Breathing Rate

This article describes breathing rate as it is reported in the results of a Pulsewave reading. It also provides a summary of some key topics relating to breathing rate, such as its measurement, classification, and relationship to pulse rate.

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Introduction

Breathing is the process of transporting oxygen from the atmosphere into the body and the process of eliminating carbon dioxide from the body. Inhalation, or breathing in, starts with the contraction of the diaphragm muscle, causing the volume in the chest to increase and allowing air to move into the lungs. Exhalation, or breathing out, occurs when the diaphragm relaxes, causing the lungs to relax thereby pushing the air out. The rate at which breathing occurs is the called the breathing rate (BR). It may also be referred to as the respiration rate, pulmonary ventilation rate or breathing frequency.

Breathing rate is a vital sign and is usually measured at rest by counting the number of breaths within a minute. The average number of breaths per minute is the breathing rate average (BRA), and is expressed in units of /min – breaths per minute. This is displayed as part of the results for each Pulsewave reading.

Breathing Rate Measurement

Breathing rate is normally measured by listening to breathing sounds using a stethoscope, or by visually observing the associated chest movements. In addition to being measured manually, BR can be measured using sensors on a chest belt, which detect the movement of the chest associated with breathing, or based on the change in temperature of the air flowing through the nasal passage as a person inhales and exhales. Breathing rate can also be measured indirectly by measuring changes in the heart rate that are associated with breathing, a phenomenon known as respiratory sinus arrhythmia. This technique can be applied to an electrocardiogram, or to the pulse waveform that is displayed during each Pulsewave reading.

Breathing Rate Classification

Normal adult resting BR is considered to be in the range of 12 to 20 /min. However, even at rest, this may be affected by various factors, such as emotional state and medical conditions. Outside of this range exist categories of high and low BRs. A consistently high BRA at rest, greater than the normal range, is known as tachypnea, while a consistently low BRA at rest, less than the normal range, is known as bradypnea. Both tachypnea and bradypnea may be caused by physiological or medical conditions, or as a result of drug use.

Some physiological conditions that may cause tachypnea are exertion, exercise, and pregnancy. A few of the medical conditions which may cause tachypnea include cardiac heart failure, chronic obstructive pulmonary disorder, metabolic disorders, neurological disorders, and hyperthyroidism. The main risks and complications associated with tachypnea include fainting, respiratory alkalosis, and muscle spasticity.

Some physiological conditions that may lead to bradypnea are ageing and sleep. A few of the medical conditions which may cause bradypnea include diabetic ketoacidosis, increased intracranial pressure, respiratory failure, and liver and kidney failure. The main risks associated with bradypnea include apnea and respiratory arrest.

Although there are levels of risk associated with these conditions, it is very important that your physician determine this for you. This is because the risks are determined based on various other factors as well, such as the state of the lungs and breathing patterns, which, in addition to the BR, includes breathing depth, mode, and regularity.

Relationship to Pulse Rate

Humans have developed highly sophisticated mechanisms to match their rate of oxygen uptake to their aerobic metabolic rates. In other words, the rate of flow of air and blood over the respiratory surfaces are matched. A careful study of respiratory and cardiac rhythms shows them to be temporally related in order to optimize respiratory gas exchange. Generally, a change in the breathing rate is associated with a corresponding (but not necessarily proportional) change in heart rate. Under normal circumstances, the pulse rate (PR) and pulse rate variability coincide with the heart rate and heart rate variability. Thus, changes in the BR tend to be reflected in the PR. However, the nature of this relationship is complex, and measurement of BR is not necessarily indicative of PR. Similarly, a change in BR is not necessarily indicative of a change in PR.

Additional Resources

Introduction:

S. R. Braun, “Respiratory rate and pattern”, in Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd ed. Boston: Butterworth Publishers, 1990, ch. 43.

Wikipedia. Breathing [Online]. Available: http://en.wikipedia.org/wiki/Breath. Accessed: 2011-01-31.

Breathing Rate Measurement:

Royal College of Nursing, United Kingdom. Standards for assessing, measuring and monitoring vital signs in infants, children and young people [Online]. Available: http://www.rcn.org.uk/__data/assets/pdf_file/0004/114484/003196.pdf. Accessed: 2011-01-31.

S. R. Braun, “Respiratory rate and pattern”, in Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd ed. Boston: Butterworth Publishers, 1990, ch. 43.

B. George, R. G. Moody, M. A. Zoccola, “Derivation of Respiratory Signals from Multi-lead ECGs”, Computers in Cardiology, vol. 12, pp. 113-116, 1985.

Wikipedia. Respiratory sinus arrhythmia [Online]. Available: http://en.wikipedia.org/wiki/Respiratory_sinus_arrhythmia. Accessed: 2011-02-04.

Breathing Rate Classification:

S. R. Braun, “Respiratory rate and pattern”, in Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd ed. Boston: Butterworth Publishers, 1990, ch. 43.

Wikipedia. Respiratory rate [Online]. Available: http://en.wikipedia.org/wiki/Respiratory_rate. Accessed: 2011-01-31.

MedlinePlus. Breathing – slowed or stopped [Online]. Available: http://www.nlm.nih.gov/medlineplus/ency/article/003069.htm. Accessed: 2011-02-07.

MedlinePlus. Rapid shallow breathing [Online]. Available: http://www.nlm.nih.gov/medlineplus/ency/article/007198.htm. Accessed: 2011-02-07.

Relationship to Pulse Rate:

E. W. Taylor, D. Jordan, J. H. Coote, “Central control of the cardiovascular and respiratory systems and their interactions in vertebrates”, Physiological reviews, 1999.

Wikipedia. Heart rate variability [Online]. Available: http://en.wikipedia.org/wiki/Heart_rate_variability. Accessed: 2011-02-08.

R. Shields, “Heart rate variability with deep breathing as a clinical test of cardiovagal function”, Cleveland Clinic journal of medicine, 2009.