by Dr Kirsty Wydenbach BSc. MBBS FRCA
We have all heard about it, life couldn’t exist without it, but what are the true benefits of oxygen? Should giving oxygen to those who need first aid not be left to professionals and those with advanced skills? Some of you may even say that oxygen can be dangerous.
Oxygen administration is often a topic for debate. However, oxygen therapy is essential in many cases, particularly serious or potentially serious injuries or illnesses. Basic first aid courses will teach how to assist in asthma, bleeding, choking, burns, fainting, and much more. But as a first aider or first responder would you be happy to give them oxygen? No? Why not? Possibly because you haven’t been trained, but this should not be the case.
The cells in our body all require energy to function and this energy is derived form chemical reactions that utilise oxygen. It is vital to receive a constant supply of oxygen, even more so for organs such as the brain and heart. The brain can survive little more than 3 minutes without oxygen. Illness and injury can interfere with the delivery of oxygen to these organs in many ways, from problems with ventilation so that the patient simply isn’t taking in enough oxygen to circulation problems and disorders at a cellular level where cells cannot utilise oxygen properly. Reviewing the conditions covered in basic first aid it can be seen that many of these issues can occur in first aid situations. Choking affects oxygen delivery to the lungs, as does asthma. Bleeding and fainting all affect the blood supply to body organs and thus the delivery of oxygen. Poisoning can affect how cells use oxygen. Thus, anything that can be done to increase the amount of oxygen can potentially be beneficial. Equally it is unlikely to cause harm. There are exceptions of course. Like any other drug, oxygen has possible side effects, but it is something that could be taught much more widely.
So what are the actual benefits of oxygen therapy?
A little physiology is required to understand what happens when we administer oxygen to patients. The atmosphere has 21% oxygen at a pressure of 21 kilopascals (kPa) that we then inhale. However, even by the time this reaches the alveoli where it will pass into the blood, it has been diluted with water and carbon dioxide so the oxygen concentration drops to approximately 14kPa, and once in the capillaries there is only 6-7kPa of oxygen. By the time oxygen has reached the cells and the intracellular structures where it is actually needed the concentration is only 1-5kPa. The difference between atmospheric oxygen concentration and cellular levels is essentially fixed so it can be seen that even a very small drop in the concentration taken in by the lungs or any disruption to the circulation will quickly impact the tissues and drop oxygen concentrations dangerously low. Even the 16% (16kPa) provided by exhaled air during mouth-to-mouth resuscitation is only barely enough to keep the tissues functioning at a level approaching normal. If a patient is administered oxygen, such as the 24-40% concentration achievable with nasal cannulae, this will help balance out any problems with oxygen uptake in the lungs or delivery in the circulation due to injury or disease. Increase that further to 50%, as achieved with a facemask, and it can be seen that even more major problems can be helped.
And what happens if oxygen levels do become low?
The effects on the brain are most evident in situations including severe blood loss and carbon monoxide poisoning, but are all due to lack of oxygen – you become unable to function properly as neurotransmitters are affected and impulses are not transmitted as they should be in different areas of the brain. You become dizzy, speech may be affected as well as eyesight, movement becomes uncoordinated, thought processes slow down and eventually unconsciousness prevails followed by coma. Permanent damage can occur quickly. But effects can also be more subtle or be masked by other symptoms. For example in an asthma attack the patient may not be thinking in a coherent manner anyway, but this may in part be due to reduced oxygen delivery to the brain, particularly in severe cases.
The heart is also vulnerable and effects are most obvious during a heart attack where the direct blood supply to the heart muscle is reduced. Pain and chest tightness exacerbate the lack of oxygen by affecting breathing, and heart muscle cells die. The ultimate effect, depending on severity, is that the heart just cannot work and cardiac arrest will follow if no treatment is given.
Have you changed you mind?