Vital signs

In short

Vital signs — body temperature, pulse, respiration, blood pressure, oxygen saturation and pain — are the measurable indicators of the body's basic physiological functions and the earliest objective signs that a patient's condition is changing. They are recorded on admission, at shift change, before and after procedures, before and after giving cardiovascular or respiratory drugs, and whenever the patient's condition or complaint changes. In the B.Sc Nursing curriculum prescribed by the Indian Nursing Council they sit in Nursing Foundations (Year I) with both theory marks and an OSCE/practical station, and reappear in Medical-Surgical Nursing, Critical Care and Community Health. For jobs — staff nurse recruitment at AIIMS, ESIC, DSSSB, RRB, state health services, and interviews at Apollo, Fortis, Manipal, Max and Narayana Health — the normal ranges, the procedure and the "what will you do if" judgement questions are asked almost every time.

Explained

What vital signs are, and when to take them

• Vital signs (cardinal signs): temperature (T), pulse (P), respiration (R), blood pressure (BP); SpO₂ is routinely added and pain is called the "fifth vital sign" (SpO₂ is sometimes called the fifth or sixth — both usages exist, so state which you mean).
• Purpose: establish a baseline, detect deterioration early, evaluate response to treatment, and screen in community settings.
• When to measure: on admission and discharge; per hospital routine (ward usually 12-hourly or 6-hourly, ICU hourly or continuous); pre- and post-operatively; before, during and after blood transfusion; before and after drugs that affect heart rate, BP or respiration (digoxin, beta-blockers, antihypertensives, opioids); before and after any invasive procedure or ambulation after bed rest; whenever the patient reports feeling unwell or you observe a change.
• Documentation: TPR chart / graphic sheet — temperature plotted as a continuous line, pulse and respiration as separate lines or figures, BP as a vertical line or paired figures. Record immediately after measuring, never from memory; report abnormal values to the nurse in charge or doctor at once. In the legal sense the nurse's record is evidence — unrecorded observation is treated as not done.
• Nursing responsibility: know the patient's baseline, know the normal range for that age, control the equipment, interpret rather than merely record, and act on the deviation.

Body temperature

• Definition: the balance between heat produced (metabolism, muscle activity, thyroxine, shivering) and heat lost (radiation, conduction, convection, evaporation, respiration). Regulated by the hypothalamus; the anterior hypothalamus controls heat loss, the posterior heat conservation.
• Core vs surface: core (rectal, tympanic, oesophageal, pulmonary artery, temporal artery) is stable; surface (oral, axillary, skin) varies with environment.
• Normal adult ranges: oral 36.5–37.5 °C (average 37 °C / 98.6 °F); rectal about 0.5 °C higher; axillary about 0.5 °C lower; tympanic close to core. Normal diurnal variation of 0.5–1 °C — lowest early morning (about 4–6 a.m.), highest late afternoon/evening (4–8 p.m.).
• Sites — choice and contraindications: oral is convenient but avoid in unconscious, confused, convulsing, mouth-breathing patients, after oral surgery, in children under about 5 and if hot/cold fluids were taken (wait 15–30 min). Rectal is accurate but contraindicated in rectal surgery, diarrhoea, haemorrhoids, cardiac patients (vagal stimulation) and low platelet counts. Axillary is safest but slowest (needs 5–10 min with a glass thermometer). Tympanic is fast but affected by wax and technique.
• Thermometer types: clinical (mercury) glass thermometer — being withdrawn worldwide under the Minamata Convention on Mercury, to which India is a party, so Indian hospitals have largely shifted to digital electronic thermometers; infrared tympanic and non-contact forehead thermometers (widely deployed for screening since COVID-19); chemical dot/strip; continuous probes in ICU.
• Terms: pyrexia/fever above 37.5–38 °C oral; low-grade up to 38 °C; moderate 38–39 °C; high 39–40 °C; hyperpyrexia above 41 °C; hypothermia below 35 °C; afebrile normal.
• Fever patterns: *continuous* (varies <1 °C, never normal — typhoid, lobar pneumonia); *intermittent* (touches normal daily — malaria, pyogenic infection); *remittent* (fluctuates >1–2 °C but never normal — viral fevers); *relapsing/recurrent* (febrile days alternate with normal days — dengue saddleback, Pel-Ebstein in Hodgkin's lymphoma).
• Stages of fever: onset/chill phase (vasoconstriction, shivering, cold extremities), plateau/course (hot flushed skin, thirst, tachycardia — roughly 10 beats/min rise and 7–8 % metabolic rise per 1 °C), defervescence/crisis (diaphoresis, vasodilatation) — lysis is gradual, crisis is sudden.
• Nursing care in fever: tepid sponging, light clothing and bedding, adequate oral fluids (2–3 L/day unless restricted), oral hygiene, antipyretics as prescribed (paracetamol), monitor for febrile convulsions in children, measure intake-output, and watch for dehydration. Hyperthermia (heat stroke) is a failure of thermoregulation — needs rapid active cooling, not antipyretics; India's National Action Plan on Heat Related Illness guides district heat-stroke protocols.

