Vital Signs: Measurement and Interpretation

Vital Signs

Overview of Vital Signs

Vital signs are key physiological measurements used to assess the health status of individuals. They provide critical information about the functioning of the body's most essential systems.

• Temperature (T): Indicates the body's thermal state.

• Pulse (P): Reflects heart rate and rhythm.

• Respiration (R): Measures breathing rate and quality.

• Blood Pressure (BP): Assesses the force of blood against arterial walls.

• Pain: Often considered the fifth vital sign.

• Pulse Oximetry: Measures oxygen saturation in the blood.

When to Assess Vital Signs

• Upon admission to a healthcare facility

• According to institutional policy

• When there is a change in patient condition

• After loss of consciousness

• Before and after surgical or invasive procedures

• Before and after activities that may increase risk (e.g., ambulation post-surgery)

• Before administering medications affecting cardiovascular or respiratory function

Normal Ranges for Vital Signs in Healthy Adults

• Oral Temperature: 35.8–37.5°C (96.4–99.5°F)

• Pulse Rate: 60–100 beats/min (80 average)

• Respirations: 12–20 breaths/min

• Blood Pressure: <120/80 mm Hg

Body Temperature

Heat Production

Body heat is primarily generated through metabolism. Hormones, muscle activity, and exercise increase metabolic rate, thus raising heat production.

• Epinephrine and Norepinephrine: Released to increase metabolism and heat production.

• Thyroid Hormone: Elevates metabolic rate.

• Shivering: Increases heat production via muscle activity.

Sources of Heat Loss

• Skin: Primary site for heat loss.

• Evaporation of Sweat: Removes heat as sweat evaporates.

• Respiratory Tract: Warming and humidifying inspired air.

• Urine and Feces: Elimination contributes to heat loss.

Transfer of Body Heat to External Environment

• Radiation: Diffusion of heat via electromagnetic waves (e.g., heat lost from an uncovered head).

• Convection: Transfer of heat by air or fluid movement.

• Evaporation: Conversion of liquid (sweat) to vapor.

• Conduction: Direct transfer of heat to another object.

Factors Affecting Body Temperature

• Circadian Rhythms: Daily fluctuations in temperature.

• Age and Gender: Children and elderly may have different baseline temperatures; hormonal differences affect temperature.

• Physical Activity: Increases metabolic rate and heat production.

• State of Health: Illness can alter temperature.

• Environmental Temperature: External conditions influence body temperature.

Fever

• Afebrile: Without fever.

• Pyrexia (Febrile): With fever.

• Intermittent Fever: Returns to normal at least once every 24 hours.

• Remittent Fever: Does not return to normal, fluctuates up and down.

• Sustained/Continuous Fever: Remains above normal with minimal variation.

• Relapsing/Recurrent Fever: Returns to normal for one or more days, then recurs.

Types of Thermometers and Equipment

• Electronic and digital thermometers

• Tympanic membrane thermometers

• Disposable single-use thermometers

• Temporal artery thermometers

• Automated monitoring devices

Normal Temperatures by Site

Site	Temperature (°C)	Temperature (°F)
Oral	35.9–37.5	96.6–99.5
Rectal	36.3–38.1	97.4–100.5
Axillary	35.4–36.9	95.6–98.5
Tympanic	36.8–38.3	98.2–100.9
Forehead (Temporal Artery)	36.3–38.1	98.7–100.5

Pulse

Regulation of Pulse

The pulse is regulated by the autonomic nervous system via the cardiac sinoatrial (SA) node.

• Parasympathetic Stimulation: Decreases heart rate.

• Sympathetic Stimulation: Increases heart rate.

• Pulse Rate: Number of heart contractions per minute over a peripheral artery.

Characteristics of Peripheral Pulse

• Rate: Normal, tachycardia (fast), bradycardia (slow).

• Amplitude and Quality: Strength (strong or weak).

• Rhythm: Regularity of beats.

• Stroke Volume: Volume of blood ejected with each heartbeat.

Pulse Strength (Amplitude) Grading

Grade	Description
0	Absent, unable to palpate
+1	Diminished, weaker than expected
+2	Normal; brisk, expected
+3	Bounding

Sites for Detecting Pulse

• Temporal: Side of the head

• Radial: Wrist

• Femoral: Groin

• Brachial: Inner elbow

Respiration

Mechanisms of Respiration

Respiration involves ventilation, diffusion, and perfusion.

• Ventilation: Movement of air in and out of lungs (inhalation and exhalation).

• Diffusion: Exchange of oxygen and carbon dioxide between alveoli and blood.

• Perfusion: Exchange of gases between blood and tissue cells.

Control of Breathing

• Respiratory centers in the medulla and pons regulate rate and depth.

• Chemoreceptors respond to changes in blood gases.

• Increase in carbon dioxide is the most powerful stimulant for breathing.

Respiratory Rates and Terms

• Eupnea: Normal, unlabored respiration; typically one respiration to four heartbeats.

• Tachypnea: Increased respiratory rate.

• Bradypnea: Decreased respiratory rate.

• Apnea: Absence of breathing.

• Dyspnea: Difficult or labored breathing.

• Orthopnea: Difficulty breathing except in upright position.

Blood Pressure

Definition and Measurement

Blood pressure is the force exerted by circulating blood upon the walls of blood vessels. It is measured in millimeters of mercury (mm Hg).

• Systolic Pressure: Maximum pressure during ventricular contraction.

• Diastolic Pressure: Lowest pressure during ventricular relaxation.

• Pulse Pressure: Difference between systolic and diastolic pressure.

Formula:

• $\text{Pulse Pressure} = \text{Systolic Pressure} - \text{Diastolic Pressure}$

Regulation of Blood Pressure

• Neural Regulation: Baroreceptors in heart and arteries signal the cardiovascular center in the brain.

• Humoral Regulation: Renin–angiotensin–aldosterone system increases blood pressure.

• Cardiac Output: Strength of heart contractions affects blood pressure.

• Vagus Nerve: Parasympathetic impulses slow heart rate.

• Sympathetic Stimulation: Increases heart rate.

Factors Affecting Blood Pressure

• Age

• Race

• Circadian rhythm

• Biologic sex

• Food intake

• Exercise

• Weight

• Emotional state

• Body position

• Drugs/medications

Decreased Blood Pressure

• Hypotension: Blood pressure <90/60 mm Hg

• May result from disease, medication, or inability to maintain normal pressure

• Orthostatic Hypotension: Drop in blood pressure upon standing; caused by dehydration, blood loss, or neurologic/cardiovascular/endocrine issues

Equipment for Assessing Blood Pressure

• Stethoscope and sphygmomanometer

• Doppler ultrasound

• Electronic or automated devices

Assessing Blood Pressure

• Listen for Korotkoff sounds with stethoscope

• First sound: Systolic pressure

• Change or cessation of sounds: Diastolic pressure

• Brachial and popliteal arteries commonly used

Summary Table: Vital Signs Normal Ranges

Vital Sign	Normal Range
Oral Temperature	35.8–37.5°C (96.4–99.5°F)
Pulse Rate	60–100 beats/min
Respirations	12–20 breaths/min
Blood Pressure	<120/80 mm Hg

Examples and Applications

• Example: A patient with a temperature of 38.5°C is considered febrile (pyrexia).

• Application: Monitoring vital signs before and after surgery helps detect complications early.