Impact of auto-PEEP on trigger sensitivity and inspiratory effort

To trigger a breath, alveolar pressure (Palv) must decrease by the amount of auto-PEEP, plus the set trigger sensitivity. The large dip in esophageal pressure (Pes) reflects this effort. The addition of external PEEP reduces the Palv-Pes gradient and decreases the breathing workload, without a significant increase in end-inspiratory Palv.