Types of NIV

1. BiPAP (Bilevel Positive Airway Pressure)

Provides:

• IPAP: Inspiratory pressure (helps ventilation → ↓ CO₂)

• EPAP: Expiratory pressure (like PEEP → improves oxygenation)

Best for:

• COPD exacerbation

• Hypercapnic respiratory failure (high CO₂)

• Congestive heart failure (pulmonary edema)

• Obesity hypoventilation

• Neuromuscular weakness

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2. CPAP (Continuous Positive Airway Pressure)

One constant pressure during the whole breathing cycle.

Best for:

• CHF with flash pulmonary edema

• OSA

• Mild/moderate hypoxemia

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3. High-Flow Nasal Cannula (HFNC)

Not technically NIV but often used as alternative.

• Up to 60 L/min flow

• Provides small PEEP

• Improves oxygenation and decreases work of breathing

Best for:

• Hypoxemic respiratory failure

• Post-extubation

• Pneumonia/ARDS with moderate oxygen needs

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When to use NIV (ICU Indications)

A. Hypercapnic respiratory failure

• COPD exacerbation

• Obesity hypoventilation

• Neuromuscular diseases (if alert)

B. Hypoxemic respiratory failure

• Cardiogenic pulmonary edema

• Early ARDS (mild/moderate)

• Pneumonia (selected, alert patients)

C. To avoid intubation

• DNI (Do-not-intubate) patients

• Temporary bridging

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When NOT to use NIV

• Impaired consciousness

• Active vomiting

• Inability to protect airway

• Excessive secretions

• Facial trauma or burns

• Hemodynamic instability

• Severe acidosis (pH < 7.20) — NIV may still be attempted but high failure risk

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Signs NIV is working

Check after 30–60 min:

• ↓ RR

• ↓ CO₂ (in COPD)

• ↑ O₂ sat

• ↓ Work of breathing

• Better ABG

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Signs NIV is failing (intubate!)

• Persistent hypoxia

• Worsening CO₂ / pH

• Fatigue

• Altered mental status

• Cannot tolerate mask