The Collaborative International Dictionary of English v.0.48:

Asphyxia \As*phyx"i*a\, Asphyxy \As*phyx"y\, n. [NL. asphyxia,
   fr. Gr. ?; 'a priv. + ? to throb, beat.] (Med.)
   Apparent death, or suspended animation; the condition which
   results from interruption of respiration, as in suffocation
   or drowning, or the inhalation of poisonous or irrespirable
   gases.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ASPHYXY, med. jur. A temporary suspension of the motion of the heart and
arteries; swooning, fainting. This term includes persons who have been
asphyxiated by submersion or drowning; by breathing mephitic gas; by the
effect of lightning; by the effect of cold; by heat; by suspension or
strangulation. In a legal point of view it is always proper to ascertain
whether the person who has thus been deprived of his senses is the victim
of another, whether the injury has been caused by accident, or whether it
is. the act of the sufferer himself.
     2. In a medical point of view it is important to ascertain whether the
person is merely asphyxiated, or whether he is dead. The following general
remarks have been made as to the efforts which ought to be made to restore a
person thus situated,
     1st. Persons asphyxiated are frequently in a state of only apparent
death.
     2d. Real from apparent death, can be distinguished only by
putrefaction.
     3d. Till putrefaction commences, aid ought to be rendered to persons
asphyxiated.
     4th. Experience proves that remaining several hours under water does
not always produce death.
     5th. The red, violet, or black color of the face, the coldness of the
body, the stiffness of the limbs, are not always signs of death.
     6th. The assistance to persons thus situated, maybe administered by any
intelligent person; but to insure success, it must be done without
discouragement for several hours together.
     7th. All unnecessary persons should be sent away; five or six are in
general sufficient.
     8th. The place where the operation is performed should not be too warm.
     9th. The assistance should be rendered with activity, but without
precipitation.