What is the recommended approach to assess and treat acute respiratory failure, including oxygen supplementation, non‑invasive positive‑pressure ventilation, intubation criteria, and specific management for COPD exacerbation, cardiogenic pulmonary edema, pneumonia/ARDS, and sepsis?

Acute Respiratory Failure: Assessment and Management

Immediate Oxygen Therapy

Target oxygen saturation of 88-92% using controlled-delivery devices (Venturi mask 24-28% or nasal cannula 1-2 L/min) to correct life-threatening hypoxemia while minimizing CO₂ retention. 1, 2

• Obtain arterial blood gas within 60 minutes of starting oxygen to detect hypercapnia (PaCO₂ >45 mmHg) or acidosis (pH <7.35) 1, 2
• If initial ABG shows normal pH and PaCO₂, increase target to 94-98% unless the patient has prior hypercapnic failure requiring NIV or usual stable saturation <94% 1, 2
• Repeat ABG at 30-60 minutes if clinical deterioration occurs; pH <7.26 with rising PaCO₂ mandates immediate NIV 1, 2
• Higher oxygen concentrations (>28% FiO₂ or >4 L/min) worsen hypercapnic respiratory failure and increase mortality in COPD 2, 3, 4

Non-Invasive Positive-Pressure Ventilation (NIV)

Initiate NIV immediately as first-line therapy when acute hypercapnic respiratory failure (PaCO₂ >45 mmHg) with acidosis (pH <7.35) persists >30 minutes after standard medical management. 1, 2

NIV Benefits and Success Rates

• Reduces intubation rates by approximately 50% 1, 2
• Improves gas exchange and reduces work of breathing 1, 2
• Shortens hospital stay and improves survival 1, 2
• Success rate of 80-85% in appropriately selected patients 2

Contraindications to NIV

• Respiratory arrest 1
• Cardiovascular instability (hypotension, arrhythmias, myocardial infarction) 1
• Impaired mental status, somnolence, inability to cooperate 1
• Copious and/or viscous secretions with high aspiration risk 1
• Recent facial or gastro-oesophageal surgery 1
• Craniofacial trauma or fixed naso-pharyngeal abnormality 1

Intubation Criteria

Consider intubation when respiratory failure leads to hypoxemia (PaO₂ <60 mmHg), hypercapnia (PaCO₂ >50 mmHg), and acidosis (pH <7.35) that cannot be managed non-invasively. 1

Specific Intubation Indications

• NIV failure: worsening ABGs and/or pH in 1-2 hours; lack of improvement after 4 hours 1
• Severe acidosis (pH <7.25) with hypercapnia (PaCO₂ >60 mmHg) 1
• Life-threatening hypoxemia (PaO₂/FiO₂ <200 mmHg) 1
• Tachypnea >35 breaths/min 1

COPD Exacerbation Management

Bronchodilator Therapy

Administer combined short-acting β₂-agonist (salbutamol 2.5-5 mg) plus short-acting anticholinergic (ipratropium 0.25-0.5 mg) via nebulizer every 4-6 hours during the acute phase. 1, 2

• This combination provides superior bronchodilation lasting 4-6 hours compared to either agent alone 1, 2
• Nebulizers should be powered with compressed air, not oxygen, when PaCO₂ is elevated 2
• Avoid intravenous methylxanthines (theophylline) due to increased side effects without added benefit 1, 2

Systemic Corticosteroids

Give oral prednisone 30-40 mg once daily for exactly 5 days starting immediately. 1, 2

• This 5-day course is as effective as 14-day regimens while reducing cumulative steroid exposure by >50% 2
• Improves lung function, oxygenation, shortens recovery time, and reduces treatment failure by >50% 2
• Oral administration is equally effective to intravenous unless oral intake is impossible 2
• Do not extend beyond 5-7 days unless separate indication exists 1, 2

Antibiotic Therapy

Prescribe antibiotics for 5-7 days when increased sputum purulence is present together with either increased dyspnea or increased sputum volume (two of three cardinal symptoms). 2

• Reduces short-term mortality by ~77%, treatment failure by ~53%, and sputum purulence by ~44% 2
• First-line agents (based on local resistance patterns): amoxicillin/clavulanate 875/125 mg twice daily, doxycycline 100 mg twice daily, or macrolides 1, 2
• Most common organisms: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis 1, 2

Cardiogenic Pulmonary Edema Management

Non-invasive positive pressure ventilation (CPAP or BiPAP) should be considered in patients with respiratory distress (respiratory rate >25 breaths/min, SpO₂ <90%) and started as soon as possible to decrease respiratory distress and reduce mechanical intubation rates. 1

• CPAP is particularly indicated in cardiogenic pulmonary edema unresponsive to initial therapy 1
• Monitor blood pressure regularly as NIV can reduce blood pressure and should be used cautiously in hypotensive patients 1
• BiPAP allows inspiratory pressure support that improves minute ventilation, especially useful in patients with hypercapnia 1

Pneumonia/ARDS Management

High-Flow Nasal Oxygen (HFNO) Considerations

HFNO may reduce intubations by a moderate amount (absolute risk difference -9.4%) and may reduce all-cause mortality by a large amount (absolute risk difference -15.8%) compared with NIV in hypoxic acute respiratory failure. 1

• HFNO may improve patient comfort compared to NIV 1
• Baseline SpO₂ weighted mean in initial management trials was 88% 1
• HFNO may reduce hospital-acquired pneumonia compared to NIV 1

Severe Hypoxemia Management

• NIV is not indicated in severe hypoxemia or impaired consciousness 1
• Intubation is recommended if respiratory failure with hypoxemia (PaO₂ <60 mmHg), hypercapnia (PaCO₂ >50 mmHg), and acidosis (pH <7.35) cannot be managed non-invasively 1

Sepsis-Related Respiratory Failure

In sepsis with acute respiratory failure, prioritize controlled oxygen to maintain SpO₂ 88-92% while addressing the underlying septic process. 2

• Obtain ABG within 60 minutes to guide ventilatory support decisions 2
• Initiate NIV if hypercapnic respiratory failure develops (pH <7.35, PaCO₂ >45 mmHg) 2
• Consider early intubation if hemodynamic instability, altered mental status, or inability to protect airway 1

Common Pitfalls to Avoid

• Never administer high-flow oxygen (>28% FiO₂ or >4 L/min) without concurrent blood-gas monitoring as this worsens hypercapnic respiratory failure and increases mortality 2, 4
• Do not power nebulizers with oxygen in patients with hypercapnia; use compressed air with supplemental oxygen via nasal cannula 2
• Avoid delaying NIV in patients with acute hypercapnic respiratory failure as early initiation improves outcomes 2
• Do not use methylxanthines in acute exacerbations due to side effect profile without benefit 1, 2
• Prevention of tissue hypoxia supersedes CO₂ retention concerns—correct hypoxemia first with controlled oxygen 1