Is diving safe? Of course it is, don’t worry!
We are going to give you a detailed, point-by-point explanation of the state of the human body while diving so your immersions will always be safe, and to clear up any doubts you might have:
What does the air we breathe consist of? The following is the mix of gases in Earth’s atmosphere: nitrogen (78%), oxygen (21%) argon (0,9 %) carbon dioxide (0,035 %) neon (0.001 %) helium (0.0005 %) methane (0.0001 %) krypton (0.0001 %) hydrogen (0.00005 %).
As you can see, there are many elements, and even more, but we will focus on oxygen and nitrogen. First, oxygen is vital for life. Our organism metabolizes it and converts it into carbon dioxide.
However, nitrogen is an inert gas for our organism and just as we inhale it, we exhale it naturally. This all happens on the surface, where there is one atmosphere of pressure (1 ATA). Later we’ll talk about how gases act while a diver is underwater.
This sea level atmosphere (1 ATA) is just the air that surrounds us, and which exercises a gentle pressure on our bodies which we do not notice. So imagine diving with hundreds of liters of water surrounding your body, and the deeper you get, the more liters are surrounding you and pressuring your organism. All these liters are going to cause a change, and Boyle’s Law explains why.
It is important to know that every 10 meters of saltwater around our body are going to exercise one atmosphere of pressure. We have to remember that we already have one atmosphere from the pressure of surface air, and we need to add the water pressure. The table below illustrates this:
The volume of any flexible recipient, such as our body, will always decrease in proportion to the increase in pressure of what is surrounding it, as shown in the table.
This pressure will not modify the 80% of our body which is made of water, but rather the air spaces in our organism, such as our lungs, our nostrils and inner nasal passages, our middle ear and, lastly, the artificial air space we create when using a dive mask. To avoid problems or pain when these spaces are reduced by the pressure, a diver must compensate or equalize for them when descending. We use simple techniques to send air, or by breathing normally and never holding our breath to compensate for our lungs, or with our mouth closed and nose clamped close and blowing GENTLY to send air to our ears (Valsava maneuver). One can also swallow saliva and move one’s jaw (Toynbee maneuver) and blow out of one’s nose if the mask is too tight. Rule number one, and the most important rule in diving: NEVER hold your breath. Breathing should be constant and natural, so we can feel relaxed and enjoy the experience. There is another rule we can never break: NEVER ascend quickly to the surface, as the body and the gases a diver breathes need to adapt to the changes of the falling pressure. A diver should not ascend at more than 9 or 8 meters a minute, depending on the depth. If you do not have a computer to see these figures, never ascend more quickly than the smallest bubbles you expel when exhaling, and make sure you do not break this fundamental rule. If you have deteriorated fillings in your teeth, they might hurt a little due to the accumulation and expansion of air inside you when ascending, although this is rare. You can deal with this by halting the ascent, equalizing and moving your head and jaw to help release the air. This technique also works when diving with congestion, which is not recommended, and you feel an inverse block when ascending, which proves to be quite painful, as the congestion does not allow for the air spaces in your nostrils and nasal passages to equalize automatically. While ascending, equalization or compensation of the air spaces manually is not necessary if they are properly cleared, as they do it automatically.
Now we know what happens physiologically to the air spaces in a diver’s organism. Now let’s find out what happens with oxygen and nitrogen while diving. An adult man has a lung capacity of about 4.5 liters, and a woman has about 3 liters. The air we breathe goes through our respiratory system to our lungs and the alveolus, where a gas exchange happens through the capillaries. This is where oxygen goes into the blood and is carried by hemoglobins to feed the body, yielding carbon dioxide. The same thing happens to nitrogen, but it does not benefit us at all. Nitrogen takes the form of micro-bubbles in our tissue called silent bubbles, which are harmless. This phenomenon occurs when nitrogen is subjected to the pressures of a certain depth: so the deeper we go, the larger the accumulation of nitrogen in a diver’s body. The gas will accumulate more quickly and in greater quantity in fatty tissues, so this must be taken into account if one is overweight. You will also accumulate much more nitrogen after consuming alcohol, if you haven’t slept well the night before or you are not physically fit. Because of this nitrogen in your body, you must NEVER ascend quickly, and between immersions you have to take a break to release it properly and never surpass the maximum natural limit set by the human body. After diving with compressed air, as in recreational diving, you have to be aware of a number of rules. You have to rest for 12 hours to release nitrogen before engaging in freediving, heavy exercise, an intense massage or climbing mountains of more than 2000 meters in height, as you could increase the size of the nitrogen micro-bubbles. It is also important to not fly in an airplane for 18 hours, for the same reason. Ask us if you have any questions about this important subject.