Pulse

• Definition: the palpable wave of blood created in the arteries by each left-ventricular contraction; it reflects heart rate when every beat reaches the periphery.
• Sites: temporal, carotid, apical (5th intercostal space, left mid-clavicular line), brachial, radial (routine), ulnar, femoral, popliteal, posterior tibial, dorsalis pedis. Carotid is used in emergencies in adults; brachial in infants for BLS pulse check; apical in infants and children, and whenever the radial pulse is irregular or weak.
• Technique: two or three middle fingers (never the thumb — its own pulse confuses) over the artery against bone, moderate pressure; count 30 s × 2 if regular, a full 60 s if irregular, in children, or on a new patient.
• Characteristics to assess: rate, rhythm (regular/irregular/intermittent), volume or amplitude (graded 0 absent, 1+ weak/thready, 2+ normal, 3+ bounding), tension, equality on both sides, and condition of the arterial wall.
• Normal rates: newborn 120–160; infant 100–140; toddler 90–140; preschool 80–110; school age 75–100; adolescent 60–100; adult 60–100 (average about 72); well-trained athlete may be 50–60. Tachycardia >100/min in adults; bradycardia <60/min.
• Factors affecting: age, sex (female slightly higher), exercise, fever, emotion/stress and pain (raise); drugs (digoxin, beta-blockers lower; adrenaline, atropine, salbutamol raise); haemorrhage (rapid thready), position change, raised intracranial pressure (bradycardia with hypertension — part of Cushing's response).
• Abnormal pulses: *pulsus alternans* (alternating strong-weak — left ventricular failure), *pulsus paradoxus* (volume falls on inspiration — cardiac tamponade, severe asthma), *water-hammer/collapsing* (aortic regurgitation), *pulsus bigeminus*, *thready*, *bounding*.
• Pulse deficit: apical rate minus radial rate — measured by two nurses simultaneously for one minute; a deficit means some ventricular contractions are too weak to reach the wrist, classically in atrial fibrillation.

Respiration

• Definition: exchange of oxygen and carbon dioxide between atmosphere and body — external respiration (lung-blood), internal (blood-cell). Controlled by the medulla and pons, driven chiefly by arterial CO₂ (central chemoreceptors) and, when PaO₂ falls low, by peripheral chemoreceptors in the carotid and aortic bodies.
• Technique: count without telling the patient (voluntary control alters it) — keep fingers on the wrist as if taking the pulse and watch chest rise and fall for a full minute (at least 30 s × 2 if regular).
• Assess: rate, depth (shallow/normal/deep — tidal volume about 500 mL in an adult), rhythm, effort (use of accessory muscles, nasal flaring, retractions, orthopnoea), sound (stridor, wheeze, grunting), symmetry, and colour/cyanosis.
• Normal rates: newborn 30–60; infant 25–40; toddler 20–30; preschool 20–25; school age 18–25; adolescent 16–20; adult 12–20 per minute. Tachypnoea >20 (adults); bradypnoea <12; apnoea absence; dyspnoea difficult breathing; orthopnoea breathless lying flat; eupnoea normal.
• Abnormal patterns: Cheyne-Stokes — depth waxes and wanes with apnoeic pauses (heart failure, raised ICP, terminal illness); Kussmaul — deep rapid sighing (metabolic acidosis, diabetic ketoacidosis); Biot's/ataxic — irregular with pauses (meningitis, brainstem damage); apneustic; agonal.
• In the Indian IMNCI programme, a respiratory rate ≥50/min in infants 2–12 months or ≥40/min in children 1–5 years with cough is classified as fast breathing/pneumonia and treated — a frequently examined community-nursing cut-off.

