The respiratory rate in humans 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.
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.
Average resting respiratory rates by age are:
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.