Vital Sign Temperature:
Vital Sign Temperature or Body temperature is an indicator of the heat present within an individual's body. The vital sign temperature is influenced by the balance between the heat generated by metabolic processes within the body and the heat lost through various mechanisms such as radiation, conduction, convection, and evaporation.
When we refer to normal body temperature, particularly when measured orally, it's typically measured as around 37 degrees Celsius or 98.6 degrees Fahrenheit. This temperature reading has been considered the average or baseline for human body temperature. However, it's important to note that individual variations in body temperature can exist, influenced by factors such as age, activity level, hormonal fluctuations, and time of day. We will be discussing all these factors influencing the vital sign temperature and methods of measuring vital sign temperature in the content below.
What are Vital Signs?
Vital signs are indicators of the body's physiological condition and offer information about the physiological condition of the body and play an important role in assessing its state of balance or equilibrium, known as homeostasis. These signs are termed 'vital' because they provide the most distinct and reliable information about an individual's overall health status. The four most important vital signs are:
-
Body temperature
-
Pulse rate
-
Breathing rate
-
Blood pressure
Types of Body Temperature
There are generally two types of body temperature, which are discussed below.
Core Temperature:
-
This represents the temperature of the body's deep-seated tissues, including vital areas such as the cranium (skull), thorax (chest), abdominal cavity, and pelvic cavity.
-
The core temperature usually remains relatively constant, serving as an indicator of the body's internal thermal balance.
-
When we refer to measuring body temperature with a thermometer, it's typically the core temperature that we're assessing.
Surface Temperature:
-
Surface temperature refers to the temperature of the outer layers of the body, including the skin, subcutaneous tissue (tissue beneath the skin), and adipose (fat) tissue.
-
Unlike core temperature, surface temperature can vary more readily in response to environmental factors, physical activity, and circulation dynamics.
Method to Measure Body Temperature
A person's body temperature can be measured in any of the following ways:
Orally:
A digital thermometer that measures body temperature using an electronic probe can be used to take a temperature orally.
Rectally:
When measured rectally, temperatures are typically 0.5°F to 0.7°F higher than when measured orally. Babies are more likely to experience this because their bodies are not as effective at regulating their body temperature as those of older children or adults.
Axillary:
A digital thermometer can be used to take temperatures under the arm. This method often gives temperatures that are 0.3°F to 0.4°F lower than oral measurement.
Tympanic:
The tympanic temperature is measured by putting a thermometer on the patient’s outer ear canal. Many pediatric and intensive care units use this type of thermometer because it records a temperature so rapidly in just 1 to 2 seconds.
Changes in Vital Sign Temperature
Typical body temperature averages 37.0°C or 98.6°F, with a normal range from 36-38°C (96.8–100°F). Different terms used for changes in body temperature are:
Pyrexia: Pyrexia indicates a temperature crossing these normal limits, ranging from 38-41°C (100.4–105.8°F).
Hyperpyrexia:
Hyperpyrexia denotes an extremely elevated fever, exceeding 41°C (>42°C), potentially leading to fatal outcomes.
Hypothermia:
Hypothermia occurs when the body temperature falls between 34-35°C; temperatures below 34°C can result in death.
What is Heat Loss in the Human Body?
Heat loss in the human body refers to the process by which excess heat generated by metabolic processes is transferred from the body to the surrounding environment in order to maintain a stable internal temperature. Roughly 90% of heat loss occurs through the skin, making it the primary organ involved in heat loss.
Mechanism of Heat Loss in the Human Body
Heat loss from the body occurs through four primary mechanisms: radiation, evaporation, convection, conduction, and evaporation.
Radiation:
The majority of heat loss, around 60%, is through radiation, where heat from the body's core tissues is emitted as infrared rays through the skin, driven by temperature differences between the body and the environment.
Evaporation:
Accounting for approximately 22% of heat loss, involves the conversion of water into vapor, which consumes energy and facilitates heat dissipation, even without sweating. It becomes important for cooling when the environmental temperature exceeds that of the skin, or when radiation and convection are insufficient.
Conduction and Convection:
Conduction and convection contribute around 15% of heat loss, involving the transfer of heat through direct contact with surfaces or through the movement of air or water over the skin, respectively.
Factors Affecting Vital Sign Temperature (Body Temperature)
The following factors have a direct effect on the body temperature:
Age:
-
Children experience more fluctuations in body temperature compared to adults until they reach puberty.
-
Elderly individuals, especially those aged 75 and above, are more vulnerable to hypothermia due to age-related changes in thermoregulation.
Diurnal Variations (Circadian Rhythms):
-
Body temperature undergoes rhythmic changes throughout the day, influenced by circadian rhythms.
-
The peak temperature usually occurs between 8:00 p.m. and midnight, while the lowest temperature is observed during the sleep phase, typically between 4:00 and 6:00 a.m.
Exercise:
-
Engaging in physical activity can considerably raise body temperature, sometimes reaching levels of 38.3–40°C when measured rectally. This increase is a result of increased metabolic activity during exercise.
Hormones:
-
Hormonal fluctuations, such as increased progesterone levels in women during ovulation, can lead to a slight elevation in body temperature, typically ranging from 0.3–0.6°C above the normal temperature.
Stress:
-
Stressful situations can trigger the release of stress hormones like epinephrine and norepinephrine, which stimulate metabolic activity and thus increase heat production in the body.
Environment:
-
Environmental factors, particularly extreme temperatures, can disrupt the body's ability to regulate its temperature effectively.
