Vital Signs – CNA Exam Study Guide
Overview
Vital signs are the four core physiological measurements used to assess a patient's basic health status: temperature, pulse, respiration, and blood pressure (often abbreviated as TPR & BP). Accurate measurement and timely reporting of abnormal findings are among the most critical responsibilities of a CNA. Mastering normal ranges, proper techniques, and medical terminology is essential for both the exam and clinical practice.
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1. Temperature
Key Concepts
Temperature reflects the balance between heat produced and heat lost by the body. CNAs must select the appropriate measurement site based on the patient's condition and understand how each site differs from the oral baseline.
Normal Range
| Site | Reading |
|---|---|
| Oral (standard) | 97.6°F – 99.6°F (avg. 98.6°F / 37°C) |
| Rectal | ~1°F higher than oral (most accurate) |
| Axillary | ~1°F lower than oral (least accurate) |
| Tympanic | Approximates core temperature |
Site Selection Guidelines
Contraindications for Oral Temperature
Key Terms
> ⚠️ Watch Out For:
> - Forgetting the 15–20 minute wait rule before oral temperature — a very common exam question
> - Confusing which site reads higher vs. lower than oral: Rectal = Higher, Axillary = Lower (think R-H, A-L)
> - Hypothermia is often overlooked as dangerous — always report readings below 95°F immediately
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2. Pulse
Key Concepts
The pulse is the wave of pressure felt in an artery each time the heart beats. CNAs assess three characteristics and must recognize when values fall outside normal parameters.
Normal Range
Three Characteristics to Assess and Document
1. Rate – Number of beats per minute
2. Rhythm – Regular or irregular pattern
3. Strength/Volume – Strong, weak, or thready
Common Pulse Sites
Counting Guidelines
Key Terms
> ⚠️ Watch Out For:
> - Always count an irregular pulse for a full 60 seconds — shortcuts cause errors
> - The apical pulse is the go-to when the radial cannot be detected — know its exact location
> - Tachycardia and bradycardia both require reporting to the nurse, not independent intervention by the CNA
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3. Respiration
Key Concepts
Respiration is the process of breathing. Because patients unconsciously alter their breathing if they know it's being observed, CNAs use a technique of measuring respirations covertly — typically while appearing to still take the pulse.
Normal Range
What Counts as One Respiration
> One inhalation (inspiration) + One exhalation (expiration) = One complete respiration
Measurement Technique
Key Terms
> ⚠️ Watch Out For:
> - Students commonly forget that apnea = zero breathing and is an emergency — not just slow breathing
> - Do not tell the patient you are counting respirations — this is specifically tested on exams
> - Tachypnea has multiple causes (fever, pain, anxiety, distress) — know the common triggers
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4. Blood Pressure
Key Concepts
Blood pressure (BP) measures the force of blood against arterial walls. It is recorded as systolic over diastolic (e.g., 118/76 mmHg). Accurate technique and site selection are critical for valid readings.
Normal Range
Understanding the Numbers
| Number | What It Represents |
|---|---|
| Systolic (top number) | Pressure when the heart contracts/beats |
| Diastolic (bottom number) | Pressure when the heart is at rest between beats |
Measurement Technique
Sites to AVOID for Blood Pressure
Never take blood pressure on an arm that has:
Rationale: Risk of inaccurate readings, damage to the IV/shunt, infection, lymphedema, or patient injury
Key Terms
Orthostatic Hypotension Precautions
1. Have patient change positions slowly
2. Allow patient to sit at the edge of bed before standing (dangling)
3. Watch for dizziness, lightheadedness, or fainting
4. Report symptoms to the nurse immediately
> ⚠️ Watch Out For:
> - Never take BP on the mastectomy side — this is a high-frequency exam question
> - The brachial artery (not radial or carotid) is always used for standard BP measurement
> - Orthostatic hypotension = a fall risk — always assist patients when changing positions
> - Hypertension is often asymptomatic, which is why regular monitoring is so important
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Normal Ranges – Quick Reference Chart
| Vital Sign | Normal Adult Range | Too Low | Too High |
|---|---|---|---|
| Temperature (Oral) | 97.6°F – 99.6°F | Hypothermia < 95°F | Hyperthermia/Fever > 100.4°F |
| Pulse | 60 – 100 bpm | Bradycardia < 60 | Tachycardia > 100 |
| Respiration | 12 – 20 breaths/min | Bradypnea < 12 | Tachypnea > 20 |
| Blood Pressure | < 120/80 mmHg | Hypotension < 90 systolic | Hypertension ≥ 130/80 |
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Key Medical Terminology Summary
| Term | Definition |
|---|---|
| Hyperthermia/Pyrexia | Elevated body temperature (fever > 100.4°F) |
| Hypothermia | Dangerously low body temperature (< 95°F) |
| Bradycardia | Slow pulse (< 60 bpm) |
| Tachycardia | Fast pulse (> 100 bpm) |
| Bradypnea | Slow breathing (< 12 breaths/min) |
| Tachypnea | Fast breathing (> 20 breaths/min) |
| Apnea | Absence of breathing — medical emergency |
| Hypertension | High blood pressure (≥ 130/80 mmHg) |
| Hypotension | Low blood pressure (systolic < 90 mmHg) |
| Orthostatic Hypotension | BP drop with position changes; fall risk |
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Quick Review Checklist
Use this checklist to confirm you are exam-ready:
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📝 Exam Tip: The CNA exam frequently tests your ability to recognize abnormal values and identify the correct response — which is always to report findings to the nurse. CNAs do not diagnose or independently treat abnormal vital signs.