What is non-invasive ventilation (NIV)?

Non-invasive Ventilation (NIV)

Non-invasive ventilation (NIV) is a method of providing ventilatory support through the patient's upper airway using a mask or similar interface rather than an endotracheal tube, effectively delivering positive pressure ventilation without the need for invasive airway access. 1

Definition and Basic Concept

NIV delivers mechanical ventilation to patients with respiratory failure through interfaces such as:

• Nasal masks
• Full face masks
• Nasal pillows
• Mouthpieces
• Total face masks

Unlike invasive mechanical ventilation, NIV preserves the patient's natural airway defenses, speech, and swallowing abilities while reducing complications associated with endotracheal intubation.

Types of NIV

1. Bi-level Positive Airway Pressure (BiPAP):

   • Provides two levels of pressure: higher inspiratory positive airway pressure (IPAP) and lower expiratory positive airway pressure (EPAP)
   • Assists with both inspiration and expiration
   • Most commonly used for hypercapnic respiratory failure

2. Continuous Positive Airway Pressure (CPAP):

   • Delivers constant pressure throughout the respiratory cycle
   • Primarily used for obstructive sleep apnea and cardiogenic pulmonary edema
   • Not technically ventilation but often grouped with NIV modalities

3. Other modes:

   • Pressure support (PS)
   • Proportional assist ventilation (PAV)
   • Spontaneous/timed (S/T) modes

Key Clinical Indications

NIV is particularly indicated in 1:

• COPD exacerbations with respiratory acidosis (pH 7.25–7.35)

  • Reduces mortality by 46% compared to standard care 2
  • Decreases need for endotracheal intubation by 65% 2

• Hypercapnic respiratory failure secondary to:

  • Chest wall deformities (scoliosis, thoracoplasty)
  • Neuromuscular diseases
  • Obesity-hypoventilation syndrome 3

• Cardiogenic pulmonary edema unresponsive to CPAP

• Weaning from invasive mechanical ventilation

• Chronic respiratory conditions requiring nocturnal ventilatory support 3

Contraindications and Limitations

NIV should not be used in patients with 1:

• Impaired consciousness
• Severe hypoxemia without hypercapnia
• Copious respiratory secretions
• Inability to protect airway
• Recent facial or upper airway surgery
• Vomiting or high aspiration risk
• Hemodynamic instability

Clinical Benefits

Implementation of an NIV service provides significant clinical advantages 1, 2:

• Reduced mortality in appropriate patients
• Decreased need for endotracheal intubation
• Shorter hospital and ICU stays (average reduction of 3.39 days) 2
• Fewer complications compared to invasive ventilation
• Improved arterial blood gas parameters (pH and PaO2)
• Preservation of airway defense mechanisms

Implementation Requirements

To establish an effective NIV service, hospitals require 1:

• A committed consultant to develop and oversee the service
• Trained nursing staff in respiratory wards, HDU, or ICU
• Backup ICU support for patients who fail NIV
• Appropriate equipment (ventilators and mask interfaces)
• Protocols for patient selection, monitoring, and escalation of care

Monitoring and Management

Patients on NIV require:

• Regular assessment of vital signs
• Continuous pulse oximetry
• Periodic arterial blood gas measurements
• Evaluation of patient comfort and synchrony with the ventilator
• Assessment for mask-related complications (skin breakdown, air leaks)

Common Pitfalls to Avoid

1. Inappropriate patient selection: NIV is not suitable for all types of respiratory failure. Careful assessment is crucial to identify patients who will benefit.

2. Delayed intubation: Recognizing NIV failure early is essential. Continuing NIV when a patient requires intubation can worsen outcomes.

3. Inadequate interface fitting: Poor mask fit leads to air leaks, patient discomfort, and treatment failure.

4. Insufficient monitoring: NIV patients require close observation, especially in the initial hours of therapy.

5. Inadequate humidification: Can lead to upper airway dryness and patient intolerance.

NIV has transformed the management of acute and chronic respiratory failure, providing effective ventilatory support while avoiding the complications associated with invasive mechanical ventilation. When applied to appropriately selected patients with proper technique and monitoring, it significantly improves clinical outcomes and reduces mortality.