2.2 Vital Signs: Temperature, Pulse, Respiration, and Blood Pressure

2.2 Vital Signs: Temperature, Pulse, Respiration, and Blood Pressure

Clinical Pillar: Vital signs—temperature, pulse, respiration, and blood pressure (along with pain assessment and oxygen saturation as additional parameters)—provide critical baseline data regarding a patient's cardiovascular, respiratory, and metabolic homeostasis.

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Normal Baseline Vital Signs Across the Lifespan

Vital sign expectations change dramatically from infancy to adulthood due to physiological maturation.

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Body Temperature (T)

Body temperature reflects the balance between heat produced by metabolic activity and heat lost to the environment, regulated by the hypothalamus.

Temperature Routes & Clinical Considerations

• Oral (O): Standard route for older children and adults. Thermometer probe placed in the posterior sublingual pocket. Normal: 98.6°F (37.0°C). Wait 15–30 minutes if patient consumed hot/cold liquids or smoked.
• Tympanic (T/TM): Measures infrared heat emitted by the tympanic membrane (shares blood supply with hypothalamus). Pull ear pinna up and back for adults, down and back for children under 3 years.
• Temporal Artery (TA): Non-invasive scanner swiped across forehead to hair line and touched behind earlobe. Highly accurate, reflecting core vascular temperature.
• Axillary (AX): Probe placed in dry axilla with arm adducted. Reads 1.0°F (0.6°C) lower than oral (Normal: ~97.6°F). Least accurate, used when other routes are contraindicated.
• Rectal (R): Gold standard core body temperature. Reads 1.0°F (0.6°C) higher than oral (Normal: ~99.6°F). Lubricated probe inserted 1 inch for adults, 1/2 inch for infants.
  • Contraindications: Cardiac patients (risk of vagal nerve stimulation causing severe bradycardia), neutropenic patients, bleeding disorders, or rectal surgery/anomalies.

Temperature Classifications

• Afebrile: Absence of fever.
• Pyrexia / Febrile: Body temperature exceeding 100.4°F (38.0°C).
• Hyperpyrexia: Extreme fever exceeding 105.8°F (41.0°C); medical emergency.
• Hypothermia: Core body temperature dropping below 95.0°F (35.0°C).

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Pulse (P)

Pulse represents the expansion and recoil of an artery as the left ventricle contracts, pumping blood into the systemic circulation.

Anatomical Pulse Sites

1. Radial: Located on the thumb side of the wrist; most common site for routine adult assessment.
2. Apical: Auscultated with a stethoscope at the 5th intercostal space, left midclavicular line for 1 full minute. Required for infants, patients taking cardiac medications (e.g., digoxin), or when radial pulse is irregular.
3. Brachial: Located in the antecubital fossa; primary site for blood pressure measurement and infant CPR pulse check.
4. Carotid: Located along the anterior border of the sternocleidomastoid muscle in the neck; emergency site during CPR/collapse.
5. Femoral, Popliteal, Posterior Tibial, Dorsalis Pedis: Lower extremity sites evaluated to assess peripheral arterial circulation.

Pulse Characteristics

• Rate: Normal adult rate is 60 to 100 beats per minute (bpm).
  • Bradycardia: Heart rate < 60 bpm.
  • Tachycardia: Heart rate > 100 bpm.
• Rhythm: Pattern of beats (regular vs. irregular/dysrhythmia).
• Volume / Force (Pulse Amplitude):
  • 0: Absent (non-palpable)
  • 1+: Weak, thready, easily obliterated
  • 2+: Normal, easily palpable
  • 3+: Full, bounding, hyperdynamic

Respirations (R)

Respiration is the mechanism of gas exchange involving inspiration (inhalation of oxygen) and expiration (exhalation of carbon dioxide). One full breath equals one inspiration plus one expiration.

Assessment Technique

Evaluate respirations covertly while pretending to count the radial pulse so the patient does not involuntarily alter their breathing pattern. Count for 30 seconds and multiply by 2 (or count for 60 seconds if irregular).

Respiratory Rates & Abnormal Patterns

• Eupnea: Normal, unlabored breathing (12–20 breaths per minute in adults).
• Tachypnea: Respiratory rate > 20 rpm.
• Bradypnea: Respiratory rate < 12 rpm.
• Apnea: Temporary cessation of breathing.
• Dyspnea: Difficult, painful, or labored breathing.
• Orthopnea: Ability to breathe comfortably only in an upright position.
• Cheyne-Stokes Respirations: Rhythmic pattern characterized by alternating periods of deep, rapid breathing followed by apnea; commonly seen in end-stage heart failure, brain injury, or impending death.
• Kussmaul Respirations: Rapid, deep, sighing respirations without pauses; classic sign of diabetic ketoacidosis (DKA) to blow off excess carbon dioxide.

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Blood Pressure (BP)

Blood pressure measures the force exerted by circulating blood against the arterial walls during cardiac contraction (Systolic) and cardiac relaxation (Diastolic).

Korotkoff Sounds

When deflating an auscultatory BP cuff, five distinct phases of sound are identified:

• Phase I: Clear, crisp tapping sound. The first sound heard marks the Systolic Blood Pressure (SBP).
• Phase II: Soft swishing or murmuring quality.
• Phase III: Crisp, louder tapping sound.
• Phase IV: Muffled, soft blowing sound.
• Phase V: Complete disappearance of sound. Marks the Diastolic Blood Pressure (DBP) in adults.

Equipment Sizing & Technical Pitfalls

• Cuff Selection: The inflatable bladder length must encircle at least 80% of the patient's arm circumference, and the bladder width must equal 40% of the arm circumference.
• Cuff Sizing Errors:
  • Cuff too small / narrow: Yields falsely high BP reading.
  • Cuff too large / wide: Yields falsely low BP reading.
  • Arm below heart level: Falsely high reading.
  • Deflating cuff too fast (>2–3 mmHg/sec): Underestimates systolic, overestimates diastolic.

AHA / ACC 2017 Hypertension Guidelines

• Orthostatic Hypotension: A drop in SBP of ≥ 20 mmHg or DBP of ≥ 10 mmHg within 3 minutes of moving from a lying/sitting position to a standing position, accompanied by dizziness or tachycardia.