Lessons for Life: Computer Table Errors

One of the characteristics of safety technology diving is that the equipment is complicated. Leisure divers have the opportunity to reach the water quickly. Technical divers do not have such preferential treatment, so they must be more self-reliant. Murphy's Law for technical diving means that two equally functional equipment should be considered as one piece of equipment. When there is only one piece of specific equipment used by a diver, he must plan how to complete the dive with complete loss of the equipment. Ignoring this rule can lead to disaster.

That dive

Trevor, who was in his early 30s, is a seasoned technical diver and coach. At the time, he was conducting a series of deep space (deep air) scuba training with two experienced students and conducted several dive sessions to check the equipment configuration. After a few days of training, Trevor completed three diving trips at a depth of 200 feet (approximately 61 meters) and two approximately 150 feet (approximately 46 meters) at a technical training site in North Florida.

In these freshwater activities, they carried the mixed air used at the bottom of the water supply, and 80% of nitrogen to reduce the pressure from 30 feet (about 9 meters) to the surface of the water. Each diver carries the right amount of redundant equipment: twin cylinders with isolation manifolds, dual air pressure valves, independent vacuum cylinders, and pre-stored decompressed gas for emergency use. Divers use a dual computer watch or a computer watch with a depth gauge, a timer, and a decompression table to prepare for the day. Trevor not only has two computer watches, but also equipped with a decompression watch with a watch and depth gauge for spare.

All diving activities are going smoothly. In addition to training diving, Trevor also completed an independent dive the next day to check the equipment and completed a single dive for a safety device on the third day. All divers stayed hydrated and fully rested during the weekend, and Trevor took due diligence to keep the rate of increase, scheduled decompression stop, and additional safety stops. Immediately after the dive, the divers completed a 30-minute decompression of the water and immediately began the daunting task of loading the technical equipment back home.

Symptoms and treatment

About two and a half hours after the dive, the divers stopped and prepared a regular dive. When enjoying a good meal, the coach suddenly showed DCS symptoms: sudden fatigue, numbness in both hands, and weakness in the left part of the body. The symptoms were discovered immediately. The instructor immediately breathes pure oxygen, begins intravenously and is immediately transferred to a nearby hyperbaric chamber. Emergency medical staff quickly diagnosed the condition and immediately responded to a series of symptoms of the coach according to the “Navy High Pressure Treatment Schedule 6”.

(Note: "Navy High-Pressure Treatment Schedule." Timetable for Emergency Hyperbaric Oxygen Treatment for Diving Disorders, based on the "Navy Diving Scale" used in Canada and the United States)

Accident analysis

Although the outcome was satisfactory, all divers in this incident were skeptical about what went wrong. The answer is redundant spare equipment.

Each diver's computer watch comes with a separate file based on his own. Trevor uses a state-of-the-art “Hoseless, pneumatic integrated dive computer watch.” There were several problems with the computer before it was returned to the factory. Trevor just got back from the manufacturer this computer that has been adjusted and verified to be safe to use. Unfortunately, this computer watch is not safe for him, because the computer table provides wrong depth information and decompression records. Although Trevor carried two computer watches, the other computer was only used as a backup for system errors.

(Note: "Hoseless, pneumatic integrated dive computer", refer to ScubaPro Galileo series dive computer)

Trevor had never checked his spare computer before the last safe dive of the series. When the last decompression stopped, the host computer stopped providing the correct information and he used the timer to perform the final safe stop. For safety reasons, he used 80% nitrogen at 15 feet (about 5 meters) and added an extra 10 minutes of safety stop. During this stay, Trevor checked the standby computer but was surprised to find that the computer was locked in "barometric mode". In a subsequent comparison of the Trevor computer with other diver computer watches, it was confirmed that his main computer continuously provided wrong decompression files for the first two or three days.

(Note: Barometric mode. Part of the unique features of the dive computer, combined with the cylinder, only provides the state and content of pressure)

The lesson of life

1. For technical diving, complex equipment must be durable and should be checked regularly during the dive to ensure that it is working properly.

2. Electronic devices, such as computer watches, may inadvertently make mistakes. Divers must remain vigilant and cross-check with alternate computers to select and comply with more conservative computer information.

3. Do not use divers who have recently maintained or newly started equipment to perform challenging dives, unless they are properly functioning in shallow depths and conservative diving activities.

4. Never delay treatment when suspected DCS. In this accident, the rapid response to DCS symptoms brought satisfactory results.

5. All divers should perform oxygen management, CPR (CPR) and basic first aid training. Fortunately, the divers in this accident have all taken proper training and equipment so that they can be quickly rescued when the barometric disease begins to show up.