Fundamentals of Nursing · Vital Signs

Indicators of Physiologic Functioning

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In 30 seconds
Why this matters
The college version
Eli explains
Worked example
Key takeaway
Check yourself
Study tools
Sources & references

In 30 seconds

are the classic indicators of physiologic functioning: temperature, , respirations, blood pressure, oxygen saturation, and pain. Each one is a window into a specific system — thermoregulation, the heart, breathing, circulation, and oxygen delivery — and together they give a fast, repeatable picture of how the body is doing right now.

Three ideas organize this topic. First, each vital sign reflects one part of physiology, so interpreting it requires knowing what it measures. Second, a single reading is almost meaningless without context and trend — the same pulse can be normal for one person and alarming for another, so nurses compare each reading to the patient's . Third, vital signs are measurements, not diagnoses: they raise questions and guide next steps, but they never tell you what is wrong by themselves.

One caution applies throughout this chapter: reference values vary by age, route, and source, and institutions use their own standards. Always follow your program's and facility's values and policies.

Why this matters

Vital signs are the most frequently collected data in health care and the early-warning system for deterioration: changes often appear before the patient "looks bad," which is why routine measurement catches problems early enough to act. Trends, not single numbers, trigger concern — a temperature climbing over several readings, a pulse drifting upward, respirations getting faster or more labored.

Vital signs also drive handoffs between clinicians and are a fixture of nursing exams. And measurement is only as good as the technique behind it (next topic) — understanding what you measure is the prerequisite for measuring it well.

The college version

Core Concepts

Temperature: the body's thermostat

Body temperature reflects the balance between heat produced and heat lost, regulated by the hypothalamus. Most commonly cited adult oral reference values fall around 36°–37.5°C (roughly 97°–99.5°F), varying by route (oral, tympanic, axillary, rectal, temporal), time of day, and person. A temperature above a person's usual range is — a regulated rise in the set point, often a response to infection — while temperatures below range are hypothermia and uncontrolled rises are hyperthermia. The route must always be documented.

Pulse: the heart's rate, rhythm, and strength

The pulse is the palpable wave of blood pushed through arteries with each heartbeat. Assessment covers three things: rate (beats per minute), rhythm (regular or irregular spacing of beats), and strength (bounding, strong, weak, or thready). Commonly cited adult resting rates fall roughly between 60 and 100 beats per minute, but infants run faster, athletes may run slower, and medications shift the rate. An irregular pulse — or a rate far from the person's baseline — is a reason to count a full minute and report.

Respirations: ventilation in motion

Respirations are breaths per minute, assessed by observing the rise and fall of the chest. Commonly cited adult resting rates are roughly 12–20 breaths per minute, with children generally faster. The nurse also notes depth (shallow or deep), rhythm, and effort — including labored breathing, noise, or use of accessory muscles. Respirations are usually counted without telling the patient, because people change their breathing when they know they are watched. (air moving in and out) is not the same as oxygenation (oxygen reaching the blood), and both matter.

Blood pressure: the pressure of flow

Blood pressure is the force blood exerts on artery walls, reported as systolic (pressure during heart contraction) over diastolic (pressure while the heart relaxes between beats). It is determined by cardiac output and the resistance of the blood vessels. Classifications and targets vary by age, condition, and which guideline a facility follows, so use the reference values your program and clinical site use rather than memorizing one number. Position, activity, stress, caffeine, and even talking shift readings, which is why measurement conditions are standardized (next topic).

Oxygen saturation and pain: the newer "vitals"

estimates the percentage of hemoglobin carrying oxygen via non-invasive pulse oximetry. Commonly cited room-air values for healthy adults are in the mid-to-high 90s, but acceptable values vary by patient and facility guidance, and the estimate can be affected by poor perfusion, motion, and device issues. Pain is often called the fifth vital sign because it is assessed routinely — but unlike the others it is entirely subjective: the patient's self-report is the measurement.

Factors that shift vital signs

Age, sex, time of day, exercise, emotion, pain, medications, food and caffeine, illness, and environment all shift readings — which is why baseline and trend matter more than any single number. Knowing that a patient's usual resting pulse is 52 makes a reading of 88 meaningful in a way it would not be otherwise.

