Respiratory Rate (Breathing Rate)

What Is Respiratory Rate?

Respiratory rate is the number of complete breaths a person takes in one minute, where each breath is one inhalation followed by one exhalation. It is written in breaths per minute, often abbreviated RR or f, and it is one of the main vital signs recorded alongside heart rate, blood pressure and temperature.

Respiratory rate definition

In physiology, respiratory rate is defined as the frequency of the breathing cycle, the rhythm of inhalation and exhalation produced by the breathing muscles. Breathing rate means the same thing in everyday language. It describes how often air is moved in and out of the lungs, not how much air each breath moves; that is the tidal volume.

Rate, depth and minute ventilation

Rate and depth together decide how much air the lungs move. Minute ventilation equals respiratory rate multiplied by tidal volume, so an adult breathing 12 times a minute with breaths of about 500 mL moves about 6 liters of air per minute. Because the first 150 mL or so of each breath only fills the airways, the dead space, a fast rate with very shallow breaths delivers less fresh air to the alveoli than the same total from slower, deeper breaths.

Explained simply

Respiratory rate is simply how many times a person breathes in one minute. Counting the rise and fall of the chest gives the number. At rest an adult breathes slowly and steadily, a little more often than once every five seconds, while a small baby breathes about twice as fast.

What Is a Normal Respiratory Rate?

A normal respiratory rate for a healthy adult at rest is typically about 12 to 20 breaths per minute, and many relaxed adults sit near the lower half of that range. Children breathe faster, and the typical range narrows and slows steadily from birth to the teenage years.

The table below lists typical textbook ranges by age. Different medical references draw the boundaries a little differently, so these numbers describe common values for healthy people at rest, not strict cutoffs. A single count also depends on the moment: talking, eating, moving or feeling nervous all change it.

Breathing rate per minute and per day

At 12 to 20 breaths per minute, an adult takes roughly 17,000 to 29,000 breaths a day without thinking about any of them. Each quiet breath cycle lasts about 3 to 5 seconds, and in quiet breathing the exhalation usually lasts a little longer than the inhalation, often with a short natural pause at the end of the breath out.

Older adults

In healthy older adults the resting breathing rate is usually similar to that of younger adults. What changes with age is the reserve: the lungs lose some elastic recoil and the chest wall stiffens, so breathing has less room to deepen during exertion and may rely a little more on rate.

What Is the Breathing Rate While Sleeping?

The breathing rate while sleeping is usually a little slower than the waking resting rate, and in deep non-REM sleep it becomes especially slow and regular. During REM sleep, the dreaming stage, breathing becomes faster and more irregular, with small changes in both rate and depth.

Several things change at sleep onset. The brain's waking drive to breathe switches off, the breathing centers become slightly less sensitive to carbon dioxide, and the muscles of the throat relax, which narrows the upper airway a little. As a result, blood carbon dioxide rises slightly during sleep, a normal change in healthy people.

Babies during sleep

Newborns and young infants often breathe in a pattern called periodic breathing, with bursts of breaths separated by short pauses of a few seconds, especially during sleep. This pattern is common in healthy newborns and usually fades over the first months as the breathing centers mature. Breathing patterns in sleep are covered further on our breathing patterns and sleep apnea pages.

How Is Respiratory Rate Controlled? The Respiratory Rate Process

Respiratory rate is controlled by groups of nerve cells in the brainstem that fire in a repeating rhythm, adjusted moment to moment by signals about carbon dioxide, oxygen and acid in the blood. The process works as a feedback loop, shown in the diagram at the top of the page, and is described in full on our control of breathing page.

1. The rhythm starts in the medulla. A small cluster of neurons in the medulla oblongata, the pre-Bötzinger complex, acts as the main rhythm generator. The dorsal and ventral respiratory groups around it turn that rhythm into signals for inhalation and, when needed, active exhalation.
2. The pons smooths the pattern. The pontine respiratory group fine-tunes the switch between breathing in and breathing out, which helps set the rate and makes the rhythm smooth.
3. Nerves carry the signal. The phrenic nerve carries the signal to the diaphragm, and the intercostal nerves carry it to the muscles between the ribs.
4. The muscles move air. The diaphragm contracts and air flows in; when the signal stops, the muscles relax and the lungs recoil, pushing air out.
5. Sensors check the result. Central chemoreceptors in the medulla respond to carbon dioxide and acidity in the fluid around the brain, and peripheral chemoreceptors in the carotid and aortic bodies respond mainly to low oxygen. Stretch receptors in the lungs add information through the Hering-Breuer reflex.
6. The brainstem adjusts. If carbon dioxide rises, breathing speeds up and deepens; if it falls, breathing slows until the level returns to normal.

Carbon dioxide, not oxygen, is the main signal at rest. The role of the sensors is explained on our respiratory chemoreceptors page. The upper brain can also override the rhythm for a while, which is why people can hold a note, speak or pause their breath, but rising carbon dioxide soon forces breathing to restart.

What Changes Your Breathing Rate?

Breathing rate changes whenever the body's demand for oxygen or its production of carbon dioxide changes, and also with emotions, temperature, altitude, sleep and some medicines. Most changes are normal and temporary.

