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What is it?

Respiratory rate is the rate at which a complete breathing cycle occurs. While voluntary control can take over this, respiratory rate is an autonomic process controlled by the autonomic nervous system. This happens due to many inputs, including the brain’s respiratory center, which collects physiological sensory information throughout the body.

These sensory inputs into the respiratory center of the brain include blood CO2, O2, and pH levels, lung stretch receptors, joint and muscle proprioceptors, other peripheral receptors, and additional information from higher brain centers that process emotion, speech, motor pathways, voluntary control, and more

How is it measured?

Respiratory rate can be measured through photoplethysmography (PPG) by measuring the baseline shifts that occur with breathing. The baselines move up and down in an oscillatory pattern corresponding to the breath cycle.

Correlations with health conditions

Respiratory rate is subject to change and may be an important vital sign to monitor. The two primary drivers of these changes are lung complications and sympathetic stress response.

Alterations to lung function, such as acute respiratory illnesses (pneumonia, upper respiratory tract infection, etc.), acute bronchoconstriction (such as asthma), and chronic illnesses (COPD, emphysema, pulmonary fibrosis, etc.) all can cause impaired gas exchange at the levels of the lung.

This impaired gas exchange leads to acidosis (increased acidity in the blood) and hypercapnia (a condition of abnormally elevated carbon dioxide levels in the blood), which increase the respiratory rate through the respiratory control center. Through different mechanisms, sympathetic stress leads to increased respiratory rate, typically viewed as an anticipatory response to stress.

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Normal or Acceptable Range

Breathing rate is individual-specific but can range from 12 to 20 breaths per minute (bpm). Within a particular individual, the breathing rate can stay relatively constant across days at basal levels (coefficient of variation ~ 5%). However, certain factors such as respiratory illness, high levels of fatigue, infection, and more can cause the respiratory rate to change significantly.

Interpreting Trends

This combination of low variability but high responsiveness allows the respiratory rate to be a good indicator of acute problems. For example, the respiratory rate appears to be highly predictive of respiratory infection and responds before a typical diagnosis, which makes for an excellent biomarker for predicting the risk of respiratory infection.

In general, besides acute illnesses, the respiratory rate should remain relatively stable or trend downward with increased cardiorespiratory function.

References

  1. Schaefer KE. Respiratory Pattern and Respiratory Response to CO2. Journal of Applied Physiology. 1958;13(1):1–14. doi:10.1152/jappl.1958.13.1.1
  2. Javaheri S, Kazemi H. Metabolic alkalosis and hypoventilation in humans. The American Review of Respiratory Disease. 1987;136(4):1011–1016. doi:10.1164/ajrccm/136.4.1011
  3. Brinkman JE, Toro F, Sharma S. Physiology, Respiratory Drive. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2021. http://www.ncbi.nlm.nih.gov/books/NBK482414/
  4. Schelegle ES, Green JF. An overview of the anatomy and physiology of slowly adapting pulmonary stretch receptors. Respiration Physiology. 2001;125(1):17–31. doi:10.1016/S0034-5687(00)00202-4
  5. Bishop B, Bachofen H. COMPARATIVE INFLUENCE OF PROPRIOCEPTORS AND CHEMORECEPTORS IN THE CONTROL OF RESPIRATORY MUSCLES. :10.
  6. Guz A. Brain, breathing and breathlessness. Respiration Physiology. 1997;109(3):197–204. doi:10.1016/S0034-5687(97)00050-9
  7. Miller DJ, Capodilupo JV, Lastella M, Sargent C, Roach GD, Lee VH, Capodilupo ER. Analyzing changes in respiratory rate to predict the risk of COVID-19 infection. PLOS ONE. 2020;15(12):e0243693. doi:10.1371/journal.pone.0243693
  8. Sun G, Okada M, Nakamura R, Matsuo T, Kirimoto T, Hakozaki Y, Matsui T. Twenty‐four‐hour continuous and remote monitoring of respiratory rate using a medical radar system for the early detection of pneumonia in symptomatic elderly bedridden hospitalized patients. Clinical Case Reports. 2018;7(1):83–86. doi:10.1002/ccr3.1922
Reading time: 5 min

Respiratory rate is one of the main vital signs that measure a person’s health. Alongside body temperature, blood pressure, heart rate, respiratory rate is an essential measurement for determining well-being. 

Respiratory rate is the rate at which a full breathing cycle occurs, both inhalation and exhalation. While this is something that can be taken over by voluntary control, the majority of respiratory rate is an autonomic process, which occurs as a result of many inputs, including the respiratory center of the brain, which sends physiological sensory information throughout the body.

Age, weight and certain illnesses can all influence a person’s respiration rate. That’s why your normal respiratory rate may differ from the next person’s. If you learn to measure your respiratory rate, you’ll gain a better understanding of what is normal for you.

What Is a Normal Respiratory Rate?

The normal ranges for respiratory rate vary depending on a number of factors. For example, people who regularly practice deep breathing exercises, or those who play woodwind instruments, may take less breaths per minute, whereas people who are less physically fit may take more breaths per minute.

“We don’t really believe in comparing someone to a normal curve,” explains Kevin Longoria, MSc, a clinical exercise physiologist and the Chief Science Officer for Biostrap. “More importantly, we believe in comparing them to themself. We can see what someone’s normal respiratory rate may be and establish a trend. Then, you look at changes in the trend.” This allows you to determine what is a normal respiratory rate and what is abnormal for you as an individual.

