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Cardiac arrest can occur during saturation or transfer under pressure (TUP) bell runs. Taking into consideration that the recovery of the bell to the surface, connection to the system, and transfer of the casualty to the chamber would obviously take too long, the only solution to recovering the casualty within an acceptable time is to perform cardiopulmonary resuscitation (CPR) in the bell. The main problem with diving bells is that they are spherical in shape and offer a limited space occupied by piping, umbilicals, helmets, bailout systems, fins, etc., especially near the bottom hatch, so that the space for CPR is very limited, as we can see in the picture below.
To address this issue, companies have provided guidelines for alternative cardiopulmonary resuscitation (CPR) techniques to the traditional supine position. These include CPR with the casualty in a sitting position at the bottom of the bell or in the moonpool with the casualty still held by his harness. Other techniques that have been commonly taught are head-to-chest and knee-to-chest compressions (see the pictures below). However, these methods were not supported by efficacy data, and recent tests discussed in a document titled "Delivering Manual Cardiopulmonary Resuscitation (CPR) in a Diving Bell: An Analysis of Head-to-Chest and Knee-to-Chest Compression Techniques" by Dr. Graham Johnson, Dr. Philip Bryson, Dr. Nicholas Tilbury, Dr. Benjamin McGregor, Dr. Alistair Wesson, Dr. Gareth D. Hughes, Dr. Gareth R. Hughes, and Dr. Andrew Tabner conclude that these two techniques are poorly effective and that the head-to-chest technique has been found to cause harm to providers and should no longer be taught, which confirms what many saturation divers think.
In another document titled "An Evaluation of the NUI Compact Chest Compression Device (NCCD), a Mechanical CPR Device Suitable for Use in the Saturation Diving Environment", which is, in fact, the continuation of the above one, the same team of scientists has compared the efficiency of the Compact Chest Compression Device (NCCD), a CPR device developed by the Norwegian Underwater Institute (NUI), with classical CPR techniques performed by experts. In addition to providing guidelines for implementing this device, the authors conclude that it is efficient. We can, therefore, suggest that such devices should be systematically included in the bell's medical kit. The NUI Compact Chest Compression Device (NCCD) is not the first cardiac resuscitation device designed for hyperbaric conditions. For example, we can refer to the excellent study entitled "Report on tests of Zoll automatic external defibrillator function in hyperbaric heliox conditions" by the Helix company, published on the Diving Medical Advisory Committee (DMAC) website (https://www.dmac- An automated external defibrillator (AED) is a portable electronic device that can automatically diagnose and treat a patient's potentially life-threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia by defibrillating the heart. However, despite the advantages of these devices, they have the inconvenience of being powered by batteries, which, in addition to the precautions to be implemented with lithium batteries stored in a hyperbaric environment, may have an availability problem, resulting in the preferred solution proposed that consists of having the device outside the chamber with only the electrodes inside the chamber, resulting in the device being operated by an operator outside the chamber on the instructions of the diver medic. This solution would be challenging to use with a diving bell for many technical reasons.  Unlike defibrillators, the Compact Chest Compression Device (NCCD) is powered by compressed gas at a pressure of 10 bar above the ambient pressure of the bell. Finding a gas supply source in the bell is not a problem, so the availability problem is solved. The manufacturer recommends not using mixtures with more than 22% PPO2 (NORSOK standard limit is 22%) and continuously monitoring the PPO2 and ambient pressure of the bell, which any trained supervisor is accustomed to doing at all times. The machine consists of the following parts, stored in a reinforced sealed box: The compression unit, which includes the piston house, the bottom plate, and the piston foot that transmit the movements of the piston (see #1) The hand control unit that allows starting and stopping the compressions (see #2). The supply hose connecting the hand control unit to the compression unit (see #3). The supply hose of the hand control unit equipped with a quick connector (see #4). A Velcro strap with adjustment markings (see #5) to secure the compression unit in place. An adjustable support strap designed to prevent the compression unit from sliding down, ensuring the system provides adequate compressions when the patient is in a vertical position. It is equipped with carabiner hooks for attachment to the slots on the compression unit's plate (see #6). An extension hose of 1.5 m (see #7) and scissors that are strong enough to cut fabrics (see #8) are also provided.
Note that in the study "An Evaluation of the NUI Compact Chest Compression Device (NCCD), a Mechanical CPR Device Suitable for Use in the Saturation Diving Environment", it is highlighted the the compression unit may slide down when the casualty is in vertical position, suggesting that the adjustable support strap (see #6) may have to be better adapted. The "User Manual" for this equipment is available in the "Medical Equipment" subsection of the "Logistics" section on our website. It can also be downloaded from the Norwegian Underwater Institute's (NUI) website.  The Norwegian Underwater Institute (NUI) was established in 1973 to continuously improve equipment safety, reduce health risks, and enhance awareness in these areas. It is owned by the Association of Operators for Hyperbaric Lifeboat Reception Facilities (OFHB), which represents major oil operators and subsea contractors on the Norwegian Continental Shelf. NUI is renowned for offering a range of products and services, including research and development, engineering, equipment testing, medical treatments and advisory services, as well as courses and training. The organization can be contacted through the links below. Address: Gravdalsveien 245 - 5165 Laksevåg, Norway Website: Email: Phone: +47 55 94 28 00
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About the Compact Chest Compression Device by NUI