Common Confusions

Do Not Confuse	With	Difference
Pulse rate	Pulse rhythm	Rate is beats per minute; rhythm is the pattern of beats (regular or irregular)
Systolic pressure	Diastolic pressure	Systolic is pressure during contraction; diastolic is pressure during relaxation
Ventilation	Oxygenation	Ventilation is air moving in and out; oxygenation is oxygen reaching the blood and tissues
Fever (pyrexia)	Hyperthermia	Fever is a regulated rise in the set point (commonly with infection); hyperthermia is an uncontrolled rise in body temperature — mechanisms and meaning differ
A "normal" number	This patient's baseline	The same value can be normal for one person and a change for another
SpO₂	PaO₂	SpO₂ is the pulse-oximetry estimate of hemoglobin saturation; PaO₂ is oxygen's partial pressure in arterial blood, measured by blood gas analysis

Eli explains

The same idea, in plain words

Explain it like I’m 10

Vital signs are like the gauges on a car dashboard — temperature, speed, and fuel. None of them tells you everything about the car, but if the temperature gauge suddenly climbs, you stop ignoring it and check the engine. One gauge moving is a clue; several moving together is a bigger clue.

Worked example

Mr. Okafor, 65, recovering from surgery, tells the nurse he feels "a little off." The nurse measures: temperature 0.4°C above his documented baseline, pulse 8 beats per minute faster than his usual morning readings, and respirations 4 breaths per minute faster. None of these is dramatically "abnormal" on its own — but as a pattern, three indicators drifting together from one person's baseline is exactly the kind of trend vital signs are meant to catch. The nurse rechecks, looks for other clues (color, pain, cough, comfort), and reports the trend to the care team per facility policy.

Now imagine the identical numbers in a patient who just returned from a walk, hot and out of breath. Same readings, different meaning — nurses always interpret vital signs in context, never in isolation.

Key takeaways

Vital signs = temperature, pulse, respirations, blood pressure, oxygen saturation, and pain.
Each sign reflects a specific system: temperature → thermoregulation; pulse → heart; respirations → ventilation; blood pressure → circulation; SpO₂ → oxygenation; pain → subjective experience.
Trends and baseline beat single numbers — always compare to the patient's usual values.
Vital signs are measurements, not diagnoses; they guide assessment and reporting.
Reference values vary by age, route, and source — use your program's and facility's standards.
Technique affects readings (route, cuff size, timing, activity) — covered next in this chapter.
Report changes per facility policy; roles and delegation vary by setting.

Check yourself

6 review questions from the chapter. Try each one, then open the answer.

What does each classic vital sign primarily reflect?
Show answer
Temperature → thermoregulation; pulse → heart rate, rhythm, and strength; respirations → ventilation; blood pressure → circulation; oxygen saturation → oxygenation; pain → subjective experience.
Why is a trend more informative than a single reading?
Show answer
Because vital signs vary with activity, time of day, emotion, and other factors; a change from the patient's own baseline, or a pattern across several readings, carries meaning that one isolated number cannot.
Name three factors that can shift vital signs.
Show answer
Any of: age, time of day, exercise, emotion/stress, pain, medications, caffeine, food, illness, and environment.
Why should respirations be counted without telling the patient?
Show answer
Because people often alter their breathing when they know it is being observed — counting unobtrusively gives a more accurate rate.
Why is pain sometimes called the fifth vital sign?
Show answer
Because it is assessed routinely alongside the other vital signs as an indicator of status — but unlike the others, it is subjective: the patient's self-report is the measurement.
A patient's readings drift from their documented baseline. What should the nurse do?
Show answer
Reassess the patient, consider context (recent activity, pain, medications), compare with the baseline, and report per facility policy — documenting the readings and the response.

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Study tools & related lessonsKey vocabulary · Related

Key vocabulary

Vital signs: The key measurable indicators of physiologic functioning: temperature, pulse, respirations, blood pressure, oxygen saturation, and pain
Pyrexia (fever): A regulated rise in body temperature above the person's usual range
Pulse: The palpable wave of blood through arteries with each heartbeat
Systolic blood pressure: Pressure in the arteries while the heart contracts
Diastolic blood pressure: Pressure in the arteries while the heart relaxes between beats
Ventilation: The movement of air into and out of the lungs
Oxygen saturation (SpO₂): Estimated percentage of hemoglobin carrying oxygen, via pulse oximetry
Baseline: A person's usual value for a given measurement

Sources & references

openstax.org — Fundamentals Nursing

This lesson was adapted from the open educational references above; their licenses and attributions are preserved. See Copyright & Licensing.

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