Pressure-Controlled Near-Continuous (PNC) Ventilation: Principles and Clinical Application

Pressure-Controlled Near-Continuous (PNC) Ventilation is an advanced ventilatory strategy targeting alveolar recruitment while minimizing ventilator-induced lung injury (VILI) in severe ARDS.

Core Principles

• High PEEP: Set near or slightly above peak inspiratory pressure (PIP) → maintains alveolar inflation throughout respiratory cycle.
• Pressure-Controlled: Inspiratory pressure (ΔP) added to high baseline PEEP; tidal volume varies with compliance.
• Flow-Cycled (Not Time-Cycled): Inspiration ends when flow decays to a threshold (e.g., 25–30% peak) → synchronizes with patient effort, prevents dynamic hyperinflation.
• Near-Continuous Flow: Minimal expiratory pause; maintains mean airway pressure (MAP) for recruitment.

Physiologic Goals

• Recruit collapsed alveoli (open lung approach).
• Prevent cyclic atelectrauma (repeated open/close).
• Limit overdistension (volutrauma) via pressure control + flow cycling.
• Improve V/Q matching, oxygenation.

Indications

• Severe ARDS (PaO₂/FiO₂ <100–150) refractory to conventional lung-protective ventilation.
• Rescue for life-threatening hypoxemia.

Risks & Monitoring

• Hemodynamic compromise (↑ intrathoracic pressure → ↓ venous return).
• Barotrauma (pneumothorax) — despite pressure control.
• Auto-PEEP if expiratory time insufficient.
• Requires heavy sedation/paralysis; continuous hemodynamic + SpO₂ + transpulmonary pressure monitoring.

Evidence

Small trials (e.g., Crit Care Med 2000s) show improved oxygenation vs. conventional PCV. No large RCT mortality benefit. Used as rescue in experienced centers. Not standard first-line.

PNC is a specialized tool for refractory hypoxemia — requires expertise, monitoring, and protocolized weaning.