Respiratory Status Monitoring And Support - NCLEX Pn

SECTION 1

Historical Context & Motivation

The ability to monitor and support respiratory status has been one of the most transformative developments in nursing and critical care medicine. For centuries, practitioners relied solely on observation and auscultation to detect respiratory compromise, often recognizing deterioration only when patients were already in life-threatening distress. The evolution of monitoring technologies and respiratory support interventions has dramatically improved outcomes for patients with conditions ranging from chronic obstructive pulmonary disease to acute respiratory distress syndrome. Understanding this historical trajectory helps today's practical nursing students appreciate why specific assessment parameters and interventions are prioritized in clinical practice.

1816 • Invention of the Stethoscope

René Laënnec invented the stethoscope, enabling clinicians to auscultate lung sounds systematically. This marked the beginning of non-invasive respiratory assessment and remains a fundamental tool in nursing practice today.

1952 • Modern Mechanical Ventilation

The Copenhagen polio epidemic drove the development of positive-pressure ventilation, replacing the iron lung. Björn Ibsen's approach laid the foundation for modern intensive care units and ventilator management protocols.

1972 • Arterial Blood Gas Analysis Standardized

Standardized arterial blood gas (ABG) analysis became widely available, allowing clinicians to quantify PaO₂, PaCO₂, pH, and HCO₃⁻ levels. This revolutionized the precision with which respiratory and metabolic derangements could be identified and treated.

1983 • Pulse Oximetry Enters Clinical Use

Continuous, non-invasive pulse oximetry became standard in perioperative and critical care settings. SpO₂ monitoring enabled nurses to detect hypoxemia rapidly without arterial puncture, fundamentally changing bedside respiratory surveillance.

2020 • COVID-19 & Respiratory Nursing Advances

The global pandemic underscored the critical role of nurses in respiratory monitoring. Prone positioning protocols, high-flow nasal cannula therapy, and early warning score systems were rapidly refined, highlighting the LPN/LVN's essential role in physiological surveillance.

These milestones collectively shaped the modern landscape of respiratory care. Today's practical nurse must synthesize multiple data streams—auscultation findings, pulse oximetry readings, capnography waveforms, arterial blood gas values, and observable clinical signs—to recognize respiratory compromise early and initiate or assist with appropriate interventions. The central question guiding this lesson is: How does the practical nurse systematically assess respiratory status, recognize deterioration, and support oxygenation and ventilation across the continuum of care?

SECTION 2

Core Principles of Respiratory Monitoring

Effective respiratory status monitoring rests on a foundation of physiological principles that guide clinical assessment and decision-making. The respiratory system's primary function is gas exchange—delivering oxygen to the blood and eliminating carbon dioxide from the body. When this process is compromised, every organ system is at risk. The practical nurse must understand the interplay between ventilation (the mechanical movement of air in and out of the lungs), diffusion (the transfer of gases across the alveolar-capillary membrane), and perfusion (the blood flow through pulmonary capillaries) to appreciate the full picture of respiratory function.

Oxygenation Assessment

Evaluate the adequacy of oxygen delivery using SpO₂, PaO₂, skin color, and level of consciousness. Normal SpO₂ ranges from 95–100%, while PaO₂ should be 80–100 mmHg. Cyanosis, restlessness, and confusion are late clinical indicators of hypoxemia.

Ventilation Assessment

Evaluate the effectiveness of CO₂ elimination through respiratory rate, depth, pattern, PaCO₂ levels (normal 35–45 mmHg), and end-tidal CO₂ (EtCO₂). Hypoventilation leads to respiratory acidosis, while hyperventilation causes respiratory alkalosis.

Work of Breathing

Assess for signs of increased respiratory effort including accessory muscle use, nasal flaring, intercostal retractions, tripod positioning, and paradoxical breathing. Increased work of breathing often precedes overt respiratory failure.

Acid-Base Balance

Interpret ABG values to identify respiratory versus metabolic imbalances. Normal arterial pH is 7.35–7.45. The respiratory system compensates rapidly for metabolic disturbances by adjusting CO₂ elimination, making ABG interpretation a critical skill.

Airway Patency

Ensure the airway is patent and protected. Assess for stridor, gurgling, snoring respirations, secretion management, and proper positioning. Airway compromise is the most immediately life-threatening respiratory emergency.

