What is the recommended approach for non-invasive ventilation (NIV) in patients with respiratory failure?

Recommended Approach for Non-Invasive Ventilation in Respiratory Failure

Non-invasive ventilation (NIV) should be considered first-line therapy for patients with acute exacerbation of COPD who have respiratory acidosis (pH <7.35) despite maximum medical treatment on controlled oxygen therapy. 1

Primary Indications for NIV

NIV has proven effectiveness in several specific clinical scenarios:

• COPD exacerbations with respiratory acidosis: Strong evidence supports NIV use when pH <7.35 and PaCO₂ >45 mmol/l despite optimal medical therapy 2, 1
• Cardiogenic pulmonary edema: CPAP should be tried first; NIV reserved for patients in whom CPAP is unsuccessful 2
• Neuromuscular disease or chest wall deformity: NIV indicated in acute or acute-on-chronic hypercapnic respiratory failure 1
• Weaning from invasive ventilation: NIV should be used when conventional weaning strategies fail 2, 1
• Immunocompromised patients: NIV reduces both intubation rate and mortality 2

Patient Selection Algorithm

1. Assess respiratory failure type:

   • Type 1 (hypoxemic): Consider CPAP first
   • Type 2 (hypercapnic): Consider bi-level NIV first

2. Determine severity:

   • Mild-moderate acidosis (pH 7.30-7.35): Can be managed on respiratory ward
   • Severe acidosis (pH <7.30): Requires HDU/ICU setting 1

3. Evaluate for contraindications:

   • Absolute: Recent facial/upper airway surgery, facial abnormalities, fixed upper airway obstruction, active vomiting 2
   • Relative: Inability to protect airway, copious secretions, life-threatening hypoxemia, severe confusion/agitation 1

Equipment Selection

• Ventilator type: Bi-level pressure support ventilators are recommended for acute NIV services (simpler, cheaper, more flexible) 2
• Interface: Full-face mask initially in acute settings, transitioning to nasal mask after 24 hours as patient improves 2, 1
• Settings: Start with low pressures and gradually increase:
  • IPAP: 10-12 cmH₂O initially, increase as tolerated to 20-25 cmH₂O
  • EPAP: 4-5 cmH₂O initially, increase as needed for oxygenation
  • FiO₂: Titrate to maintain SpO₂ 85-90% in COPD patients 2

Monitoring Protocol

1. Initial assessment (first 1-2 hours):

   • Continuous monitoring of vital signs, SpO₂, and work of breathing
   • Arterial blood gas analysis after 1-2 hours of NIV 1

2. Ongoing assessment:

   • Repeat ABG after 4-6 hours if earlier sample showed little improvement
   • Monitor for signs of NIV failure: worsening respiratory distress, deteriorating gas exchange, inability to tolerate mask 2

3. Success indicators:

   • Improvement in pH and PaCO₂ within 1-4 hours
   • Reduction in respiratory rate and work of breathing
   • Improved patient comfort and synchrony with ventilator 2

Special Clinical Scenarios

• Pneumonia: NIV should only be used in HDU/ICU settings with immediate intubation capabilities 1
• Chest wall trauma: CPAP recommended for patients who remain hypoxic despite adequate regional anesthesia and high-flow oxygen 2
• Asthma: NIV should not be used routinely 2
• Bronchiectasis: NIV may be tried in patients with respiratory acidosis, but excessive secretions likely limit effectiveness 2

Treatment Failure Management

If NIV is failing, systematically evaluate:

1. Medical treatment optimization: Ensure prescribed treatments have been administered
2. Complications: Consider pneumothorax, aspiration pneumonia
3. Technical issues: Check for mask fit, circuit setup, excessive leakage
4. Ventilator settings: Adjust pressure/volume settings, inspiratory time, respiratory rate 2

Duration and Weaning

• Acute phase: Ventilate for as many hours as possible in first 24 hours 2
• Weaning: Gradually reduce ventilator support as patient improves
• Duration: Most patients can be weaned within a few days; if NIV still needed after one week, consider referral for long-term NIV 2

Common Pitfalls to Avoid

• Delayed escalation: Promptly recognize NIV failure and intubate before crisis develops 3
• Inappropriate setting: Patients with severe acidosis or conditions with limited NIV evidence should be managed in HDU/ICU 1
• Inadequate monitoring: Continuous monitoring is essential during the first 24 hours 1
• Mask-related problems: Ensure proper mask fit and rotation between different interfaces to prevent pressure ulcers
• Unclear treatment goals: Document whether NIV is a trial with intubation as backup or ceiling of treatment 2, 1

NIV has revolutionized the management of acute respiratory failure, reducing mortality, hospital stay, and need for intubation when applied appropriately in selected patients 4, 5. The key to success lies in proper patient selection, appropriate setting, careful monitoring, and having trained staff familiar with the equipment 6.