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.
Various other methods to measure respiratory rate are commonly used, including impedance pneumography, and capnography which are commonly implemented in patient monitoring. In addition novel techniques for automatically monitoring respiratory rate using wearable sensors are in development, such as estimation of respiratory rate from the electrocardiogram, photoplethysmogram and accelerometry signals.
The typical respiratory rate for a healthy adult at rest is 12–20 breaths per minute.
- birth to 6 weeks: 30–40 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: 17–23 breaths per minute
- Adults: 12-18-breaths per minute
- Elderly ≥ 65 years old: 12-28 breaths per minute.
- Elderly ≥ 80 years old: 10-30 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.
Nonetheless respiratory rate is widely used to monitor the physiology of acutely-ill hospital patients. It is measured regularly to facilitate identification of changes in physiology along with other vital signs. This practice has been widely adopted as part of early warning systems.
Abnormal respiratory rates
- Biot's respiration
- Cheyne-Stokes respiration
- Kussmaul breathing
- Simoes EA, Roark R, Berman S, Esler LL, Murphy J. Respiratory rate: measurement of variability over time and accuracy at different counting periods. Archives of Disease in Childhood. 1991;66(10):1199-1203 
- 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 
- "Advanced Methods and Tools for ECG Data Analysis - ECG Derived Respiratory Frequency Estimation - Chapter 8; Raquel Bail�n, Leif S�rnmo, and Pablo Laguna". www.robots.ox.ac.uk. Retrieved 2016-02-23. replacement character in
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- Karlen, Walter; Raman, Srinivas; Ansermino, J. Mark; Dumont, Guy A. (2013-07-01). "Multiparameter respiratory rate estimation from the photoplethysmogram". IEEE transactions on bio-medical engineering 60 (7): 1946–1953. doi:10.1109/TBME.2013.2246160. ISSN 1558-2531. PMID 23399950.
- Lapi, Sara; Lavorini, Federico; Borgioli, Giovanni; Calzolai, Marco; Masotti, Leonardo; Pistolesi, Massimo; Fontana, Giovanni A. "Respiratory rate assessments using a dual-accelerometer device". Respiratory Physiology & Neurobiology 191: 60–66. doi:10.1016/j.resp.2013.11.003.
- Ganong's Review of Medical Physiology (24 ed.). p. 619. ISBN 0071780033.
- Scott L. DeBoer (4 November 2004). Emergency Newborn Care. Trafford Publishing. p. 30. ISBN 978-1-4120-3089-2.
- Wilburta Q. Lindh; Marilyn Pooler; Carol Tamparo; Barbara M. Dahl (9 March 2009). Delmar's Comprehensive Medical Assisting: Administrative and Clinical Competencies. Cengage Learning. p. 573. ISBN 978-1-4354-1914-8.
- Rodríguez-Molinero A. et al., Normal respiratory rate and peripheral blood oxygen saturation in the elderly population. J Am Geriatr Soc. 2013 Dec;61(12):2238-40.
- Smith, Gary B.; Prytherch, David R.; Meredith, Paul; Schmidt, Paul E.; Featherstone, Peter I. (2013-04-01). "The ability of the National Early Warning Score (NEWS) to discriminate patients at risk of early cardiac arrest, unanticipated intensive care unit admission, and death". Resuscitation 84 (4): 465–470. doi:10.1016/j.resuscitation.2012.12.016. ISSN 1873-1570. PMID 23295778.