Fig. 3

Variation of dyssynchrony. Combination of airway pressure and tidal volume curves showing various types of dyssynchrony. a Ineffective triggering (miss triggering): Small waveform changes during expiration indicate the presence of weak spontaneous breathings that was not triggered (white arrows). It can be associated with a weak patient respiratory drive. Ineffective triggering can occur in situations combined with underlying auto-PEEP and excessive ventilation. It can be adjusted by extended expiratory time and increased trigger sensitivity. b Double triggering: Prolonged spontaneous breathing is generating a second mechanical ventilation immediately after the completion of the first mechanical ventilation (white arrow). It can occur when second breathing starts before the first ventilation delivery has completed. Double triggering may be adjusted by extended inspiratory time. c Auto triggering: Excessive mechanical ventilation (black arrows) is occurring despite the lack of patient’s respiratory effort (white arrows), which might be associated with the water in the circuit or circuit leakage. This type of asynchrony can occur in cases of sputum in the circuit, condensation, circuit leakage, or heart oscillations. Auto triggering can be adjusted by lowering the triggering sensitivity of the mechanical ventilator or by removing sputum or condensation. d Reverse triggering: Spontaneous breathing is paradoxically triggered by mechanical ventilation, resulting in a generation of double triggering (white and black arrows). Reverse triggering is frequently observed in highly sedated patients. Reverse triggering can be adjusted by decreasing sedation. e Premature cycling: Since mechanical ventilation is completed earlier than the completion of spontaneous breathing, there remains spontaneous breathing in the expiratory phase. Waveform swinging is observed in the exhalation phase (white and black arrows). Premature cycling can be adjusted by extending inspiratory time. f Delayed cycling: Since spontaneous breathing is completed earlier than the completion of mechanical ventilation, the inspiratory phase is rapidly terminated (white and black arrows). Delayed cycling can be adjusted by reducing inspiratory time. Gray bars indicate the time periods of spontaneous breathing. P, airway pressure curve; V, tidal volume curve