A History of Respirations
- V. A. Cyr
- Sep 18, 2024
- 7 min read
Updated: Oct 7, 2024
This Wisdom Wednesday, we are finishing off the vital signs. Along with Blood Pressure, Temperature, Heart Rate (and Pulse Oximetry), we will conclude the vitals sign with Respirations. Why is knowing how many breaths someone takes essential? Why would someone be breathing slower or faster than expected? What is incentive spirometry? Let’s look into what we do all the time without even thinking about it: breathing!
Definitions & Types
The word respirations comes from the Latin word respiratio, meaning “to breathe” (-spirare) “again” (re-) (Etymonline, 2021). Respirations are simple: the number of times someone breathes in one minute (breaths per minute). Respirations are essential to ensure the patient has proper gas exchange in the lungs and enough oxygen reaches the tissues. An adult’s average range of respirations at rest is 12 to 20 breaths per minute. During every breath, about 500 mL of air goes into the lungs, or about 6 to 10 litres per minute. Inhalation is the process of breathing in, and exhalation is breathing out. Ventilation is the term used to describe air movement in and out of the lungs. A review of the inhalation and exhalation process is under the “Anatomy of the Respiratory System” section of the Auscultation post. In addition to the anatomy of the lungs, breathing also encompasses other body structures. Although respirations seem simple, many different aspects can affect it.
Mechanics of Respiration
As mentioned above, respiration involves many other things than just the lungs and airway. Here, we will review the other anatomical structures related to breathing.
Diaphragm
The diaphragm is a large muscle located between the thoracic and abdominal cavities. It is responsible for about 70% of lung volume displacement during breathing (Welch et al., 2019). Contraction of the diaphragm changes the pressure within the cavities of the body. As the diaphragm pushes the abdominal cavity downward, the abdominal pressure increases and allows the lungs to expand fully (Welch et al., 2019).
Ribcage Muscles
These muscles include the external rib and intercostal (between the rib) muscles. During inspiration, these muscles pull the ribs away from the lungs, allowing full lung expansion (Welch et al., 2019).
Abdominal Muscles
Also referred to as the “abs,” these are the muscles that protect the abdomen. When breathing deeply, the abdomen expands as the diaphragm is pushed downward to allow lung expansion. This is why the abdomen moves when someone takes a deep breath. During expiration, these are used to expel all of the air out of the lungs (by pushing the diaphragm upward).
This diagram gives an excellent overview of the muscles involved in the inspiratory and expiratory phases of breathing (Welch et al., 2019).
Spirometry
Spirometry is a test that measures lung function. It measures lung capacities and volumes on a graph. Spirometry is good in diagnosing lung disease, monitoring pulmonary function, and can assist with smoking cessation (Lamb et al., 2023). A portable spirometer is used after surgeries to increase lung capacity and avoid complications (e.g., atelectasis). The various measurements are examined below.
Here is an example of a modern portable incentive spirometer used in hospitals (Diamond Athletic, n.d.). A small ball will elevate inside the main tube as the patient blows into the flexible tube. Numbers on the tube indicate the patient’s volume. More elaborate electronic ones can also be used in specialty clinics.
Tidal Volume (TV)
TV = normal inhalation + normal expiration
TV is the amount of air that moves in and out of the lungs during one normal respiration.
Total Lung Capacity (TLC)
TLC = maximal inspiratory volume
TLC is the maximum amount of air that can be in the lungs upon maximal inspiratory effort.
Vital Capacity (VC)
VC = TLC - maximal expiratory volume
VC is the amount of air exhaled after maximal inhalation.
Inspiratory Capacity (IC)
IC = TV + IRV
The volume of air that can be inspired after a normal exhalation. IRV, or inspiratory reserve volume, is the extra air that can be inhaled after a regular inspiration.
Residual Volume (RV)
RV = TLC - VC or RV = FRC - ERV
RV is the amount of air left in the lungs after forceful exhalation. FRC is functional residual capacity (FRC = TLC - IC), which is the amount of air still present in the lungs after a normal expiration. ERV is expiratory residual capacity, the extra air that can be forcefully exhaled after a normal expiration.
This graph shows all lung volumes measured during spirometry (Kapwatt, 2024).