Blood pressure

• Definitions: force exerted by blood on the arterial walls. Systolic = peak during ventricular ejection; diastolic = lowest during ventricular relaxation; pulse pressure = systolic − diastolic (normally about 30–40 mmHg); mean arterial pressure (MAP) = average perfusion pressure, must stay above about 60–65 mmHg to perfuse organs.
• Determinants: BP = cardiac output × peripheral vascular resistance; cardiac output = stroke volume × heart rate. Also blood volume, blood viscosity, arterial elasticity, and neuro-hormonal control (sympathetic, renin-angiotensin-aldosterone, ADH).
• Equipment: aneroid or digital (oscillometric) sphygmomanometer — mercury sphygmomanometers are being phased out under the Minamata Convention; stethoscope; correctly sized cuff. Cuff width should be about 40 % of arm circumference and the bladder should encircle 80 % of the arm; a cuff too narrow, too short, or wrapped too loosely gives a falsely high reading, while too wide a cuff or one applied too tightly reads falsely low.
• Procedure: patient seated and rested 5 minutes, back supported, legs uncrossed, feet flat, no caffeine/smoking/exercise for 30 min, bladder empty, arm bare and supported at heart level, cuff lower edge 2–3 cm above the antecubital fossa; palpate the radial pulse and inflate 20–30 mmHg above its disappearance (prevents missing an auscultatory gap); deflate at 2–3 mmHg per second; take two readings 1–2 minutes apart and average; measure in both arms at the first visit and use the higher arm thereafter.
• Korotkoff sounds: Phase I = first clear tapping = systolic; II = swishing/murmur; III = crisper tapping; IV = muffling; Phase V = disappearance = diastolic in adults. In children and pregnancy where sounds persist to zero, phase IV (muffling) is taken as diastolic — record which was used. Auscultatory gap = silence between phases I and II (sounds disappear after the systolic tapping and reappear lower down), common in hypertension.
• Sites and contraindications: upper arm (brachial) routinely; thigh (popliteal) if arms unusable — readings there are higher. Avoid an arm with an IV line or transfusion running, an AV fistula or shunt, mastectomy with axillary node dissection on that side, lymphoedema, fracture, plaster or burns.
• Classification (adults): normal <120/<80; "elevated"/prehypertension 120–139/80–89 depending on the guideline used; hypertension generally ≥140/90 mmHg on repeated measurement (the ACC/AHA uses ≥130/80, while the Indian Guidelines on Hypertension and the India Hypertension Control Initiative run by ICMR-NCD programmes use ≥140/90 as the treatment threshold — quote the threshold with the guideline, since they differ); hypertensive crisis/emergency ≥180/120 with organ damage; hypotension generally <90/60 with symptoms.
• Orthostatic (postural) hypotension: a fall of ≥20 mmHg systolic or ≥10 mmHg diastolic (or a rise in pulse >20/min) within 3 minutes of standing — measure lying, sitting and standing; a key fall-risk assessment in elderly and post-bed-rest patients.
• Errors: arm below heart level, unsupported arm, cuff over clothing, loose or narrow cuff, rapid deflation, re-inflating without full deflation (venous congestion), observer bias to end-digit 0, talking during measurement, and "white-coat" hypertension (home/ambulatory monitoring clarifies it).

