Asphyxia

• Author: D. P. Lyle
• Pages: 139-157

Asphyxia 139

CHAPTER 9

ASPHYXIA

Under normal circumstances, oxygen (O

2) is inhaled into the lungs’ air

sacs, where it crosses into the blood, combines with the hemoglobin of the

red blood cells (RBCs), and is transported throughout the body. The cells

then extract the O2 from the hemoglobin. An interruption at any step in

this O2 supply chain can lead to asphyxia, which can best be defined as

the deprivation of O2 to the cells of the body, re sulting in cellular dysfunc-

tion and ultimately death.

Asphyxia occurs by severa l mechanisms. The air m ight be oxygen-poor

or some airway obstruction might prevent it from entering the lungs. The

lungs might be damaged or f illed with water so that the O2 can’t reach the

blood. Certain toxins interfere with the uptake of O2 by the blood or its

utilization by the cells of the body. Asphyxia can als o follow obstruction of

the arteries in the neck, as occurs dur ing strangulation, which prevents

oxygen-filled blood from reaching the brain. Each of these defects can lead

to death from asphyxia.

Asphyxia can result from suffocation, strangulation, toxic gases, and

drowning.

140 Asphyxia

Suffocation

Suffocation occurs whenever sufficient oxygen is unable to reach the

blood stream, whether from air poor in oxygen or from some impediment

to it reaching the lungs or the bloodstream. There are five general catego-

ries of suffocation: environmental suffocation, smothering, choking,

mechanica l asphyxi a, and suffocating gase s.

Environmental suffocation occur s whenever the inhaled air is low

in O2. Even if the lungs and circulatory system function normally, if the

O2 content of the air is deficient, it is of little use to the body. Normal air

contains 21 percent oxygen. If this percentage drops to 10 to 15 percent,

judgment and coordination suffer, while below 10 percent consciousness is

lost, with death occurring at around 8 percent. This is the rea son adults are

warned as part of the pre-flight routine on commercial airlines that if the

cabin pressure fails, they should put on their oxygen mask before helping

children with their masks. If the adult can’t coordinate— or worse, loses

consciousness—there might be no one to help either of them.

Deaths from an oxygen-po or environment are a lmost always acciden-

tal, though homicide is a possibility. A child might accidentally lock himself

into an old refrigerator where once the oxygen is consumed, death from

asphyxia follows. The same occurs whenever a victim enters an under-

ground chamber or mine that is poor in oxygen. Deaths in structure fires

are most often due to asphyxia as the f lames consume oxygen.

There are no specific autopsy findings in most ca ses of environmental

suffocation, so the determination of the cause and manner of death relies

more on the circumstances surrounding the death. If the victim is found

in an oxygen-poor environment or an airtight enclosure and there is no

evidence of trauma, toxin exposure, or natura l causes, the ME would likely

determine that the death was due to accidental suffocation.

Smothering occurs when some external device prevents air from

entering the nose or mouth. Th is is distingu ished from c hoking (see below),

in which the obstructing material is within the mouth or throat. Smother-

ing deaths can be accidental, homicidal, or suicida l.

Suicidal and accidental smothering usually involves a plastic bag. The

suicidal individual wil l place the bag over his head, often securing it with

tape or a rope, and occasionally binding his own ha nds. This is particul arly