Basic Health

What is body temperature?

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Body temperature is one of the core 'observations' or 'vital signs' that reflects the balance between heat production and heat loss within the body. It is measured in degrees Celsius (°C) or Fahrenheit (°F).

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The average adult's normal body temperature hovers around 37 degrees Celsius (98.6 degrees Fahrenheit) but like blood pressure, individual variation exists with a range from 36.1°C (97°F) to 37.2°C (99°F).

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Temperature can also vary slightly depending on the time of day, activity level, and other factors. It is a useful marker to measure, especially when we are feeling unwell to confirm if there is fever. In some instances, our body temperature can drop too low and when extreme, this is called hypothermia.

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Why is it useful to measure body temperature?

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Measuring body temperature can help to:

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• ‍Detect an infection: When you have an infection, your body temperature will often rise. This is because your body is fighting off the infection and trying to raise the temperature of your body to make it more difficult for the bacteria or virus to grow.

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• ‍Identify other health problems: Sometimes, a high or low body temperature can be a sign of an underlying health problem, such as a thyroid disorder.

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How do you measure body temperature?

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There are several ways to measure your body temperature. The most common methods include:

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Oral thermometer:

This is one of the commonest types of thermometers. Place the thermometer under the tongue and with your mouth closed hold the thermometer in place until a reading is taken.

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Wait at least 15-30 minutes after eating or drinking hot/cold substances before taking an oral temperature.

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Rectal thermometer:

This is the most accurate type of thermometer, but it is not recommended for adults. Insert the probe gently into the rectum until the device beeps or the specified time elapses.

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Use a water-soluble lubricant (such as KY-Jelly).

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Axillary (armpit) thermometer:

‍This is a good option for children and babies. Place the thermometer under the armpit and hold the arm snugly against the body for the recommended time until the thermometer beeps.

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Keep the area as dry as possible when taking a measurement.

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Tympanic (ear) thermometer:

‍This is a quick and easy way to measure your temperature. Place the thermometer in the ear, click the button and hold it in place until it beeps.

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Pulling the ear gently can help straighten the ear canal and ensure a snug fit for an accurate reading.

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Infrared (forehead) thermometer:

This method is quick, non-invasive and suitable for children and adults. It is also useful when many measurements need to be taken quickly (e.g. in a screening setting). However, it may be less accurate than other forms of measurement. Point the thermometer at the forehead, click the button and wait until a reading is taken.
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Keep the forehead dry, free from sweat or hair for optimal results.

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Tips for accurate temperature readings

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1. Choose the right thermometer: different thermometers have specific uses, so choose the one most appropriate for the age group and situation.

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2. Follow manufacturer instructions: always adhere to the instructions provided with the thermometer as each device may have slightly different specifications.

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3. Rest before measurement: wait for at least 15 minutes after physical activity or consuming hot/cold substances before checking temperature.

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4. Consistent method: sticking to one method for consistency can help to monitor trends in body temperature over time.

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What is considered a fever?

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Fever: A body temperature of 38°C (100.4°F) or higher is indicative of a fever.

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Low-Grade Fever: some sources might use the term "low-grade fever" for temperatures slightly above the normal range but below 38°C (100.4°F).

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What is considered hypothermia?

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Hypothermia is when the body temperature drops dangerously low, to below 35°C (95°F).

Summary

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It is important to be aware that the method of measurement can affect the recorded temperature to a degree (not literally!). For example, oral, rectal, ear, and forehead temperature measurements may yield slightly different readings, however the cut-off ranges above for fever and hypothermia hold true.

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It can be helpful to be familiar with your own baseline temperature and recognize any significant deviations from your normal range.

What is oxygen saturation?

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As the name suggests - oxygen saturations, often referred to as "O₂ sats", or "SpO₂" is a measure of how saturated our blood is with oxygen. It is often considered as the 'fifth'vital sign' or core observation.

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(More technically, a measure of the percentage of haemoglobin - an oxygen-carrying substance in our blood that is bound to oxygen).

Why is oxygen saturation important?

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Oxygen is life because it is required for nearly all metabolic processes in the body. Without oxygen, we would cease to exist and damage to vital organs can happen within minutes of oxygen deprivation.

