top of page
  • Writer's pictureChristie Roberts

Vital signs

Updated: Jan 22, 2023

It's been a while since I've sat down to write a blog post (have been busy and super stressed with starting my new job as a Clinical Research Nurse (CRN) and also taking on part time work as an Associate Lecturer (AL)) so I thought I'd get back into the swing of things with a simple one- vital signs! I had to research this extensively for my first teaching session as an AL so have a lot of knowledge just sitting in my head, and it doesn't benefit anyone just sitting in my head! So without further ado-


NEWS2 is the National Early Warning Score system used across England. It scores observations within certain parameters to create a totalled score, affectionately known as 'track and trigger' in many areas, which is used to guide decision making in frequency of observations and escalation of care. It was updated form NEWS to introduce changes such as a second SpO2 scale for CO2 retention, addition of oxygen scores and introduction of 'confusion' into the AVPU (Alert, Voice, Pain, Unresponsive) scale we all know and love.

Scoring parameters for NEWS2


It's important to remember that these parameters exist to pick up acutely unwell or deteriorating patients- just because an observation doesn't trigger, doesn't mean it's normal (for example, a systolic pressure of 219mmHg. Please don't ignore that- it just means the patient is less likely to be acutely unwell).


Airway and Breathing-


Respiratory Rate

Respiration is controlled (generally- see SpO2 scale 2 below) by a hypercapnic drive. That is, rising levels of CO2, detected by chemoreceptors in the brainstem, trigger increased ventilation. As the partial pressure of carbon dioxide in arterial blood rises, ventilation increases nearly linearly to maintain homeostatic balance. The body normalises CO2 concentrations by adjusting the minute volume (volume of air inhaled and exhaled in 1 minute) which is calculated by RR x Tidal Volume (volume of air inhaled or exhaled in 1 breath). Therefore, to increase minute volume and blow off any excess CO2, RR will increase or TV will increase- more frequent, deeper breaths. Conversely, to retain Co2 the minute volume will fall, so less frequent, shallower breaths.

Normal range for respiratory rate is 12-20 breaths per minute (sources vary- check local policy). High = tachypnoea, low = bradypnoea.

RR is seen as an early and sensitive predictor in acute illness- this is largely due to increased metabolic demands in acute and critical illness causing an increase in respiratory effort. An increased RR will often be seen in conjunction with decreased SpO2, accessory muscle use and dyspnoea.

A key point in measuring a respiratory rate is to try and not be obvious about measuring it, as patients are likely to become conscious of their breathing and this may speed up or slow down the rate. It is important to get consent to measure the rate prior to starting. Many people will tie in measuring RR with measuring heart rate- whilst you still have a hand on the patient, RR should be counted for a minimum of 30 seconds, but ideally a full 60 seconds.

The video below by HEE (2020) describes the process for counting RR, and also touches on why tachypnoea and bradypnoea can be of concern.



This case study by the Nursing Times really nicely presents a patient presenting with an increased RR in acute illness and also demonstrated other important aspects of a respiratory assessment.

Breathing should also be assessed for depth (deep vs shallow), symmetry (are both sides of the chest moving equally, with bilateral air entry to all zones of lungs on auscultation?), and pattern (see picture below for normal vs abnormal breathing patterns).


Oxygen Saturation (SpO2)

This is the percentage of saturated oxyhaemoglobin present in arterial blood. In arterial blood, there will be some deoxyhaemoglobin and some oxyhaemoglobin with 4 oxygen molecules attached ready to go to the tissues and be used for cellular aerobic respiration. Oxyhaemoglobin is a bright red colour and deoxyhaemoglobin is a darker red colour. This difference means that they absorb light differently.

This becomes relevant when you consider how SpO2 sensors work. Red and infrared light is emitted, which are absorbed in different amounts by oxy and deoxyhaemoglobin. The light that is not absorbed is sensed, which gives a proportion of oxygen saturated haemoglobin compared to unsaturated. This becomes an oxygen saturation percentage.



Normal range for SpO2 is 94-98% (sources vary- check local policy). High = hyperoxaemia, low = hypoxaemia. Worth noting that aiming for 100% sats if a person is on supplementary oxygen is not necessary- oxygen is a drug that can be overdosed, and hyperoxaemia has risks, so titrate your oxygen to achieve sats within the target range.

This video by HEE (2020) outlines the process of taking an SpO2 reading, and also touches on the limitations or challenges of doing this.



