Which action will lead to a decrease in mean airway pressure for a patient on a mechanical ventilator in assist/control mode?

• A. Decreasing inspiratory flow
• B. Use of expiratory retard
• C. Decrease in inspiratory time
• D. Institution of a 1.0 sec inspiratory plateau

Answer: (C)

A decrease in inspiratory time directly affects mean airway pressure by allowing for a shorter duration of ventilation during each breath cycle. In assist/control mode, each breath includes a set inspiratory time; by reducing this time, the overall time spent delivering positive pressure to the lungs is decreased. This leads to lower mean airway pressure since the mean airway pressure is influenced not just by peak inspiratory pressures but also by the duration of time those pressures are applied.

By shortening the inspiratory time, the positive pressure is being applied for less time, which can result in a lower average pressure being maintained in the airway throughout the respiratory cycle. This understanding is crucial because balancing airway pressures is a vital component of effective mechanical ventilation, especially in patients with various pulmonary challenges.

Other choices are less effective in leading to a decrease in mean airway pressure. Decreasing inspiratory flow may lead to reduced peak pressures, but it doesn't directly change the mean airway pressure significantly unless the inspiratory time is also adjusted. The use of expiratory retard increases the time during which the airway remains under pressure, potentially increasing mean airway pressure. An inspiratory plateau can maintain airway pressures longer, which is counterproductive to decreasing mean airway pressure. Thus, the action of decreasing inspiratory time is