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KEY TAKEAWAY

Think of the respiratory system like a building's HVAC system. The airway is the ductwork—if blocked, no air flows regardless of how hard the system works. Ventilation is the fan motor—it moves air through the ducts. Diffusion is the heat exchanger—where the actual transfer of energy (or in our case, gases) occurs across a membrane. Perfusion is the coolant loop—without adequate blood flow past the exchange surface, O₂ cannot reach the body. A failure at any one level compromises the entire system, just as a broken duct, fan, exchanger, or pump would render an HVAC system ineffective.

SECTION 3

Visual Explanation — Respiratory Assessment Framework

This flowchart illustrates the systematic approach to respiratory assessment. Starting with airway patency at the top, the nurse evaluates breathing parameters, then simultaneously assesses oxygenation, ventilation, and work of breathing. Abnormal findings trigger interpretation and targeted interventions, followed by continuous reassessment.

The framework depicted above follows the ABC (Airway, Breathing, Circulation) prioritization model that is foundational to nursing assessment. The practical nurse always evaluates airway patency first—if the airway is compromised, no amount of supplemental oxygen or ventilatory support will be effective. Once the airway is confirmed as patent, breathing parameters are assessed quantitatively (respiratory rate, oxygen saturation, capnography values) and qualitatively (depth, pattern, symmetry, adventitious sounds). These findings are then interpreted in context—a SpO₂ of 88% in a patient with severe COPD may represent their baseline, whereas the same value in a previously healthy postoperative patient demands immediate action. The cyclic nature of the framework emphasizes that respiratory monitoring is never a one-time event; it requires ongoing vigilance and documentation of trends.

SECTION 4

Mechanisms of Respiratory Assessment & ABG Interpretation

While respiratory monitoring is primarily a clinical skill rather than a purely mathematical discipline, the practical nurse must be conversant with key quantitative parameters and their normal ranges. Arterial blood gas (ABG) analysis is the gold standard for evaluating respiratory function, and interpreting these values requires a systematic approach. Additionally, understanding the alveolar gas equation and the A-a gradient provides deeper insight into why a patient may be hypoxemic.

ALVEOLAR GAS EQUATION

PAO₂ = FiO₂ × (Pᵦ − PH₂O) − (PaCO₂ ÷ R)

Where PAO₂ = alveolar partial pressure of O₂, FiO₂ = fraction of inspired oxygen (0.21 on room air), Pᵦ = barometric pressure (760 mmHg at sea level), PH₂O = water vapor pressure (47 mmHg), PaCO₂ = arterial CO₂, and R = respiratory quotient (≈ 0.8).

A-a GRADIENT

A-a gradient = PAO₂ − PaO₂

A normal A-a gradient is approximately 5–15 mmHg in a young adult breathing room air. An elevated A-a gradient suggests a diffusion impairment, V/Q mismatch, or shunt, whereas a normal gradient with hypoxemia points toward hypoventilation or low FiO₂ as the cause.

Systematic ABG Interpretation Method

A reliable four-step approach to ABG interpretation helps the practical nurse quickly categorize acid-base disturbances. First, examine the pH to determine acidosis (< 7.35) or alkalosis (> 7.45). Second, evaluate the PaCO₂ (normal 35–45 mmHg) to assess the respiratory component. Third, evaluate the HCO₃⁻ (normal 22–26 mEq/L) to assess the metabolic component. Fourth, determine whether the body is compensating—if the non-primary system is moving in the opposite direction to normalize pH, compensation is occurring. This systematic approach prevents the common error of jumping to conclusions based on a single value.

EXPECTED PaO₂ BY AGE

Expected PaO₂ ≈ 104.2 − (0.27 × age in years)

This approximation helps clinicians contextualize oxygenation values for elderly patients. For example, a 70-year-old patient's expected PaO₂ would be approximately 104.2 − (0.27 × 70) ≈ 85 mmHg, which is within a normal range for that age.

SECTION 5

Oxygen Delivery Systems & Respiratory Support Interventions

Selecting the appropriate oxygen delivery system is a critical nursing decision that depends on the patient's level of hypoxemia, breathing pattern, comfort needs, and clinical stability. Delivery systems are broadly categorized as low-flow systems (which deliver variable FiO₂ because inspired air mixes with room air) and high-flow systems (which deliver a precise, fixed FiO₂ because flow rates meet or exceed the patient's inspiratory demand). The practical nurse must understand not only the FiO₂ ranges each device provides but also the indications, contraindications, and nursing considerations unique to each system.