The video and image above helps to explain why good blood flow is needed to the periphery where the reading is being taken from- a lack of blood will throw off the light absorption and provide an inaccurate reading, or no reading at all. Therefore, poor circulation or cold hands (due to the presence of vasoconstriction, therefore reduced blood flow) may pose a challenge.

Dirt, false nails or nail polish can affect the absorption of red and infrared light so ideally should be removed/cleaned.

If not possible to use a finger, ear lobe probes are also available. It's really important that they are only used on the ear, and conversely that finger probes are only used on fingers rather than being used interchangeably.



SpO2 scale 2

in people with CO2 retention (examples- COPD, severe chest wall deformities), their body functions with a higher level of CO2 and as such, their hypercapnic drive shifts and becomes a hypoxic drive. This means that instead of a rising CO2 acting as a trigger to breathing, a decreasing O2 saturation will act as that trigger. By providing supplemental oxygen to these patients, there is a risk of inhibiting that hypoxic drive (as their O2 theoretically will not fall) and causing apnoea. Therefore, adapted target oxygen saturations of 88-92% are used to reduce this risk. The decision to use scale 2 should be clearly documented by the medical team caring for the patient, and the scale not in use should be crossed out.



Oxygen

Nothing much to say about this except that it's a good move to have it included in NEWS2. If you have 2 identical patients triggering a 1 for sats 94% but one is on room air and one is on 15L via a non-rebreathe mask, you're not going to have the same level of concern about those patients so deservingly, that second patient will get an extra 2 points.

Bear in mind the above point about hyperoxaemia (and see this 2018 NIHR alert for more info about the use of liberal vs conservative oxygen therapy, and its effects on mortality), and ensure that oxygen is prescribed and signed for.


Circulation-


Blood Pressure

Blood pressure is defined as the force of blood exerted against artery walls. The systolic (first, higher number) is the maximum pressure point at systole (contraction) of the ventricles. The diastolic (second, lower number) is the minimum pressure point in diastole (relaxation) of the ventricles as the heart is refilling. As it is a measurement of pressure, it is measured in mmHg (millimetres of mercury)

Blood pressure is dependent on a huge number of factors including peripheral vascular resistance, cardiac output and elasticity of vessel walls, and is regulated by multiple systems including the autonomic nervous system and the Renin Angiotensin Aldosterone System (RAAS)

Normal range for blood pressure is 100-140 systolic/60-90 diastolic mmHg (sources vary- check local policy). High = hypertension (HTN), low = hypotension.

This video by HEE (2020) outlines the process of taking a blood pressure. Key points include NEWS only using the systolic value in calculating a score.


Make sure to line up the bladder of the cuff/the arrow marked 'artery' on the cuff with the brachial artery, and position the cuff a few centimetres above the ante cubital fossa.


If taking a manual blood pressure, the most difficult part is getting used to listening out for Korotkoff sounds. The video below demonstrates really clearly the points where you can hear K1, the point where the artery begins to open up again and a thumping noise is heard, which indicates the systolic pressure, and also K5, the point where the artery is fully open and the noise stops, indicating the diastolic pressure.




Pulse

When feeling for a pulse, what you are feeling is the elastic recoil of the artery walls, as they expand and relax in time with blood being pumped from the heart under high pressure. It is counted in beats per minute and represents the number of full cardiac cycles (systole and diastole) in one minute.



Pulses can be felt in superficial arteries around the body, both centrally and peripherally. Central pulses include the carotid below the angle of the jaw (make sure not to feel bilaterally at the same time due to the (admittedly very small) risk of occluding blood flow to the brain) and femoral halfway in between the anterior superior iliac spine and the pubic symphysis. Peripheral pulses include the radial, on the thumb side of the wrist, brachial, in the centre of the arm just around the iliac fossa, popliteal behind the knee, posterior tibial behind the medial malleolus and the dorsalis pedis on the top of the foot.



Normal range for heart rate is 60-100 beats per minute (sources vary- check local policy). High = tachycardia, low = bradycardia.

This video by HEE (2020) outlines the process of taking a pulse and also covers some situations that may lead to tachy or bradycardia. It does also raise the important point that electronic devices (BP cuffs or pulse oximeters) are not reliable in irregular heartbeats and therefore a manual pulse should be taken.


