The First Diver

The first known diver in history

Story of the First Diver

Perhaps one of the first famous divers in history is the greek Skyllias from Skione, a breath-hold diver who played an important role in the war between Greece and the Persian Empire, around the year 490 BCE.

Diving for treasure

In ancient times, diving was an activity strictly for the lower classes and the main objective was to use marine creatures as food rather than the greed to find gold and other valuable objects.
During the Medic Wars, Skyllias and his daughter Hydna served persian king Xerxes (486-465 BC), rescueing for him several underwater treasures.

Skyllias and Hydna

But when king Xerxes threathened to attack Greece with his fleet, Skyllias and Hydna took advantage of a storm and and approached the persian base to cut off the ships anchor lines, leaving the fleet defenseless and at the mercy of the storm. Finally, the storm dragged the ships against the rocks destroying them and leaving the persian army helpless and defeated.
Although there are is not much information about this heroic deed, the Amphictyonic League ( an ancient religious association of Greek tribes) dedicated statues of Skillias and Hydna at the sacred site of Delphi.

Effects of pressure on a diver lungs

Never hold your breath while scuba diving!

The lung capacity on an average adult is 6 Lts of air. This air volume will be affected by the increasing underwater pressure as the diver descends, as stated in this article.
As the diver descends, the lungs volume will decrease as a result of the increase of pressure. This change of volume will be proportional to the number of atmospheres at a given depth.
At 10 Mts / 33 Feet, where the pressure is 2 bar /ata, lung volume will be one half smaller than at the surface. At 30 Mts / 100 Feet (The recommended depth for recreational divers) the lungs volume will be as small as one quarter smaller than at the surface.

Pressure in our lungs

But even when the lung volume keeps becoming smaller as the diver descends, the air capacity remains the same. So when we breath compressed air at depth, we are actually adding an extra amount of air to our lungs in order to equalize them to the surrounding pressure. If a diver holds his / her breath while scuba diving, serious lung damage may occur.
That is why rule number one of scuba diving states: "Never Hold your Breath"

Diving and Asthma

Diving & Asthma

In general, asthma is a lung disorder in which there is a tendency for the muscle surrounding the bronchi (breathing tubes) to contract excessively, causing narrowing, or broncho-constriction. As a result, this causes increased breathing resistance, which can manifest as wheezing, chest "tightness", cough, or breathlessness. In asthmatics, broncho-constriction can be precipitated by exposure to allergens, noxious fumes, cold air, exercise or respiratory infections such as a "cold". People with asthma may experience broncho-constriction due to more than one of these factors, but many asthmatics will experience a measurable increase in breathing resistance after exposure to any one or several of them. The increase in breathing resistance caused by bronchial narrowing may be compounded by the accumulation of mucus within the airways.

Serious potential risks may make scuba diving, which is often performed in isolated locations and far from competent medical care, an unwise elective sport for an individual with asthma. There are primarily two issues.

1. During scuba diving the diver experiences a reduction in breathing capacity due to the effects of immersion and an increase in breathing resistance caused by the higher gas density at depth. At 33-feet underwater, the maximum breathing capacity of a normal scuba diver is only 70-percent of the surface value. At 100-feet underwater, this reduction is approximately 50-percent. If, for example, a diver’s breathing capacity is already reduced because of asthma, there may not be sufficient reserve to accommodate the required increase demanded by exertion.
2. Both narrowing of the bronchi and excessive mucus production can inhibit exhalation of air during ascent, and could predispose the diver to pulmonary barotrauma leading to pneumothorax, pneumo-mediastinum and/or arterial gas embolism.

For these reasons, physicians trained in diving medicine have traditionally recommended that people with asthma should never dive. However, a consensus of experts at a 1995 workshop held under the auspices of the Undersea and Hyperbaric Medical Society (UHMS) proposed more liberal guidelines. Essentially, the UHMS workshop panel felt that the risk of diving is probably acceptable if, the diving candidate with some asthmatic ‘history’ demonstrates normal pulmonary function at rest (FVC, mid-expiratory flow, FEV1, FEF 25-75) and then again after strenuous exercise. It was also concluded that the degree of competency in making a medical assessment of diving fitness is enhanced if the examining doctor has relevant knowledge or experience of the diving environment and its associated hazards.

It is important to note that asthma severity can wax and wane. Symptoms may worsen for 4-6 weeks after a "cold" or during certain seasons (for example in response to high levels of pollen in the air.) Therefore, even if a person with asthma fulfills the criteria listed above, diving is not recommended unless the diver is free of respiratory symptoms before each dive.

Reference:

Elliott, D.H. (1996) Are Asthmatics Fit To Dive?, Undersea and Hyperbaric Medical Society (UHMS) – Annual Scientific Meeting, 21-June-1995

http://www.diversalertnetwork.org/

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