Nursing Foundations · Vital Signs

Vital Signs

Vital Signsdefinition

The four primary vital signs are temperature, pulse, respiration and blood pressure.

in simple words: Basic measurements that reflect the body's essential functions.

e.g. Some modern frameworks also include pain and pulse oximetry.

Why They Matter

Abnormal vital signs are often the earliest indicators of deterioration such as infection (fever), shock (low blood pressure with high pulse) or respiratory distress. They prompt immediate nursing assessment and escalation.

Pain – 5th vital sign

Assessed as routinely as TPR and BP.
Promoted by American Pain Society and The Joint Commission.
Untreated acute pain can impair recovery.

Vital Signs · Nursing Foundations

Temperature Measurement

Core Temperaturedefinition

Temperature of deep tissues and organs; remains relatively constant.

in simple words: The body's internal temperature, little affected by environment.

e.g. Surface (skin) temperature fluctuates with ambient temperature.

Temperature Sites

Site	Accuracy	Notes
Oral	Surface	Altered by hot/cold drinks, food, smoking, mouth breathing. Wait 15–20 min after intake.
Axillary	Least accurate	Underestimates core temperature.
Rectal	Most accurate non-invasive core	Reads ~0.5°C (1°F) higher than oral. Avoid in newborns, cardiac disease, rectal surgery, diarrhoea, neutropenia.
Tympanic	Core	Reflects carotid blood supply to hypothalamus. Avoid if otitis media or cerumen impaction.
Temporal	Core	Infrared over temporal artery; non-invasive.

A clinical thermometer used to measure body temperature orally or axillary. — Clinical thermometer for temperature measurement

A single-use disposable thermometer for measuring body temperature. — Disposable thermometer

Temperature Conversion

°F to °C°C = (°F − 32) × 5/9
°C to °F°F = (°C × 9/5) + 32
Example99°F ≈ 37.2°C; 101°F ≈ 38.3°C

Vital Signs · Nursing Foundations

Temperature Measurement (contd.)

Vital Signs · Nursing Foundations

Fever Patterns

Fever (Pyrexia)definition

Core body temperature at or above 38°C (100.4°F).

in simple words: A regulated rise in the hypothalamic set-point caused by pyrogens.

e.g. Bacteria and viruses act as pyrogens.

Fever Patterns

Pattern	Description
Intermittent	Temperature rises and returns to normal at least once in 24 hours.
Remittent	Temperature fluctuates but does not return to normal.
Sustained	Persistently elevated with fluctuations <1°C (1.8°F).
Relapsing	Febrile episodes lasting days separated by afebrile periods of days.
Inverse	Highest temperature in morning, lowest in evening; clue to miliary TB.

Crisis vs Lysisdefinition

Crisis: sudden fall of high fever to normal within hours, often with profuse sweating. Lysis: gradual decline over days.

in simple words: Crisis is abrupt; lysis is gradual.

e.g. Monitor for dehydration and hypotension during crisis.

Vital Signs · Nursing Foundations

Pulse Assessment

Pulsedefinition

A wave of blood created by contraction of the left ventricle.

in simple words: The heartbeat felt at peripheral arteries.

e.g. Normal adult resting pulse: 60–100 bpm.

Pulse Characteristics

Term	Definition
Tachycardia	Pulse >100 bpm in adults.
Bradycardia	Pulse <60 bpm in adults.
Pulse deficit	Difference between apical and radial rates; indicates weak beats.
Pulse pressure	Difference between systolic and diastolic BP.
Thready pulse	Weak, low volume, disappears with light pressure; grade 1+.
Bounding pulse	Forceful, difficult to obliterate; grade 4+.

Apical Pulse

Best assessed at the point of maximal impulse: 5th intercostal space, left mid-clavicular line. Count for a full minute before giving digoxin or beta-blockers. In children under 7, PMI is at 4th intercostal space.

Vital Signs · Nursing Foundations

Respiration

Respirationdefinition

The exchange of oxygen and carbon dioxide.

in simple words: Breathing.

e.g. Normal adult rate: 12–20 breaths per minute.

