Respiratory Failure
Key Points
- Respiratory failure = impaired gas exchange → hypoxemia (PaO2 <60 mm Hg) and/or hypercapnia (PaCO2 >50 mm Hg)
- Two types: hypoxemic (oxygenation failure) and hypercapnic (ventilation failure)
- ARDS is the most severe form of ARF, with ~40% mortality rate
- Priority interventions: airway management, supplemental O2, mechanical ventilation when indicated
- VAP bundle is a critical nursing quality measure for intubated patients
Pathophysiology
Acute respiratory failure (ARF) is a sudden failure of the lungs that causes impaired gas exchange, resulting in the inability to meet the body’s metabolic oxygen demands. ARF leads to hypoxemia (low blood oxygen) causing inadequate organ perfusion, and/or hypercapnia (elevated CO2 accumulation).
Hypoxia and hypoxemia are related but not synonymous. Hypoxia is reduced tissue oxygenation, while hypoxemia is decreased arterial oxygen partial pressure (PaO2).
Classification
| Type | Definition | Diagnostic Criteria | Common Causes |
|---|---|---|---|
| Hypoxemic | Lungs fail to provide adequate oxygen | PaO2 <60 mm Hg without elevated CO2 | Pneumonia, ARDS, intrapulmonary shunting, V/Q mismatch |
| Hypercapnic | Lungs fail to eliminate CO2 | PaCO2 >50 mm Hg | Pump failure, decreased respiratory drive, airway obstruction, COPD exacerbation |
Acute Respiratory Distress Syndrome (ARDS): The most severe form of ARF. Widespread lung inflammation causes alveolar fluid accumulation, severely reducing gas exchange. Mortality ~40%.
ARDS Causes — Direct: gastric aspiration, respiratory infection (pneumonia, COVID-19), chest trauma, near-drowning. Indirect: sepsis, burns, drug overdose, multiple blood transfusions.
Nursing Assessment
NCLEX Focus
Know the diagnostic criteria for ARDS: acute onset within 1 week + bilateral infiltrates on CXR + PaO2:FiO2 ratio <300 mm Hg. Also memorize ABG normal values — these appear frequently in respiratory questions.
Signs and Symptoms:
- Dyspnea, tachypnea → progressing to respiratory alkalosis
- Fine crackles on auscultation
- Restlessness, irritability → decreased level of consciousness
- Hypoxemia that does NOT improve with supplemental oxygen (hallmark of ARDS)
- Cyanosis (late sign)
Diagnostic Criteria for ARDS:
- Acute onset (within 1 week of insult)
- Bilateral lung infiltrates on chest X-ray (ground-glass opacities) — noncardiac origin
- PaO2:FiO2 ratio <300 mm Hg
ABG Values (Normal Reference):
| Component | Normal Range | Significance |
|---|---|---|
| PaO2 | 80–100 mm Hg | <60 mm Hg = hypoxemia |
| pH | 7.35–7.45 | <7.35 = acidemia |
| PaCO2 | 35–45 mm Hg | >45 mm Hg = respiratory acidosis |
| HCO3⁻ | 22–26 mEq/L | <22 = metabolic acidosis |
Nursing Interventions
Airway and Oxygenation:
- Position HOB ≥30° to optimize lung expansion and prevent aspiration
- Administer supplemental oxygen; titrate to SpO2 target
- Prepare for endotracheal intubation and invasive-mechanical-ventilation-modes when oxygen therapy is inadequate
- Suction airway as needed (in-line catheter for ventilated patients)
Mechanical Ventilation Care:
- Collaborate with respiratory therapy team for ventilator settings
- Monitor ETT cuff pressure regularly
- Assess and document ventilator mode, tidal volume, PEEP settings
- Perform spontaneous breathing trials (SBTs) as ordered
VAP Bundle (Ventilator-Associated Pneumonia Prevention)
For all intubated patients, implement the VAP bundle:
- Maintain ETT cuff pressure
- HOB elevated ≥30°
- Oral care with chlorhexidine swabs every 2–4 hours
- Daily sedation vacation with assessment for extubation readiness
- Stress ulcer prophylaxis (proton pump inhibitor or H2 blocker)
- DVT prophylaxis
Pharmacological Support:
- Sedatives/paralytics: Used during mechanical ventilation; pause daily for neurological assessment (“sedation vacation”)
- IV opioids: Manage pain from ETT and immobility; assess for nonverbal pain cues
- Corticosteroids: Reduce airway inflammation; monitor for infection risk and hyperglycemia
- Bronchodilators: Treat bronchospasm contributing to ventilatory failure
Prone Positioning: Used in ARDS to improve oxygenation by redistributing lung perfusion.
Clinical Judgment Application
Clinical Scenario
A 58-year-old with sepsis develops worsening dyspnea. SpO2 drops to 82% despite 100% non-rebreather mask. ABG shows PaO2 58 mm Hg, PaCO2 30 mm Hg, pH 7.50.
- Recognize Cues: SpO2 82%, PaO2 58 mm Hg (hypoxemia), respiratory alkalosis (hyperventilating to compensate), non-rebreather ineffective
- Analyze Cues: Hypoxemic respiratory failure; meets ARDS criteria given sepsis etiology and non-responsive hypoxemia
- Prioritize Hypotheses: Acute respiratory failure secondary to sepsis-induced ARDS
- Take Action: Notify provider immediately; prepare for intubation/mechanical ventilation; continue high-flow O2; position HOB 30-45°
- Evaluate Outcomes: SpO2 ≥90%, PaO2 >60 mm Hg post-intubation; ventilator settings adjusted per ABG
Related Concepts
- invasive-mechanical-ventilation-modes — Primary intervention for severe respiratory failure
- Sepsis — Leading indirect cause of ARDS
- Pneumonia — Common direct cause of ARF
- arterial-blood-gas-abg — Essential diagnostic tool for monitoring gas exchange
- oxygen-therapy-device-selection-and-monitoring — First-line treatment before mechanical ventilation
- bronchial-hygiene-techniques — Airway clearance strategies in respiratory compromise
- respiratory-system — Underlying physiological basis for gas exchange
Self-Check
- What distinguishes hypoxemic respiratory failure from hypercapnic respiratory failure, and what are the ABG criteria for each?
- A ventilated patient’s SpO2 drops to 88%. List three nursing actions in priority order.
- What are the five components of the VAP bundle, and why is each important?