Ineffective triggering is the most common type of ventilator dyssynchrony. The differential diagnosis includes:
Auto peep (the most common cause)
Neuromuscular weakness
Improper ventilator settings
Auto peep is the most common cause of ineffective triggering and will often occur as a patient cannot create enough inspiratory force to overcome their own intrinsic peep (PEEPi). Patients who are severely tachypnic or those with obstructive lung disease are at high risk for auto peep (not enough time to exhale).
Ineffective triggering can also occur if the patient cannot create enough of a negative inspiratory force to trigger the vent to deliver a positive pressure breath. Prolonged period of mechanical ventilation, over sedation, high cervical spine injuries, or diaphragmatic weakness are common causes.
Lastly, improper trigger sensitivities may make it difficulty for the ventilator to sense when the patient is attempting to take a spontaneous breath.
Chao DC, Scheinhorn DJ, Stearn-hassenpflug M. Patient-ventilator trigger asynchrony in prolonged mechanical ventilation. Chest. 1997;112(6):1592-9.
Esteban A, Anzueto A, Alía I, et al. How is mechanical ventilation employed in the intensive care unit? An international utilization review. Am J Respir Crit Care Med. 2000;161(5):1450-8.
