To safely ascend when scuba diving, there are three key factors to consider: ascent speed, safety stop, and body positioning. While novice divers learn to ascend slowly, it’s important to strike the right balance as a too-slow ascent can increase the risk of decompression sickness.
In this article, we’ll explore the optimal ascent rate, the importance of conducting safety stops, and why horizontal trim is crucial for a safe and effective ascent. Read on to learn more.
Novice scuba divers learn to ascend very slowly from depth. This is an appropriately simplistic ‘rule’ that helps them avoid an uncontrolled ascent. However, it is not the correct approach to ensure safety from decompression illness (DCI).
This is because a very slow ascent promotes continued on-gasing (absorption of inert gas) into the slower body tissues. As a result, there is delay in reaching a depth where an optimal super-saturation gradient promotes faster removal of nitrogen from the body.
As such, the optimal approach to ascending is to maintain an accurate ascent rate of 9-10m per minute, combined with one or more stops at shallow depth.
Conduct a safety stop as you ascend when scuba diving
Mainstream recreational agencies like PADI teach a simplistic “safety” stop protocol of 3 minutes at 5m depth. Some other agencies, and more advanced-level divers, favour an approach doing multiple levels of safety stop; for instance, at depths of 9, 6 and 3m.
Again, the approach of using multiple level safety stops stimulates fewer bubbles than either no stop whatsoever or a single stop.
A sample safety stop schedule for enhanced DCS protection
Ascend at a rate of 9m (30ft) per minute.
Stop at 9m (30ft) for 1 minute
Stop at 6m (20ft) for 2 minutes
Stop at 3m (10ft) for 3 minutes
Ascend to the surface at a rate of 3m (10ft) per minute
Body positioning during ascent on a dive
Another factor is body positioning on the ascent. If the diver is vertical in the water, then they create a significant pressure differential across the height of their body. This has two downsides:
Firstly, it means that inert-gas diffusion is inconsistent across the length of their body.
Secondly, pressure differential across the body can contribute to a cause of Immersion Pulmonary Edema (IPE) – a malady increasingly believed to play a role in many diving accidents.
For those reasons, a horizontal body positioning is far more optimal throughout the ascent and safety stops. The primary caveat being that the diver needs to possess sufficient buoyancy and trim proficiency to actually perform a horizontal ascent.
About Immersion Pulmonary Edema
Immersion Pulmonary Edema causes and symptoms:
Immersion pulmonary edema (IPE) is a life-threatening condition that can occur during water immersion activities.
IPE occurs when fluid from the blood leaks abnormally from the small vessels of the lung into the airspaces, leading to difficulty in breathing.
IPE is not typically related to any underlying medical cause.
The effects of immersion and increased cardiac filling pressures can cause IPE.
Symptoms of IPE include shortness of breath, coughing, chest pain, and frothy sputum.
Immersion Pulmonary Edema incidence and risk factors:
Fatal cases are often mistaken for drowning, so the exact incidence of IPE is unknown.
IPE tends to recur and can be fatal.
It can affect surface swimmers, snorkelers, and scuba divers.
The issue effects young, otherwise healthy individuals, as well as in older divers with high blood pressure.
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The best way to ascend when diving
In summary, ascending when scuba diving is a critical part of the sport, and it’s important to do it safely. By considering ascent speed, conducting safety stops, and maintaining a horizontal body position, divers can minimize their risk of decompression sickness and other diving-related illnesses.
Remember to strike the right balance and maintain an ascent rate of 9-10m per minute, combined with one or more stops at shallow depths. By following these guidelines, divers can enjoy a safe and enjoyable experience exploring the underwater world.
Currently residing in Subic Bay, Philippines; he has amassed more than 10,000 open-circuit and CCR dives over three decades of challenging diving across the globe.
Andy has published numerous diving magazine articles and designed advanced certification courses for several dive training agencies, He regularly tests and reviews new dive gear for scuba equipment manufacturers. Andy is currently writing a series of advanced diving books and creating a range of tech diving clothing and accessories.
Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize, and Cyprus.
Yes, immersion pulmonary edema is known to occur on scuba dives. The exact figures are unknown because many fatal cases may be confused with drowning.
Is it better to ascend in a vertical or horizontal position when scuba diving?
It is best to ascend horizontally from a scuba dive. Beginners with poor buoyancy control can ascend vertically as a precaution against an uncontrolled ascent.
What happens when divers ascend?
As a diver ascends, the gas in their BCD and exposure protection expands to increase their buoyancy. As a result, they must release air from their BCD to retain neutral buoyancy.
Is it best to ascend slowly when scuba diving?
Aim to ascend slowly when you are a beginner and there is risk of an uncontrolled ascent. With experience, aim to ascend at an optimal rate of 9m or 30ft per minute until you reach your safety stop.
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