Vital signs are the most basic and universal physiological indicators of a person's health status. Their correct measurement, interpretation, and documentation is one of the most important responsibilities of a nursing professional. Knowing normal ranges by age group and recognizing alarm values enables rapid response to clinical deterioration.
Heart Rate (HR)
Normal heart rate varies significantly with age. In general, the younger the patient, the higher the normal resting heart rate.
| Age Group | Normal HR (bpm) | Bradycardia | Tachycardia |
|---|---|---|---|
| Newborn (0–28 days) | 100 – 160 | < 100 | > 160 |
| Infant (1–12 months) | 90 – 150 | < 90 | > 150 |
| Toddler / preschool (1–5 yr) | 80 – 130 | < 80 | > 130 |
| School-age (6–12 yr) | 70 – 110 | < 70 | > 110 |
| Adolescent (13–18 yr) | 60 – 100 | < 60 | > 100 |
| Adult | 60 – 100 | < 60 | > 100 |
| Older adult (> 65 yr) | 60 – 100 | < 60 | > 100 |
Blood Pressure (BP)
Adult BP values are defined by international guidelines (AHA/ESC 2018). In pediatrics, ranges are defined by percentiles based on age, sex, and height.
| Classification (adults) | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | < 120 | < 80 |
| Elevated | 120 – 129 | < 80 |
| Hypertension Stage 1 | 130 – 139 | 80 – 89 |
| Hypertension Stage 2 | ≥ 140 | ≥ 90 |
| Hypertensive crisis | > 180 | > 120 |
| Hypotension | < 90 | < 60 |
| Shock (severe hypotension) | < 70 | — |
Respiratory Rate (RR)
Respiratory rate is the vital sign most sensitive to clinical deterioration — and paradoxically the least accurately documented in practice. It should be measured for at least 30 seconds, observing chest movement.
| Age Group | Normal RR (breaths/min) | Bradypnea | Tachypnea |
|---|---|---|---|
| Newborn | 30 – 60 | < 30 | > 60 |
| Infant | 24 – 40 | < 24 | > 40 |
| Child (1–8 yr) | 18 – 30 | < 18 | > 30 |
| Adolescent | 12 – 20 | < 12 | > 20 |
| Adult | 12 – 20 | < 12 | > 20 |
Body Temperature
Normal temperature varies by measurement site. Oral temperature is generally 0.3–0.5 °C lower than rectal, and axillary up to 0.5 °C lower than oral.
| Category | Temperature (oral) |
|---|---|
| Severe hypothermia | < 32 °C (89.6 °F) |
| Moderate hypothermia | 32 – 35 °C (89.6 – 95 °F) |
| Mild hypothermia | 35 – 36 °C (95 – 96.8 °F) |
| Normal | 36 – 37.5 °C (96.8 – 99.5 °F) |
| Low-grade fever | 37.5 – 38 °C (99.5 – 100.4 °F) |
| Fever | 38 – 40 °C (100.4 – 104 °F) |
| Hyperpyrexia | > 40 °C (104 °F) |
Oxygen Saturation (SpO₂)
Pulse oximetry provides non-invasive measurement of peripheral oxygen saturation. It is a complement — not a substitute — for arterial blood gas analysis.
| Classification | SpO₂ | Action |
|---|---|---|
| Normal | ≥ 95% | Routine monitoring |
| Acceptable lower limit | 92 – 94% | Close monitoring, consider supplemental O₂ |
| Hypoxemia | 88 – 91% | Administer O₂, evaluate cause |
| Severe hypoxemia | < 88% | Urgent oxygen therapy, consider ventilatory support |
Common Causes of Vital Sign Abnormalities
| Vital Sign | Elevated: common causes | Low: common causes |
|---|---|---|
| HR | Fever, pain, hypovolemia, anxiety, arrhythmia, hyperthyroidism | Trained athletes, beta-blockers, AV block, hypothyroidism |
| BP | Essential hypertension, pain, anxiety, fluid retention | Hemorrhage, dehydration, sepsis, anaphylaxis, antihypertensives |
| RR | Respiratory infection, sepsis, metabolic acidosis, pain, anxiety | Excessive sedation, opioids, high cervical spinal cord injury |
| Temperature | Infection, inflammation, heat stroke, transfusion reaction | Cold exposure, advanced sepsis, severe hypothyroidism |
| SpO₂ | — | Pneumonia, bronchospasm, PE, COPD, pulmonary edema |
Conclusion
Vital signs are the most direct window into a patient's physiological status. Measuring them correctly, interpreting values in clinical context, and identifying alarm signs are skills every healthcare professional must master. An abnormal respiratory rate or a drop in oxygen saturation may be the first sign of a deterioration that is still reversible — if caught in time.