Capnography
Capnography measures gases during respiration, usually during surgical procedures when the patient is being monitored (e.g., nasal prongs, intubation). The respirations on a vital signs machine will be seen as a waveform, and the machine will indicate the end-tidal (ET) carbon dioxide (CO2). ETCO2 is the amount of CO2 exhaled by the patient (Richardson et al., 2016). The normal range for an ETCO2 is 35 to 45 mmHg (millimetres of mercury). ETCO2 becomes higher as the patient is asleep or sedated (45-55 mmHg) and returns to normal when they are awake. Many factors beyond this discussion can affect capnography.
This demonstrates the phases of respiration during capnography (ACLS Medical Training, n.d.).
Here is an example of a vital sign machine showing the number of respirations and the waveform in yellow (India Mart, n.d.).
Factors Affecting Respirations
Age
Newborns breathe much faster than adults (about 44 breaths per minute). Infants (less than one year old) can vary from 20 to 40 breaths per minute. Children aged 1 to 7 years old breathe in the range of 18 to 30 breaths per minute. Once an adult, a person usually has little variability in their breathing rate. However, adults over 65 have a range of 12-25 breaths, and adults over 85 vary from 10-30 breaths (Wheatley, 2018).
Activity
The more you exercise, the more you breathe. This ensures your tissues (muscles) are getting all of the oxygen they need to continue to exercise and function. When a body moves, it uses more oxygen and produces more carbon dioxide (Breathe (Sheff), 2016). Breathing can increase to 40-60 times per minute (20-30 L per minute) to cope with the extra needs during exercise (Breathe (Sheff), 2016). As a result, your heart will also beat faster to circulate the oxygenated blood to the body.
Anatomy
Anatomical abnormalities affecting breathing are variability in the oral, palatal, pharynx, larynx, trachea, and lungs (bronchi, bronchioles, alveoli, etc.). For example, patients with large tongues can have obstructive sleep apnea, where they stop breathing while they sleep as the tongue moves into the airway (Patwa & Shah, 2015).
Origins
It was noted in biblical times that respiration was necessary for life (Brewer, 1979). In the 6th century BC, Greeks said that a substance called pnuema (meaning “breath” or “soul”) was essential for life (West, 2011). For centuries, it was thought the pneuma was mixed with blood in the lungs by passing through the heart (West, 2011). Galen brought about this idea as he explained that the lungs absorbed the inhaled air and heated the blood, allowing it to flow into the left heart (West, 2011)).
In the 15th century, Leonardo da Vinci described the lungs as “spongy” (Findlen & Bence, n.d.). Although he did not understand their physiology, he did draw many images of their anatomy (see below).
In Medieval times, Master Nicolaus described the lungs as hollow to “cool the heart” and “renew the spirits” (Findlen & Bence, n.d.). The idea of “spirits” continued into Alessandro Benedetti’s work in 1497, saying that the lungs change the air into “food for the vital spirit” (Findlen & Bence, n.d.).
Research was conducted on respiratory system anatomy during the 17th and 18th centuries, which led to the discovery of blood circulation and the understanding of oxygen’s roles (Brewer, 1979).
World War II saw many advancements in resuscitation (now known as cardiopulmonary resuscitation or CPR). In 1944, the concept of “wet lung trauma” (respiratory distress syndrome) was discovered in many thoracic war injuries (Brewer, 1979). The treatment for pulmonary edema (fluid in the lungs) was found by treating patients with positive-pressure oxygen therapy (Brewer, 1979). The discovery of antibiotics in the 1940s improved outcomes for patients with pneumonia (lung infection) (Chow, 2023). The 1960s saw the creation of blood gas electrodes to measure oxygen and CO2 in the blood (West, 2011).
A drawing of the lungs done by Leonardo da Vinci (Royal Collection Trust, 2020).
Uses in Medicine
Normal Respiratory Findings
Eupnea means “good” (eup) “breathing” (pnea). This is breathing at the normal rate for the person’s age (i.e., 12-20 breaths per minute for a healthy adult).
Abnormal Respiratory Findings
Bradypnea means “slow” (brady) “breathing” (pnea). This usually occurs as a result of medication use (e.g., sedatives, opioid overdose) and disorders like increased intracranial pressure, diabetic coma, and sleep apnea (Wheatley, 2018).
