OT: Not Really-Hypoxic Death (Long)

The Hypoxic Death

Hypoxia is the term meaning 'low oxygen', and a death that
results from inhaling insufficient oxygen is a hypoxic death.

In normal everyday life, we live in an atmosphere that is 21%
oxygen. Interestingly, when there is a decline in the level of
oxygen in the air we are breathing, we do not experience any
particular alarm or concern. As long as one can breathe easily,
the sensation one experiences as the oxygen level drops is one
of disorientation, confusion, lack of coordination and eventual
loss of consciousness. This experience is sometimes likened
to being drunk (alcohol intoxication). If the oxygen level falls
too far death will result.

Accidental hypoxic deaths are not uncommon and there are a
number of scenarios that can bring them about. One example is
the sudden drop in oxygen level that occurs when an aeroplane
de-pressurises at high altitude. This can lead to a rapid loss of
consciousness and the death of all those in the plane. When the
plane de-pressurizes, one can still breath easily but there will be
little oxygen in the inhaled air. This will cause a sudden drop
in the oxygen level in the blood reaching the brain, leading to
loss of consciousness and death. It is not uncommon for planes
that have suddenly de-pressurized to travel on autopilot until
they run out of fuel while everyone aboard has died. Witnesses
(from planes sent to investigate) say that it often appears as
though everyone on board has just gone to sleep.

Pneumonia is a more common cause of a hypoxic death. Its
peaceful reputation led to its common description as the 'old
person's friend'. While the air inhaled may contain the full
21% of oxygen, the inflammation of the lungs (caused by the
pneumonic infection) makes it impossible for the necessary
oxygen to be extracted. The blood reaching the brain will have
less oxygen than that required for life, and a peaceful death
often results.

The Role of Carbon Dioxide (CO2)

In normal respiration, the body makes use of oxygen and
produces as waste the gas, carbon dioxide. Carbon dioxide is
removed from the body as we breath out. While the human
body is relatively insensitive to falling levels of oxygen, it
is very sensitive to any rise in the level of carbon dioxide in
inhaled air.

When the body detects a slight increase of carbon dioxide in
the air that we breathe, a warning message from the brain alerts
the person. They will be roused and may react by gasping.
This reaction is known as a Hypercapnic (high carbon dioxide)
Alarm Response.

Sleep Apnoea provides an example of hypercapnic alarm.
Here the person with sleep apnea, snores so heavily that they
deny themselves the oxygen they need.
This they got wrong, we all know the airway usually closes off,
except for central apnea However, it is not the
lowering of the oxygen level that alarms and wakes the person,
but the accompanying rise in the level of carbon dioxide. If
the fall in oxygen were not accompanied by this rise in carbon
dioxide, the Sleep Apnoeic would be far more likely to die.
In the depressurized aircraft, the oxygen level drops but there
is no accompanying rise in carbon dioxide, hence a peaceful
death is the common outcome.