Oxygen saturation, pain and early-warning scoring

• Pulse oximetry (SpO₂): a probe passes red and infrared light through a pulsatile capillary bed and computes the percentage of haemoglobin carrying oxygen. Normal 95–100 %; below 90 % needs urgent action; in known COPD/CO₂ retainers a target of about 88–92 % is often prescribed. Sites: finger, toe, earlobe, forehead; infant foot or palm.
• Causes of unreliable SpO₂: poor perfusion, hypothermia, hypotension, vasoconstrictors, motion, nail polish or artificial nails, bright ambient light, dark pigmentation (known to overestimate saturation), severe anaemia, and especially carbon monoxide poisoning and methaemoglobinaemia where SpO₂ reads falsely high. SpO₂ shows oxygenation, not ventilation — a patient retaining CO₂ can have a normal SpO₂.
• Pain as the fifth vital sign: assess at every vital-sign round using a numeric rating scale 0–10, Wong-Baker FACES (children), FLACC (infants/non-verbal), or the Visual Analogue Scale; record site, onset, character, radiation, aggravating/relieving factors, and reassess 30–60 min after analgesia. India's Narcotic Drugs and Psychotropic Substances (Amendment) Act, 2014 simplified access to morphine as a Recognised Medical Institution-based "essential narcotic drug" for pain relief.
• Capillary refill time: press a nail bed 5 s — normal return of colour under 2–3 s; prolonged suggests poor perfusion/shock.
• Early-warning tools: NEWS2 / MEWS in adults and PEWS in paediatrics convert the vital signs into a score that triggers escalation; shock index = heart rate ÷ systolic BP (>0.9 suggests occult shock). Indian NABH accreditation standards and the Nursing Excellence/NQAS quality framework expect a documented vital-sign monitoring and escalation protocol in every ward.
• Infection control overlap (kept brief, as it belongs to its own topic): hand hygiene before and after each patient and disinfection of the shared thermometer, cuff and oximeter probe between patients.

Key points

• Vital signs - temperature, pulse, respiration and BP; SpO₂ and pain are routinely added.
• Normal adult values - T 36.5–37.5 °C oral, P 60–100/min, R 12–20/min, BP <120/80 mmHg, SpO₂ 95–100 %.
• Hypothalamus - the thermostat; anterior controls heat loss, posterior heat conservation.
• Site differences - rectal ≈ oral + 0.5 °C; axillary ≈ oral − 0.5 °C; tympanic ≈ core.
• Diurnal variation - temperature lowest 4–6 a.m., highest 4–8 p.m., range 0.5–1 °C.
• Fever response - pulse rises roughly 10 beats/min and metabolism 7–8 % per 1 °C rise.
• Fever patterns - continuous, intermittent, remittent, relapsing; typhoid continuous, malaria intermittent.
• Pulse rule - never use the thumb; count a full minute if the rhythm is irregular or the patient is a child.
• Pulse deficit - apical minus radial, counted simultaneously by two nurses; typical of atrial fibrillation.
• Respiration rule - count unobserved; respiration is the only vital sign the patient can consciously alter.
• Abnormal breathing - Cheyne-Stokes (waxing-waning, heart failure/raised ICP), Kussmaul (deep rapid, DKA), Biot's (irregular, meningitis).
• BP equation - BP = cardiac output × peripheral resistance; CO = stroke volume × heart rate.
• Korotkoff - Phase I = systolic, Phase V = diastolic (Phase IV in children and pregnancy).
• Cuff size - width about 40 % of arm circumference, bladder encircling 80 %; small cuff reads high.
• Hypertension - generally ≥140/90 mmHg (India Hypertension Control Initiative threshold); ACC/AHA uses ≥130/80 — always name the guideline.
• Orthostatic hypotension - systolic fall ≥20 or diastolic ≥10 mmHg within 3 minutes of standing.
• SpO₂ pitfalls - falsely high in carbon monoxide poisoning and methaemoglobinaemia; unreliable in shock, cold, motion, nail polish.
• Record and report - abnormal values are reported immediately; an unrecorded observation is legally treated as not done.

