Feedback control: Temperature and other vital signs Flashcards
What are the commonly assessed vital signs?
Pulse HR (60-100)
BP
Temp
RR (12-20)
CRT <2 sec
Oxygen saturation >95%
Consciousness AVPU
What is the outer shell of the human body?
Skin and subcutaneous tissue
What it the core body temp?
37.8
What is normothermia?
Core body temperature that is optimal for cellular metabolism and function
what does increased core body temperature do?
Speeds up cellular metabolism
What does overheating cause?
Protein denaturation
Nerve malfunction
Convulsions
Death
What does decreased body temperature do?
Slows down cellular response
Fatally slow down the metabolism
List the sites for body temperature monitoring?
Ear drum (tympanic) -35.5-37.5
Rectal
-36.7-37.5
Oral
How does normal body temperature vary?
> Differ slightly in different individuals
> Varies slightly during the day (lowest temperature in early morning) - diurnal variation in body temperature
> May be altered by activity, emotions, exercise, or exposure to extremes of temperature
> Varies slightly during menstrual cycle in menstruating females (higher during the 2nd half of cycle from the time of ovulation)
How can heat gain happen?
From internal environment
>metabolic heat
From external environment
>radiation
>convection
>conduction
How can heat loss happen?
To external environment >convection >conduction >radiation >evaporation
What is metabolic heat?
Oxidation of metabolic fuel derived from food in body
What is BMR?
Basal Metabolic Rate - BMR (minimum amount of energy required to sustain vital body functions) leads to basic level of Heat Production
What increases BMR?
hormones such as adrenaline, noradrenaline, and thyroxine
How can metabolic heat be increased?
> Muscle Activity and hence metabolic heat production can be increased enormously
> Shivering increases heat production by increasing Muscle Activity
Where is nonshiverisg thermogenesis?
Brown fat
Describe radiation?
Emission of heat energy in the form of electromagnetic waves from a surface
Electromagnetic waves travel through the space and transformed into heat on striking another surface
The human body both emits and absorbs radiant heat
What does net heat transfer depend upon?
relative temperature of body and surrounding objects (including the sun)
How important is radiation in humans?
half the body’s heat loss is through radiation
Describe conduction?
Transfer of heat between objects in contact
Heat moves from warmer to cooler object
What does heat conduction depend upon?
temperature gradient and thermal conductivity (e.g. water is a better thermal conductor than air)
How important is conduction in humans?
a small percentage of total heat exchange takes place through conduction alone
Describe convection?
Transfer of heat energy by air (or water) currents that help to carry the heat away from the body
Combines with conduction to dissipate heat from the body
Air next to the skin warmed by conduction, warmed air becomes less dense and rises while cooler air moves in next to the skin
Forced air movement across the body surface (caused by e.g. wind or a fan) increases the combined effect of conduction-convection
Forced air movement allow a greater total amount of heat to be carried away from the body in a given period of time - the wind chill factor
Air trapping clothing reduces convection
Describe evaporation
Energy is required to convert water in the skin surface and the lining of the respiratory airways into vapour
This energy comes from the body resulting in evaporative heat loss and hence cooling of the body
