This patient with severe COPD has developed auto–positive end-expiratory pressure (auto-PEEP) on mechanical ventilation. Her obstructive lung disease slows her expiratory flow rate so that she cannot completely exhale before the next breath is initiated by the ventilator (breath stacking). The volume of air that remains in the lungs after each breath builds up, resulting in increased intrathoracic pressure; this can progress to severe consequences such as hypoxemia, cardiovascular collapse (due to decreased venous return and reduced cardiac preload), and barotrauma. When auto-PEEP is diagnosed, the ventilator circuit should be disconnected from the patient's endotracheal tube to allow for a prolonged exhalation which enables trapped intrathoracic air to escape, intrathoracic pressure to drop, and venous return to improve. The ventilator settings should then be adjusted to allow for more effective exhalation to avoid further air trapping. Slowing the respiration rate, decreasing the tidal volume, and increasing the inspiratory flow rate while tolerating respiratory acidosis are ways to increase the exhaled volume with each cycle.

Partial tube obstruction (as with a kink or partially obstructing mucus plug) usually causes a rise in only the peak inspiratory pressure because it affects resistance to flow of air through the tube. Plateau pressure is measured in the absence of flow, so it is unaffected by changes in resistance. Because this patient's plateau pressure increased along with the peak inspiratory pressure, partial tube obstruction is not the most likely cause of her findings.

If a patient has anxiety and triggers breaths more frequently than the set rate, sedation may be required to slow the respiration rate and avoid potential auto-PEEP. This is especially true with hypercapnia, as it is a potent stimulus to increase respiration rate. However, sedation itself is not associated with increased airway and plateau pressures.