Speleology, a sporting activity in nature, is practiced in France by a small number of people. The French Federation of Speleology (FFS) has 7,000 licensees, but practitioners are estimated at about 20,000.
This activity has the particularity of organizing its own assistance, under the supervision of the Prefects and in collaboration with the Departmental Fire and Rescue Services (SDIS). The Federation has a specialist committee called Speleo-Secours Français (SSF), which manages not only relief but also training, supervision and monitoring of operations.
This systematic follow-up of accidents for more than 25 years makes it possible to produce statistics on the causes of accidents and is the subject of several medical theses.Through this follow-up, the recent presence of non-traumatic deaths intrigued the Federation Medical Commission. A working group of three physicians worked on these deaths of “physiological” cause, whose cardiovascular origin might seem logical.
Methodology of the study:
It consisted of studying the documents in our possession: medical theses, SSF activity reports, federation’s insurance files, articles gleaned from various medical and speleological magazines, questioning of some nearby sports federations (mountain, canoe- kayaking, canyoning, diving).
The major difficulty was the almost total absence of medical findings during the rescue operation (the doctor usually arriving after the death) and the lack of reliable data on the precise circumstances and symptoms observed.
In addition, the different sources of information are sometimes contradictory.
Cross-checking of the various sources found 18 deaths from non-traumatic causes between 1987 and 2003. This is a fairly rare event, representing only 5% of underground deaths. Comparatively, non-traumatic deaths account for 24% of skiing deaths and 42% for hiking …
The distribution by sex found 15 men for every 3 women (but women are very minor among the practitioners).
The age distribution ranges from 15 to 56 years (average 43.8). If the death rate of an unusual age of 15 is set, the average age is 46.7 years.
The important thing is the novelty of the phenomenon: no such deaths were reported until 1990. It is this recent character that justified the study, in order to find its characteristics and, above all, prevention.
Death of cardiovascular origin?
The question may seem ridiculous, but we are not sure we have come to the conclusion … As we said before, we were not able to put together precise descriptions. However, apart from diving deaths and immediate deaths, the victims presented a disabling state of disability before dying more or less rapidly. The delay (not quantified) between discomfort, loss of consciousness and death seems to be a few dozen minutes at the most.
This rapidly progressive character towards a fatal outcome brought us closer to these sudden deaths.
Sudden death in sport:
The medical literature is quite rich in publications on the subject. Without going into detail, two fields of investigation have to be taken into account: cardiological factors and general factors.
The direct cause of death is essentially related to two mechanisms: a ventricular rhythm disorder in 75% of cases (tachycardia or fibrillation), infarction in 15% of cases, and various conduction disorders.
Deaths whose etiology is not found are fairly few (about 4%). The pathologies causing death are quite varied:
– coronary atherosclerotic pathology and cardiomyopathy are the main causes;
– more anecdotal then comes the whole cohort of rhythmic conduction disorders and viral myocarditis.
The general factors:
They are better known as risk factors: smoking, overweight, hypertension, diabetes, hyperlipemia, a family history of cardiovascular disease, to which stress will be added.
The absence of possible interrogation of the entourage does not give us a key to reading these risk factors, but some factors are found in the files.
Characterization of effort in speleology:
Recent research has measured the cardiac frequencies observed during rope climbing in “jumar” technique. Young and trained speleologists were able to measure frequencies up to 212 pulses per minute.
A study in occupational medicine at the sewer leakage station (similar to caving practice) found that heart rates between 67% and 87% of the theoretical maximum heart rate (FMT) as strong.
Caving is an activity requiring permanent muscular effort, enduring, for many hours (8 h represents an average exit), linking very varied progressions (walking, climbing, river, ramping, descent and ascent of wells), including passages more intense (or even maximum effort) like the rope lifts and the narrowings.
The siphons accessible only to diving speleologists pose the classic problems of diving (gas exchanges among others), but complicated by the fact that the dive is not homogeneous as at sea. In the case of embedded cavities, the diver alternates climbs and descents complicating the bearing calculations and the gas mixtures used, as well as narrow areas and often visibility due to sludge suspended by the passage of the plunger.
Cardiac stress can be estimated as very significant in speleo: if the effort is usually endurance, the cavities involved and the difficult passages cause phases of resistance effort which can therefore reach or even exceed the FMT.
The influence of the environment:
To this concept of effort will be added the characteristics of the environment, which will amplify the cardiac stress.
Even though the caves have sheltered humans since prehistory, the environment remains fundamentally hostile!
The average temperature of the cavities depends on various factors (climate, latitude, altitude of entry, depth, ventilation, presence of running water), but it is rather cool !! In our climates, the mean is around 11 ° C, the coldest falling to 0 ° C, the hottest reaching 17 ° C.
