Response, Risk Scenarios and Defences of Hypoxia

Published: June 13, 2019


What is Hypoxia? Why is it so dangerous? These common questions may have simple answers, but there is more to it than what meets the eyes such as the question of what does the aircrew do when a passenger is suffering from hypoxia? When does risk of hypoxia cross the border from safe to unsafe? Buckle up, because we will be breaking it all down here.

Hypoxia is defined as the lack of oxygen in body tissues which are due to a shortage of oxygen molecules present in the air or due to physiological/pathological issues that affects the blood circulation/quantity of oxygen carried by haemoglobin (Hb) in blood such as carbon monoxide poisoning or cardiovascular diseases. The human blood contains haemoglobin (Hb) that carries oxygen molecules from the lungs to the rest of the body and carries carbon dioxide back from the rest of the body back to the lungs. Enough oxygen concentration in air and adequate Hb amount in body is vital for the body to function properly.

Response, Risk Scenarios, and Defences of Hypoxia

There are various factors that may affect the severity of hypoxia, which often depends on the capabilities of the person, as there are other external factors that may cause severe hypoxia for some and minor hypoxia for others. Some factors that affect the severity of hypoxia would be the physical fitness of the person, cabin temperature, altitude of the aircraft, rate of ascent, and the duration of the aircraft at high altitudes where hypoxia is prone to occur. Hypoxia may occur suddenly or gradually. Sudden ones require a rapid and instinctive response by the aircrew while gradual ones gives the aircrew some ample time to restore adequate oxygen concentration back into the cabin before incapacitation occurs.

The effects of hypoxia would include a sense of fatigue, confusion, impaired decision making, the inability to concentrate, reduction in reflex, loss of consciousness, and even death on the worst cases. The dangers of hypoxia are due to the fact that hypoxia may come unnoticeable as there are no major visible/noticeable symptoms making it more dangerous for oblivious aircraft crew members.

In greater altitudes, there are lower levels of oxygen or otherwise called as partial pressure of oxygen. Above 10 000 ft. In altitude, blood’s Hb is less saturated with oxygen and may bring up any previous cardiovascular diseases of aircrew and/or passengers. When there is an abrupt drop in the partial pressure of oxygen of the cabin due to rapid depressurisation in high altitudes, often caused by structural errors such as a broken window or damaged cabin body, hypoxia will occur. The gradual increase in altitude of the aircraft at about 10 000 ft. In the absence of normal pressurisation would also cause aircraft passengers to experience hypoxia. This is achieved by ascending above 10 000 ft. without the pressurisation system functioning well or it being damaged. These are the risk scenarios of hypoxia.

The technical response towards the increasing altitude of the aircraft above 10000 ft. Is shown during the pressurization of the aircraft cabin. By pressurizing the aircraft cabin, the pressure within the cabin is equivalent to that of the aircraft being in 8000 ft. In altitude. Aircraft pressurization systems normally operates automatically, however, aircrew members are still required to undergo the correct procedures to monitor the cabin altitude to prevent any unnoticeable errors.

So, how can we defend ourselves from hypoxia during flight? What can we do, as passengers, and what can be done by the aircrew? As per the responsibilities of the aircrew, they are all required to undergo the appropriate training that would enable them to spot any underlying symptoms of hypoxia and have a quick response towards decompression. Pilots are required to ensure that the aircraft is still under control and cabin pressure can be returned to its “normal” altitude. As for the passengers, we are required to pay attention to the safety cabin briefing done before take-off and remain calm during depressurization.

Response, Risk Scenarios, and Defences of Hypoxia

Although, have you ever wondered how the body reacts to hypoxia, if at all? Well, the body does undergo its own defences that acts as a hypoxia ‘sign’. This could save your life! The body will show blueness of the lips or fingertips, have an increased rate and depth of breathing, excessive yawning, fatigue, feeling of euphoria, impaired concentration, loss of consciousness, etc. If any of these symptoms are seen, do not hesitate to call the air stewardess and inform them of the current situation. If you are already mid-flight, there is little that can be done up in the air, however, prior to take off the aircrew may delay the flight and get you to safety.

With all this in mind, hypoxia may be scary and intimidating to encounter but, just remember to not panic and inform someone immediately if you are showing any of the symptoms. Fortunately for us, the aircrew in this modern era are required to have prior trainings regarding hypoxia before they are allowed to take off in the aviation world. So sit back, relax, and enjoy the flight.


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