Vital Signs: Body Temperature

• Vital signs are procedures that measure basic physiological functions, including temperature, pulse, respiration, and blood pressure.

Body Temperature

• Core temperature is the temperature of deep body tissues like the abdominal and pelvic cavities.
• Surface temperature is the temperature of the skin, subcutaneous tissue, and fat, which fluctuates with the environment.

Factors Affecting Body Heat Production

• Basal Metabolic Rate (BMR) is the energy utilization rate required for essential activities like breathing.
• Muscle activity increases the metabolic rate.
• Increased thyroxine output raises the cellular metabolism rate.
• Epinephrine and norepinephrine increase cellular metabolism in body tissues.
• Fever increases the cellular metabolic rate, raising body temperature.

Regulation of Body Temperature

• The body temperature regulation system consists of sensors, an integrator, and an effector system.
• Sensors in the periphery and core detect temperature changes.
• The hypothalamus acts as the integrator.
• The effector system adjusts heat production and loss.
• Skin sensors are more efficient at detecting cold than warmth.
• Shivering increases heat production, sweating is inhibited to decrease heat loss, and vasoconstriction decreases heat loss.

Alterations in Body Temperature

• Normal adult body temperature ranges from 36°C to 37.5°C.
• Pyrexia (hyperthermia or fever) is a body temperature above the normal range.
• Hypothermia is a core body temperature below the lower limit of normal.

Assessing Body Temperature

• Common sites for measuring body temperature include oral, rectal, axillary, tympanic membrane, and skin/temporal artery.
• Rectal readings are considered very accurate.
• The axillary site is often preferred for newborns due to its accessibility and safety.
• The tympanic membrane site is readily accessible, reflects core temperature, and is very fast.
• The temporal artery site is safe, noninvasive, and very fast.
• Temperature scales include Centigrade and Fahrenheit.

Pulse

• A pulse is a wave of blood caused by the contraction of the heart's left ventricle.
• A peripheral pulse is located away from the heart.
• An apical pulse is a central pulse located at the apex of the heart.

Pulse Sites

• Temporal: where the temporal artery passes over the temporal bone of the head.
• Carotid: at the side of the neck where the carotid artery runs between the trachea and the sternocleidomastoid muscle.
• Apical: at the apex of the heart.
• Brachial: at the inner aspect of the biceps muscle of the arm or medially in the antecubital space.
• Radial: where the radial artery runs along the radial bone, on the thumb side of the inner aspect of the wrist.
• Femoral: where the femoral artery passes alongside the inguinal ligament.
• Popliteal: where the popliteal artery passes behind the knee.
• Posterior tibial: on the medial surface of the ankle where the posterior tibial artery passes behind the medial malleolus.
• Dorsalis pedis: where the dorsalis pedis artery passes over the bones of the foot.

Factors Affecting the Pulse

• Age: Pulse rate decreases with age.
• Gender: After puberty, the male pulse rate is typically lower than the female pulse rate.
• Exercise: Pulse rate increases with activity.
• Fever: Increases pulse rate, which in turn increases heart rate.
• Stress: Increases heart rate.
• Positioning change: Can increase heart rate.
• Normal range for adults: 60-100 beats/min.

Considerations Before Assessing Pulse

• Ensure the patient is in a comfortable and relaxed position.
• Note any medications that may affect heart rate.
• If the patient has been physically active, wait 10-15 minutes before taking a pulse.

Assessing the Pulse

• Pulse rate (60-100 bpm, average 72 bpm for adults)
• Rhythm (regular pattern of beats and intervals)
• Volume (force of the pulse beat)
  • Absent Pulse (0): None felt
  • Thready Pulse (1): Difficult to feel, disappears with slight pressure
  • Weak Pulse (2): Somewhat stronger than thready, disappears with light pressure
  • Normal Pulse (3): Easily felt, disappears with moderate pressure
  • Bounding Pulse (4): Full and spring-like, even under moderate pressure
• Arterial wall elasticity: Normal artery feels straight, smooth, and soft.
• Presence or absence of bilateral equality

Respiration

• Respiration involves ventilation, which is the movement of gases in and out of the lungs.
• Inhalation (inspiration) is the act of breathing in.
• Exhalation (expiration) is the act of breathing out.
• Normal breathing is almost invisible, effortless, quiet, automatic, and regular.

During Inhalation

• The diaphragm contracts.
• The ribs move upward and outward.
• The sternum moves outward.
• The thorax enlarges, allowing the lungs to expand.

During Exhalation

• The diaphragm relaxes.
• The ribs move downward and inward.
• The sternum moves inward.
• The thorax size decreases.
• The lungs are compressed.

Normal Respiratory Rates

• Neonate: 36-60 breaths/min
• Infant: 40-46 breaths/min
• Toddler: 20-30 breaths/min
• School age (6-10 years): 22-24 breaths/min
• Adolescent (10-18 years): 16-22 breaths/min
• Adult: 12-20 breaths/min

Factors Affecting Respiration

• Factors that increase respiratory rate:
  • Exercise
  • Stress
  • Lower oxygen concentration
• Factors that decrease respiratory rate:
  • Medications (narcotic drugs)
  • Increased intracranial pressure

Assessing Respiration

• Respiratory rate (breaths per minute), normal range 12 to 20 breaths/min
  • Bradypnea: slow breathing (usually less than 10-12/min in adult)
  • Tachypnea: fast respiratory rate (usually above 20-24/min in adult)
  • Apnea: the absence of breathing
• Respiratory depth
  • Deep respiration: involves a large volume of air inhaled and exhaled
  • Shallow respiration: involves the exchange of a small amount of air

Blood Pressure

• Blood pressure is the measure of pressure exerted by blood as it flows through the arteries.
• Systolic blood pressure is the pressure of the blood as a result of the contraction of the ventricles.
• Diastolic blood pressure is the pressure when the ventricles are at rest.
• Pulse pressure is the difference between the systolic and diastolic pressure.

Normal Blood Pressure Range

• Systolic: 100-140 mmHg
• Diastolic: 60-90 mmHg
• Hypertension: blood pressure persistently above the normal range.
• Hypotension: blood pressure below the normal range.
• Orthostatic hypotension: blood pressure falls when the client sits or stands.

Factors Influencing Blood Pressure

• Age
• Stress
• Ethnicity
• Gender
• Daily Variations
• Medications
• Activity, weight
• Smoking

Hypertension

• More common than hypotension
• Can cause Thickening of walls.
• Loss of elasticity.
• Family history of hypertension is a risk factor.

Hypotension

• Systolic pressure below 90 mm Hg
• Can result from Dilation of arteries.
• Loss of blood volume.
• Decrease of blood flow to vital organs.
• Orthostatic/postural hypotension may occur.

Measurement of Arterial Oxygen Saturation

• Pulse oximeter allows indirect measurement of oxygen saturation.
• SpO2 is a reliable estimate of SaO2.
• Measurement is affected if the extremity is cold, edematous, or if nail polish is present.