It’s lucky we haven’t all got heartbeat like champion runner Mo Farah

THE normal range for an adult resting heart rate is from 60 to 100 beats per minute.

The average resting heart rate is reckoned to be 72 bpm but it’s possible that our average pulse rates have risen over the years due to our sedentary lifestyles and insatiable appetites for things like tea and coffee.

If that were the case, those given to flights of fancy might wonder whether the origin of our decision to split a minute into 60 seconds was perhaps related in some way to the internal metronomes we all carry around within us.

Wild theories aside, the consensus is that our ancestors developed our timescales through a combination of the cycles of our sun (dividing the day into two periods from sunset to sunrise and from sunrise to sunset) and the mathematical advantages of the numbers 12 and 60 (both being divisible by multiple numbers).

This system has been used since ancient Babylonian and Sumerian times for timekeeping purposes.

Our heart rate can tell us a lot about our health and that is why it is one of the set of observations doctors and nurses use regularly to assess a patient.

You might have heard reference to someone’s “obs” or, if you are watching an American medical drama, “vitals”, Historically, alongside heart rate (or pulse rate, which is essentially the same thing aside from a few niche clinical abnormalities), doctors have also looked to core temperature, blood pressure and respiration rate to perform a quick but informative assessment of a patient’s clinical status.

Taking an abnormally high heart rate (tachycardia) as an example, this could indicate anything from a recent bout of exercise or a heightened emotion to an infection.

Your body increases heart rate during infections as part of its response to fight pathogens. Conversely, if one has an abnormally slow heart rate it could indicate something wrong with the heart itself, such as a heart block.

Of course, a very slow heart rate could just mean you are very fit. Mo Farah’s resting heart rate is apparently 33 beats per minute.

Blood pressure is the measure of the pressure of blood within our circulation. It is displayed as two numbers, systolic and diastolic. The systolic number is always higher and records the pressure when the heart has contracted at the height of the pulse.

The lower number, the diastolic, records the pressure between beats, when the heart is relaxing.

If your blood pressure is too high it puts you at risk of things like heart attacks and strokes. If, however, your blood pressure is suddenly very low, this can be a warning sign for infection.

As your body fights infection, your blood vessels dilate, reducing the force of the blood on their walls, which is part of the process involved in sepsis.

If your blood pressure drops too low, the amount of blood getting to vital organs, including the brain, reduces.

Looking at heart rate and blood pressure together becomes relevant here. If your pulse is very high but your blood pressure very low, it is not a good sign. Before the digital age of recording observations, we used to use paper charts, often using the same scale for heart rate and blood pressure.

The systolic blood pressure was denoted by an inverted “v” shape and the heart rate by an “x” If the x went above the inverted v, it spelt out a warning that a patient might be deteriorating and becoming septic, something known colloquially as the seagull sign.

Respiration rate is another warning sign that your body might be suffering and trying to compensate, hence its inclusion on the basic list of observations.

The average respiration rate for an adult is between 12 and 16 breaths each minute. Again, benign causes for an elevation in this might include heightened emotion or exercise.

But infection can also drive up your breathing rate. As your body fights infection, it requires more oxygen and that is what a high respiration rate is designed to provide. One might think that this is confined to respiratory infections but even if there is nothing wrong with your lungs and there is an infection elsewhere, your breathing rate will increase as part of the body’s physiological response.

Core temperature for an adult is considered normal within the range 36 to 37.5 degrees centigrade (96.8 to 99.5 Fahrenheit).

A raised temperature of 38C or above is a sign that there is an infection somewhere. Higher temperatures will often trigger more attention, thus a temperature above 39C is more concerning than a more mildly raised temperature below 38C.

It should be noted that a temperature below 36 can also be a feature of infection and is a sign we look out for in sepsis.

Our use of the above signs is often combined, most often in hospitals, into something called a modified early warning score. Deviations from the normal ranges of each observation are given a score depending on how far they have deviated. If you score a certain value across your set of observations, this triggers a response from clinicians.

It is an objective way to warn us if your body is struggling and is an important tool in the battle against things like sepsis.

Of course, there is another sign I have so far not touched on but which more people are familiar with now than ever before.

Known as the fifth vital sign, oxygen saturation has joined the illustrious company of those already mentioned to give us yet more information.

The technical term for oxygen saturation measurement is pulse oximetry (we just call it “sats”).

Before the Eighties, this was not readily available but now many people have a pulse oximeter in their homes.

These devices clip on to a finger and, through the use of red and infrared lights, are able to measure the concentration of oxygen in the blood in the capillaries at the end of the finger. This then gives an indication of how well oxygenated your blood is.

A well-known game among medical professionals is the sats game, wherein one limits one’s breathing as much as possible to drive the sats down — the lowest one is the winner. I would definitely not recommend this game.

Sats are measured as a percentage and anything above 92 per cent is generally acceptable although above 95 per cent is what I would consider “normal”.

If you have, for example, low sats, a raised temperature and perhaps a raised respiration rate, it might indicate pneumonia. Low blood pressure and a high pulse rate would further indicate a severe pneumonia that might not be adequately dealt with without the more intensive treatment and monitoring available in hospital.

We use all these observations on a regular basis to perform basic assessments and there’s often a lot we can glean from these numbers before we even get onto further examination.

As more of us have these tools in our own homes, it’s worth knowing a bit about what is being measured. It’s also worth mentioning again that these numbers can vary for lots of different reasons, not always bad. Babies have a heart rate range of 100 to 160 bpm for example.

Clinical context remains as important as ever, otherwise people like Mo Farah would have been whisked off to hospital long ago for heart monitoring and pacemaker insertion before they even knew what had hit them.