• Exercise: working muscles produce more carbon dioxide, and both rate and depth rise; in hard exercise the rate can reach two to three times its resting value. See how exercise affects the respiratory system.
• Body temperature: fever raises the body's metabolic rate, and breathing speeds up to remove the extra carbon dioxide.
• Emotions and pain: stress, fear, excitement and pain activate the sympathetic nervous system and quicken breathing, sometimes to the point of hyperventilation.
• Altitude: thinner air with less oxygen pressure stimulates the peripheral chemoreceptors, so people breathe faster and deeper, as explained on breathing at high altitude.
• Acid in the blood: when the blood becomes more acidic for metabolic reasons, the body breathes deeper and faster to blow off carbon dioxide and raise the pH.
• Sleep: the rate slows slightly in deep sleep and becomes irregular in REM sleep.
• Medicines and substances: some sedating medicines and alcohol can slow breathing by depressing the brainstem.
• Age: the rate is fastest in newborns and slows through childhood.
• Voluntary actions: talking, singing, eating and laughing change the rhythm for short periods.

In each case the body is usually adjusting breathing to keep blood carbon dioxide and oxygen within narrow limits, part of how the respiratory system maintains homeostasis.

How Is Respiratory Rate Measured?

Respiratory rate is usually measured by counting how many times the chest or abdomen rises in a set period while the person is at rest. Health workers often count for 30 seconds and double the number, or count for a full 60 seconds when breathing is irregular and in babies.

Counting by observation

Because people change their breathing as soon as they know it is being watched, the count is often taken quietly, for example right after measuring the pulse. One rise and one fall of the chest count as one breath. In infants, who breathe mostly with the diaphragm, the movement of the belly is often easier to see than the chest.

Measuring with devices

• Capnography measures carbon dioxide in each exhaled breath and gives a breath-by-breath rate, often used during anesthesia.
• Impedance pneumography uses the electrodes of a heart monitor to detect the small electrical changes as the chest expands.
• Spirometers and ventilators record every breath directly from airflow, as described on our spirometry page.
• Wearable sensors estimate breathing rate from chest movement or from small changes in the pulse signal, mainly during sleep.

Respiratory rate is one of the simplest vital signs to measure, yet it is often called the neglected vital sign because it is easy to estimate instead of count, which is why careful counting over a full interval is stressed in training.

Tachypnea, Bradypnea and Other Breathing Rate Terms

Doctors and physiologists use a set of standard terms to describe breathing rate and depth: eupnea is normal breathing, tachypnea is a faster-than-normal rate, bradypnea is a slower-than-normal rate and apnea is a pause in breathing. These words describe what is observed; they do not name a cause.

Some terms describe rate, some describe depth and some describe the feeling of breathing. Hyperpnea means deeper, faster breathing that matches a higher demand, as in exercise, while hyperventilation means breathing more than the body needs, which lowers blood carbon dioxide. Dyspnea is not a rate at all but the unpleasant feeling of being short of breath. The table below summarizes the most common terms, and our page on breathing patterns covers rhythms such as Cheyne-Stokes and Kussmaul breathing.

Respiratory Rate vs Heart Rate

Respiratory rate counts breaths per minute, while heart rate counts heartbeats per minute; at rest an adult's heart beats about 60 to 100 times a minute, roughly four to five beats for every breath. Both rise during exercise, fever and stress, because the respiratory and circulatory systems work together to deliver oxygen and remove carbon dioxide.

Different pacemakers

The two rhythms are set in different places. Breathing is generated by neurons in the brainstem and depends entirely on nerve signals, which is why it can be paused or changed on purpose. The heartbeat is generated inside the heart itself by the sinoatrial node, so it keeps beating without any signal from the brain, which only speeds it up or slows it down.

How breathing changes the heart rate

The two rates are linked breath by breath. In healthy people, especially children and young adults, the heart rate speeds up slightly during each inhalation and slows slightly during each exhalation, a normal pattern called respiratory sinus arrhythmia. It reflects the vagus nerve easing its brake on the heart while breathing in, and it tends to become less marked with age.

Common Conditions That Affect Respiratory Rate

Many lung, heart, nervous system and metabolic conditions change respiratory rate, most often by making breathing faster, and some medicines and brain conditions make it slower. A change in breathing rate is a sign, not a diagnosis, and anyone with breathing symptoms should see a doctor. Our respiratory diseases section describes the conditions in more detail.

• Lung infections: pneumonia fills alveoli with fluid and usually makes breathing faster and shallower.
• Airway diseases: flare-ups of asthma and COPD narrow the airways and often raise the rate.
• Blood clots in the lungs: a pulmonary embolism commonly causes sudden fast breathing.
• Low oxygen: any cause of hypoxemia, including high altitude, stimulates faster breathing.
• Metabolic acidosis: conditions that make the blood acidic, such as diabetic ketoacidosis, can cause deep, rapid Kussmaul breathing.
• Anxiety and panic: can trigger fast breathing and hyperventilation.
• Slow breathing: sedating medicines, some head injuries and severe hypothermia can slow the rate.