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HLT-LPN37-06 · Lesson 4 · 14 clock hours · lab

Vital Signs: Accuracy, Trending, and Reporting Critical Values

Objective. Students will accurately obtain and record a full set of vital signs—temperature, pulse, respirations, blood pressure, oxygen saturation, and pain score—and correctly identify which values require immediate reporting to the supervising nurse.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Why Vital Signs Matter

Vital signs are the most frequently performed assessment in nursing. They give a snapshot of a patient's cardiovascular, respiratory, and neurological status. As an LPN, you will obtain and document vital signs at the start of every shift, after procedures, when a patient reports a new symptom, and whenever a change in condition is suspected. Accuracy is not optional—an error of just a few millimeters of mercury on a blood pressure reading, or missing a subtle change in oxygen saturation, can delay life-saving treatment. Your role is to measure correctly, document completely, recognize abnormal values, and report critical findings promptly.

The Six Components of a Full Vital Sign Set

Temperature reflects the body's heat balance. Normal adult oral temperature is approximately 97–99 °F (36.1–37.2 °C). Fever is generally defined as a temperature above 100.4 °F (38 °C). Hypothermia is below 95 °F (35 °C). Route affects the reading: rectal values run slightly higher than oral, axillary slightly lower, and tympanic readings vary by technique. Always document the route used.

Pulse is assessed for rate, rhythm, and quality. Normal adult resting rate is 60–100 beats per minute (bpm). Bradycardia is below 60 bpm; tachycardia is above 100 bpm. Count for a full 60 seconds when the rhythm is irregular. Palpate the radial artery with your index and middle fingers—never your thumb, which has its own pulse.

Respirations should be counted without telling the patient, because awareness of breathing alters the rate. Normal adult rate is 12–20 breaths per minute. Note depth and effort as well as rate. Count for a full 60 seconds. Rates below 12 (bradypnea) or above 20 (tachypnea) are abnormal. Absent or very shallow breathing is an emergency.

Blood Pressure (BP) measures the force of blood against arterial walls. It is recorded as systolic over diastolic (e.g., 120/80 mmHg). Standard adult normal range is less than 120/80 mmHg; hypertensive crisis thresholds and hypotension cutoffs vary by facility protocol, but a systolic above 180 mmHg or below 90 mmHg typically triggers immediate reporting. Always use the correct cuff size—a cuff that is too small reads falsely high, and one that is too large reads falsely low. Support the patient's arm at heart level, and do not take a reading over clothing.

Oxygen Saturation (SpO₂) is measured with a pulse oximeter, usually on a fingertip. Normal SpO₂ in a healthy adult is 95–100%. Values below 90% represent significant hypoxemia and require immediate intervention. Nail polish, poor perfusion, hypothermia, and patient movement can cause inaccurate readings—reposition the probe or try an alternate site before assuming a low reading is artifactual.

Pain Score is included as the "sixth vital sign" in many clinical settings. Use the facility's standardized scale (commonly a 0–10 numeric scale for adults who can self-report). Document the score, location, character, and any change from the previous assessment. Pain is subjective—record what the patient reports without judgment.

Normal Adult Ranges at a Glance

| Parameter | Normal Adult Range |

|---|---|

| Temperature (oral) | 97–99 °F (36.1–37.2 °C) |

| Pulse | 60–100 bpm |

| Respirations | 12–20 breaths/min |

| Blood Pressure | <120/<80 mmHg |

| SpO₂ | 95–100% |

| Pain | 0/10 (goal) |

Trending: One Reading Is Never Enough

A single vital sign value is far less informative than a pattern over time. Trending means comparing each new set of values to previous readings for the same patient. A blood pressure of 98/60 mmHg may be normal for one patient and a sign of impending shock for another whose baseline is 140/90 mmHg. Always review the flowsheet before taking vitals so you know what is normal for your patient, and note the direction of change—improving, stable, or deteriorating.

