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Chapter 3: Measuring and Recording the Vital Signs

Learning objectives for this chapter

By the end of this chapter, we would like you:

-To describe the place of measuring and recording the vital signs in the health observation and assessment process.

-To state the normal parameters of each vital sign for a healthy adult.

-To understand how to accurately measure each vital sign.

-To understand how to collect other key health data.

-To describe how to correctly record this data.

-To explain how this data should be interpreted and used in nursing practice.

Measurement and recording of the vital signs

The measurement and recording of the vital signs is the first step in the process of physically examining a patient. This step involves collecting objective data.

The normal parameters for each of the vital signs of healthy adults are listed following:

VITAL SIGN

HEALTHY RANGE

Blood pressure (BP)

120/80 mmHg

Pulse or heart rate (HR)

60-100 beats per minute

Temperature (T°)

36.5°C to 37.5° Celsius

Respiratory rate (RR)

10 to 16 breaths per minute

Blood oxygen saturation (SpO2)

98%-100%

Nurses should become familiar with the parameters for each of the vital signs. However, it is important for nurses to remember that these are average values for healthy adults. When interpreting vital signs, it is important that nurses use critical thinking to interpret the entire clinical picture of the individual patient with whom they are working.

Measurement of blood pressure

Blood pressure is often abbreviated to 'BP'. Blood pressure uses two measurements, each recorded in millimetres of mercury (mmHg). Blood pressure is defined as the pressure of the blood against the arterial walls:

  • When the heart contracts (systolic BP).
  • When the heart rests (diastolic BP).

The difference between the systolic and diastolic blood pressures is referred to as the pulse pressure. This normally ranges between 30mmHg and 40mmHg.

In most settings, blood pressure is measured indirectly using: (1) a sphygmomanometer and a stethoscope, or (2) a non-invasive blood pressure monitor:

  • Measuring blood pressure using a sphygmomanometer and a stethoscope: The arm used to take the blood pressure should be at the client's side, slightly flexed and with the palm turned upwards. The nurse should palpate the brachial pulse, in the antecubital space. A blood pressure cuff should be placed 2.5 centimetres above the site, with the bladder of the cuff centred over the artery. The cuff should be secured so it fits evenly and snugly around the arm.

Place the stethoscope over the patient's brachial pulse, and hold it with your non-dominant hand. Using your dominant hand, inflate the cuff to around 180mmhg. Then, deflate the cuff, slowly and steadily. You are listening for two things:

  • The first Korotkoff sound. Read the pressure on the manometer at the point this occurs.
  • The disappearance of all Korotkoff sounds. Read the pressure on the manometer at the point this occurs.
  • Measuring blood pressure using a non-invasive blood pressure monitor: This involves using an electronic monitoring device. The cuff of an automatic blood pressure monitor is applied in the same way as described above. The nurse then presses a 'start' button to instruct the machine to inflate the cuff, take a measurement and provide a reading.

The upper arm is the most common site to measure blood pressure; however, if this is not possible, blood pressure may also be measured from the thigh.

It is important for nurses to note that there are a number of common errors associated with blood pressure measurement. Errors may result if:

  • The client's arm is positioned above or below the level of their heart.
  • The cuff used is too large or too narrow for the client's arm.
  • The cuff is wrapped too loosely or unevenly around the client's arm.
  • The cuff is not deflated to a pressure higher than the patient's systolic blood pressure.
  • The cuff is deflated at a rate slower or faster than 2 to 3mmHg per second.
  • The cuff is reinflated before it is completely deflated.
  • The stethoscope is pressed too firmly against the brachial artery.
  • The nurse fails to wait 2 minutes before repeating the blood pressure measurement.

As described above, the majority of the common errors associated with blood pressure measurement are related to the size and position of the cuff. Blood pressure cuffs come in a variety of sizes, and it is essential that nurses select the correct size for the patient.

When measuring a client's blood pressure, a nurse may identify that it is high or low. There may be a number of pathophysiological causes of hypertension and hypotension, but it is important for nurses to recognise that there are also a number of physiological factors which affect blood pressure measurement.

Measurement of pulse or heart rate

Heart rate is often abbreviated to 'HR'. It is defined as the number of times a person's heart beats in a one-minute period. In addition to assessing the rate at which a person's heart is beating, when measuring a person's HR, a nurse should also assess for the rhythm and quality of the pulse.

A patient's pulse may be measured using the same types of non-invasive, automatic monitors used to measure blood pressure. However, it is generally preferred that heart rate is assessed by palpating a pulse.

To measure a pulse, a nurse should place their fingers over an artery and feel for the pulse. Generally, pulses are palpated with the pads of the index and middle fingers. Firm pressure is applied to the pulse, but not so much that the artery is occluded. There are a number of locations on the body in which a nurse may feel for a pulse:

  • The radial artery, located on the outer edge of each wrist.
  • The brachial artery, located in the antecubital space on each arm.
  • The carotid artery, located on the inner sides of the sternocleidomastoid muscle in the neck.

A patient's heart rate can also be assessed by auscultating the heart. This is referred to as measuring the apical pulse.

When measuring the HR, a nurse may:

  • Count the number of pulses for 60 seconds.
  • Count the number of pulses for 30 seconds, and multiply by 2 - if the HR is regular.
  • Count the number of pulses for 15 seconds, and multiply by 4 - if the HR is regular.

As described, it is important that a nurse assesses the pulse for regularity. If the pulse is irregular, the pulse must be counted for one full minute. Additionally, an irregular pulse must be documented when recording the vital signs.

