Evaluation of Trigger Asynchrony in Five Adult Ventilators

Background: Trigger asynchrony is a common problem during mechanical ventilation and occurs primarily in patients with dynamic hyperinflation and COPD. We were curious if the brand of ventilator platform also played a role in trigger asynchrony. In other words, do some ventilators inherently allow for easier triggering than others. Our null hypothesis is that no variation of missed triggers will occur across 5 different ventilator platforms. Methods: An Ingmar Medical ASL 5000 breathing simulator was used to evaluate 5 adult ventilators: Servo-U, Servo-i, Hamilton G5, Hamilton C6, and Dräger V500. Three different patient models were also evaluated: normal, ARDS, and COPD. The ASL was set for 20 breaths/min across all model types, but compliance, resistance, and waveform patterns were left pre-set for the given patient model. Four different inspiratory muscle pressures (IMP) of 20, 10, 5, and 2.5 cm H2O were used to simulate strong to weak muscle movement. The simulator was then set for one of the three patient models, 5 cm H2O PEEP, and IMP of 20 cm H2O. Each ventilator was placed in pressure support mode, flow trigger of 2 L/min, and allowed to run for 1 min while the total number of triggered breaths were counted. The process was repeated for IMPs of 15, 5, and 2.5 cm H2O. Three runs were performed at each IMP level. The PEEP was then increased to 10 cm H2O and this process was repeated. After collecting data for one of the model types, the entire process was repeated for the other two model types. Results: When using normal and ARDS models all ventilator platforms triggered 100% of ASL set breaths at all muscle pressures and both PEEP levels. When using the COPD model, the Servo-i and Servo-U triggered 100% of set breaths at all IMPs except 2.5 cm H2O in which 90% of breaths were triggered. The Hamilton C6 triggered 90% of set breaths at all IMPs except 2.5 cm H2O in which 67% were triggered. When PEEP was increased to 10 cm H2O on the Hamilton C6, triggering improved from 67% to 90%. The Hamilton G5 and Dräger V500 triggered 100% of set breaths at all IMPs except 2.5 cm H2O in which 40% were triggered. When PEEP was increased to 10 cm H2O on the Hamilton G5, triggering improved from 40% to 52%. Increasing the PEEP on the Dräger V500 did not improve triggering. Conclusions: We rejected our null hypothesis and concluded that the Servo-i and Servo-U distal flow sensor was the most responsive in detecting flow in the weak COPD patient model when compared to the Hamilton C6, Hamilton G5, and Drager V500.