In Ohmeda 7900 ventilator, which statement is true regarding tidal volume delivery?

In Ohmeda 7900 ventilator, which statement is true regarding tidal volume delivery?

• A. Delivered tidal volume is always equal to the dial setting
• B. Delivered tidal volume depends on fresh gas flow and is higher than the dial setting
• C. Delivered tidal volume is always lower than the dial setting
• D. Delivered tidal volume is independent of dial setting

Answer: (A)

On the Ohmeda 7900, the tidal volume delivered per breath is defined by the dial setting. The ventilator’s drive mechanism (piston/bellows) displaces a fixed volume with each inspiration, and this per-breath volume is what reaches the patient, so the delivered tidal volume matches the dial setting under normal conditions. Fresh gas flow into the circuit adds to the overall gas in the circuit and can affect minute ventilation or gas concentrations, but it does not change the volume that the ventilator is programmed to deliver per breath. If there’s a leak or miscalibration, the actual delivered volume could differ, but with proper operation, the dial setting equals the delivered tidal volume.

On the Ohmeda 7900, the tidal volume delivered per breath is defined by the dial setting. The ventilator’s drive mechanism (piston/bellows) displaces a fixed volume with each inspiration, and this per-breath volume is what reaches the patient, so the delivered tidal volume matches the dial setting under normal conditions. Fresh gas flow into the circuit adds to the overall gas in the circuit and can affect minute ventilation or gas concentrations, but it does not change the volume that the ventilator is programmed to deliver per breath. If there’s a leak or miscalibration, the actual delivered volume could differ, but with proper operation, the dial setting equals the delivered tidal volume.