Formulas and examples

Example 1 — MAP and pulse pressure. A post-operative patient's BP is 96/54 mmHg.

• PP = 96 − 54 = 42 mmHg.
• MAP = (96 + 2 × 54)/3 = (96 + 108)/3 = 204/3 = 68 mmHg.
• Interpretation: MAP is just above the 65 mmHg perfusion threshold and the BP is borderline low — recheck in 15 minutes, assess urine output, skin and consciousness, and inform the surgeon; do not wait for the next routine round.

Example 2 — temperature conversion and the fever response. A child's axillary temperature reads 103 °F.

• °C = (103 − 32) × 5/9 = 71 × 5/9 = 39.4 °C (axillary) — core is roughly 0.5 °C higher, about 39.9 °C, i.e. high-grade fever.
• Rise above normal 37 °C ≈ 2.4 °C → expected pulse rise ≈ 2.4 × 10 = 24 beats/min above the child's baseline; metabolic rate up roughly 2.4 × 7.5 ≈ 18 %.
• Action: tepid sponging, prescribed paracetamol, extra oral fluids, watch for febrile convulsion, repeat temperature after 30–60 minutes.

Example 3 — pulse deficit in atrial fibrillation. Two nurses count simultaneously for 60 s: apical 118 beats/min, radial 86 beats/min.

• Pulse deficit = 118 − 86 = 32 beats/min — about 27 % of contractions fail to generate a palpable peripheral pulse.
• Interpretation: ineffective, irregularly irregular ventricular contractions; report at once, obtain an ECG, and base any rate-dependent drug decision (digoxin, beta-blocker) on the apical rate, never the radial.

Example 4 — cardiac output and shock index. A trauma patient has HR 124/min, BP 88/60 mmHg, stroke volume estimated 45 mL.

• Cardiac output = 45 × 124 = 5,580 mL/min = 5.58 L/min (appears normal because tachycardia is compensating for the small stroke volume).
• Shock index = 124/88 = 1.41 (>0.9) → significant hypovolaemia despite an apparently adequate cardiac output.
• MAP = (88 + 120)/3 = 208/3 = 69.3 mmHg. Action: flat position with legs raised if not contraindicated, oxygen, large-bore IV access and fluids as prescribed, continuous monitoring, urgent medical review.

Example 5 — orthostatic hypotension screening. An 80-year-old after 6 days of bed rest: lying 138/82, pulse 76; standing at 1 minute 112/70, pulse 102.

• Systolic fall = 138 − 112 = 26 mmHg (≥20) and pulse rise = 26/min (>20) → orthostatic hypotension present.
• Action: sit her down, document, review antihypertensives and diuretics with the doctor, teach slow staged rising with dangling of legs, ensure hydration, and flag her as a fall risk.

Where it is used

• Hospital wards and ICUs: staff nurses on TPR charts, NEWS2/MEWS escalation and multi-para monitors at AIIMS, PGIMER, CMC Vellore, Apollo, Fortis, Manipal, Max and Narayana Health.
• Emergency and ambulance services: triage at casualty and in 108 ambulance services — vital signs plus GCS decide red/yellow/green triage category and pre-hospital alerts.
• Community health and national programmes: ASHA, ANM and community health officers at Ayushman Arogya Mandirs screen BP and blood sugar under the NP-NCD and IHCI programmes, and classify childhood pneumonia by respiratory rate under IMNCI.
• Maternity care: four-hourly vital signs in labour, BP for pre-eclampsia screening under the Pradhan Mantri Surakshit Matritva Abhiyan, and newborn temperature monitoring for hypothermia in SNCUs.
• Occupational, insurance and school health: pre-employment and periodic medical examinations, corporate health camps, insurance medicals and school health screening under Rashtriya Bal Swasthya Karyakram.
• Device and nursing-informatics roles: work with digital sphygmomanometers, pulse oximeters and central monitors, NABH-aligned documentation audits, telemonitoring and eSanjeevani teleconsultation support.