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When oxygen levels are low in the blood (hypoxaemia), we may start to experience symptoms such as:

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• Shortness of breath
• Rapid and shallow breathing
• A fast heart rate which might feel pounding
• Irritability and confusion
• Changes in skin colour to blue/grey (cyanosis) when severe

What are normal oxygen saturations?

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• At sea level, it is generally accepted that normal oxygen saturations range from 95 to 100%
• Oxygen saturations may be lower at higher altitudes
• Oxygen saturations <95% are usually associated with an intercurrent illness
• Persistent oxygen saturations <92% usually require further investigation for lung disease
• Values <70% are life-threatening

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However, there are certain medical conditions where baseline oxygen saturations are accepted to be lower, for example in chronic obstructive pulmonary disease (COPD).

How do you measure oxygen saturations?

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Oxygen saturations can be measured with a medical device called a pulse oximeter, which is commonly clipped onto the finger (but sometimes toes or earlobes).

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A light emitted from the pulse oximeter passes through the finger and is picked up on the other side by a photodetector, measuring the amount of light absorbed. This feeds into an algorithm which uses this information to calculate the oxygen saturation that displays on the device.

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Because the signs and symptoms of low blood oxygen may not always be apparent until oxygen levels drop very low, pulse oximetry is invaluable in early detection of hypoxaemia and widely used in the medical setting. Using a pulse oximeter is also painless and non-invasive, which makes it accessible for home use.

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In the hospital setting, oxygen saturations can also be measured with a blood test called an arterial blood gas (ABG) which is usually taken from the wrist or groin.

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A number of things may affect the accuracy of a reading from a finger including:

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• Finger being too small for the probe (usually babies and children)
• Finger deformities (due to injury or medical conditions such as rheumatoid arthritis)
• Excessive sweating or motion preventing a good connection
• Nail polish/varnish and false nails
• Tattoos
• Darker skin pigmentation

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When taking an oxygen saturation reading:

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• Power on the pulse oximeter
• Ensure appropriate placement of the pulse oximeter so that a good seal is formed around the fingertip
• Remain still while waiting for the flashing bars to stabilise as a measurement is being taken
• The number labelled with SpO₂ % will be the oxygen saturation reading

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What is pulse rate?

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Pulse is the rhythmic expansion and contraction of the arteries as blood is pumped by the heart and which can be felt at certain locations of the body, most commonly the wrist (radial) and neck (carotid).

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Each pulsation represents a heartbeat, and the pulse rate is the number of heart beats per minute (bpm).

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Why measure pulse rate?

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A regular pulse indicates that your heart is effectively pumping blood throughout the body and our pulse rate can be reflective of our health in general such as physical fitness.

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In practice, it is most useful and the easiest to determine two features of the pulse:

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1. Pulse rate:

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At times, when the pulse is too high (tachycardia) or too low (bradycardia), it can be a sign of an underlying abnormality such as cardiovascular (heart) or thyroid problems.

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2. Pulse rhythm:

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Our heart (for the most part) should beat at a regular interval. When our heart beats irregularly this usually requires further investigation as it can be a sign of a rhythm abnormality of the heart.

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How do you measure pulse rate?

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To obtain an accurate pulse reading:

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1. Find a quiet and comfortable space:

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Choose a calm environment to minimize external influences on your pulse rate.

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2. Locate your pulse:

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Common pulse points include the wrist (radial artery) towards the thumb side (see below) and the neck (carotid artery).

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It is often easiest to use two to three fingertips (index, middle and fourth fingers) and applying light pressure at the site to feel the pulse.

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3. Count the beats:

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Using a timer or watch, count the number of beats you feel within a 60-second interval. Alternatively, count for 15 seconds and multiply by 4 to get your beats per minute.

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4. Ensure proper technique:

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Maintain a light touch when feeling for your pulse. Pressing too hard may obstruct blood flow, leading to inaccurate readings.

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5. Record your findings:

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Keep a log of your pulse rate, noting the time of day and any relevant activities or emotions. Regular monitoring helps identify patterns over time.

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What is a normal pulse rate?

