Adult vs pediatric vital signs: Normal ranges and when to stop the exam

Why radiographers assess vital signs

As a radiographer, you are not a clinician. You do not diagnose. But you do assess the patient’s physiologic state before and sometimes during imaging to identify unsafe conditions that require stopping the exam and escalating to the radiologist or physician.

Vital signs are the foundation of that assessment: they tell you whether the patient’s cardiovascular, respiratory, and neurologic systems are functioning within safe bounds for the exam you’re about to do. A patient with critically low oxygen saturation, dangerously high heart rate, or severe hypotension may need the exam delayed or modified.

The ARRT tests your knowledge of normal vital sign ranges (adult and pediatric) and your ability to recognize when a patient’s vitals cross into the “stop and escalate” zone. This is a patient-care competency, not a technical one, but it carries patient safety stakes.

Adult normal vital signs (canonical ranges)

These are the reference values for adults 18 years and older. They are used across ARRT questions, medical textbooks, and clinical practice.

Vital	Normal Range	Notes
Pulse (heart rate)	60-100 bpm	Measured at rest. Sinus arrhythmia (slight variation with breathing) is normal. Athletes may run lower.
Respiration	12-20 breaths/min	Measured at rest, typically counted for 60 seconds. Include all inspirations and expirations.
Systolic BP	100-120 mmHg	2017 AHA guideline update: “normal” is now <120. Values 120-129 with diastolic <80 are “elevated.”
Diastolic BP	<80 mmHg	Diastolic 80-89 with systolic <120 is “elevated.”
SpO2 (oxygen saturation)	95-100%	On room air, sea level. Values below 95% indicate hypoxemia. Below 90% is a critical finding.
Temperature	98.6°F (37°C)	Oral measurement. Normal range is typically 97-99°F depending on method (axillary, rectal, tympanic).

These ranges are the ARRT canonical values and appear in official content specifications. Memorize them word-for-word for the exam.

Pediatric vital signs by age (the critical difference)

This is where student errors cluster: applying adult ranges to children and calling normal findings abnormal.

Pediatric vital signs are significantly higher than adult values because children have faster metabolic rates, smaller stroke volumes, and rely on heart rate (rather than stroke volume) to maintain cardiac output. As a child grows, these parameters normalize toward adult ranges.

Age Group	Pulse (bpm)	Respiration (breaths/min)	Systolic BP (mmHg)	Key Point
Newborn (0-1 month)	100-160	30-60	60-90	Fastest rates; wide normal range due to rapid growth and variable tone
Infant (1-12 months)	80-140	24-40	70-100	Still very high; respiration gradually normalizes
Toddler (1-3 years)	80-130	20-30	80-110	Pulse remains elevated; respiration narrowing toward adult range
Preschool (3-6 years)	80-120	22-34	80-110	Continued maturation; ranges begin to plateau
School age (6-12 years)	70-110	18-30	84-120	Pulse approaching adult range; respiration fully normalized
Adolescent (12+ years)	60-100	12-20	100-120	Converging to adult ranges

This table is ARRT-testable material. You will see questions like “A 2-year-old has a heart rate of 115 bpm. This is:” and the answer is “normal” because 115 falls in the toddler range (80-130). The same heart rate in an adult would be tachycardia and a “stop the exam” finding.

The common wrong answer (applying adult ranges universally)

The cardinal mistake in pediatric vital sign assessment is this: treating a child’s normal vital signs as abnormal because they exceed adult thresholds.

Example: An 8-month-old infant presents for a chest x-ray. Vital signs are measured: pulse 125 bpm, respiration 38 breaths/min. A radiographer unfamiliar with pediatric norms might think, “That’s tachycardia and tachypnea. Something is wrong.” In reality, both values fall squarely in the normal range for an infant (pulse 80-140, respiration 24-40). The exam can proceed.