This diagram compares low-flow and high-flow oxygen delivery systems with their FiO₂ ranges and flow rates. Key nursing considerations for each device are listed below the comparison.

Assessment Finding	Possible Cause	Nursing Action
SpO₂ < 90% on room air	Hypoxemia from V/Q mismatch, shunt, hypoventilation, or diffusion impairment	Apply supplemental O₂, elevate HOB to 30–45°, notify provider, obtain ABG as ordered
Crackles (rales) bilaterally	Pulmonary edema, heart failure, pneumonia, ARDS	Position upright, administer diuretics as ordered, monitor I&O, reassess breath sounds
Wheezing on expiration	Bronchospasm (asthma, COPD exacerbation, anaphylaxis)	Administer bronchodilators (e.g., albuterol), assess for allergen exposure, monitor peak flow
Stridor (inspiratory)	Upper airway obstruction—croup, epiglottitis, foreign body, post-extubation edema	Maintain airway, do NOT examine throat if epiglottitis suspected, prepare for emergent intubation
Absent breath sounds unilaterally	Pneumothorax, hemothorax, large pleural effusion, mainstem bronchus intubation	Notify provider stat, prepare for chest tube insertion or tube repositioning, monitor vitals

Common Respiratory Assessment Findings with Causes and Nursing Actions

SECTION 6

Worked Example — ABG Interpretation & Nursing Response

A 68-year-old patient with a history of COPD is admitted with increasing dyspnea over the past two days. The patient is sitting upright, using pursed-lip breathing, and has audible wheezing. Vital signs: RR 28, HR 110, BP 148/88, SpO₂ 86% on room air. An ABG is drawn and the results are: pH 7.31, PaCO₂ 58 mmHg, PaO₂ 55 mmHg, HCO₃⁻ 32 mEq/L. The nurse must interpret these results and determine appropriate interventions.

ABG Interpretation & Respiratory Support Decision

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Step 1 — Evaluate pH

The pH is 7.31, which is below the normal range of 7.35–7.45. This indicates acidosis. The direction of pH deviation tells us the primary process is producing excess acid or inadequate buffering.

Acidosis present (pH 7.31)
2
Step 2 — Evaluate PaCO₂ (Respiratory Component)

PaCO₂ is 58 mmHg, which is above the normal range of 35–45 mmHg. Elevated PaCO₂ indicates CO₂ retention (hypoventilation). Since the CO₂ is elevated and would cause the pH to drop (become more acidic), the respiratory component matches the direction of the pH deviation. This means the primary disorder is respiratory acidosis.

Primary respiratory acidosis (↑PaCO₂ = 58 mmHg)
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Step 3 — Evaluate HCO₃⁻ (Metabolic Component)

HCO₃⁻ is 32 mEq/L, which is above the normal range of 22–26 mEq/L. An elevated bicarbonate level in the setting of respiratory acidosis indicates that the kidneys are retaining bicarbonate to compensate for the chronic CO₂ retention. However, because the pH remains below 7.35, the compensation is incomplete—this is partially compensated respiratory acidosis.

Partially compensated respiratory acidosis with metabolic compensation (↑HCO₃⁻ = 32)
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Step 4 — Evaluate Oxygenation

PaO₂ is 55 mmHg, which is significantly below the normal range of 80–100 mmHg (and below the age-adjusted expected value of ≈85.8 mmHg for a 68-year-old). This confirms hypoxemia. The SpO₂ of 86% correlates with this PaO₂ on the oxyhemoglobin dissociation curve.

Hypoxemia confirmed (PaO₂ = 55 mmHg, SpO₂ = 86%)
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Step 5 — Determine Nursing Interventions

For this COPD patient with partially compensated respiratory acidosis and hypoxemia, the nurse should: (1) Apply low-flow supplemental oxygen via Venturi mask at 24–28% FiO₂ to avoid suppressing the hypoxic drive. (2) Position the patient in high Fowler's or tripod position to maximize diaphragmatic excursion. (3) Administer prescribed bronchodilators and corticosteroids. (4) Monitor SpO₂ continuously with a target of 88–92% for this COPD patient. (5) Reassess ABG in 30–60 minutes after intervention. (6) Notify the provider of the ABG results and current status. The critical principle here is that excessive oxygen administration in a patient with chronic CO₂ retention may paradoxically worsen hypoventilation.

