What is the nature of volume-support ventilation (VSV) regarding trigger, limit, and cycle?

• A. Patient triggered, volume limited, time cycled
• B. Patient triggered, pressure limited, flow cycled
• C. Time triggered, volume limited, pressure cycled
• D. Flow triggered, pressure limited, time cycled

Answer: (B)

Volume-support ventilation (VSV) is designed to support a patient’s spontaneous breathing efforts while ensuring a set tidal volume is delivered. This mode allows for enhanced patient autonomy and comfort while also providing necessary respiratory support.

In VSV, the trigger mechanism responds to the patient's effort to breathe, meaning it is patient-triggered. This ensures that the ventilator can detect when the patient initiates a breath, allowing them to have control over their ventilation.

The limit in VSV is set as pressure limited, which means that while the machine ensures the delivery of a specific volume, it does so without exceeding a predetermined pressure level. This safeguards against barotrauma and other complications that can arise if high pressures are delivered to the lungs.

Finally, the cycling mechanism in VSV is time cycled. Once a breath is recognized and the volume is delivered, the ventilator cycles based on time rather than the flow reaching a certain threshold. This aspect helps in managing the breathing pattern while ensuring the patient receives the necessary volume of air.

Thus, option B accurately describes the characteristics of volume-support ventilation by highlighting its patient-triggered approach, pressure limitation, and time cycling.