Tachypnea is an abnormally rapid rate of breathing. In
adult humans at rest, this is defined as more than 20
breaths per minute. Twelve to twenty breaths a minute
is considered normal in adults at rest. The normal
breathing rate differs in children according to age.
Specifically, the normal breathing rate for newborns
until 6 months is 30 to 60 breaths per minute but
declines to 24 to 30 breaths per minute from 6 to 12
months, 20 to 30 breaths per minute from 1 to 5 years,
and 12 to 20 breaths per minute from age 6 onwards.
While tachypnea is often used to refer to rapid
breathing at rest, it can refer more broadly to any rapid
rate of breathing, such as during exercise. 

FEATURED BOOK: Murray & Nadel's Textbook of Respiratory Medicine

Some consider tachypnea to be abnormally rapid respiration. Although some use the
terms breathing and respiration interchangeably, they are actually different terms.
Breathing refers to the external mechanical process of bringing air in and out of the lungs
whereas respiration is an internal chemical process when glucose (a type of sugar) and
oxygen combine to produce carbon dioxide, water, and adenosine triphosphate (a
molecule that stores energy). Normal reasons for tachypnea include exercise, fast body
movements, and labor during pregnancy. However, sometimes the cause can be because
something is wrong with the body. For example, tachypnea is sometimes seen in patients
who have a high fever.
"Where Medical Information is Easy to Understand"™
Tachypnea is also known to occur due to poisoning with carbon
monoxide (a type of gas) because it blocks the delivery of oxygen to
tissues and organs, causing injury to cells. To compensate for this,
breathing rate increases in an attempt to give the body more
oxygen. Tachypnea can also occur as a result of lung cancer
because the body is not receiving enough oxygen. Cancer is any of
a large group of malignant diseases characterized by an abnormal,
uncontrolled growth of new cells in one of the body organs or
tissues. Chronic obstructive pulmonary disease (COPD) can also
cause tachypnea. COPD is a general term for diseases that are
characterized by long-term or permanent narrowing of small airways
(known as bronchi) connected to the lungs.

Severe anemia can also cause tachypnea. Anemia is a condition in which there is an abnormally low
amount of hemoglobin in the blood. Anxiety can also cause tachypnea, such as periods of panic, even
when the body is actually getting enough oxygen.

Other terms related to tachypnea are hyperpnea and hyperventilation. Hyperpnea is defined as any
abnormal increased rate and depth of breathing, breathing more rapid and deep than breathing at rest, or
an increase in breathing that is approximately proportional to an increase in the rate of metabolism.
Metabolism is a term for the chemical actions in cells that release energy from nutrients or that use energy
to create other substances. Hyperventilation is defined as increased rate of breathing at rest or abnormally
increased rate and depth of respiration causing decreased levels of carbon dioxide in the blood.  Another
definition of hyperventilation is increased ventilation of the alveoli. Alveoli are tiny sacs where gases are
exchanged in the lungs so that breathing can take place. This can occur due to increased rate and/or depth
of breathing. In hyperventilation, there is a smaller rise in metabolic carbon dioxide compared to the
increase in ventilation.

Tachypnea can be transient (usually less than 24 hours), which typically occurs in newborns. This is
sometimes referred to as transient tachypnea or transient tachypnea of the newborn. Tachypnea often co-
occurs with dyspnea,which is  the sensation of shortness of breath. Tachypnea is also known as polypnea
and is sometimes spelled as tachypnoea. Tachypnea comes from Greek word “tachys” meaning “quick,”
and the Greek word “pnoe” meaning “breathing.” Put the words together and you have “quick breathing.”