Firstly, what is a vital sign?

Vital signs are “critical indicators of a person’s health and current medical status”.¹

Traditionally, clinicians were interested in four vital signs:

• Body temperature (36.5°C to 37.3°C, average 37°C)²
• Pulse or heart rate (60 to 100 beats per minute at rest)²
• Respiratory rate or rate of breathing (12 to 18 breaths per minute at rest)²
• Blood pressure (as close to 120/80 mm Hg at rest)²

However, the oxygen saturation level of the blood (known as SpO2) is monitored so widely in modern day care that it is often regarded as the fifth vital sign.³ Like the other vital signs, oxygen saturation can now be measured painlessly and non-invasively – just like taking your temperature.

Let’s take a look at how these signs are measured and what the measurements mean.

Body temperature

As the name suggests, it’s simply the temperature of your body and a variation from what is considered normal (37^oC) usually indicates that something unusual may be going on. A high temperature or fever usually means an infection is present.⁴

Body temperature is measured with a thermometer, either a contact type (oral, axillary/armpit, or rectal), or non-contact (using infrared beams on the forehead or in the ear canal).

Pulse or heart rate

Your pulse tells us the number of times your heart beats every minute. In addition to the beats per minute, doctors and nurses are interested in the rhythm (is it consistent?) and the strength of the pulse.⁵

Heart rate will increase when exercising, as the heart pushes more blood to the muscles. The pulse can be measured by placing two fingers on the inside of the wrist, or lower neck and counting the number of beats in a one-minute period. There are more sophisticated heart rate monitors built into medical equipment and even wearable devices such as watches and fitness trackers.

Respiratory rate

Another simple one to measure – just count the number of breaths you take in one minute. Normal respiration rate for an adult is 12 to 16 breaths per minute, but an increase in that rate (while at rest) might indicate fever, illness, or medical condition.⁵

Blood pressure

Blood pressure is the force of the blood pushing against the artery walls during contraction and relaxation of the heart. High blood pressure, also known as hypertension, increases the risk of a heart attack, heart failure and stroke. So, it’s a very important vital sign, which can be monitored using a blood pressure monitor.⁵

Oxygen level/saturation (SpO2)

Oxygen saturation is measured using a simple device called a pulse oximeter. It usually clips onto your finger. If you’ve ever been in hospital or visited a patient, there’s a good chance you will have seen one.

When the pulse oximeter is attached, it passes light through one side of your finger onto a light detector on the other side. As it passes through your finger, the light hits your blood cells and reacts differently to the cells carrying oxygen, compared to the cells not carrying oxygen. Basically, it measures the colour of blood, which is brighter red when there is more oxygen in it.⁶

A pulse oximeter is useful because it can show whether your heart and lungs are supplying enough oxygen to vital organs – including your brain.⁷

Under certain conditions, oxygen levels can fall, and that can cause serious problems. For example, if you suffer from a condition or disease that affects your lung function, or you have heart disease, that can impact the capacity of your red blood cells to carry enough oxygen.⁷

A normal reading is between 95% and 99%.

While nothing beats a consultation with a health professional, each of the five vital signs can be measured by you or someone in your family at home using very affordable (or free) devices.

Check out the Heart Sure Home Blood Pressure Monitor and Pulse Oximeter here.

And if you’re in need of a good digital thermometer, head over to Smart Wellness, where we have a range of thermometers including Welcare or Omron.

*Always read the label and follow the directions for use. Consult your health professional to evaluate the readings. Blood pressure monitors are for people with high blood pressure. Consult your doctor to evaluate the readings. Check your device periodically for accuracy.

Sources:

1. https://www.sciencedirect.com/sdfe/pdf/download/eid/3-s2.0-B9780721603612500259/first-page-pdf
2. https://medlineplus.gov/ency/article/002341.htm
3. https://reader.elsevier.com/reader/sd/pii/S095461111300053X?token=79DC5486F17CDFEA97AD0E2F44A79C6F458B0251D181D0785F66E1742E6455A2D10B6998BC8052264D845674129482F1&originRegion=us-east-1&originCreation=20220624044540
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7195085/
5. https://www.hopkinsmedicine.org/health/conditions-and-diseases/vital-signs-body-temperature-pulse-rate-respiration-rate-blood-pressure
6. https://www.theguardian.com/australia-news/2022/jan/20/what-is-a-pulse-oximeter-and-can-i-still-buy-one-in-australia-demand-for-devices-climbs-as-more-people-manage-covid-at-home
7. https://www.webmd.com/lung/pulse-oximetry-test
8. https://exercise.lovetoknow.com/about-physical-fitness/understanding-blood-oxygen-levels-during-exercise