If you observe these simple rules, diving will always be an incredible experience that is always safe, and you can be a good diver who takes good care of your body.
If we do not observe them, we may contract a dysbaric illness or decompression sickness. Your qualified instructor in an open water course will explain them to you.
Any pressurized gas can become toxic and harm the human body. When we dive, this is what we do with gases. Oxygen becomes toxic at a depth of some 56 meters and nitrogen may become toxic starting at 25 meters.
Oxygen is dangerous at that depth because the human body stops metabolizing it and this would create a critical situation. This is why the maximum depth allowed in recreational diving is 40 meters for divers with the deep diving specialty; otherwise, the recommended maximum is 30 meters.
Nitrogen is not lethal, and would only cause a state of intoxication or confusion, which is called nitrogen narcosis, which is solved by lowering the pressure of the gas in the body a bit. It is very important to dive with your partner nearby in order to deal with this symptom. It is not an illness, and it is easy to solve.
Now, because water is about 800 times denser than air, you will be exposed to certain physiological changes relating to sound, sight, temperature and the buoyancy of your body.
Do you know how the body can process sound while we scuba dive? It can do this because the waves of sound in the water reach your eardrum, causing vibrations that are sent to the brain through the complex system of nerve endings.
The difference in time and intensity between your two ears allows the brain to determine where sound comes from. Diving and moving in a much denser environment, where sound travels four times as fast, renders this system unable to determine where sound comes from the way it does on the surface, and it will almost always perceive sound to be coming from above. Listen for when your instructor calls out to you underwater!
Colors are merely a sensation on your retina, and the vision centers in your brain produce an interpretation of the external world.
Light has different wavelengths that give color to objects via the interpretation made by our complex brain system. Sunlight, both ultraviolet and infrared, lose energy when entering the water: so they will be weaker the greater the depth, and this is how the absorption of colors can be seen.
The first colors lost are shades of red, and this happens at about 10 meters, followed by warm colors like yellows and oranges; after that come the greens and, at last, the blues, at depths of about 45 to 50 meters.
We will also see objects about 33% larger and 25% nearer, although the human brain quickly adapts to these changes and you will not have to adjust for this: just take it into account and enjoy. This phenomenon is called light refraction.
Other changes that occur in human body relate to temperature, as you will lose your body heat between 20 and 25 times more quickly. Hence the need to use a well-adjusted wetsuit to keep yourself warm and stable.
Take care to ensure the suit is not too tight at the neck, as this could bring down the cardiovascular frequency and make you pass out. If a diver starts feeling unbearable cold or starts to shiver should end the dive immediately, because the next step is hypothermia, a complicated illness that requires specialized medical attention.
You can also suffer a heat stroke if you keep the suit on for too long on the surface, especially if the suit is dry. So avoid these adverse circumstances and freshen yourself: you’ll enjoy the experience much more.
You need to also stay well hydrated and drink water or juice both before and after each dive, because the sea dehydrates the human body very quickly. A drysuit is recommended in waters with temperatures below 18 degrees.
This characteristic is very important in diving: because the better your buoyancy, the less air you will consume, and you will be able to dive for longer.
Buoyancy is an object’s capacity to to float. According to Archimedes, an object that moves less water than its own weight will float.
On the other hand, if it moves more water than its own weight, it will sink. The human body almost always moves more water than its own weight, so you will sink and have to use the only two tools we have to achieve the right buoyancy; a buoyancy control device or jacket, and your lungs.
There are three types of buoyancy:
– Positive buoyancy, which is when you ascend.
– Negative buoyancy, which is when you sink.
– Neutral buoyancy, which is when you neither sink nor ascend. You hover the way an astronaut does in space.
This the sensation that every diver needs to be a good diver, and we will achieve it by mixing a certain amount of air with our jacket and lungs. Each diver must find his own mix according to his weight, gear, ballast, and lung capacity, among other factors.
Height changes always happen with the turns of a diver’s body, combining movements with fins and/or use of lungs at will in order to have more or less air.
Never ascend using the jacket air! This would make a diver ascend too quickly, thus breaking one of the fundamental rules of diving. Jackets always have two buttons: one to inflate and another to release air: pay close attention to this when diving and identify your gear.
Perfect buoyancy is when a diver causes no damage to the surroundings, while keeping a prudential distance from the bottom, and not impacting anything with the fins so as to avoid causing damage, even to one’s self. The better the buoyancy, the better the air consumption. Try it.
Pregnant women should not dive. There are no studies indicating that it is safe.
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