Apart from the particularly dry fossil networks, the air humidity is always close to 100%. This saturation alters the sensation of thirst and destroys the evapotranspiration. The presence of mud, which complicates the progression and of the aquatic parts, is often associated with the risk of keeping wet and cold attire for hours (in the absence of suitable clothing such as the neoprene suit).
The presence of gas:
The cavities of certain regions often contain a non-negligible proportion of carbon dioxide, resulting from the fermentation of the surface vegetation cover, which varies according to the season.
A rate of 3 to 4% is not uncommon and can go up to 7%. Cardiac performance will be all the more threatened by these rates which cause dyspnea and headache, or even electrocardiographic changes such as repolarization or ESV disorders.
The presence of other gases is rarer.
It is mainly because of explosives in confined spaces, which are widely used to widen passages that are too narrow, that carbon monoxide can be found in a significant way, preventing further exploration before its complete dissipation.
Under this general term, which refers to the organism’s obligation to adapt itself to external stimuli, we can group various notions: darkness, silence (total) or ambient noise sometimes deafening (river, waterfall), technical difficulty , mental commitment (vertical, narrow), technical level, flood risks, loss of time passing, anxiety and claustrophobia, etc.
The physiological state of the individual:
Not to mention the general health of the practitioner, a state of general fatigue, a convalescence of recent disease, hypoglycemia, dehydration, hypothermia can accentuate the effects of the effort. At most, the conjunction of these three disease states characterizes the state of exhaustion, which can be fatal without proper treatment.
All these constraints however have a specific prevention, making it possible to minimize their deleterious effects.
Training, technique, equipment, supervision and weather monitoring limit the objective risks of the activity. The very low rate of caving accidents shows that this accumulation of constraints remains manageable in the vast majority of cases: there are only about thirty accidents per year in France, one third of which require medicalization.
Knowing that most of the relief is for non-federated speleologists and very often tourists, it can be said that volunteer rescue speleologists perform a public service mission.
In the absence of precise arguments, but on the basis of the few symptoms recorded, we have constructed the plausible hypothesis that sudden deaths, observed in speleology outside of any traumatic context, had a cardiovascular origin.
The rare symptoms reported in the records include malaise, abrupt asthenia, precordial pain, oppression, digestive disorders (nausea, vomiting, diarrhea), followed by loss of consciousness and then death.
The notion of stress was also noted in several files.
Sudden death in sports is a well-known phenomenon and we have classified deaths in this category because of the rapid occurrence of death after a disabling condition of general discomfort.
An information sheet, to be completed by the doctor or rescuers, will be disseminated through Speleo-Secours Français, in order to better characterize these events whose scarcity should not make us forget the recent development and possible prevention.
The possibility of preventing these accidents is the questioning that led to this study. Cardiovascular risk factors are well known to any physician and we felt it would be useful to strongly advise a practitioner’s medical examination as long as risk factors existed, starting with age.
Caving is not a competitive sport: it is open to all ages and can be practiced at any desired level, from the simple horizontal and family walk to exceptional cavities requiring a major commitment or “non-standard” activities, such as siphon diving. It will be understood that this is a case-by-case study, the role of the physician being essential to advise the adequacy between the type of effort required and the physiological state of the practitioner.
The medical contraindications of speleology are: syncopal conditions and epilepsy, insulin-dependent diabetes, true dizziness, cardiovascular disease (dystolic left ventricular dysfunction and impediment to ventricular ejection, of the recovery), progressive pleuro-pulmonary lesions, severe static or dynamic morphological affections (in particular of the spine). In the context of leisure, we must discuss: renal insufficiency, heart disease, severe bone, ligament or joint damage, convalescence of serious diseases. Pregnancy is a contraindication from the second trimester.
On the whole, these contraindications are rarely a problem. The physician’s role will be fully fulfilled if he draws the practitioner’s attention to the general risk factors: tobacco, overweight, hypertension, metabolic overload (diabetes, hyperlipemia), stress and lifestyle management (sleep, rest, nutritional balance).
Speleology does not generate a significant risk, as the rare hypermediated accidents do not obscure a rich and fulfilling practice.
The underground environment, however, requires a cautious and careful approach, best disseminated by federal structures and clubs. Of the relatively small number of accidents reported over the past 25 years, we have identified the rather recent nature of deaths due to non-traumatic “physiological” causes. Despite the poor descriptions, we classified these deaths as an athlete’s sudden death. A collection of data, which we hope will be more exhaustive, can provide us with more convincing evidence.
In the meantime, we emphasize the interest for practitioners to see their attending physician to assess their health status and their ability to cope with a full-time sport activity that can lead to maximum cardiovascular effort.
The Federal Medical Commission is interested in any contribution in this field.