Facts on File Encyclopedia of Health and Medicine

components, an emitter and a tiny computer chip.
The emitter is a small device that fits over the fin-
gertip or on the EARlobe. It projects beams of red
and infrared light, which pass through the tissue
to a sensor on the other side. The volume of blood
in the tissue at systole (peak contraction of the
HEART) is greater, resulting in more light being
absorbed than with the lesser volume of blood in
the tissue at diastole (relaxation of the heart). The
oximeter’s computer chip measures this difference
and uses it to mathematically calculate the per-
centage of oxygen the hemoglobin carries.
See also OXYGEN–CARBON DIOXIDE EXCHANGE; OXY-
GEN THERAPY.

oxygen therapy The administration of oxygen
via nasal cannula, face mask, endotracheal tube
(tube inserted into the THROAT), or transtracheal
catheter (small tube surgically placed through the
outside of the throat into the TRACHEA). Oxygen
therapy delivers oxygen at a percentage higher
than that of normal air, which is 21 percent oxy-
gen at sea level. Oxygen therapy can deliver oxy-
gen from about 25 percent to 100 percent. This
boosts the OXYGEN SATURATIONof the BLOOD, which
becomes necessary when the LUNGScannot ade-
quately diffuse oxygen into the blood or the HEART
cannot circulate oxygenated blood at a level that
meets the body’s needs.

Oxygen is highly flammable. Do not

smoke, have an open flame, or use elec-

trical appliances (including extension

cords) in the vicinity of the oxygen sup-

ply.

Because 100 percent oxygen can be harmful to
body tissues, doctors administer this level of oxy-
gen therapy only to treat respiratory crisis. Sup-
plemental oxygen therapy may be an element of
treatment for cardiovascular conditions such as

ISCHEMIC HEART DISEASE(IHD) and HEART FAILUREas

well as pulmonary conditions such as CHRONIC

OBSTRUCTIVE PULMONARY DISEASE(COPD), PNEUMONIA,

severe ASTHMA, and ATELECTASIS.

In the hospital setting the oxygen supply is cen-

tralized, with access ports in patient care areas.

Oxygen-delivery tubing plugs into the port, with

an individualized flow regulator to adjust the per-

centage of oxygen. Oxygen tanks for home oxy-

gen therapy contain compressed or frozen (liquid)

oxygen, with flow regulators and often a device

that releases oxygen only on inhalation. Home

oxygen therapy may use an oxygen concentrator

instead of supplemental oxygen. An oxygen con-

centrator extracts nitrogen from room air to

increase the air’s concentration of oxygen. Oxygen

concentrators can deliver oxygen only at low flow

rates, however, making them useful only for

people who require minimal oxygen supplemen-

tation. It is important to have adequate supple-

mental humidification as well during oxygen

therapy, as the higher concentration of oxygen is

drier than environmental air. Oxygen therapy

may be short-term or long-term treatment,

depending on the condition that causes its use.

The person may also use oxygen therapy continu-

ously, only during sleep, or only during physical

activity depending on his or her underlying dis-

ease and respiratory needs.

OXYGEN THERAPY

Oxygen Therapy Device Percentage of Oxygen

nasal cannula 25 to 40 percent

face mask 30 to 50 percent

nonrebreathing mask 50 to 90 percent

transtracheal catheter up to 100 percent

endotracheal tube up to 100 percent

bag and mask resuscitator up to 100 percent

See also OXYGEN–CARBON DIOXIDE EXCHANGE; TRA-

CHEOSTOMY.

oxygen therapy 217