Double-Triggering During Noninvasive Ventilation in a Simulated Lung Model.

Background: Double-triggering is a well-recognized form of patient-ventilator asynchrony in noninvasive ventilation (NIV). This benchtop simulated lung study aimed to determine under which patient and device-specific conditions double-triggering is more prevalent, and how this influences the delivery of NIV.

Methods: Two commonly used proprietary NIV devices were tested using a benchtop lung model. Lung compliance, airway resistance, respiratory effort, and breathing frequency were manipulated, and the frequency of double-triggering was assessed. A lung model of very low lung compliance (15 mL/cm HO) was then used to assess the frequency of double-triggering when breathing frequency and respiratory effort were varied, along with basic NIV settings, including inspiratory pressure and expiratory pressure. Minute ventilation and total inspiratory work (as calculated by the simulated lung model) were also correlated with frequency of double-triggering.

Results: In both devices, double-triggering was observed with reduced lung compliance ( = .02 and < .001 for the two devices, respectively). Reduced airway resistance was associated with double-triggering with the one device only ( = .02). Respiratory effort and breathing frequency were not independent predictors of double-triggering across all lung models. In the lung model of very low lung compliance, both devices showed increased double-triggering at a lower breathing frequency ( < .001 and < .001), higher respiratory effort ( = .03 and < .001), and greater pressure support ( = .044, < .001). Importantly, double-triggering was associated with reduced minute ventilation ( = .007) with one device and increased inspiratory work ( < .001) with the other device.

Conclusions: Both simulated-patient and device characteristics influenced the frequency of double-triggering in NIV, resulting in meaningful consequences in a simulated lung model.