Interview questions

• Q: Which are the vital signs and why is pain called the fifth? A: Temperature, pulse, respiration and blood pressure, with SpO₂ added routinely; pain is called the fifth vital sign because it must be assessed, scored and reassessed as regularly as the other four, and it changes management.
• Q: Why should the thumb not be used to feel a pulse? A: The thumb has a prominent pulse of its own, which the nurse may mistakenly count instead of the patient's.
• Q: Why is respiration counted without informing the patient? A: Breathing is under voluntary as well as automatic control, so a patient who knows they are being watched alters the rate and depth.
• Q: What is pulse deficit and when does it occur? A: The difference between the apical and radial rates counted simultaneously; it occurs when ventricular contractions are too weak to reach the periphery, classically in atrial fibrillation.
• Q: How does using a cuff that is too small affect the reading? A: It gives a falsely high reading because more pressure is needed to compress the artery; an over-wide cuff reads falsely low.
• Q: Which Korotkoff phase gives the diastolic pressure? A: Phase V, the disappearance of sounds, in adults; Phase IV muffling is used in children and in pregnancy where sounds continue to zero, and the phase used must be documented.
• Q: Where would you never take a blood pressure, and why? A: On an arm with an IV infusion or transfusion, an AV fistula, lymphoedema or post-mastectomy axillary dissection, fracture, burn or plaster — because of damage, inaccuracy or risk of thrombosis and infection.
• Q: A patient's SpO₂ reads 99 % but they are drowsy and breathing 8 times a minute. What is happening? A: SpO₂ measures oxygenation, not ventilation — the patient may be retaining CO₂, as in opioid-induced respiratory depression; check the respiratory rate, consciousness and arterial blood gases and inform the doctor urgently.
• Q: Why does a pulse oximeter read falsely high in carbon monoxide poisoning? A: Carboxyhaemoglobin absorbs light much like oxyhaemoglobin, so the device counts it as saturated; co-oximetry or blood gas analysis is needed.
• Q: Calculate MAP for BP 120/80 and say why it matters. A: MAP = (120 + 160)/3 = 93 mmHg; MAP is the average pressure driving organ perfusion and must generally stay above about 60–65 mmHg.
• Q: What is orthostatic hypotension and how do you test for it? A: A fall of ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 minutes of standing; measure BP and pulse lying, sitting and standing, and record the position with each reading.
• Q: How do fever and hypothermia differ from hyperthermia in management? A: Fever is a hypothalamic set-point rise and responds to antipyretics plus fluids; hyperthermia such as heat stroke is thermoregulatory failure and needs rapid physical cooling, since antipyretics do not work; hypothermia below 35 °C needs gradual rewarming with core temperature monitoring.
• Q: A patient is found with BP 190/120 mmHg and a headache. What do you do? A: Recheck with a correct cuff on the other arm after rest, keep the patient calm and upright, assess for chest pain, visual and neurological signs, and inform the doctor immediately as this may be a hypertensive emergency.

Common mistakes

• Quoting adult normal ranges for infants and children — paediatric pulse and respiratory rates are much higher and systolic BP lower.
• Taking BP over clothing, with the arm unsupported or below heart level, or without the 5-minute rest — all shift the reading by 5–15 mmHg.
• Deflating the cuff too fast (more than 2–3 mmHg/s) or re-inflating without full deflation, giving a low systolic and high diastolic reading.
• Counting pulse or respiration for 15 seconds and multiplying by 4 when the rhythm is irregular, which magnifies the error fourfold.
• Recording a temperature without noting the site (oral, axillary, rectal, tympanic), so the 0.5 °C correction cannot be applied.
• Trusting SpO₂ alone and missing hypoventilation, shock, anaemia or carbon monoxide poisoning.
• Charting values later from memory, rounding BP to the nearest 10 mmHg, or recording a value that was not actually measured — a documentation and professional-conduct failure.
• Observing an abnormal value, charting it correctly, but not reporting or acting on it.

Related topics

Health assessment and physical examination · Fluid and electrolyte balance · Oxygenation and oxygen therapy · Shock and haemodynamic monitoring · Hypertension and cardiovascular nursing · Paediatric growth, development and assessment