Non-Invasive Ventilation (NIV)
Objectives — Identify the design features of a non-invasive ventilator; initiate mask or nasal CPAP/BiPAP; and apply all features for a non-invasive mechanical ventilator.
What Is NIV?
Non-Invasive Ventilation (NIV) provides ventilatory support without a controlled airway — the patient is not intubated. It is positive pressure ventilation delivered via a mask or similar interface.
NIV encompasses:
- NPPV — Non-Invasive Positive Pressure Ventilation
- CPAP — Continuous Positive Airway Pressure
- HFNC — High-Flow Nasal Cannula
Indications
Acute Care Settings
- Hypoxemic Respiratory Failure (Type I)
- Hypercapnic Respiratory Failure (Type II)
- Asthma exacerbation
- Facilitate weaning in COPD patients
- Acute cardiogenic pulmonary edema
- Pneumonia
- ARDS / ALI
- ARF in immunocompromised patients
- Palliative care
- Post-operative respiratory failure
- Prevent reintubation in high-risk patients
- Post-extubation respiratory failure
Goals — Acute Care
- Improve gas exchange
- Avoid intubation
- Decrease:
- Mortality
- Length of time on invasive ventilator
- Length of hospitalization
- Ventilator-Associated Pneumonia (VAP)
Contraindications
| Contraindication | Reason |
|---|---|
| Apnea | Cannot maintain breathing between support cycles |
| Inability to protect airway / high aspiration risk | Secretions could be aspirated |
| Hemodynamic or cardiac instability | Positive pressure may worsen hemodynamics |
| Lack of patient cooperation | Mask cannot be maintained |
| Excessive secretions | Airway cannot be managed without intubation |
| Cannot use interface (facial burns, trauma, abnormal anatomy) | Adequate seal cannot be achieved |
Side Effects
| Side Effect | Details |
|---|---|
| Nasal irritation and congestion | From dry gas flow |
| Dry mouth / throat | Particularly with mouth breathing |
| Eye / skin irritation | From mask leaks or straps |
| Pressure or pain in ears | From pressure changes |
| Gastric bloating | Excess air swallowed |
| Claustrophobia | Particularly with full-face masks |
| Pressure sores | From mask straps over time |
| Excessive air leak | Especially in mouth-breathers |
Interfaces
The choice of interface significantly affects patient comfort, compliance, and effectiveness.
| Interface | Pros | Cons |
|---|---|---|
| Nasal Mask | Well-tolerated, less claustrophobic, allows communication and coughing, lower dead space | Mouth must remain closed |
| Nasal Pillows | Minimal contact, very comfortable | Pressure sores at nares, less effective seal |
| Hybrid | Combines nasal and oral coverage | — |
| Full Face Mask | Better seal, can treat respiratory failure | Claustrophobic, aspiration risk, pressure sores, poorly tolerated |
| Total Face Mask | Covers entire face; less cooperation needed, improved vision, no pressure sores | Fewer sizes available, moisture can fog the mask |
| Helmet | Full head enclosure; no pressure sores | Less common, requires special circuit |
NIV Devices vs. Invasive Mechanical Ventilators
Key Differences
| Feature | NIV Device | ICU Mechanical Ventilator |
|---|---|---|
| Power source | Electric (blower driven) | Electric + compressed gas (combination) |
| Circuit | Single-limb | Dual-limb |
| Exhalation valve | None | Yes |
| Leaks | Tolerates continuous leak | Does not tolerate leaks |
Because NIV devices use a single-limb circuit with no exhalation valve, they must allow a continuous air leak for CO₂ to escape. This leak exits via:
- The mask itself
- A dedicated circuit port
- Whisper Valve / Whisper Swivel
- Plateau Valve
Modes and Settings
CPAP
Spontaneous breathing maintained at a continuous pressure above atmospheric. There is no inspiratory augmentation. The set CPAP level improves oxygenation (similar to PEEP) and reduces work of breathing.
BiPAP — Bi-Level Positive Airway Pressure
Two levels of pressure:
| Setting | Function |
|---|---|
| IPAP — Inspiratory Positive Airway Pressure | ↑ IPAP → ↑ ventilation, ↓ PaCO₂ |
| EPAP — Expiratory Positive Airway Pressure | ↑ EPAP → ↑ oxygenation, ↑ PaO₂ |
Memory aid: IPAP ≈ Pressure Support (affects ventilation/CO₂); EPAP ≈ PEEP (affects oxygenation/PaO₂).
Spontaneous / Timed Mode (S/T)
Similar to A/C — Pressure Control. Used when spontaneous breathing is unreliable.
| Setting | Purpose |
|---|---|
| IPAP | Inspiratory pressure |
| EPAP | Expiratory pressure |
| Respiratory Rate | Backup rate — ensures minimum breaths per minute if patient fails to breathe spontaneously |
| I-Time | Inspiratory time |
| Rise | Adjusts flow rate from EPAP to IPAP — higher values for patients who are short of breath |
AVAPS — Average Volume-Assured Pressure Support
- Targets a set tidal volume
- IPAP is automatically adjusted between a minimum pressure (Min P) and maximum pressure (Max P) to maintain the target Vt
- No fixed IPAP is set by the clinician
Example:
- Target Vt = 400 mL
- Min P (low IPAP) = 12 cmH₂O
- Max P (high IPAP) = 20 cmH₂O
- Current IPAP = 18 cmH₂O
- Inhaled volume = 370 mL → device will increase IPAP toward 20 to meet the 400 mL target
Initial Application of NIV
- Position patient in a location with appropriate monitoring
- Elevate the head of the bed > 30°
- Select appropriate ventilator and interface
- Set initial settings low (or zero) to minimize patient discomfort at application
- Hold the mask to the patient's face — do not strap immediately; let the patient acclimate
- Adjust FiO₂ to achieve adequate oxygenation
- Check for air leak — especially around the eyes (indicates poor mask seal)
- Reassess patient frequently — every 30 minutes, especially during the first few hours
Troubleshooting NIV Side Effects
| Side Effect | Intervention |
|---|---|
| Nasal irritation and dryness | Add a humidifier; use nasal moistening sprays |
| Dry mouth / throat | Add a heated humidifier; offer sips of water; moisturizing solutions |
| Skin irritation | Strict hygiene of face and device; wipe face and device before and after use; wash face well |
| Pain or pressure in ears | Reduce ventilation pressure if possible; consult MD for other remedies |
| Gastric bloating | Anti-gas therapy (simethicone) |
| Claustrophobia | Consult MD for alternative therapies |
| Pressure sores | Hygiene; do not over-tighten straps during use |
| Excessive air leak (mouth breathing) | Use a chin strap; change to an oral/nasal (full face) mask |
| Feeling too much pressure | Use the ramp mode — allows pressure to gradually increase over 5 to 45 minutes |