Oxygen and Scuba Diving: Science Made Simple

Most divers strive for good air consumption, but do we really understand what makes us more or less efficient underwater? Here we’ll give you some insight into the science behind oxygen and scuba diving, and will provide some simple suggestions on how you can tailor your diving and your lifestyle to make you more efficient underwater. Oxygen is a common gas and one we may take for granted. But it holds the key to metabolic efficiency.

Oxygen and scuba diving

As divers, we generally know the wider applications of oxygen. It constitutes 21 percent of air, but we can change the concentration in our tank for nitrox or trimix diving. In cases of suspected DCS, we administer 100 percent oxygen. We also use it in recompression chambers to help patients off-gas nitrogen bubbles. It can be toxic at pressures greater than 1.6 ATA or with chronic exposure, particularly affecting the eye, nerves and lungs.

In fact, this ordinary gas makes an extraordinary journey into our body. It comes from nuclear reactions during explosions of stars. Our planet is absolutely full of the stuff and most life on earth is completely dependent on it. Plants harness the sun’s energy to make oxygen in a process called photosynthesis. Our bodies are intricately designed to extract it from air and take it to our cells, where it is used to create energy. When we exhale, we blow out the metabolic waste products (carbon monoxide and water) and the plants reuse our waste to recreate oxygen.

Roadblocks to good air consumption

Diving poses a few obstacles when it comes to this process.

• Resistance to flow in our airways increases as we breathe through long hoses and also with depth as the gases compress. Oxygen is denser than nitrogen, so those diving on nitrox may suffer more from this. Helium, on the other hand, is less dense and so is used to overcome this problem. It is eminently more expensive, however, so mainly tec and commercial divers use it. Help reduce this resistance by using appropriate-length hoses and making sure air is flowing smoothly through your regulator.

• With a standard scuba kit, diving in a head-up position will make it harder to breathe. This is because the lungs are lower than the mouth, which means they’re experience higher pressure. This reduces the diver’s ability to take a full inspiration or full exhalation. This is one of many reasons why good trim is important.

• The filter in the lungs, which oxygen passes through, is under strain as the water pressure redistributes peripheral blood into the chest. Although we can’t change this when we dive, we can help protect our lungs by not smoking, a habit that hardens and destroys this fine filter.

• An iron-based molecule called hemoglobin carries oxygen. Iron deficiencies reduce your body’s capacity to carry oxygen. Eating iron-rich foods such as leafy greens, lentils and chickpeas will help keep these levels steady. In addition, avoid smoking since it saturates hemoglobin with carbon monoxide, meaning there is less space left for it to carry oxygen. It takes around 24 hours to blow off the carbon monoxide you inhale in just one cigarette.

• The physical rigors of diving mean we need higher levels of oxygen to meet the demands of our tissues. Keeping fit is an obvious solution. The World Health Organization recommends 150 minutes of moderate aerobic exercise per week, plus two weight sessions. Exercise will not only improve your cardiovascular health and therefore your diving efficiency, but will also improve your general well being and keep you more relaxed underwater.

• The energy we use to keep warm while underwater increases our oxygen requirement, so make sure to wear adequate exposure protection. There’s no trophy for wearing a shorty on a winter day.

In short, oxygen has an exquisitely complex role in our body and on our planet. Since we are not naturally designed to breathe oxygen at depth, diving makes its journey from the stars to our cells even more arduous. Although there are several unavoidable obstacles, we can take charge of these and many other dive- and lifestyle factors to help oxygen along the way.

By guest author Suzanne Gaskell

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