In general, an abnormal respiratory rate is when the number of breaths per minute is under 12 or over 25 — but again, this can vary for every individual. A high respiratory rate means that the respiratory system is being overworked when it circulates oxygen through the blood and body. Conditions like asthma or sudden episodes, like an anxiety attack, can increase the number of times a person breathes per minute, resulting in a high respiratory rate.

In contrast, a child’s breathing rate would be different. “The normal respiratory rate changes significantly throughout the first several years of a child’s development,” says Longoria. For example, a baby up to 6-month old will usually have a breathing rate between 30 and 60 breaths per minute. A child between one and five will usually have a breathing rate between 20 and 30. By the time a child is 12, their breathing rate will usually be under 20.

According to Longoria, “abnormally high respiratory rates in children may be a sign of fever, dehydration, or conditions including bronchiolitis or pneumonia. Children may also experience rapid respiratory rates similar to adults due to other medical conditions including acidosis (with diabetes) and asthma.” And these are just a few of the factors that influence respiratory rate.

Factors That Influence Respiratory Rate

There are a number of common conditions that influence a person’s respiratory rate. For example, having anxiety and suffering from panic attacks can result in shallow breathing patterns and an acutely high respiratory rate for a short period of time (also referred to as hyperventilation).

“What’s really important when you look at respiratory rate is understanding autonomic control,” says Longoria. “When we look at the autonomic nervous system, it’s controlling all these voluntary processes like heart rate, respiratory rate, response to exercise, stress hormones, inflammatory processes — essentially things we don’t have to think about.” Factors such as exercise, stress, or changes in heart rate can influence respiratory rate involuntarily.

Shallow breaths or hyperventilation could be caused by the following conditions.

Lung and Airway Diseases

Lung diseases cause reduced oxygen uptake and prevent the lungs from working properly. For example, emphysema, severe/refractory asthma, and chronic bronchitis block a person’s airflow and contribute to an increasing sense of breathlessness.

These diseases are classified under the term Chronic Obstructive Pulmonary Disorder (COPD). Symptoms include shortness of breath, wheezing, chest tightness and chronic cough with and without mucus. COPD is primarily caused by smoking cigarettes but can also be associated with genetic conditions.

When it comes to factors that influence respiratory rate, “smoking is an obvious one,” notes Longoria. “If you’re smoking, then you’re getting more tar buildup and essentially causing what’s called a respiratory restriction.” Tar buildup in the lungs will damage your air sacs (alveoli) where gas diffusion takes place. “If we’re limiting the surface area of our lungs, our body will have to compensate with a higher respiratory rate.”

Having COPD is a risk indicator of cardiac arrest, in which the heart suddenly stops beating. Sudden cardiac arrest is a medical emergency that requires immediate treatment with a defibrillator. According to Harvard Medical School, more than 13 million Americans have COPD, and it tends to coexist with other conditions, like heart disease. Yet, many people are unaware of COPD.

Anyone who suspects they have COPD can be diagnosed by a spirometry test. This is a simple non-invasive process that evaluates your exhalation to see how well your lungs are working.

Sleep Disorders

Sleep disorders are another leading cause of airway obstruction and respiratory irregularities. During non-REM sleep, the part of our sleep cycle in which we spend 80% of the night, it’s normal to breathe slowly and steadily.

Breathing normally increases and decreases through different sleep stages, and the number of breaths a person takes will vary. However, having a sleep disorder can cause irregular sleep patterns and contribute to respiratory abnormalities. One example is sleep apnea, a common sleep disorder where a person stops breathing for as much as several seconds in their sleep. 

Heart Conditions

Heart problems can also affect a person’s respiratory rate. For example, atrial fibrillation (marked by irregular and rapid heart rate) can cause shortness of breath. When your heart beats irregularly due to atrial fibrillation, you may experience a tight chest and shortness of breath because the heart’s electrical signals don’t fire properly.

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Cardiovascular Fitness

Cardiovascular fitness is defined as the ability of your heart and lungs to deliver oxygen-rich blood to muscles throughout the body. “If you are frequently exercising, you tend to maintain better lung volume, resting lung capacity, and you have more arterial elasticity,” says Longoria. “Per breath, you’re consuming more oxygen than the next guy.” As a result, your respiratory rate will be lower because it will require fewer breaths to consume the same amount of oxygen.

How to Measure Respiratory Rate

Understanding your respiratory rate can make you more familiar with your body and help you monitor changes as you age. Plus, it can ensure that you recognize when it might be time to consult a medical professional about any changes to your body if changes to your respiratory rate occur.

Respiratory rate can be measured through photoplethysmography (PPG) by measuring the baseline shifts that occur with breathing. The baselines move up and down in an oscillatory pattern, which corresponds to the breath cycle.

A way to use PPG to measure is through a wearable that tracks vital biometrics for both sleep and fitness like Biostrap. “Biostrap is the only clinically-validated sensor system out there,” says Longoria. Wearable trackers can measure your oxygen saturation to indicate how much oxygen is pumping through the blood. It also helps you monitor the effectiveness of your workouts to better understand how blood oxygen levels could be increased through exercise, diet, deep breathing, and other healthy lifestyle changes.

Knowing Your Respiratory Rate

Your respiratory rate tells how much oxygen is flowing through your blood, but it also provides deeper clues to your health. For example, an abnormal respiratory rate can shed light on potential sleep disorders, lung disease, and heart conditions. “It’s an extremely important biometric,” Longoria stresses. “But it’s almost more important to know how and when you’re measuring it.”

Respiratory rate helps us understand changes in our own bodies, especially as we age or try out new approaches to fitness. Measuring your respiratory rate with a wearable that measures and tracks vital biometrics for both sleep and fitness can ensure that you’re always in tune with your body and the breath that keeps it alive.

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