In Synchronized Intermittent Mandatory Ventilation (SIMV), which statement correctly describes spontaneous breaths between mandatory breaths?

• A. They are always fully assisted by the ventilator
• B. They are never allowed
• C. They are unassisted between mandatory breaths
• D. They count toward the total respiratory rate

Answer: (C)

In SIMV, a fixed number of breaths are delivered by the ventilator as mandatory breaths, but the patient can also breathe on their own between these breaths. Those spontaneous breaths are not supported or augmented by the ventilator; the patient must generate the full inspiratory effort themselves. This unassisted nature of breaths between mandatory ones is what makes the statement correct. The ventilator provides assistance for the scheduled breaths, while the spontaneous breaths between them occur without ventilator help.