How To Do Pelvic Floor Exercises In Pregnancy

The History of Diving

The excerpt that opens this chapter is believed to be the first description of breath-hold diving as a sporting activity figure Yet, commercial diving has existed since at least B.C. The accounts of the Greek historian Herodotus explain that the diver Scyllis was employed by the Persian king Xerxes to recover treasure from ships wrecked in the Mediterranean Sea during the -year war between Greece and Persia. Similar accounts of military and salvage operations appear throughout the histories of the Roman and Japanese cultures. Military divers cut anchor cables to set enemy ships adrift, bored or punched holes in the bottom of ships, and built harbor defenses.

However, human underwater exploits were limited to breath- hold diving until about three hundred to four hundred years ago, when a series of technological developments prolonged submergence. These advances provided external air to divers in a variety of ways. Infor example, a practical diving bell was produced. Literally bell- shaped, with the bottom open to the sea, this device was weighted

Walker’s depiction of breath-hold diving as a sport and sank in a vertical position. A diver could either remain inside the bell, if positioned directly over his work by the support ship, or could venture outside for short periods of breath-holding activity. Much later, inastronomer Sir Edmund Halley devised a leather tube to carry surface air to submerged barrels; this tube supplied air to manned diving bells at a depth of. In an early demonstration of this system, Halley remained at under the Thames River in Great Britain, with four other people, for almosth.

InEnglishman John Lethbridge developed the first one-person diving suit figure pageHis apparatus was basically a reinforced, leather-covered barrel of trapped air, equipped with a glass window and two armholes with watertight sleeves, allowing useful work for up to min. This apparatus and succeeding equipment suffered from the same limitations as diving bells. They contained no practical way to supply air continuously to a diver.

Fortunately, during a -year period beginning infour vital technological breakthroughs enhanced diving. The first was a pump that delivered compressed air from the surface to either a diving bell or a diver. The second was a full-length waterproof diving suit, invented by August Siebe inthat included a helmet with viewing ports, surface-supplied air, and an exhaust valve figure The third breakthrough, the ”demand regulator, was patented by a French engineer inThis device supplied air to divers, on the demand of inhaling,

The first one-person diving suit, developed in by John Lethbridge at pressures that were much greater than the atmosphere of pressure atm found at sea level. The final advance was the first successful self-contained breathing apparatus. Developed in by Henry Fluess and August Siebe, this apparatus utilized pure oxygen with a carbon dioxide absorbent system see next paragraph. Although it exposed divers to the risk of oxygen poisoning the breathing of gas containing at very high levels, no cases of this illness were recorded during extended underwater operations in a flooded tunnel.

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The next major improvement in underwater equipment did not arise untilas a part of the French resistance activities against Nazi Germany. Renowned undersea explorer Jacques-Yves Cousteau and Emile Gagnon combined a demand regulator with a compressed air tank, forming what they called a self-contained underwater breathing apparatus scuba, the first truly efficient and safe open-circuit device of its kind. In an open-circuit design, pressurized air is taken from a supply tank, inhaled, and exhausted to the surrounding water. But, because this design was detrimental to military operations since it left a telltale trail of bubbles on the water’s surface, and because it

Siebe’s full-length waterproof diving suit with helmet, produced in wasted compressed air, various closed-circuit breathing apparatuses were soon developed that eliminated these two disadvantages. When using a closed-circuit scuba system, a diver breathes either pure which limits depth because of potential oxygen poisoning or a gas mixture containing oxygen and an inert gas helium, nitrogen, and the expired gas is recirculated, not released to the surrounding water. A chemical filter removes carbon dioxide while oxygen is added slowly from the tank, to replace that which is consumed by the body. Today’s closed-circuit scuba equipment avoids oxygen poisoning by electronically sensing and providing a constant concentration at any depth see section below, Medical Considerations: Breathing Gas Mixtures, page .

After World War II, the development and sale of open-circuit scuba equipment figureto the general public made the underwater world accessible to increasing numbers of people. The growth of

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