Hypoxia

By Chris Kyle



It's a fact that many pilots give very little thought to THE ENVIRONMENT IN WHICH THEY WORK AND OPERATE!!
Here's a profound thought! Imagine taking a SHORT 4.5 kilometer stroll along the esplanade of a sea side resort. Now if the day time temperature was a pleasant 25 degrees Celsius it would remain pretty much the same when you arrived at your destination depending on the time of day. If you had no specific health problems then you would also be able to breath easily and freely with a good flow of oxygen being fed to your body and brain and you would feel happy and comfortable - no problem - ALL GOOD!

But now imagine if it was possible to walk vertically up into the atmosphere from the same departure point for the same SHORT distance of 4.5 kilometers the picture would be dramatically different because you would now be 15,000 feet above sea level. Dressed in your, t-shirt and sandals, you'd start to get really cold because the temperature could now be as low as minus 5 degrees Celsius(depending on the Environmental Lapse Rate). Your body core temperature would start dropping and you would soon begin to suffer the effects of HYPOTHERMIA. If left in this state for long enough your speech would become slurred, your thought patterns would progressively become more and more confused and you'd have difficulty in thinking straight. Your heart and vital organs would slowly start to shut down.

Worst of all now at this vertical distance from the nice warm sea side resort where the air was dense and there was plenty of oxygen to sustain you, you would soon begin to suffer the effects of HYPOXI
A caused by the lack of sufficient oxygen in the thin rarified air.

Now, here's another profound thought. The life sustaining layer of the atmosphere that enshrouds the surface of the Earth is shockingly thin!!!!

To bring this into perspective, imagine a large round melon of sorts wrapped in a very thin layer of 'cling-wrap'. The thin layer of 'cling wrap' would be representative of the life sustaining layer of atmosphere in which human life can exist without special equipment or apparatus. Quite a thought this, isn't it?

Believe it or not, if you were to speak to the Architects and Engineers of Super Skyscrapers, they'd tell you that one of the big challenges is to provide systems within these very high buildings that are capable of providing constant environmental conditions that will make the building comfortable and habitable by human beings.

So this is the work place of the Pilot - an unfriendly one - if not treated with due respect can be a very hazardous one!

Not just radical changes of temperature and composition of the air with changes in altitude but also noise, vibration and many other stressors are placed on the human body in flight.

So it is safe to say then that during flight with all of the dynamic and atmospheric changes that occur, we as humans are placed in a most unnatural environment that we were not designed for. If we were meant to fly we would have been given wings.

We need to be very aware of this and make it part of our every day Threat and Error Management protocol.

In many countries non pressurized aircraft can be safely flown with adequate terrain clearance at altitudes seldom exceeding 8,000 foot but because of the topography in our country we frequently need to operate at 10,000 foot and above in order to ensure safe terrain clearance.

Because of this we need to be acutely aware of HYPOXIA and its' affects.

Hypoxia is a condition where the body is deprived of a sufficient supply of oxygen from the air to supply body tissues whether in quantity or molecular concentration.

Hypoxia will lead to a loss of cognitive abilities, which will be detrimental, particularly for pilots who have to make important decisions that affect the safety of all passengers and crewmembers onboard.

Hypoxia generally tends to affect most people above 10,000ft. Above this height supplementary oxygen is needed. In people who are stressed, ill or fatigued, symptoms can often be noticed as low at 8,000ft. Also people who live at low altitudes such as at the coast could become affected at lower altitudes than those accustomed to living in thinner air at higher altitudes.

Signs and Symptoms

Initial symptoms are often hardly noticeable to the sufferer at first, but
the problem is that generally there will be a feeling of euphoria and wellbeing which has a tendency to mask the signs and symptoms of the onset of hypoxia!

The signs and symptoms vary from person to person. However, below is a list of the most common symptoms of hypoxia:
Fatigue
Lack of cognition
Lethargic
Headaches
State of euphoria
Shortness of breath
Loss of Consciousness
Pins and needles
High pulse rate
Deterioration of vision
Blue lips and fingernails
Moodiness
Drowsiness

A pilot or member of an aircrew suffering from hypoxia is highly likely to:
Suffer changed behaviour patterns.
Loose situational awareness.
Become spatially disorientated.
No matter how skilled or experienced, lose the ability to perform normal in flight functions and tasks vital to the operation of the aircraft.
Be unable to perform normally simple tasks such as BASIC arithmetic calculations.
Make poor decisions.
Make fatal errors.
Suffer impaired visual acuity.
Have difficulty in understanding communication between himself, other aircrew and Air Traffic Controllers.

In extreme cases there can be a complete loss of consciousness!!

Now when last did you recap what the LAW has to say about Supplemental Oxygen?

I would urge you to visit the SA CATS (Civil Aviation Technical Standards) and make yourself fully acquainted with PART 91 (General Aviation and Operating Rules) SUPPLEMENTAL OXYGEN.

Also do a little research on this subject on the Internet.

As a matter of interest here is a table showing TIME OF USEFUL CONCIOUSNESS (TUC)

The length of time that a person has to act to combat the effects of Hypoxia.



The problem with Hypoxia is that the symptoms and effects are not immediately reduced when the pilot descends to lower altitudes but it takes the body a fair amount of time to fully recover. This means that the likelihood of a pilot making poor decisions and even hazardous errors is elevated when workload is high such as in commencing an approach procedure or approaching to land after operating at high altitudes.

So next time you plan to operate at high altitudes make sure that you are aware of this and the applicable CIVIL AVIATION TECHNICAL STANDARDS. It should all form part of your preflight risk and threat assessment for the flight.

Until next time please fly safely!!!!

The contents of this article is not meant to be prescriptive but was created to offer guidelines only. Information may not be technically correct and should therefore not be used for actual flight situations.



Chris Kyle - Training Track
Aviation Safety








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