Identifying and Reporting Critical Values

Facilities define their own critical-value thresholds, but general red-flag values that require immediate notification of the supervising nurse include:

Always follow your facility's specific protocols. When in doubt, report—it is never wrong to inform the RN of a concerning change.

Reporting with SBAR

SBAR is the structured communication tool used to hand off critical information clearly and safely:

Safety Points

Key terms9

Vital signsMeasurable indicators of basic body functions: temperature, pulse, respirations, blood pressure, oxygen saturation, and (in many settings) pain score.
BradycardiaA heart rate below 60 beats per minute in an adult at rest.
TachycardiaA heart rate above 100 beats per minute in an adult at rest.
SpO₂Peripheral oxygen saturation measured non-invasively by a pulse oximeter; expressed as a percentage of hemoglobin saturated with oxygen.
TrendingThe practice of comparing a patient's current vital sign values to their previous values to identify patterns of improvement, stability, or deterioration.
Critical valueA vital sign result that falls outside the range defined by facility protocol as requiring immediate notification of the supervising nurse or provider.
SBARA structured communication framework standing for Situation, Background, Assessment, and Recommendation, used to relay urgent patient information clearly and completely.
Hypertensive crisisA severely elevated blood pressure (commonly defined as systolic at or above 180 mmHg and/or diastolic at or above 120 mmHg) that requires urgent clinical evaluation.
HypoxemiaAn abnormally low level of oxygen in the blood; clinically reflected by an SpO₂ below 90% on pulse oximetry, requiring prompt intervention.

Worked examples4

1. You count 7 heartbeats in 30 seconds with an irregular rhythm. What pulse rate do you document, and what should you do differently next time?
  1. Step 1: Calculate the rate — 7 beats × 2 = 14 bpm. This is clearly below normal (60–100 bpm) and would be a critical value, but the very low count over only 30 seconds suggests measurement error.
  2. Step 2: Recognize the problem — an irregular rhythm must be counted for a full 60 seconds to be accurate. A 30-second count multiplied by 2 introduces too much error when beats are unevenly spaced.
  3. Step 3: Retake the pulse by counting for a full 60 seconds. Suppose the 60-second count yields 52 beats.
  4. Step 4: Document 52 bpm and note the irregular rhythm. Because 52 bpm is below 60 bpm, report this finding to the supervising RN promptly.
Answer: Document 52 bpm with an irregular rhythm after the full 60-second count; report immediately because this is bradycardia.
2. A patient's SpO₂ reads 87% on the right index finger. Before calling the RN, what steps do you take to verify the reading?
  1. Step 1: Assess the patient clinically — check for signs of respiratory distress (cyanosis, labored breathing, altered consciousness). If the patient is in obvious distress, notify the RN immediately without delay.
  2. Step 2: Check for interfering factors — inspect the finger for dark nail polish, artificial nails, or poor perfusion (cold, clammy hands). Remove nail polish if present.
  3. Step 3: Reposition the probe to ensure it is seated properly with the light emitter and detector aligned across the fingertip.
  4. Step 4: Try an alternate site such as the other hand, earlobe, or forehead if the reading remains unstable.
  5. Step 5: If the reading persists at 87% after correcting all interfering factors, the value is confirmed. SpO₂ below 90% is a critical value — notify the RN immediately using SBAR.
Answer: After ruling out artifact (nail polish, poor probe placement, cold extremity), if SpO₂ remains at 87%, this is a confirmed critical value requiring immediate RN notification.
3. Your patient's blood pressure cuff is one size too small. If the true blood pressure is 122/78 mmHg, will the reading be falsely high or falsely low, and by how much?
  1. Step 1: Recall the principle — a cuff that is too narrow for the arm must be inflated to a higher pressure to compress the underlying artery, causing the manometer reading to overestimate true blood pressure.
  2. Step 2: The direction of error is falsely HIGH. Standard references note that an undersized cuff can artificially elevate systolic readings by roughly 10–40 mmHg depending on the degree of mismatch, though the exact value varies by patient and cuff.
  3. Step 3: Apply this to the scenario — the displayed reading could be substantially higher than 122/78 mmHg, potentially appearing as hypertension when the patient is actually normotensive.
  4. Step 4: The correct action is to select the proper cuff size (the bladder should encircle at least 80% of the upper arm) and retake the measurement.
Answer: The reading will be falsely HIGH. Obtain the correct cuff size and retake the blood pressure before documenting or reporting.
4. You need to deliver an SBAR communication to the charge nurse about a patient, Ms. Rivera, in room 318, whose blood pressure has risen from her baseline of 128/82 mmHg to 192/110 mmHg. Write out each SBAR component.
  1. Step 1 – Situation: 'This is [your name], LPN student on the medical unit. I'm calling about Ms. Rivera in room 318. Her blood pressure is 192/110 mmHg.'
  2. Step 2 – Background: 'Ms. Rivera was admitted yesterday for monitoring after a transient ischemic attack. Her baseline blood pressure has been running around 128/82 mmHg. She has a history of hypertension and takes a daily antihypertensive.'
  3. Step 3 – Assessment: 'Her blood pressure is significantly elevated above her baseline. She reports a 7/10 headache that started about 20 minutes ago. I am concerned this could be a hypertensive emergency.'
  4. Step 4 – Recommendation: 'I would like you to come assess her right away and review whether she needs additional medication or further evaluation.'
Answer: A complete SBAR covers all four elements: who/what is the problem (S), relevant history and baseline (B), your clinical concern (A), and a specific request for action (R).