Tachypnea means “fast” (tachy) “breathing” (apnea). It can be caused by anxiety, pain, and underlying disorders. Tachypnea can also be normal when someone is exercising, as the body requires more oxygen. Some disorders that cause tachypnea are pulmonary embolism, anaphylaxis, and diabetic ketoacidosis (Wheatley, 2018).
Hyperpnea means “high” (hyper) “breathing” (pnea), or heavy breathing.
Hyperventilation means “high” (hyper) ventilation (movement of air) or taking breaths too fast.
Hypoventilation means “low” (hypo) ventilation (movement of air) or taking slow, shallow breaths (Whited et al., 2023).
Apnea means complete absence of breathing or "without" (a-) "breath" (pnea).
Here is a diagram showing the normal and abnormal breathing rates (Martillano, 2022).
How can something so simple also be so complicated? This is why the human bnody is so fascinating! Of all of the vial signs: which one do you find most important?
– V. A. Cyr
References
ACLS Medical Traning. (n.d.). Quantitative Waveform Capnography [Image]. https://www.aclsmedicaltraining.com/quantitative-waveform-capnography/
Breathe (Sheff). (2016). Your lungs and exercise. NIH, 12(1), 97-100. 10.1183/20734735.ELF121
Brewer, L. A. (1979). Respiration and respiratory treatment: A historical overview. The American Journal of Surgery, 138(3), 342-354. https://www.sciencedirect.com/science/article/abs/pii/0002961079902629
Chow, S. (2023). Pneumonia History. News Medical. https://www.news-medical.net/health/Pneumonia-History.aspx#:~:text=In%20the%201930s%2C%20the%20first,penicillin%20in%20the%20early%201940s.
Diamond Athletic. (n.d.). Incentive Spirometer [Image]. https://www.diamondathletic.com/products/incentive-spirometer
Etymonline. (2021). Etymology of respiration. https://www.etymonline.com/word/respiration
India Mart. (n.d.). Portable Vital Signs Monitor [Image]. https://www.indiamart.com/proddetail/portable-vital-signs-monitor-13885477962.html
Findlen, P. & Bence, R. (n.d.). A History of the Lungs. https://web.stanford.edu/class/history13/earlysciencelab/body/lungspages/lung.html
Kapwatt. (2014). Lung Volumes Updated [Image]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Lungvolumes_Updated.png
Lamb, K., Theodore, D. & Bhutta, B. S. (2023). Spirometry. StatPearls: NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK560526/
Martillano, D. (2022). Breathing patterns base on respiratory rate according to USMLEAid [Image]. Research Gate. https://www.researchgate.net/figure/Breathing-patterns-base-on-respiratory-rate-according-to-USMLEAid_fig2_364257166
Patwa, A. & Shah, A. (2015). Anatomy and physiology of respiratory system relevant to anaesthesia. Indian Journal of Anaesthesia, 59(9), 533-541. 10.4103/0019-5049.165849
Richardson, M., Moulton, K., Rabb D, et al. (2016). Introduction: Capnography for Monitoring End-Tidal CO2 in Hospital and Pre-hospital Settings: A Health Technology Assessment. Canadian Agency for Drugs and Technologies in Health, 142. https://www.ncbi.nlm.nih.gov/books/NBK362376/
Royal Collection Trust. (2020). Leonardo da Vinci - RCIN 919054, Verso The lungs c.1508 [Image]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Leonardo_da_Vinci_-_RCIN_919054,_Verso_The_lungs_c.1508.jpg
Welch, J. F., Kipp, S. & Sheel, A. W. (2019) Respiratory muscles during exercise: mechanics, energetics, and fatigue. Current Opinion in Physiology, 10, 102-109. https://doi.org/10.1016/j.cophys.2019.04.023
West, J. B. (2011). History of respiratory gas exchange. Comprehensive Physiology, 1(3), 1509-1523. 10.1002/cphy.c091006
Wheatley, I. (2018). Respiratory rate 3: how to take an accurate measurement. Nursing Times, 114(7), 21-22. https://www.nursingtimes.net/clinical-archive/respiratory-clinical-archive/respiratory-rate-3-how-to-take-an-accurate-measurement-25-06-2018/
Whited, L., Hashmi, M. F. & Graham, D. D. (2023). Abnormal Respirations. StatPearls: NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK470309/#:~:text=Respiration%2C%20a%20physiological%20process%2C%20involves,and%20efficiently%20removing%20carbon%20dioxide.
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