Which statement best describes the oscillator's amplitude in relation to gas movement during the respiratory cycle?

• A. Amplitude increases gas delivery during expiration and gas removal during inspiration
• B. Amplitude increases gas delivery during inspiration and gas removal during expiration
• C. Amplitude only affects inspiratory gas delivery
• D. Amplitude only affects expiratory gas removal

Answer: (B)

Amplitude in high-frequency oscillatory ventilation is the size of the piston’s swing, the peak-to-peak pressure change that drives each oscillation. A larger amplitude moves more gas with every cycle, increasing the tidal volume. Gas movement happens in both phases of the cycle: during inspiration, higher pressure pushes gas into the lungs (gas delivery); during expiration, the pressure drop allows gas to leave (gas removal). So increasing amplitude enhances gas delivery during inspiration and gas removal during expiration, improving ventilation and CO2 clearance. It isn’t limited to just one phase of the cycle or to expiratory or inspiratory gas alone.