Respiratory Rate

General 

Respiratory rate (V_f, R_f or RR) is also known by respiration rate, pulmonary ventilation rate, ventilation rate, orbreathing frequency is the number of breaths 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. 

Measurement

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. 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.

Normal range

Average respiratory rate reported in a healthy adult at rest is usually given as 12-18 breaths per minute (V_f) 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.

By Age

Average Respiratory Rates (V_f) By Age:

• Newborns: 30-40 breaths per minute
• Less Than 1 Year: 30-40 breaths per minute
• 1-3 Years: 23-35 breaths per minute
• 3-6 Years: 20-30 breaths per minute
• 6-12 Years: 18-26 breaths per minute
• 12-17 Years: 12-20 breaths per minute
• Adults Over 18: 8–20 breaths per minute.

Minute volume

Respiratory minute volume is the volume of air which can be inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs in one minute.

Diagnostic value

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

• Apnea
• Dyspnea
• Hyperpnea
• Tachypnea
• Hypopnea
• Bradypnea
• Orthopnea
• Platypnea
• Biot's respiration
• Cheyne-Stokes respiration
• Kussmaul breathing

Reference

- http://en.wikipedia.org/wiki/Respiratory_rate