Non-invasive Ventilation (NIV)/(NPPV)

When to Use NIV

Hypercapnic Respiratory Failure

• Severe dyspnea at rest
• Respiratory rate >25 breaths/min
• Use of accessory muscle of respiration
• Acute respiratory acidosis (pH <7.30)
• An alert and cooperative patient

Hypoxemic Respiratory Failure

• Respiratory rate >30 breaths/min
• PaO₂/FiO₂ <200
• Increased use of accessory muscle or PaCO₂ retention
• Alert and cooperative patient

[!Note]

Patients may feel claustrophobic, especially when increasing respiratory drive and when difficult breathing is present.
NIV is tolerated best when pressures are increased gradually, as the work of breathing and respiratory drive eases

Initial Settings

• Spontaneous trigger mode with backup rate
• Start with low pressures
  • IPAP 8–12 cm H₂O
  • PEEP 3–5 cm H₂O
• Adjust inspired O₂ to keep O₂ sat >90 %
• Increase IPAP gradually up to 20 cm H₂O (as tolerated) to:
  • alleviate dyspnea
  • decrease respiratory rate
  • increase tidal volume
  • establish patient-ventilator synchrony

Backup rates in COPD

• backup rate: 15 breaths/min
• backup inspiration:expiration ratio: 1:3

[!Note]

Airway pressures above 20 cm H₂O are not advised because they are poorly tolerated by patients, and promote air leaks around the face masks.

Success and Failure Criteria for NIPPV

• Improvements in pH and PCO₂ occurring within 2 h predict the eventual success of NIV.
• If stabilization or improvement has not been achieved during this time period, the patient should be considered an NPPV failure and intubation must be strongly considered.
• Other criteria for a failed NPPV trial include:
  • worsened encephalopathy or agitation
  • inability to clear secretions
  • inability to tolerate any available mask
  • hemodynamic instability
  • worsened oxygenation