Low-flow O₂ (Venturi 24–28%), high Fowler's position, bronchodilators, target SpO₂ 88–92%

SECTION 7

Comparing Monitoring Modalities — Strengths & Limitations

No single monitoring tool provides a complete picture of respiratory function. The practical nurse must understand the strengths and limitations of each modality to select the most appropriate combination for a given clinical scenario. Pulse oximetry, capnography, and arterial blood gas analysis each provide unique and complementary data. When used together, they create a comprehensive respiratory surveillance system that detects compromise earlier than any single modality alone.

Monitoring Modality	Strengths	Limitations
Pulse Oximetry (SpO₂)	Non-invasive, continuous, inexpensive, immediate results, widely available at bedside, requires minimal training	Unreliable with poor perfusion, dark nail polish, carbon monoxide poisoning (falsely high), severe anemia; delayed detection of hypoventilation when supplemental O₂ is in use; does not measure PaCO₂ or pH
Capnography (EtCO₂)	Non-invasive, continuous, real-time ventilation assessment, waveform analysis detects airway obstruction, confirms ETT placement, early indicator of hypoventilation	Requires specialized equipment, may be inaccurate with high supplemental O₂, does not measure oxygenation, readings affected by dead space ventilation and V/Q mismatch
Arterial Blood Gas (ABG)	Gold standard, provides PaO₂, PaCO₂, pH, HCO₃⁻, SaO₂, and base excess simultaneously; allows comprehensive acid-base analysis; identifies both respiratory and metabolic components	Invasive (arterial puncture), painful, intermittent (snapshot in time), requires lab processing time, risk of hematoma or arterial spasm, more expensive than non-invasive alternatives
Chest Auscultation	Immediately available, no equipment cost, provides qualitative airway and lung parenchyma data, can identify adventitious sounds (crackles, wheezing, stridor)	Subjective, examiner-dependent, cannot quantify gas exchange, may miss subtle changes, difficult to perform in noisy environments or with obese patients

Comparison of Respiratory Monitoring Modalities

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KEY TAKEAWAY

Think of respiratory monitoring like weather forecasting. A single thermometer tells you the temperature, but not whether it's raining or windy. Pulse oximetry is like the thermometer—it gives you one vital piece of data (oxygen level), but it tells you nothing about ventilation, acid-base balance, or the underlying cause of the problem. An ABG is like a full weather station that measures temperature, humidity, barometric pressure, and wind speed simultaneously. The skilled nurse combines multiple monitoring tools just as a meteorologist synthesizes data from many instruments to make an accurate forecast.

SECTION 8

Connection to Advanced Respiratory Support & Escalation

While the LPN/LVN scope of practice focuses on monitoring, data collection, and implementation of prescribed interventions, understanding the continuum of respiratory support helps the practical nurse recognize when escalation to advanced interventions is necessary. Non-invasive positive pressure ventilation (NIPPV), including CPAP and BiPAP, bridges the gap between supplemental oxygen and invasive mechanical ventilation. Invasive mechanical ventilation is reserved for patients who cannot maintain adequate oxygenation or ventilation despite maximal non-invasive support. Recognizing the clinical indicators for escalation—progressive respiratory acidosis, worsening hypoxemia despite increased FiO₂, patient fatigue, and declining mental status—is a critical competency for the practical nurse collaborating with the healthcare team.

Feature	Basic Respiratory Support (LPN Scope)	Advanced Respiratory Support (RN/RT/Provider)
Interventions	O₂ via NC or mask, suctioning (oral/nasal, trach care), positioning, incentive spirometry, medication administration (bronchodilators, steroids)	CPAP/BiPAP initiation, mechanical ventilator management, intubation assistance, chest tube management, bronchoscopy, ECMO
Monitoring Role	SpO₂ trending, vital signs, respiratory assessment, breath sound auscultation, documenting patterns, reporting changes	ABG interpretation, ventilator waveform analysis, hemodynamic monitoring, advanced airway assessment, titrating ventilator settings
Escalation Triggers	LPN identifies deterioration → reports to RN/provider with SBAR communication	RN/RT/provider initiates advanced assessment, adjusts interventions, activates rapid response if needed
Key Clinical Indicators for Escalation	SpO₂ persistently < 88% despite O₂, RR > 30 or < 8, increasing WOB, altered LOC, cyanosis	pH < 7.25, PaCO₂ > 60 and rising, PaO₂/FiO₂ ratio < 200 (ARDS criteria), hemodynamic instability

Basic vs. Advanced Respiratory Support — Scope & Escalation

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NCLEX-PN Focus Point

The NCLEX-PN frequently tests the practical nurse's ability to recognize and report respiratory changes rather than independently manage advanced interventions. Questions often present scenarios where the LPN must identify the most concerning finding and determine the priority action—which is almost always to notify the RN or provider after performing immediate interventions within scope (positioning, suctioning, applying O₂). Remember: LPNs collect data and implement the plan of care; RNs analyze, plan, and evaluate. When in doubt on the NCLEX, prioritize airway, then breathing, then circulation.

