When Diving At An Altitude Above 300 Metres/1000 Feet

Diving at Altitude: A Comprehensive Guide for Divers Above 300 Meters/1000 Feet

Diving at altitudes above 300 meters (1000 feet) presents unique challenges and necessitates a thorough understanding of the physiological effects of reduced atmospheric pressure on the human body and diving equipment. This comprehensive guide explores these challenges, providing crucial information for divers planning high-altitude dives. Safety is paramount, and thorough preparation is essential before embarking on such dives.

Understanding the Effects of Altitude on Diving

At higher altitudes, the atmospheric pressure decreases significantly. This reduction impacts several crucial aspects of diving:

Reduced Partial Pressure of Oxygen

The lower atmospheric pressure directly translates to a lower partial pressure of oxygen (PO2). This means less oxygen is available for your body at each breath, potentially leading to hypoxia (oxygen deficiency) which can severely impair judgment, coordination, and even lead to unconsciousness. Hypoxia is a serious risk at altitude and must be carefully mitigated.

Increased Risk of Decompression Sickness (DCS)

Lower atmospheric pressure also affects the solubility of inert gases (nitrogen) in your body's tissues. At altitude, the tissues absorb less nitrogen during the dive, but the reduced ambient pressure during ascent means that the supersaturation of nitrogen can still occur, significantly increasing the risk of DCS. The risk of DCS is notably higher at altitude and requires meticulous adherence to decompression procedures.

Altered Gas Expansion

Boyle's Law states that at a constant temperature, the volume of a gas is inversely proportional to its pressure. At altitude, the lower atmospheric pressure causes gases in the body to expand more significantly during ascent. This increased expansion can lead to barotrauma, affecting the lungs, ears, and sinuses. Careful equalization techniques and ascents are crucial to prevent barotrauma at altitude.

Planning and Preparation for High-Altitude Diving

Thorough planning and preparation are critical for safe high-altitude diving. This involves several key considerations:

Acclimatization to Altitude

Before attempting any dives, sufficient time should be spent acclimatizing to the altitude. This allows your body to adjust to the lower oxygen levels, reducing the risk of altitude sickness and enhancing performance. The required acclimatization time varies depending on the altitude and individual susceptibility. Consult with a physician specializing in high-altitude medicine for personalized advice.

Dive Planning and Profile

The dive profile should be meticulously planned, considering the reduced partial pressure of oxygen and the increased risk of DCS. Shorter dive times, shallower depths, and more conservative decompression stops are generally recommended. Using dive planning software specifically designed for altitude diving is highly advisable. This software can accurately account for the altered pressure conditions and provide tailored decompression plans.

Gas Selection and Management

The choice of breathing gases is crucial for high-altitude diving. Enriched air nitrox (EANx) might be considered to compensate for the reduced PO2, but its use requires careful planning and understanding of its limitations and potential risks. Consulting with a qualified dive instructor experienced in altitude diving is essential to choose the appropriate gas mix. Appropriate gas management techniques should be practiced to prevent running out of air during the dive.

Equipment Selection and Maintenance

Ensure all diving equipment is thoroughly inspected and well-maintained. Particular attention should be paid to the pressure gauges and regulators, ensuring they function correctly at the lower ambient pressure. Any equipment malfunctions at altitude can have catastrophic consequences.

Emergency Procedures and Communication

Establishing clear emergency procedures and communication channels is vital. Having a well-defined plan for dealing with potential emergencies, including decompression sickness, hypoxia, or equipment failure, is crucial. Regular communication with a surface support team is also highly recommended.

Physiological Considerations for High-Altitude Diving

Beyond the general risks mentioned earlier, specific physiological considerations must be addressed when diving at high altitudes:

Hypoxia and its Manifestations

Hypoxia is a significant threat at altitude, even before entering the water. Symptoms can include headache, fatigue, dizziness, shortness of breath, and impaired judgment. These symptoms should never be ignored. If experiencing any of these, immediate ascent to a lower altitude and supplemental oxygen are necessary.

Altitude Sickness (AMS)

Acute Mountain Sickness (AMS) can develop rapidly at altitude, manifesting as headache, nausea, vomiting, and fatigue. Severe AMS can progress to high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE), which are life-threatening conditions. Prevention is key through acclimatization and careful ascent planning.

Decompression Sickness (DCS) at Altitude

The risk of DCS is amplified at altitude due to the reduced ambient pressure. Symptoms can range from mild skin manifestations (itching, rash) to more severe neurological symptoms (paralysis, loss of consciousness). Immediate recompression is necessary if DCS is suspected.

Barotrauma

The expansion of gases in the body during ascent is more pronounced at altitude, increasing the risk of barotrauma to the lungs, ears, and sinuses. Proper equalization techniques are essential throughout the dive and ascent.

Advanced Techniques and Considerations

For particularly challenging high-altitude dives, more advanced techniques and considerations come into play:

Specialized Training

Undertaking specialized training in high-altitude diving is highly recommended. Courses specifically designed for this type of diving provide in-depth knowledge and practical skills necessary to mitigate the associated risks. Only trained and experienced divers should attempt high-altitude dives.

Use of Decompression Algorithms

Advanced decompression algorithms that account for the reduced ambient pressure are crucial. These algorithms provide more accurate decompression profiles, minimizing the risk of DCS. These algorithms should only be used by those with the necessary training and understanding.

Use of Mixed Gases

Using mixed gases with varying oxygen and inert gas percentages can help manage the risks of hypoxia and DCS. However, the use of mixed gases requires advanced training and careful planning. Improper use of mixed gases can be very dangerous.

Contingency Planning

Robust contingency planning is essential. This should include backup plans for equipment failure, communication breakdowns, and medical emergencies. The remote nature of many high-altitude dive sites necessitates thorough preparation for unexpected events.

Conclusion: Respecting the Altitude

Diving at altitudes above 300 meters/1000 feet is significantly more challenging and risky than diving at sea level. The reduced atmospheric pressure impacts numerous physiological factors, increasing the risks of hypoxia, DCS, barotrauma, and altitude sickness. Thorough planning, preparation, specialized training, and a deep understanding of these risks are crucial for the safety and success of high-altitude dives. Always prioritize safety, and never underestimate the power of altitude. Remember, respecting the altitude is paramount to ensuring a safe and successful dive. By adhering to these guidelines and seeking expert advice, divers can minimize the risks and enjoy the unique challenges and rewards of high-altitude diving. However, it's vital to remember that the risks remain significant, and only those with appropriate training and experience should attempt such dives.