What are the recommended Non-Invasive Ventilation (NIV)-Bi-Level Positive Airway Pressure (BiPAP) settings for a patient with type 2 respiratory failure?

NIV-BiPAP Settings for Type 2 Respiratory Failure

Start BiPAP with IPAP 10-12 cmH₂O and EPAP 4-5 cmH₂O, titrating IPAP upward based on patient tolerance and CO₂ clearance, while maintaining SpO₂ 88-92%. 1, 2

When to Initiate NIV

Initiate NIV when all three criteria persist after one hour of optimal medical therapy (controlled oxygen, bronchodilators, corticosteroids, antibiotics if indicated): 2

• pH <7.35
• PaCO₂ ≥6.5 kPa (49 mmHg)
• Respiratory rate >23 breaths/min

For PaCO₂ between 6.0-6.5 kPa (45-49 mmHg), NIV may be considered but is not mandatory—continue optimal medical care with repeat arterial blood gas measurement before committing to NIV. 1, 2

Initial Ventilator Settings

Pressure Settings

• IPAP (Inspiratory Positive Airway Pressure): 10-12 cmH₂O initially 1, 2

  • Titrate upward by 2-3 cmH₂O increments based on patient tolerance, work of breathing, and CO₂ clearance 1
  • The IPAP setting is most frequently adjusted to target adequate tidal volumes and reduce work of breathing 3

• EPAP (Expiratory Positive Airway Pressure): 4-5 cmH₂O 4, 1, 2

  • EPAP offsets intrinsic PEEP (PEEPi), facilitates triggering, and vents exhaled gas through the exhaust port 4
  • Critical pitfall: Setting EPAP greater than intrinsic PEEP in COPD can worsen air trapping and harm the patient 1
  • Normally used EPAP levels of 3-5 cmH₂O do not completely eliminate rebreathing, especially when respiratory frequency increases 4

Oxygen and Backup Rate

• FiO₂: Titrate to maintain SpO₂ 88-92% 1, 2

  • Critical pitfall: Setting FiO₂ too high (>96%) worsens hypercapnia in type 2 respiratory failure 1
  • Target oxygen saturation of 88-92% avoids worsening hypercapnia 5, 2

• Backup rate: Set to ensure minimum ventilation in patients with poor respiratory drive 1

  • A backup rate of 6-8 breaths per minute is reasonable 4

Interface Selection

• Use a full-face mask initially in the acute setting 2

Monitoring Protocol

Arterial Blood Gas Timing

• Check ABG at 1-2 hours after initiating NIV to assess early response 1, 2
• Repeat ABG at 4-6 hours if the earlier sample showed little improvement 5, 1

Target Parameters

• pH >7.20 with improvement in work of breathing 1
• Normalization of PaCO₂ 1
• SpO₂ 88-92% 1, 2

Clinical Assessment

Monitor closely within 1-2 hours to prevent delay in intubation if needed—look for: 1

• Improvement in respiratory rate and work of breathing
• Patient comfort and mask tolerance
• Level of consciousness

When to Escalate to Intubation

Failure to improve PaCO₂ and pH after 4-6 hours of NIV indicates treatment failure and need for intubation. 5, 1

Specific Failure Criteria

• Worsening respiratory acidosis despite optimal ventilator settings 1
• Increasing oxygen requirements 1
• Decreased level of consciousness 1
• Inability to clear secretions 1
• Severe acidosis (pH <7.25) or severe hypoxemia despite NIV 1

Critical pitfall: Delaying intubation when NIV is failing increases mortality. 1

Location of Care

• ICU or HDU: pH <7.25 or high risk of deterioration 2
• Respiratory ward: pH 7.25-7.35 with stable presentation, if appropriate nursing ratios and monitoring are available 2

Contraindications to NIV

Absolute Contraindications

• Recent facial or upper airway surgery 2
• Fixed upper airway obstruction 2
• Active vomiting 2
• Inability to protect airway 2
• Respiratory arrest 2
• Impaired consciousness 5
• Copious respiratory secretions 5

Relative Contraindications (Require Contingency Planning)

• Recent upper gastrointestinal surgery 2
• Severe confusion/agitation 2
• Life-threatening hypoxemia 2
• Pneumothorax 2

Advanced Considerations

AVAPS (Average Volume Assured Pressure Support) mode may result in more rapid improvement in pH and PaCO₂ compared to standard BiPAP S/T mode, though this is based on limited evidence from a single study. 6 AVAPS integrates characteristics of both volume and pressure-controlled modes, with pressure as the dependent variable rather than volume. 6