It is also important that the nurse assess the quality of the pulse. A patient's pulse may be described using terms such as thready or bounding. This is important information that is used, along with HR and regularity of the pulse, to assess the health of the cardiovascular and other body systems.

The average pulse or heart rate for a healthy adult is 60 to 100 beats per minute. If a patient's pulse is >100 beats per minute, this is referred to as tachycardia. If a patient's pulse is <60 beats per minute, this is referred to as bradycardia.

Measurement of temperature

Temperature is often abbreviated to 'T°'. This is defined as the temperature, in degrees Celsius (°C), of a person's body. Temperature is typically measured using a thermometer, which may be either automatic or manual. Temperature may be measured by one of several different routes:

  • Orally, with the thermometer placed under the tongue. This is the safest way of recording a patient's temperature, and also one of the most accurate.
  • Via the tympanic membrane, with the thermometer placed onto the tympanic membrane within the ear.
  • Via the axilla, with the thermometer placed under the arm. The accuracy of temperature measurements recorded here are uncertain.
  • Rectally, with the thermometer inserted into the patient's rectum. This is safe and accurate, but it is both uncomfortable and invasive.

When using an automatic or electronic thermometer to record a patient's temperature, the nurse should place the thermometer in the location at which the temperature is to be recorded, press 'start', and wait for an audible signal and the measurement to register on a display screen. If using a manual thermometer, the thermometer must be located on the patient's body as described, and the nurse must wait at least one full minute before reading the measurement on the gauge of the thermometer.

The average temperature for a healthy adult is 36.5°C to 37.5°C. If a patient's temperature is >37.5°C, they are said to have hyperthermia. If a patient's temperature is <36.5°C, they are said to have hypothermia.

Measurement of respiratory rate

Respiratory rate is often abbreviated to 'RR'. This is defined as the number of times a person inhales and exhales in a 1 minute period.

Respiratory rate is typically measured by counting the number of times a patient completes a full ventilatory cycle in a 1 minute period. This can be measured by watching the rise and fall of the patient's chest and / or abdomen, or the breath sounds may also be auscultated.

When measuring the RR, a nurse may:

  • Count the number of pulses for 60 seconds.
  • Count the number of pulses for 30 seconds, and multiply by 2 - if the RR is regular.
  • Count the number of pulses for 15 seconds, and multiply by 4 - if the RR is regular.

In addition to assessing a patient's heart rate, the nurse should assess:

  • The rhythm, or pattern / regularity, of the patient's breathing.
  • The depth of the patient's breathing, or level of lung expansion.
  • The effort associated with the patient's breathing.

The average respiratory rate for a healthy adult is 10 to 16 breaths per minute. If a patient's RR is >16 breaths per minute, this is referred to as tachpynoea. If a patient's RR is <10 breaths per minute, this is referred to as bradypnoea.

Measurement of blood oxygen saturation

Blood oxygen saturation is often abbreviated to 'SpO2'. This is defined as the amount of oxygen present in a person's blood at a given time. It is measured as a percentage, using a non-invasive automatic measuring device called a pulse oximeter. The probe of a pulse oximeter is usually placed on the end of a patient's finger or toe. A reading is given on the machine's screen after a period of approximately 15 seconds.

The blood oxygen saturation of a healthy adult is typically 98%-100%.

Measurement of height, weight and body mass index (BMI)

Although not strictly vital signs, a patient's height, weight and body mass index (BMI) can provide a nurse with important information about their overall health and physical condition. A patient's weight is measured using a scale, whilst their height is measured using a platform ruler or tape measure. Body mass index can then be calculated.

BMI is a useful, objective measurement of a person's body condition, based on their unique height and weight. A patient's BMI is interpreted as follows:

BMI

Interpretation

<18.5

Underweight

18.6 to 24.9

Normal weight

25 to 29.9

Overweight

>30

Obese

It is worth noting that the accuracy of the BMI measurement is subject to much conjecture. As always, it is important that nurses use critical thinking to interpret the entire clinical picture of the individual patient with whom they are working.

Measurement of pain

In many clinical areas, pain is considered the sixth 'vital sign'. Pain is generally assessed using a strategy which can be remembered using the 'OPQRST' mnemonic

O

Onset

P

Provocation and palliation

Q

Quality

R

Region and radiation

S

Severity

T

Time

It is also important to highlight that there are a number of visual scales which can be used to assess pain in patients who are non-verbal.

Recording the vital signs

The information must be documented so that it can be used to: (1) assess the patient's condition, and (2) inform the care which is appropriate for that patient. Documentation must be complete, accurate, concise, legible and free from bias.

Often in the United Kingdom, a patient's vital signs are recorded using early warning score tools. These pieces of documentation allow a nurse to graphically represent a patient's vital sign measurements to identify changes over time, and to calculate simple scores which describe a patient's risk of deterioration into serious illness.

Interpreting the vital signs

Once you have measured and recorded a patient's vital signs, it is important that you are able to analyse and interpret the data you have collected. Essentially, this means attempting to understand and make sense of this data, based on the patient's physiological condition.

Conclusion

This chapter began with an introduction to the importance of measuring the vital signs in nursing practice. It went on to describe the measurement of each of the vital signs and the collection of other supporting data, discussing key strategies and considerations. The chapter then reviewed the processes involved in recording data collected about the vital signs. Finally, the chapter discussed how a nurse should go about interpreting the data they have obtained, to build a clinical picture of the patient and plan for their care.


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