{"id":1362,"date":"2023-05-09T16:54:58","date_gmt":"2023-05-09T15:54:58","guid":{"rendered":"https:\/\/www.divertown.com\/?p=1362"},"modified":"2024-09-03T15:40:21","modified_gmt":"2024-09-03T13:40:21","slug":"altitude-diving","status":"publish","type":"post","link":"https:\/\/www.divertown.com\/en\/altitude-diving\/","title":{"rendered":"What is Altitude Diving?"},"content":{"rendered":"\n

What is Altitude Diving?<\/h2>\n\n\n\n

Altitude diving refers to the practice of scuba diving<\/a> at locations where the water surface is at an altitude that requires modification of decompression<\/a> schedules, typically more than about 300 meters (980 feet) above sea level.<\/p>\n\n\n\n

Altitude diving presents unique challenges for divers, as the reduced atmospheric pressure<\/a> at higher elevations affects both the gas laws governing scuba diving<\/a> and the body’s ability to off-gas nitrogen<\/a>. To safely participate in altitude diving, divers must understand the changes in dive planning, equipment, and physiology and adjust their practices accordingly.<\/p>\n\n\n\n

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History<\/h2>\n\n\n\n

The first recorded instance of altitude diving dates back to 1951, when American naval officers conducted a series of dives in a high-altitude lake in California. Since then, altitude diving has become increasingly popular among recreational divers, technical divers, and scientific researchers. The activity has advanced significantly over the years, with the development of specialized equipment, training, and decompression<\/a> models tailored to the unique demands of diving at high altitudes.<\/p>\n\n\n\n

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Physics of Altitude Diving<\/h2>\n\n\n\n

The primary difference between altitude diving and diving at sea level lies in the reduced atmospheric pressure<\/a> at higher elevations. This affects the pressure<\/a> of the breathing gas and the partial pressures of gases dissolved in the body, which in turn impacts the decompression<\/a> process. The primary concerns for altitude divers are:<\/p>\n\n\n\n

Reduced ambient pressure<\/h3>\n\n\n\n

At altitude, the pressure<\/a> of the air<\/a> and water is lower than at sea level, which affects the rate at which nitrogen<\/a> is absorbed and released by the body. This necessitates modified decompression<\/a> schedules and adjustments to no-decompression limits to avoid decompression<\/a> sickness (DCS<\/a>).<\/p>\n\n\n\n

Gas laws<\/h3>\n\n\n\n

The ideal gas law (PV=nRT) dictates that the volume of a gas at constant temperature is inversely proportional to the pressure<\/a>. This means that, at altitude, a given volume of gas will expand more than at sea level, affecting buoyancy<\/a> control and potentially causing overexpansion injuries.<\/p>\n\n\n\n

Partial pressure of gases<\/h3>\n\n\n\n

The reduced atmospheric pressure<\/a> at altitude also affects the partial pressures of gases in the breathing mix, leading to a lower partial pressure<\/a> of oxygen<\/a> and a higher partial pressure<\/a> of nitrogen<\/a>. This can cause hypoxia<\/a> and increase the risk of DCS<\/a>, respectively.<\/p>\n\n\n\n

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Decompression Schedules and Models<\/h2>\n\n\n\n

To account for the differences in gas absorption and release at altitude, divers must use modified decompression<\/a> schedules or dive computers<\/a> that incorporate altitude-specific algorithms. The most widely accepted altitude diving models are:<\/p>\n\n\n\n

Cross Corrections<\/h3>\n\n\n\n

This method involves modifying sea-level decompression<\/a> schedules using a correction factor based on the altitude of the dive site. The U.S. Navy and B\u00fchlmann models are examples of decompression<\/a> tables that use cross corrections for altitude diving.<\/p>\n\n\n\n

Reduced Gradient Bubble Model (RGBM)<\/h3>\n\n\n\n

The RGBM, developed by Dr. Bruce Wienke, is a decompression<\/a> model that incorporates both altitude and depth in its calculations. This model is used in many dive computers<\/a>, including those from Suunto, Scubapro, and Mares.<\/p>\n\n\n\n

Equipment and Techniques<\/h3>\n\n\n\n

Altitude diving requires some specific equipment and techniques to ensure safe and enjoyable dives:<\/p>\n\n\n\n

Exposure protection<\/h3>\n\n\n\n

The colder temperatures often found at high-altitude dive sites necessitate the use of thicker wetsuits<\/a>, drysuits, and additional thermal protection.<\/p>\n\n\n\n

Buoyancy control<\/h3>\n\n\n\n

Due to the increased expansion of gas at altitude, buoyancy<\/a> control can be more challenging. Divers may need to use additional weight<\/a> or adjust their buoyancy<\/a> compensator (BC) more frequently.<\/p>\n\n\n\n

Dive computers<\/h3>\n\n\n\n

Divers should use dive computers<\/a> with altitude-adjustable settings to ensure accurate decompression<\/a> information. It is essential to calibrate the computer to the appropriate altitude before diving.<\/p>\n\n\n\n

Ascent rates<\/h3>\n\n\n\n

Ascent<\/a> rates should be slower at altitude to allow for adequate off-gassing<\/a> of nitrogen<\/a> and to reduce the risk of DCS<\/a>. Divers should follow the recommended ascent<\/a> rates provided by their dive computer<\/a> or decompression<\/a> table.<\/p>\n\n\n\n

Pre-dive acclimatization<\/h3>\n\n\n\n

Divers should allow sufficient time to acclimate to the altitude before diving. This process can take several hours to a few days, depending on the individual and the elevation. Acclimatization helps the body adjust to the reduced oxygen<\/a> levels and reduces the risk of altitude sickness, which can be exacerbated by diving.<\/p>\n\n\n\n

Gas management<\/h3>\n\n\n\n

Due to the lower partial pressure<\/a> of oxygen<\/a> at altitude, divers may need to use enriched air<\/a> nitrox<\/a> (EAN<\/a>) mixes with higher oxygen<\/a> content to avoid hypoxia<\/a>. It is crucial to ensure proper gas analysis and planning for adequate gas reserves.<\/p>\n\n\n\n

Emergency procedures<\/h3>\n\n\n\n

Divers should be prepared for emergencies specific to altitude diving, such as hypoxia<\/a>, DCS<\/a>, and overexpansion injuries. Adequate training and familiarity with emergency procedures, including the use of oxygen<\/a>, are essential.<\/p>\n\n\n\n

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Training and Certification<\/h2>\n\n\n\n

Many diving organizations offer specialized altitude diving courses, which provide divers with the knowledge and skills needed to safely plan and execute dives at high altitudes. The courses typically cover topics such as:<\/p>\n\n\n\n