What happens to minute ventilation when expiratory time is increased in pressure controlled ventilation?

When expiratory time is increased in pressure-controlled ventilation, the minute ventilation decreases due to the extended duration of the expiratory phase. Minute ventilation is defined as the total amount of air exchanged in one minute, calculated as the tidal volume multiplied by the respiratory rate.

In pressure-controlled ventilation, the ventilator guarantees a certain pressure during inspiration, allowing the clinician to set the tidal volume indirectly. By extending the expiratory time, you effectively reduce the frequency of breaths per minute because each breath takes longer to complete. If the same tidal volume is delivered with longer expiratory times, the respiratory rate decreases, which directly affects the calculation of minute ventilation, leading to a decline in overall ventilated volume per minute.

This relationship emphasizes the importance of balancing inspiratory and expiratory times in mechanical ventilation settings to ensure adequate ventilation and prevent complications that can arise from improper timing.