What adjustment to ventilator settings is most appropriate to correct auto-PEEP in a mechanically ventilated patient?
The most appropriate adjustment to ventilator settings to correct auto-PEEP in a mechanically ventilated patient is to increase the expiratory time. Auto-PEEP, also known as intrinsic PEEP or dynamic hyperinflation, occurs when air is trapped in the lungs at the end of exhalation due to insufficient time for complete exhalation. This trapped air increases the baseline pressure within the alveoli above the set PEEP level. Increasing expiratory time allows more time for the patient to exhale completely, preventing air trapping. This can be achieved by decreasing the respiratory rate (which prolongs both expiratory and inspiratory time, but proportionally increases expiratory time more), decreasing the inspiratory time (either by decreasing the I-time directly, or increasing the flow rate, which shortens I-time), or increasing the flow rate (which shortens inspiratory time). While adjusting the inspiratory flow rate or inspiratory time can also increase expiratory time, decreasing respiratory rate is often the first and most effective adjustment. It's also important to address any underlying causes of airflow obstruction, such as bronchospasm or mucus plugging, which contribute to auto-PEEP. However, the immediate ventilator adjustment to address auto-PEEP is to increase the expiratory time.