulmonary edema a critical step in the pathophysiological mechanism of drowning? p. 20.
  5. Marabotti C. Breath hold diving-induced acute pulmonary edema. New pathophysiological insight from underwater Doppler echocardiography. p. 76
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Skin Mottling after Diving May Be Result of Brain Lesions Caused by Gas Bubbles

Cutaneous decompression sickness (DCS), or “skin bends,” most often manifests as skin mottling on the torso, upper arms and buttocks to various degrees. An associated marbled look to the skin is sometimes referred to as cutis marmorata. While cutaneous DCS is most likely related to gas occurring in body — after decompression or due to lung barotrauma or some medical procedures — there generally is no accepted explanation how the free gas is related to skin changes.

Possible explanations include the occurrence of gas bubbles in subcutaneous tissues, occlusion of subcutaneous arteries with circulating bubbles bypassing the lung filter (as with a patent foramen ovale), inflammatory reaction bubbles present locally or bubbles causing endothelial injury at remote locations.

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Bubble Production in Divers Who Have Had DCS

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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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.