When assessing pulse, also important to check the strength (weak vs bounding), symmetry (equal bilaterally?) and rhythm (regular or irregular?). If concerned, you can use a 3 lead or 12 lead ECG to get a better idea of what the heart rate is doing, but it's impossible to assess the strength and symmetry without feeling for a pulse manually so don't skip this step!


Disability and Exposure-



Level of consciousness

Level of consciousness is measured using the ACVPU scale. This used to be AVPU but has changed with NEWS2 to include new or worsening confusion.

Alert, the normal level of consciousness, indicated that a person is oriented to person, place and time ('A+Ox3'). This is compared to Confused, where a person is disoriented to person, place or time (or all 3) but is still following commands and opening their eyes spontaneously. A response to Voice indicates that there is eye opening or movement to a verbal command, whilst a Pain response indicates eye opening or movement in response to a painful stimuli (usually a trapezius squeeze, as this isn't excessively painful). No response at all would indicate that a person is Unresponsive.


The video below by HEE (2020) outlines measuring an ACVPU response and outlines some of the causes of a reduced level of consciousness, including head injury, stroke, low blood sugar, infection and hypoxia.



It can be really difficult to identify a shift from baseline, particularly if a patient is usually confused, so using family and carers is really important in this section (difficult in covid times with lack of visiting, but definitely not impossible with phone/video calls)


Important to note that anything other than alert will trigger a 3, which you can see from the table below would indicate escalation to the medical team and 1 hourly obs (as the 3 points are in a single parameter). If coupled with a total score of 5 of higher, further actions may be required.



Temperature

Temperature is maintained within homeostatic limits through thermoregulation- a process involving the hypothalamus and mechanisms such as shivering, sweating, and vasoconstriction/dilation. This makes humans endotherms, or 'animals that use thermoregulation to maintain a somewhat consistent internal body temperature even when their external environment change'. Core temperature is 37 degrees Celsius- this is the optimum functioning temperature of the body, and is most accurately measured using a rectal thermometer (for obvious reasons, rectal thermometers are not the usual first line for a well patient to check core temp).

At abnormally low temperatures, metabolic rate falls and blood vessels constrict to hold onto heat. At abnormally high temperatures, the opposite happens and blood vessels dilate to allow blood closer to the skin surface to lose heat to the environment. 43 degrees Celsius is widely accepted as the hottest that a person can be- past this point, enzymes are denatured and bodily process can no longer occur, making it incompatible with life.


Normal range for temperature is 36-37.5 degrees Celsius (sources vary- check local policy). High = hyperthermia, low = hypothermia.


To take a temperature tympanically, ensure that the tip is fully and snugly inserted into the ear canal to ensure an accurate reading, and is following the direction of the ear canal.

As the video points out, high temperatures can be due to infection, medications or heat stroke whilst low temperatures can also be due to infection, or cold environments and metabolic conditions like diabetes or thyroid problems.


Now what?

Now that you've taken your full set of observations and calculated a trigger score, it's vitally important to a) document b) escalate if necessary. The table below sums up some recommended actions depending on what the score is...


Hope you found this whizz through vital signs useful. I tried to include information on the physiology behind the observations but there's always more that you can learn, so please do go away and do some further research too. And definitely make sure to check local policy in terms of parameters for observations and for escalation of care.

Thanks for reading!

Christie x


References-


Weibel, E. et al. (2020) 'Chemoreceptors' in Encyclopedia Britannica. https://www.britannica.com/science/human-respiratory-system/Chemoreceptors



O'Driscoll, B., Howard, L., Earis J. & Mak, V. on behalf of the BTS Emergency Oxygen Guideline Development Group (2017) 'British Thoracic Society Guideline for oxygen use in adults in healthcare and emergency settings' in British Medical Journal Open Respiratory Research, 4(1). https://bmjopenrespres.bmj.com/content/bmjresp/4/1/e000170.full.pdf


Royal College of Physicians (2017) National Early Warning Score (NEWS) 2 Standardising the assessment of acute-illness severity in the NHS. https://www.rcplondon.ac.uk/file/8636/download


Royal College of Physicians (2017) National Early Warning Score (NEWS) 2. https://www.rcplondon.ac.uk/projects/outputs/national-early-warning-score-news-2


Osilla, E., Marsidi, J., Sharma, S. (2020) Physiology, temperature regulation. https://www.ncbi.nlm.nih.gov/books/NBK507838/



281 views0 comments

Recent Posts

See All

Comentarios


Post: Blog2 Post
bottom of page