SECTION 9

Practice Problems

Question 1: CONCEPTUAL

A patient on a nasal cannula at 4 L/min has an SpO₂ reading of 92%. The nurse notes that the patient's hands are cold and peripheral circulation appears poor. What should the nurse consider regarding the reliability of this SpO₂ reading, and what additional assessment should be performed?

Show answer

Pulse oximetry relies on the detection of pulsatile arterial blood flow to accurately measure oxygen saturation. When peripheral perfusion is poor—as indicated by cold extremities—the pulse oximeter may produce unreliable readings that could be falsely low or erratic. The nurse should attempt to obtain the reading from a different site with better perfusion, such as the earlobe or forehead (using an appropriate sensor). Additionally, the nurse should assess the patient's overall hemodynamic status including blood pressure, heart rate, and capillary refill time. If there is clinical concern about the patient's oxygenation, an arterial blood gas should be requested from the provider, as ABG analysis provides a direct measurement of PaO₂ and SaO₂ that is independent of peripheral perfusion.

Question 2: BASIC CALCULATION

Using the alveolar gas equation, calculate the expected PAO₂ for a patient breathing room air at sea level who has a PaCO₂ of 40 mmHg. Then determine the A-a gradient if the patient's PaO₂ is 70 mmHg. Is this A-a gradient normal?

Show answer

Using the alveolar gas equation: PAO₂ = FiO₂ × (Pᵦ − PH₂O) − (PaCO₂ ÷ R). Substituting values: PAO₂ = 0.21 × (760 − 47) − (40 ÷ 0.8) = 0.21 × 713 − 50 = 149.7 − 50 = 99.7 mmHg. The A-a gradient = PAO₂ − PaO₂ = 99.7 − 70 = 29.7 mmHg. A normal A-a gradient for a young adult is approximately 5–15 mmHg (and increases with age by roughly 1 mmHg per decade). A gradient of 29.7 mmHg is elevated, suggesting that the hypoxemia is caused by a diffusion impairment, ventilation-perfusion mismatch, or intrapulmonary shunt—rather than simple hypoventilation, which would produce a normal A-a gradient.

Question 3: INTERMEDIATE

An ABG result shows: pH 7.48, PaCO₂ 30 mmHg, PaO₂ 110 mmHg, HCO₃⁻ 24 mEq/L. The patient is post-operative and reports tingling in the fingertips. Interpret this ABG, identify the likely cause, and describe the appropriate nursing interventions.

Show answer

Step-by-step interpretation: The pH of 7.48 is above 7.45, indicating alkalosis. The PaCO₂ of 30 mmHg is below the normal range (35–45 mmHg), indicating hyperventilation—since a low PaCO₂ would cause the pH to rise, the respiratory component matches the pH direction, making this a primary respiratory alkalosis. The HCO₃⁻ of 24 mEq/L is within normal limits (22–26 mEq/L), indicating no metabolic compensation has occurred yet—this is an uncompensated respiratory alkalosis. The PaO₂ of 110 mmHg is elevated, likely due to the increased minute ventilation. The tingling in the fingertips is a classic symptom of respiratory alkalosis caused by decreased ionized calcium levels (alkalosis increases calcium binding to albumin). The likely cause in a post-operative patient is anxiety-driven hyperventilation or pain. The nurse should encourage slow, deep breathing, address pain management, provide reassurance, and notify the provider of the ABG results. If symptoms are severe, the provider may order breathing into a paper bag briefly to increase CO₂ rebreathing, though this is used cautiously.

Question 4: APPLIED

A nurse is caring for a patient with severe COPD (known CO₂ retainer with baseline SpO₂ of 89–91%) who has been placed on a non-rebreather mask at 15 L/min by an inexperienced team member after the patient complained of mild shortness of breath. The patient's SpO₂ is now reading 99%, but over the next 30 minutes the patient becomes increasingly drowsy and difficult to arouse. Explain the pathophysiology of what is likely occurring and describe the priority nursing actions.