The inverse error is rarer but equally dangerous: dismissing a truly abnormal pediatric vital sign as normal because it’s lower than an adult’s critical threshold. Example: A 3-year-old with a systolic BP of 65 mmHg might not trigger alarm bells if you’re only watching for adult hypotension (<90 mmHg), but 65 is critically low for a toddler (normal 80-110) and is a “stop the exam” finding.

The ARRT tests this distinction frequently in patient-care scenarios. Always confirm the patient’s age first, then apply the age-appropriate reference range.

Adult critical thresholds: when to stop the exam

These are the “red flag” values in adults that warrant stopping the radiographic exam and immediately notifying the radiologist and physician.

Finding	Critical Value	Action
Pulse	<50 or >120 bpm	Stop. Severe bradycardia may indicate heart block or medication effect. Severe tachycardia may indicate shock, fever, pain, or decompensation.
Respiration	<8 or >30 breaths/min	Stop. Severe bradypnea (too slow) may indicate CNS depression or airway compromise. Tachypnea may indicate hypoxemia, acidosis, or sepsis.
Systolic BP	<90 mmHg	Stop. Hypotension below 90 indicates inadequate tissue perfusion and potential shock. Do not proceed without physician evaluation.
SpO2	<90%	Stop. Significant hypoxemia. Patient needs supplemental oxygen and physician evaluation before proceeding.
Temperature	>104°F (40°C) or <96°F (35.5°C)	Stop. Fever above 104 may indicate active infection; severe hypothermia is life-threatening.

Memorize these thresholds. The ARRT will give you a scenario and ask whether vitals warrant stopping the exam. The answer depends on whether values cross into the critical range.

Pediatric critical thresholds (age matters)

Critical values for pediatric patients shift with age because normal ranges shift. You cannot apply adult “stop the exam” criteria to a child.

A pulse of 140 bpm in a toddler is normal and does not trigger the “stop” threshold. The same pulse in a 10-year-old would be tachycardia and warrants assessment. The same pulse in an adult is definitely tachycardia and warrants stopping the exam.

Pediatric critical thresholds vary by institution and are less standardized than adult values, but the ARRT expects you to recognize that:

• Pediatric hypotension is defined lower than adult hypotension. A systolic BP of 70 in a toddler is concerning; in an infant, it may be normal.
• Pediatric tachycardia thresholds shift upward (a faster pulse is tolerated in younger children).
• Pediatric hypoxemia is defined the same as in adults (SpO2 <90%), but respiratory distress in a child may manifest differently.

For ARRT purposes, if a scenario presents a pediatric patient with vital signs, always check whether the values fall within the age-appropriate normal range first. If they do, the finding is not a “stop” criterion. If they fall outside the normal range, escalate.

Assessing volume status: orthostatic vital signs

One special vital-sign scenario tested on the ARRT is orthostatic assessment, sometimes called “tilt testing” or “orthostatic hypotension check.”

When a patient is suspected of dehydration, anemia, or cardiac issues, a physician may order vital signs in both supine (lying flat) and upright (standing) positions. A significant drop in blood pressure on standing indicates the patient’s cardiovascular system cannot compensate for position change and may signal volume depletion or autonomic dysfunction.

Positive orthostatic findings are defined as:

• Drop in systolic BP of 20 mmHg or more on standing, OR
• Drop in diastolic BP of 10 mmHg or more on standing, OR
• Rise in heart rate of 15-20 bpm or more on standing (compensatory response to pressure drop)

If you are asked to obtain orthostatic vitals:

1. Measure BP and pulse with the patient supine (lying flat) after 3-5 minutes of rest.
2. Help the patient stand slowly (rapid standing can trigger syncope even in healthy people).
3. Measure BP and pulse immediately (within 1-2 minutes of standing).
4. Document both supine and upright values clearly.
5. If the patient becomes dizzy, lightheaded, or syncope is imminent, help them return to supine immediately and notify the radiologist.

