R

rales See BREATH SOUNDS.

respiration rate The number of respiratory
cycles a person completes in one minute. A typical
healthy adult has a respiration rate of 15 to 20 per
minute, measured by counting each inhalation or
each exhalation (a respiratory cycle is one of
each). Respiration rate normally is lower at rest
and during sleep, and accelerates as well as inten-
sifies with physical activity and exercise. Children
have higher respiration rates than adults. The res-
piration rate typically increases with health cir-
cumstances such as INFECTION, FEVER, trauma, PAIN,
and strong emotions such as fear. The brainstem
regulates the respiration rate, in intimate coordi-
nation with other vital functions such as HEART
RATE and BLOOD PRESSURE. The respiration rate
remains at roughly a ratio of 1 to 4 with the heart
rate (one breath for every four contractions of the
HEART).
See also BREATHING; CARDIAC CYCLE.

respiratory cycle One repetition of the pattern
of inhalation (BREATHINGair into the LUNGS), OXY-
GEN–CARBON DIOXIDE EXCHANGE, and exhalation
(breathing air out of the lungs). In health a typical
adult completes 15 to 20 respiratory cycles a
minute, called the RESPIRATION RATE. The brainstem
regulates the respiratory cycle in response to feed-
back mechanisms from other body systems that
indicate oxygen needs and consumption.
See also AEROBIC FITNESS; BREATHING EXERCISES;
DYSPNEA; HYPERVENTILATION; TACHYPNEA.

respiratory failure The inability of the LUNGSto
diffuse enough oxygen into the bloodstream to
meet the body’s needs. Respiratory failure may
arise from end-stage pulmonary disease, extensive

trauma, severe CARDIOVASCULAR DISEASE (CVD)or

crisis (such as HEART ATTACK), neurologic damage or

injury (such as SPINAL CORD INJURY, TRAUMATIC BRAIN

INJURY[TBI], STROKE, or neurodegenerative disor-

der), or severe INFECTION(sepsis). Respiratory fail-

ure may be acute or chronic.

Acute respiratory failure is a life-threatening

condition that results from the inability to breathe

enough or the inability of the lungs to diffuse ade-

quate amounts of oxygen into the blood, or a

combination of both. Symptoms of acute respira-

tory failure typically are pronounced and include

• extreme DYSPNEA(shortness of breath or diffi-
  cult BREATHING)


• CYANOSIS(bluish hue to the lips and SKIN)


• HYPOTENSION(low BLOOD PRESSURE)


• cardiovascular SHOCK

Treatment of acute respiratory failure requires

oxygen administration and immediate resuscita-

tive breathing or MECHANICAL VENTILATION; without

prompt restoration of oxygenation, death is

inevitable.

Chronic respiratory failure may also be life-

threatening, though commonly the person accom-

modates the inadequate oxygenation through

restricted physical activity and treatments such as

OXYGEN THERAPY. Chronic respiratory failure is a

consequence of progressive pulmonary disorders

such as CHRONIC OBSTRUCTIVE PULMONARY DISEASE

(COPD). Symptoms of chronic respiratory failure

may be activity related and often include

• persistent COUGH


• dyspnea, especially with exertion


• diminished cognitive ability or confusion

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