The math in this lesson1

Learners convert a 30-second pulse count to beats per minute and judge when a full 60-second count is needed.
6.RP.3
In class: Measure vital signs on three different peers under timed conditions, recording values in a clinical log; instructor compares student readings to reference values to check accuracy within acceptable variance. · Review a set of ten printed vital-sign flowsheets and identify which values fall outside normal adult ranges, stating the corresponding nursing action for each. · Simulate a critical-value call using a script: student notifies the 'charge nurse' (instructor role-playing) via SBAR when a simulated patient's blood pressure exceeds a critical threshold.
Materials: Electronic and manual blood pressure cuffs, tympanic and oral thermometers, pulse oximeters, stopwatch, vital-signs documentation flowsheet, SBAR reference card, clinical log binder
Check: Vital signs recorded within clinically accepted variance for each measurement type; clinical log reviewed by instructor for completeness; SBAR communication evaluated pass/fail—must include all four SBAR components correctly.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Physiological Integrity: Reduction of Risk Potential
1. A nurse aide reports that an adult patient's pulse oximeter reads 88% on room air. What is the nurse's first action?
Physiological Integrity: Basic Care and Comfort
2. When counting respirations on an alert adult patient, why should the nurse avoid telling the patient that respirations are being counted?
Physiological Integrity: Reduction of Risk Potential
3. A patient's blood pressure is 178/96 mmHg. Before reporting this value to the supervising RN, which action is most important?
Safe and Effective Care Environment: Safety and Infection Control
4. Which component of the SBAR framework includes the nurse's clinical interpretation of the patient's condition?
Physiological Integrity: Physiological Adaptation
5. An adult patient's oral temperature is 101.2 °F. How should the LPN student categorize this finding?
Physiological Integrity: Reduction of Risk Potential
6. A student LPN is taking a manual blood pressure and notices the patient's arm is resting at the side below heart level. What effect will this positioning have on the reading?
Physiological Integrity: Physiological Adaptation
7. The nurse is reviewing a vital-signs flowsheet. Which finding requires the most immediate nursing action?
Physiological Integrity: Basic Care and Comfort
8. When documenting a patient's pain score, which approach best reflects professional nursing practice?
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