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A normal resting pulse rate for adults typically falls between 60 and 100 bpm at rest. Athletes may have lower resting rates due to enhanced cardiovascular fitness.

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Remember, like blood pressure, pulse rate is dynamic and will go up and down depending on several factors including:

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• Age
• Body temperature
• Physical activity
• Pain
• Emotions and stress
• Medication
• Caffeine intake

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Understanding these factors can provide context to your pulse readings.

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Summary

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Monitoring your pulse can offer insights into cardiovascular fitness and help detect irregularities. If you notice persistent irregularities in your pulse rate consult a medical professional.

What is blood pressure?

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The heart pumps blood around the body, which travels through blood vessels called arteries (imagine water flowing through a pipe). The pressure of the blood flow through the arteries as the heart squeezes (systolic) and relaxes (diastolic) is measured as blood pressure.

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Thus, there are 2 numbers to blood pressure:

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• a 'top' number (systolic) which represents the pressure when the heart is squeezing and pumping blood
• a 'bottom' number (diastolic) which represents the pressure when the heart is relaxing

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You will normally see blood pressure recorded as 135/85 mmHg for example (mmHg is the unit of measurement - millimetres of mercury). You will often see this read as 135 'over' 85.

Why is blood pressure important?

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Blood is vital in supplying oxygen to the vital organs of the body to keep them working. Going back to the analogy of water flowing through a hose pipe, if the pressure is turned too low, flow will be inadequate in supplying blood to the organs. In fact, this is the reason why severe blood loss will eventually lead to death.

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Turn the pressure too high and you risk the water jet damaging its target, which will be the major organs of the body.

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Symptoms of low blood pressure might include:

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• Lightheadedness and dizziness
• Blurry vision
• Fainting
• Feeling sick
• Confusion
• General weakness

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On the other hand, note most people with high blood pressure (when not extreme) do not experience any symptoms at all. However, it is important to bear in mind that damage is still being done silently in the background - hence high blood pressure is often called 'the silent killer'.

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When blood pressure gets very high then symptoms might include:

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• Severe headaches
• Chest pain
• Dizziness
• Blurry vision
• Feeling sick
• Nosebleeds

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Over time, uncontrolled high blood pressure can lead to:

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• Heart disease
• Kidney disease
• A sudden stroke
• Dementia

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Prevention of high blood pressure is key.

What is a normal blood pressure?

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Remember, blood pressure is dynamic and there will always be some individual to individual variation (to a degree).

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Blood pressure is also reactive and it is normal that it will go up and down as blood flow is maintained (you should be worried if it didn't) e.g. with exercise, stress/emotions, caffeine, smoking, following a large meal etc.

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Therefore, blood pressure is context dependent and a single one off reading that is high does not necessarily equate to hypertension. It is when blood pressure is consistently high that it becomes a problem and important that it is managed.

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Generally speaking, measuring blood pressure when at home and most relaxed is the ideal circumstance.

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• Normal blood pressures are between 90/60mmHg to 120/80mmHg
• An ideal blood pressure is less than 120/80
• Blood pressures less than 90/60mmHg are low (hypotension)
• Blood pressures greater than 120/80mmHg but less than 140/90mmHg would be considered at risk of developing high blood pressure (referred to as pre-hypertension)
• Blood pressures consistently greater than 140/90mmHg is considered as high blood pressure (hypertension). However, this is where it gets a little bit more tricky - if measuring blood pressure at home, the targets are more strict as you are assumed to be most relaxed - so blood pressures of 135/85mmHg are considered as high blood pressure

How do you measure blood pressure?

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To ensure the reading is accurate, relax 30 minutes before taking a reading and avoid:

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• Eating or having any caffeine intake
• Exercise
• Smoking

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When taking a blood pressure reading:

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• Sit in a neutral position with legs uncrossed/flat on the floor and with arm placed at approximately chest (heart) level
• Place the cuff approximately one inch above the bend of the elbow on bare skin or over thin fabric only
• Do not talk or move while the reading is taken
• Take three measurements 1-2 minutes apart and record the readings down - do this morning and evening. Taking regular measurements over a more prolonged period e.g. over a week will help to obtain more accurate average readings

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