List four potential causes for auto-triggering during pressure support ventilation. (40% marks)
• Trigger set too low (too sensitive)
• Cardiac impulse
• ETT leak/circuit leak
• Chest drain
• Condensation in circuit
Auto-triggering can be broadly defined as "unintended initiation of breath delivery by the ventilator". The breadth of the term unintended may give rise to a large possible list of reasons, which includes:
- Myoclonoc jerks
- Cardiac oscillations
- Leak from the circuit
- Leak from the chest drain (eg. a bronchopleural fistula)
- Inappropriate sensitivity settings
- Water condensation sloshing and bubbling in the circuit
- Large volume of respiratory secretions, eg. bronchiectasis
- Swallowing or vomiting
- Peristalsis in a massive hiatus hernia or intrathoracic bowel loops
- Muscle contractions due to external pacing (or misplaced leads in transvenous pacing)
- Transmitted movement from patient transport or repositioning
In truth, this list answers the question "what are the causes of auto-triggering in a patient who is on a flow-triggered mode" as it is harder to come up with a list of non-diaphragmatic causes for pressure-based auto-triggering, apart from severe myoclonus and hiccups.
Arnaud W. Thille, MD, and Laurent Brochard, MD. Promoting Patient-Ventilator Synchrony (Clin Pulm Med 2007;14: 350 –359)
Petrof BJ, Legare M, Goldberg P et al. Continuous positive airway pressure reduces work of breathing and dyspnea during weaning form mechanical ventilation in severe chronic obstructive pulmonary disease. Am Rev Respir Dis 1990; 141: 281–9.
Arbour, Richard. "170: Ventilator Autotriggering Consequent To Intra-aortic Balloon Pump Counterpulsation." Critical Care Medicine 46.1 (2018): 68.