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This scenario illustrates the danger of administering high-flow oxygen to a patient with chronic CO₂ retention. In patients with severe COPD who chronically retain CO₂, the central chemoreceptors in the brainstem become desensitized to elevated PaCO₂ levels. Their primary drive to breathe shifts to the hypoxic drive—peripheral chemoreceptors in the carotid and aortic bodies detect low PaO₂ and stimulate ventilation. By administering high-flow oxygen (FiO₂ of 80–95% via non-rebreather), the hypoxic drive has been eliminated, resulting in progressive hypoventilation. The patient is now retaining even more CO₂, leading to hypercapnia and CO₂ narcosis—explaining the drowsiness and decreased level of consciousness. The priority nursing actions are: (1) Immediately reduce the oxygen delivery—switch to a Venturi mask at 24–28% FiO₂ or nasal cannula at 1–2 L/min, targeting SpO₂ of 88–92%. (2) Elevate the head of bed. (3) Stimulate the patient to encourage breathing. (4) Notify the provider immediately using SBAR communication. (5) Anticipate an ABG order to assess the degree of respiratory acidosis. (6) Be prepared for potential need for BiPAP or intubation if the patient does not improve.

Question 5: CRITICAL THINKING

You are monitoring four patients simultaneously. Rank the following findings in order of priority (most urgent first) and justify your reasoning using respiratory assessment principles: Patient A — SpO₂ 91%, RR 20, alert; Patient B — SpO₂ 95%, RR 32, using accessory muscles, diaphoretic; Patient C — SpO₂ 88%, RR 12, hx of COPD, drowsy but arousable; Patient D — SpO₂ 97%, RR 8, just received morphine IV 15 min ago.

Show answer

Priority ranking with justification: (1) Patient D is the highest priority. An RR of 8 with recent IV morphine administration strongly suggests opioid-induced respiratory depression, which can rapidly progress to respiratory arrest. The SpO₂ of 97% may be falsely reassuring because supplemental oxygen or the patient's previous oxygenation reserves can maintain saturation temporarily even as ventilation critically declines—SpO₂ is a lagging indicator of hypoventilation. The nurse should stimulate the patient, assess LOC, hold further opioid doses, have naloxone (Narcan) available, and notify the provider immediately. (2) Patient B is the second priority. Despite an SpO₂ of 95%, the markedly elevated RR of 32, accessory muscle use, and diaphoresis indicate significantly increased work of breathing and potential impending respiratory failure. The patient is currently compensating, but these signs suggest the patient may decompensate rapidly. The nurse should position upright, apply or increase O₂, and notify the provider. (3) Patient C is third priority. An SpO₂ of 88% with a history of COPD may be near baseline, but the drowsiness and low RR of 12 are concerning for possible CO₂ retention and narcosis. The nurse should assess whether the patient received sedating medications or excessive O₂, stimulate the patient, and obtain further assessment. (4) Patient A is lowest priority—SpO₂ of 91% with a normal RR and alertness may warrant monitoring and potential low-flow O₂, but there are no signs of acute decompensation. This question illustrates the critical principle that SpO₂ alone does not determine urgency—the clinical picture, including ventilation adequacy, work of breathing, and contextual factors, must all be integrated.

SUMMARY

Summary — Respiratory Status Monitoring and Support

Summary

Respiratory status monitoring is a foundational competency for the practical nurse that requires systematic assessment of airway patency, ventilation adequacy, oxygenation status, and work of breathing. The nurse utilizes multiple monitoring modalities—including pulse oximetry (SpO₂), capnography (EtCO₂), arterial blood gas analysis, and chest auscultation—to build a comprehensive picture of respiratory function. ABG interpretation follows a systematic four-step method: evaluate pH, assess PaCO₂, assess HCO₃⁻, and determine compensation status.

Respiratory support interventions range from low-flow oxygen delivery systems (nasal cannula, simple mask, partial and non-rebreather masks) to high-flow systems (Venturi mask, HFNC, mechanical ventilation). The practical nurse must select the appropriate device based on the patient's oxygenation needs and clinical context—particularly exercising caution with COPD patients who rely on hypoxic drive, targeting an SpO₂ of 88–92%. Escalation to advanced interventions is triggered by persistent hypoxemia, rising PaCO₂, increasing work of breathing, or altered mental status. The LPN's role in this continuum is to collect data, implement prescribed interventions, recognize deterioration, and communicate findings promptly using structured communication tools like SBAR.