Respiratory rate

Breathing (which in organisms with lungs is called ventilation and includes inhalation and exhalation) is a part of respiration. The rate at which breaths occur, usually measured in breaths per minute, is called the ventilation rate, or, by long-standing convention, the respiratory rate (despite that in precise usage ventilation is a hyponym, not a synonym, of respiration).

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.

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