Orthostatic vitals are sometimes collected before exams that require standing or significant repositioning (e.g., weight-bearing lower extremity radiography) to ensure the patient can safely tolerate the position.

Your role as a radiographer: assess, escalate, do not treat

This is the critical distinction the ARRT emphasizes in patient-care questions:

You measure vital signs. You are trained to obtain accurate readings using the correct technique (rest, correct cuff size, proper positioning, etc.).

You assess whether values are within normal range. You compare to the appropriate age-adjusted reference and recognize critical findings.

You escalate to the radiologist or physician. If vitals are abnormal or critical, you notify. You do not interpret the clinical significance or prescribe treatment.

You do not treat. Giving oxygen, starting an IV, administering medication, or performing CPR are outside the scope of radiography. If a patient is in respiratory distress or cardiovascular distress, you call for help (code team, rapid response) and follow your facility’s emergency protocol. Your first action is to notify a clinician with prescribing authority.

This distinction is tested because students sometimes conflate vital-sign assessment with clinical decision-making. The exam may present a scenario where you find abnormal vitals and ask, “What do you do next?” The answer is: “Notify the radiologist and physician immediately.” Not: “Administer oxygen” or “Start an IV” or “Give aspirin.” Those are not your scope.

Why pediatric vital signs matter on the ARRT

The ARRT tests pediatric vital signs in the patient-care domain because radiographers work with children across all modalities (radiography, fluoroscopy, CT, ultrasound) and must recognize when a child’s vitals warrant stopping an exam or modifying a technique.

Specific question patterns you can expect:

1. Age-to-range matching: “A 6-month-old has a pulse of 110 bpm and respiration of 36 breaths/min. Are these findings normal?” Answer: Yes, both fall in the normal range for infants (pulse 80-140, respiration 24-40).

2. Critical value recognition: “An 8-year-old’s oxygen saturation drops to 88% during fluoroscopy. This is…?” Answer: Below normal (<95%) and warrants stopping the exam and notifying the physician.

3. Contrast to adult norms: “Compare the normal pulse ranges of an adult and a 3-year-old.” Answer: Adult 60-100 bpm; toddler 80-130 bpm (faster).

4. Scenario-based escalation: “You measure vital signs on a 10-year-old before a CT scan. Pulse 82 bpm, respiration 24 breaths/min, BP 105/68, SpO2 96%. Do you proceed or escalate?” Answer: All values are normal for a school-age child. Proceed with exam (assuming no other contraindications).

Knowing these ranges cold is non-negotiable for passing patient-care questions on the ARRT.

Quick reference table

Metric	Adult	Infant (1-12 mo)	Toddler (1-3 yr)	School-age (6-12 yr)	Adolescent (12+)
Pulse	60-100	80-140	80-130	70-110	60-100
Respiration	12-20	24-40	20-30	18-30	12-20
Systolic BP	100-120	70-100	80-110	84-120	100-120
Critical Pulse	<50 or >120	age-dependent	age-dependent	age-dependent	<50 or >120
Critical SpO2	<90%	<90%	<90%	<90%	<90%

Print this table. It is ARRT-testable.

ARRT exam tip

Pediatric vital signs are a trap for students who memorize adult ranges but forget to age-adjust. The ARRT will present normal pediatric vitals and ask if they’re abnormal. The wrong answer is “yes, this is tachycardia” because you’re applying adult criteria. The right answer is “no, this is normal for age.”

Before you answer any vital-sign question on the ARRT, read the patient’s age. Then apply the correct reference range. If the scenario does not give you an age, treat it as an adult. But always double-check: “What is this patient’s age?” If you answer that question wrong, you will get the vital-sign assessment wrong.

For comprehensive ARRT prep across all patient-care topics, see our chapter on patient monitoring and emergencies. For communication and behavioral aspects of assessing pediatric patients, the chapter on patient communication and care covers the non-technical side. And for a complete walk-through of the patient-care domain with practice questions, check out our ARRT patient-care guide.