Which ventilation mode delivers a preset tidal volume at a variable inspiratory pressure and is most commonly used in operating rooms?

Explanation

## Volume-Controlled Ventilation (VCV) — Standard Operating Room Mode **Key Point:** VCV (also called **Assist-Control Ventilation** or **AC**) is the **gold standard** for operating room anesthesia and most ICU sedated patients because it **guarantees a preset tidal volume** regardless of lung compliance or resistance. ### VCV Mechanism 1. Clinician sets **tidal volume** (e.g., 500 mL) 2. Ventilator delivers that volume at a **variable inspiratory pressure** 3. Inspiratory pressure rises until the preset volume is delivered 4. Once volume is reached, inspiration ends and exhalation begins ### Key Characteristics | Feature | VCV | |---------|-----| | **Controlled Variable** | Tidal Volume | | **Variable Parameter** | Inspiratory Pressure | | **Minute Ventilation** | Guaranteed (if RR fixed) | | **Flow Pattern** | Typically square wave (constant flow) | | **Use in OR** | Most common | | **Risk** | High airway pressure if compliance ↓ | **High-Yield:** VCV is preferred in: - Operating room (predictable ventilation during anesthesia) - Patients with normal lung mechanics - When guaranteed minute ventilation is essential - Neurosurgery and other procedures requiring stable PaCO~2~ **Warning:** In VCV, if lung compliance **decreases** (e.g., patient positioning, pneumoperitoneum, ARDS), inspiratory pressure **rises** — monitor peak airway pressure to avoid barotrauma. **Mnemonic:** **VCV = Volume guaranteed, Pressure variable** — opposite of PCV. [cite:Stoelting Basics of Anesthesia 6e Ch 10]