Every time you breathe in and out, your lungs inhale oxygen-rich air and blow out carbon dioxide. The number of breaths you take in one minute is known as your respiration rate, or breathing rate. Your sex, weight, exercise tolerance and physical condition influence your baseline respiration rate, according to Medline Plus.
Premature newborns, with their tiny lungs, have to breathe rapidly to bring in enough oxygen. As children grow, their lungs mature and they're able to exchange more air with each breath. The normal respiration rate drops gradually through age 12, when it levels off, according to eMedicine Health.
If your baby is born prematurely, you can expect her respiration rate to be between 40 and 70 breaths a minute, notes eMedicine Health. Other newborns will take between 35 and 55 breaths a minute through the age of 3 months, and 3- to 6-month-olds will have a rate between 30 and 45. From 6 months through 1 year old, infants inhale and exhale 25 to 40 times a minute. Toddlers between 1 and 3 breathe 20 to 30 times a minute. The normal respiratory rate for 6- to 12-year-olds is 14 to 22. From 12 years of age onward, the normal respiration rate runs 12 to 18 times a minute, according to Medline Plus.
To measure the respiration rate, count the number of times a person's chest rises and falls within a one-minute period. It's best to count the number of breaths when the individual is at rest, according to the University of Iowa Hospitals and Clinics. Health-care providers might use a stethoscope to listen to the quality of your respirations.
Respiration rate, blood pressure, pulse rate and body temperature are known as the four vital signs that give your health-care provider a quick snapshot of your overall health, according to Medline Plus.
Your respiration rate can vary significantly with illness, fever and medical conditions, according to the University of Virginia Health System. Respiration rates outside the normal range warrant medical attention. For example, you should call your pediatrician if your 2-month-old is breathing 85 times a minute.
Your breathing rate is primarily regulated by neural and chemical mechanisms. Respiration is controlled by spontaneous neural discharge from the brain to nerves that innervate respiratory muscles. The primary respiratory muscle is the diaphragm, which is innervated by the phrenic nerve. The rate at which the nerves discharge is influenced by the concentration of oxygen, carbon dioxide and the acidity of the blood.
Normal Respiratory Rate
The normal respiratory rate in adults is between 14 and 18 breaths per minute on average. Newborns breathe much faster at about 44 breaths per minute on average. Over time, the respiratory rate gradually decreases to the adult rate.
There are chemoreceptors in the brain and the heart that sense the amount of oxygen, carbon dioxide and acid present in the body. As a result, they modulate the respiratory rate to compensate for any disruptions in balance of any of these chemicals. Too much carbon dioxide or acidity and too little oxygen cause the respiratory rate to increase and vice versa. Carbon dioxide chemoreceptors are much more sensitive than oxygen chemoreceptors and, thus, exert an effect with smaller changes.
There are two neural mechanisms that govern respiration -- one for voluntary breathing and one for automatic breathing. The voluntary impulse originates in the cerebral cortex region of the brain and the automatic impulse originates in the medulla oblongata.
Respiratory rate is also regulated by lung stretch receptors. The stretch receptors sense the over-inflation of the lungs, which leads to decreases in the respiratory rate. Additionally, irritant receptors in the mucous membrane lining of the respiratory tract, which are stimulated by respiratory irritants, cause increases in the depth and rate of breathing. Blood pressure receptors in the aorta and carotid arteries also influence breathing rate. Low blood pressure causes an increase in breathing rate and vice versa.