What is Non-Invasive Ventilation (NIV)?

Non-Invasive Ventilation (NIV)

Non-invasive ventilation (NIV) refers to the delivery of mechanical ventilation to the lungs using techniques that do not require an endotracheal airway, primarily through face or nasal masks rather than invasive methods such as endotracheal intubation. 1

Definition and Mechanism

NIV delivers positive pressure ventilation through external interfaces such as:

• Facial masks
• Nasal masks
• Helmets
• Mouthpieces

This approach provides ventilatory support while avoiding the complications associated with invasive mechanical ventilation, including ventilator-associated pneumonia, trauma to the airways, and the need for sedation.

Primary Modalities

There are two main types of NIV:

1. Continuous Positive Airway Pressure (CPAP):

   • Delivers constant positive pressure throughout the respiratory cycle
   • Typically set at around 10 cmH₂O
   • Simpler technique that may reduce preload and afterload, potentially increasing cardiac output
   • Used successfully for acute pulmonary edema for over 30 years 2

2. Pressure Support Ventilation (NIPSV/BiPAP):

   • Provides two levels of pressure:
     • Inspiratory positive airway pressure (IPAP)
     • Expiratory positive airway pressure (EPAP)
   • More complex mode requiring a ventilator and clinical experience
   • Usually applied with EPAP of 5 cmH₂O and inspiratory pressure between 12-25 cmH₂O 2
   • Particularly useful for patients with fatigue and hypercapnia

Key Indications

NIV is particularly indicated in:

• COPD exacerbations with respiratory acidosis (pH 7.25–7.35, H+ 45–56 nmol/l) 1, 3
• Hypercapnic respiratory failure secondary to:
  • Chest wall deformity (scoliosis, thoracoplasty)
  • Neuromuscular diseases
  • Impaired central respiratory drive 1, 3
• Cardiogenic pulmonary edema unresponsive to CPAP 1
• Weaning from tracheal intubation 1
• Chronic stable hypercapnic COPD (PaCO₂ >45 mmHg in stable state) 3

Contraindications

NIV should not be used in patients with:

• Impaired consciousness 1, 3
• Severe hypoxemia 1, 3
• Copious respiratory secretions 1, 3
• As a substitute for tracheal intubation when invasive ventilation is clearly more appropriate 1

Clinical Benefits

NIV has been demonstrated to:

• Reduce mortality by 46% in acute hypercapnic respiratory failure 4
• Decrease the need for endotracheal intubation by 65% 4
• Shorten hospital stays (average reduction of 3.39 days) 4
• Improve gas exchange (pH and PaO₂) 4
• Reduce ICU admissions 3
• Improve quality of life in chronic applications 3
• Reduce hospital readmissions in chronic applications 3

Implementation Requirements

For successful NIV implementation, hospitals need:

• A committed physician/consultant leading the service
• Nurses trained in NIV application and monitoring
• ICU support for backup when NIV fails
• Appropriate non-invasive ventilator equipment and mask selection 1, 3

Monitoring and Assessment

• Response to NIV should be evaluated within the first 1-4 hours
• Improvement in pH and/or respiratory rate are predictors of success
• Arterial blood gas analysis should be performed before and after NIV initiation
• For chronic use, targeting normalization of PaCO₂ is recommended 3

Practical Considerations

• NIV should be applied early, before severe acidosis develops
• Achieving good patient-ventilator synchrony and minimizing leakage is essential
• High FiO₂ and judicious sedation with opiates may be complementary measures in some contexts 2
• Treatment intolerance is a significant concern, occurring in approximately 11% of patients 4

Common Pitfalls to Avoid

1. Delayed application: NIV should be initiated early in the course of respiratory failure
2. Inappropriate patient selection: Recognize contraindications
3. Inadequate monitoring: Regular assessment of response is crucial
4. Poor mask fit: Leads to leaks and reduced efficacy
5. Insufficient staff training: Proper training is essential for successful implementation
6. Using NIV when invasive ventilation is clearly needed: NIV should not delay necessary intubation

NIV represents an evidence-based intervention that significantly improves outcomes in carefully selected patients with respiratory failure, reducing mortality and avoiding complications associated with invasive ventilation.