What is Non-Invasive Ventilation (NIV) respiratory?

What is Non-Invasive Ventilation (NIV)?

Non-invasive ventilation (NIV) is a method of delivering positive pressure ventilatory support through a face or nasal mask without requiring endotracheal intubation, primarily used to treat acute hypercapnic respiratory failure and avoid the complications associated with invasive mechanical ventilation. 1

Core Definition and Mechanism

NIV refers specifically to non-invasive positive pressure ventilation delivered via mask interface, distinct from older techniques like external negative pressure ventilation or rocking beds. 1 The technique provides:

• Inspiratory positive airway pressure (IPAP) to assist ventilation and reduce work of breathing 2
• Expiratory positive airway pressure (EPAP) to maintain airway patency and improve oxygenation 2
• Avoidance of endotracheal intubation and its associated complications including ventilator-associated pneumonia, airway trauma, and need for sedation 3, 4

Important distinction: NIV is different from CPAP (continuous positive airway pressure), which provides constant pressure throughout the respiratory cycle without varying inspiratory support. 1 While CPAP may provide some respiratory support, NIV delivers true ventilatory assistance with pressure cycling. 1

Primary Clinical Indications

Strongest Evidence (Grade A)

• COPD exacerbation with respiratory acidosis (pH 7.25-7.35) after maximal medical therapy - this carries the strongest evidence with demonstrated reductions in intubation rates, ICU length of stay, and mortality 1, 2, 5
• Hypercapnic respiratory failure from chest wall deformity (scoliosis, thoracoplasty) or neuromuscular disease 1, 5
• Cardiogenic pulmonary edema unresponsive to CPAP alone 1, 5
• Weaning from mechanical ventilation, particularly in COPD patients 1, 5

Conditional Indications (Weaker Evidence)

• Immunocompromised patients with hypoxemic respiratory failure 5, 4
• Mild ARDS (PaO₂/FiO₂ 200-300 mmHg) in highly selected patients with SAPS II score <34, hemodynamic stability, and close ICU monitoring 6

Absolute Contraindications

NIV should never be used in patients with: 1

• Impaired consciousness or inability to protect airway - risk of aspiration
• Severe hypoxemia unresponsive to initial therapy - requires immediate intubation
• Copious respiratory secretions - cannot be managed without suctioning
• Hemodynamic instability or multi-organ failure 6

Critical pitfall: NIV should not be used as a substitute for intubation when invasive ventilation is clearly more appropriate. 1 Delayed intubation due to inappropriate NIV trial increases mortality. 6

Initial Settings and Application

Starting Parameters 2

• IPAP: Begin at 8-12 cmH₂O
• EPAP: Begin at 3-5 cmH₂O
• FiO₂: Start at 40% and titrate to maintain SpO₂ >92% (or 85-90% in COPD patients to avoid CO₂ retention)

Interface Selection 2, 5

• Use full-face mask initially in acute settings for better seal and patient tolerance
• Switch to nasal mask after 24 hours as patient improves
• Have multiple mask sizes and types available to minimize air leaks and skin breakdown 5

Monitoring for Success or Failure

Timing of Assessment 2

• Obtain arterial blood gases at 1-2 hours to assess PaO₂, PaCO₂, and pH improvement
• Expect improvement by 4-6 hours - lack of progress indicates likely NIV failure and need for intubation 2, 6
• Monitor continuously for deteriorating consciousness level, which requires immediate consideration of intubation 2

Failure Predictors 6

• Rapid Shallow Breathing Index (RSBI) >105 breaths/min/L indicates likely need for intubation
• Persistent tachypnea, accessory muscle use, or worsening gas exchange despite optimized NIV settings

Clinical Benefits

When applied appropriately, NIV provides: 1, 5

• Fewer patients requiring ICU admission for intubation
• Shorter ICU length of stay
• Reduced mortality in acute respiratory failure
• Avoidance of ventilator-associated pneumonia and other intubation complications 3, 4

Common Pitfalls to Avoid

• Do not give excessive oxygen in COPD patients - target SpO₂ 85-90% to prevent worsening hypercapnia 2
• Do not delay intubation when NIV is failing - controlled intubation is safer than emergent intubation 6
• Do not use NIV in pneumonia with severe hypoxemia - most patients will require intubation and should be in ICU/HDU setting 2
• Do not apply NIV without adequate monitoring and backup - requires trained staff and ICU availability for failed cases 1