Evening star., 1940-11-28
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory, Field
And Study
By Thomas r. Henry.

And Study
By Thomas r. Henry
An essentially foolproof apparatus for
administration Of oxygen-helium mix
lures, likely to prove of great value in
military medicine, has just been per-
fected by the United States Public Health
Service.
BY this means it will be possible for
slightly trained personnel to give patients
q synthetic atmosphere, only third as
heavy as ordinary air. which can be
breathed with q minimum of effort.
In at least four conditions the mixture
has been found almost essential. One
Is in cases of the bends" of divers.
Helium is much less soluble In blood
than nitrogen, which constitutes about
rs per cent Of ordinary air. Conse-
quently it can be eliminated much more
rapidly from the tissues and there is
not the same likelihood Of forming
bubbles.
It is of great value for a condition
encountered in persons subjected to
rapid descent from high elevations in
airplanes. The rate of diffusion Of
helium Is nearly three times that of
nitrogen. In a mixture of helium and
oxygen the helium fraction obviously
will diffuse more rapidly through the
Eustachian tube to the middle ear than
would the nitrogen of the air. Conse-
quently it is of value in treating the
condition known as ear block.
Breathing is always made easier. This
is especially important to persons with
heart ailments where any unnecessary
effort is likely to be dangerous. One
condition for which the helium- oxygen
mixture is almost q specific Is that
known as status asthmaticus where
breathing ordinary air becomes practi-
cally impossible and a patient Is likely
to choke to death. The helium passes
easily through the breathing tubes and
carries with it sufficient oxygen to keep
the fires of life burning. The mixture
also has proved a Ifesaver in cases of
pneumonia and of obstructive LESSONS in
the trachea and larynx.
An atmosphere of pure oxygen is i'm
practical for any extended period, Public
Health Service experts point out.
Up to now apparatus for adulinistra-
tion of helium- oxygen mixtures has had
several shortcomings. Apparatus which
makes use Of a single tank of the
mixture does not allow variation in the
proportion of the two gases in accord
ance with the patients requirements.
That in which separate tanks for each
gas are used increases the danger of
asphyxia which results from too great
displacement of oxygen by an inert
gas such as helium.
When pure helium is breathed this
asphyxia comes with dramatic sudden
ness. There is no warning whatsoever,
says DR.. Paul A. Neal, one OF the invent
ors Of the new apparatus. The effect is
that OF an instantaneous transition from
full consciousness to complete black
out without any symptoms. Some years
ago, DR.. Neal says, it was suggested
that helium be used as an anesthetic.
It actually was no more of an anes-
thetic than a blow on the head.
Oxygen, of course, is absolutely essen
tial to life. Healthy individuals at rest
or slightly active can tolerate for short
periods a reduction to about IA per cent
Of the oxygen percentage Of the air at
sea level. Since mixtures of 80 per cent
helium and 20 per cent oxygen ordi-
narily are used the margin of safety
is small Consequently it has been
necessary for a person trained in the
use of such apparatus to be present at
all times during the administration of
the mixture.
In the new apparatus the adjustments
are made automatically. Helium and
oxygen are drawn from separate tanks
and pass through a face mask. A safety
valve prevents any flow Of helium until
the oxygen has been turned on. An
adjustable valve controls the percentages
of gases. Tests on normal persons with
different types of breathing showed that
the oxygen never fell more than slight
fraction of per cent below 20 per cent
when the adjustable valve was set at
that figure. On the higher settings,
above so per cent oxygen, this gas never
varied more than 3 per cent above or
below the setting.
The use Of helium In respiratory con-
ditions is in its infancy, the Public
Health Service doctors believe. Although
it has been available for As years, its
use in medicine was first suggested in
1884. 1t is colorless and odorless gas
which has the curious property of being
entirely inert. 1t will NOT mix with any
other chemical substance, in striking
contrast to oxygen, which is one of the
most reactive Of all elements. 1t weighs
only one-seventh as much, volume for
volume, as nitrogen.
The United States is by far the worlds
largest producer Of helium. At present
the United States Bureau of Mines plant
in Texas is capable of producing a.
100000 cubic feet Of the gas year at
cost of approximately l cent cubic
foot
The value of the gas for balloons and
airships, because of the impossibility of
exploding it, was recognized early but
its medical potentialities still are almost
unexplored.
Argues That Dominions