Respiratory Terms

Term	Definition
Tachypnea	Rate >20 breaths/min in adults.
Bradypnea	Rate <12 breaths/min in adults.
Apnea	Absence of breathing for several seconds or longer.
Eupnea	Normal, unlabored breathing.
Hyperventilation	Rapid deep breathing; can cause dizziness and tingling.

Counting Respirations

Count discreetly after taking the pulse, with hand still on wrist, so patient does not alter breathing. Respiratory rate is one of the earliest indicators of deterioration.

Vital Signs · Nursing Foundations

Pulse Oximetry

Pulse Oximetrydefinition

Noninvasive measurement of arterial oxyhemoglobin saturation (SpO2).

in simple words: Percentage of hemoglobin bound to oxygen.

e.g. Normal SpO2: 95–100%. Below 90% is a clinical emergency.

Factors Affecting Accuracy

Hypotension/shock – Weakens signal; false or unobtainable readings.
Oedema – Widens gap between emitter and detector; scatters light.
Dark nail polish – Absorbs light; falsely low SpO2.
Hypothermia – Vasoconstriction weakens pulse; reading may be unobtainable.
Carbon monoxide – Falsely high SpO2; cannot distinguish carboxyhemoglobin.

Troubleshooting Low SpO2

Check for warm extremity, remove nail polish, verify probe placement, try earlobe or forehead site. Confirm with clinical assessment and ABG if needed.

Vital Signs · Nursing Foundations

Blood Pressure

Blood Pressuredefinition

The force exerted by blood against arterial walls.

in simple words: Pressure in the arteries.

e.g. Normal adult BP: <120/80 mm Hg.

An aneroid sphygmomanometer with dial gauge used to measure blood pressure. — Aneroid blood pressure apparatus

BP Categories

Category	Systolic (mm Hg)	Diastolic (mm Hg)
Normal	<120	<80
Stage 1 hypertension	130–139	80–89
Stage 2 hypertension	≥140	≥90
Hypotension	<90	<60

Korotkoff Sounds

Phase I (first clear tapping) = systolic. Phase V (disappearance) = diastolic in adults. Phase IV (muffling) used in children and pregnant women.

Vital Signs · Nursing Foundations

BP Measurement

Cuff Size

Bladder width ~40% of arm circumference; length-to-width ratio 2:1. Select cuff size after assessing upper-arm circumference.

Illustration showing that a blood pressure cuff that is too small records a falsely higher reading. — Small cuff gives falsely high BP

Sites to Avoid

IV line – Use contralateral arm.
AV fistula – Avoid.
Mastectomy with lymph node removal – Avoid.
Carotid sinus – Not for routine BP; can cause vasovagal response.

Technique

Inflate cuff 30 mmHg above estimated systolic, deflate at 2–3 mmHg/sec. Arm at heart level. Avoid auscultatory gap by palpating systolic first.

Vital Signs · Nursing Foundations

Pulse Deficit

Pulse Deficitdefinition

Difference between apical and radial pulse rates counted over the same period.

in simple words: Some heartbeats are too weak to reach the wrist.

e.g. Common in atrial fibrillation.

Measurement

Two clinicians count apical and radial pulses simultaneously for a full minute. Apical is auscultated at PMI (5th ICS, left mid-clavicular line).

Significance

Indicates reduced cardiac output. New pulse deficit should be reported and may require ECG. Hold digoxin or beta-blockers if new deficit appears.

Vital Signs · Nursing Foundations

Documenting Vital Signs

Tachycardiadefinition

Pulse greater than 100 beats per minute in adults.

in simple words: Fast heart rate.

e.g. Causes: anxiety, exertion, hypovolemia, infection, arrhythmia.

Normal Values

Average normal oral temperature: 37°C (98.6°F). Normal adult pulse: 60–100 bpm. Normal adult respirations: 12–20/min. Normal adult BP: <120/80 mm Hg.

Documentation

Record vital signs accurately, including site and method. Report abnormal values promptly. In Indian healthcare, document temperature in Celsius.