Indications and Contraindications of Non-Invasive Ventilation (NIV)
NIV is particularly indicated for COPD patients with respiratory acidosis (pH 7.25-7.35), hypercapnic respiratory failure from chest wall deformity or neuromuscular disease, cardiogenic pulmonary edema unresponsive to CPAP, and weaning from intubation, while it is contraindicated in patients with impaired consciousness, severe hypoxaemia, and copious respiratory secretions. 1
Primary Indications for NIV
Strong Evidence (Grade A Recommendations)
Hypercapnic Respiratory Failure:
- COPD exacerbations with pH 7.25-7.35 (H+ 45-56 nmol/l) after initial medical treatment 1
- Hypercapnic respiratory failure secondary to:
- Chest wall deformity (scoliosis, thoracoplasty)
- Neuromuscular diseases
- Impaired central respiratory drive 1
Cardiogenic Pulmonary Edema:
- When unresponsive to CPAP alone 1
- NIV or CPAP reduces hospital-acquired pneumonia, length of stay, and mortality 2
Ventilator Management:
- Weaning facilitation in patients with hypercapnic respiratory failure 1
- Prevention of post-extubation failure 2
Immunocompromised Patients:
- Treatment of acute respiratory failure in this population 2
Moderate Evidence
Hypoxemic Respiratory Failure:
- Use with extreme caution - high failure rate of 30-50% 2
- May be considered in carefully selected patients who are cooperative, without major organ dysfunction, cardiac ischemia/arrhythmias, and able to clear secretions 3
- Community-acquired pneumonia in selected cases 3
Absolute Contraindications
NIV should NOT be used in the following situations 1, 4:
- Cardiac or respiratory arrest
- Impaired consciousness (Glasgow Coma Score <8) 5
- Note: Recent evidence suggests NIV may be feasible in moderate neurological impairment (GCS ≤13), though severe impairment predicts mortality 6
- Severe hypoxaemia (particularly when unresponsive to initial NIV)
- Copious respiratory secretions with inability to clear them
- Facial surgery or trauma
- Upper airway obstruction
- Inability to protect airway and/or high aspiration risk
- Non-respiratory organ failure:
- Severe encephalopathy
- Severe gastrointestinal bleeding
- Hemodynamic instability with or without unstable cardiac angina
Critical Implementation Requirements
Before initiating NIV, ensure these minimum facilities are available 1:
- A consultant committed to developing an NIV service
- Trained nurses on respiratory ward, HDU, or ICU
- ICU backup for patients who fail NIV
- Non-invasive ventilator and selection of masks
When to Escalate to Invasive Mechanical Ventilation
Immediate intubation is indicated for 5:
- Respiratory arrest or gasping respiration
- Severe respiratory distress
- pH <7.15 despite initial resuscitation
- Depressed consciousness (GCS <8)
- Low cardiac output state
NIV failure is suggested by:
- Persisting or worsening acidosis despite optimized NIV delivery
- pH <7.25 warrants consideration of intubation; <7.15 indicates intubation 5
- Lack of improvement in oxygenation after 1 hour of NIV 4
Common Pitfalls to Avoid
Technical failures that doom NIV success 5:
- Inadequate inspiratory pressure (IPAP) - should escalate to 20-30 cmH₂O within 10-30 minutes, not remain at 15
- Excessive mask leak
- Patient-ventilator asynchrony
- Positional upper airway obstruction
Clinical judgment errors:
- Persisting with ineffective NIV delays necessary intubation and increases mortality 5
- Using NIV as a substitute for intubation when invasive ventilation is clearly more appropriate 1
- In hypoxemic respiratory failure, prolonged NIV with high tidal volumes may exacerbate lung injury 3
Expected Benefits
When appropriately used, NIV reduces 1, 2:
- Intubation rates
- ICU admissions and length of stay
- Hospital-acquired pneumonia
- Mortality in acute respiratory failure