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 vital systems and are routinely monitored in healthcare settings.

• 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

Vital signs should be assessed:

• On admission to any 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 activity that may increase risk (e.g., ambulation after 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 and Loss

The body maintains temperature through a balance of heat production and heat loss.

• Heat Production: Primarily from metabolism; increased by hormones (epinephrine, norepinephrine, thyroid hormone), muscle activity, and shivering.

• Heat Loss: Mainly through the skin, evaporation of sweat, warming/humidifying inspired air, and elimination via urine and feces.

Mechanisms of Heat Transfer

Body heat is transferred to the environment by:

• Radiation: Loss of heat via electromagnetic waves (e.g., uncovered head in cold).

• Convection: Heat transfer 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

• Age and gender

• Physical activity

• State of health

• Environmental temperature

Fever Types and Terminology

• Afebrile: Without fever

• Pyrexia (Febrile): With fever

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

• Remittent Fever: Fluctuates but does not return to normal

• 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

Pulse

Regulation and Measurement

Pulse is regulated by the autonomic nervous system via the cardiac sinoatrial node.

• Parasympathetic stimulation: Decreases heart rate

• Sympathetic stimulation: Increases heart rate

• Pulse Rate: Number of heart contractions per minute

Characteristics of Peripheral Pulse

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

• Amplitude and Quality: Strong or weak

• Rhythm: Regularity of beats

• Stroke Volume: Volume of blood ejected with each heartbeat

Pulse Strength (Amplitude) Grading

Common Pulse Sites

• Temporal: Side of the head

• Radial: Wrist

• Brachial: Inner elbow

• Femoral: Groin

Respiration

Respiratory Processes

Respiration involves the movement and exchange of gases in the body.

• Ventilation: Movement of air in and out of lungs

• Inhalation: Breathing in

• Exhalation: Breathing out

• Diffusion: Exchange of O2 and CO2 between alveoli and blood

• Perfusion: Exchange of O2 and CO2 between blood and tissue cells

Control of Breathing

• Rate and depth change in response to tissue demands

• Controlled by respiratory centers in the medulla and pons

• Activated by impulses from chemoreceptors

• Increase in CO2 is the most powerful respiratory stimulant

Respiratory Rates and Terms

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

• Tachypnea: Increased respiratory rate

• Bradypnea: Decreased respiratory rate

• Apnea: Periods when no breathing occurs

• Dyspnea: Difficult or labored breathing

• Orthopnea: Changes in breathing when sitting or standing

Blood Pressure

Definition and Measurement

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

• Systolic Pressure: Maximum pressure during left ventricular contraction

• Diastolic Pressure: Lowest pressure when the heart rests between beats

• Pulse Pressure: Difference between systolic and diastolic pressure

Regulation of Blood Pressure

• Short-term regulation: Neural (nerves) or humoral (body fluids)

• Cardiac output affects blood pressure

• Vagus nerve stimulation slows heart rate

• Sympathetic stimulation increases heart rate

• Baroreceptors monitor pressure and signal the cardiovascular center

• Renin–angiotensin–aldosterone system raises pressure

Factors Affecting Blood Pressure

• Age

• Race

• Circadian rhythm

• Biologic sex

• Food intake

• Exercise

• Weight

• Emotional state

• Body position

• Drugs/medications

Decreased Blood Pressure

• Hypotension: <90/60 mm Hg

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

• Orthostatic Hypotension: Inadequate response to position changes; occurs when rising to an erect position

• Caused by dehydration, blood loss, or neurologic, cardiovascular, or endocrine problems

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

Parts of a Sphygmomanometer

• Three sizes of cuffs to accommodate different arm circumferences

Summary Table: Vital Signs Normal Ranges

Key Equations

• Pulse Pressure:

• Mean Arterial Pressure (MAP):

• Cardiac Output:

Examples and Applications

• Example: A patient with a blood pressure of 130/85 mm Hg has a pulse pressure of 45 mm Hg.

• Application: Monitoring vital signs helps detect early changes in health status and guides clinical decision-making.