The Limits of Breath-Hold Diving

The limits of breath-hold diving are discussed regarding both duration and depth. For duration, the calculations presented explain a possible, theoretical breath-hold duration (according to known physiology) of 10 minutes 24 seconds for comparison with the current world record of 10 minutes 12 seconds. One technique that makes the current record possible is glossopharyngeal insufflation, by which the diver may fill the lungs with an extra 3-4 liters of air, increasing oxygen stores. In terms of depth, the record has stretched from 30 m in 1949, to the current record of 214 m diving with "no limits." The depth limit is not yet known (the diver surfaced from 214 m in full health) but various factors limiting deep diving are discussed. The compression of gas, according to Boyle's Law, may cause a range of barotraumas associated with the descent, including problems with equalization of middle ear, pulmonary oedema, and haemoptysis. The increase in partial pressure of nitrogen may cause nitrogen narcosis with a risk of the diver becoming incapacitated at depth, as well as gas supersaturation in tissues leading to decompression sickness on, or after, the ascent. While divers have reached depths of 113 m by physically swimming down and up, the "no limits" divers use assisted descent and ascent. To reduce problems with compression, pulmonary gas stores can be increased by glossopharyngeal insufflation, and sinuses may be filled with (sea) water as a means of equalization. For the elite divers, the amount of oxygen they can store seems to be the limit for duration, while the problems of compression and nitrogen partial pressure are the most likely limiting factors for depth.