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The respiratory rate (RR), also known as the respiration rate, ventilation rate, ventilatory rate, ventilation frequency (Vf), respiration frequency (Rf), pulmonary ventilation rate, or breathing frequency, is the rate (frequency) of ventilation, that is, the number of breaths (inhalation-exhalation cycles) taken within a set amount of time (typically 60 seconds). A normal respiratory rate is termed eupnea, an increased respiratory rate is termed tachypnea and a lower than normal respiratory rate is termed bradypnea.
Breathing (which in organisms with lungs is called ventilation and includes inhalation and exhalation) is a part of respiration. Thus, in precise usage, the words breathing and ventilation are hyponyms, not synonyms, of respiration; but this prescription is not consistently followed, even by most health care providers, because the term respiratory rate (RR) is a well-established term in health care, even though it would need to be consistently replaced with ventilation rate if the precise usage were to be followed.
Human respiration rate is measured when a person is at rest and involves counting the number of breaths for one minute by counting how many times the chest rises. An optical breath rate sensor can be used for monitoring patients during a magnetic resonance imaging scan. Respiration rates may increase with fever, illness, or other medical conditions. When checking respiration, it is important to also note whether a person has any difficulty breathing.
Inaccuracies in respiratory measurement have been reported in the literature. One study compared respiratory rate counted using a 90 second count period, to a full minute, and found significant differences in the rates. Another study found that rapid respiratory rates in babies, counted using a stethoscope, were 60–80% higher than those counted from beside the cot without the aid of the stethoscope. Similar results are seen with animals when they are being handled and not being handled—the invasiveness of touch apparently is enough to make significant changes in breathing.
The Average respiratory rate reported in a healthy adult at rest is usually given as 18–22 breaths per minute but estimates do vary between sources, e.g., 12–20 breaths per minute, 10–14, between 16–18, etc. With such a slow rate, more accurate readings are obtained by counting the number of breaths over a full minute. Average resting respiratory rates by age are:
- birth to 6 weeks: 30–60 breaths per minute
- 6 months: 25–40 breaths per minute
- 3 years: 20–30 breaths per minute
- 6 years: 18–25 breaths per minute
- 10 years: 15–20 breaths per minute
- adults: 18–22 breaths per minute
The value of respiratory rate as an indicator of potential respiratory dysfunction has been investigated but findings suggest it is of limited value.
One study found that only 33% of people presenting to an emergency department with an oxygen saturation below 90% had an increased respiratory rate. An evaluation of respiratory rate for the differentiation of the severity of illness in babies under 6 months found it not to be very useful. Approximately half of the babies had a respiratory rate above 50 breaths per minute, thereby questioning the value of having a "cut-off" at 50 breaths per minute as the indicator of serious respiratory illness.
It has also been reported that factors such as crying, sleeping, agitation and age have a significant influence on the respiratory rate. As a result of these and similar studies the value of respiratory rate as an indicator of serious illness is limited.
Abnormal respiratory rates
- Biot's respiration
- Cheyne-Stokes respiration
- Kussmaul breathing
- Grenvik, A., Ballou, S., McGinley, E., Millen, J., Cooley, W.L., Safar P. (1972) Impedance Pneumography: Comparison between Chest Impedance Changes and Respiratory Volumes in II Healthy Volunteers. Chest. October 1972;62(4):439-443 
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- Respiratory Rate
- Brian S. Beckett, Illustrated Human and Social Biology, Oxford: Oxford University Press, 1995, ISBN 0-19-914065-0, p. 78 
- Scott L. DeBoer (4 November 2004). Emergency Newborn Care. Trafford Publishing. p. 30. ISBN 978-1-4120-3089-2.
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