Dellweg D, Höhn E, Kerl J, Klauke M, Köhler D Fachkrankenhaus Kloster Grafschaft
Background: The AirTrap Control function in the ventilator VENTImotion 2 (Weinmann,Hamburg) reduces the respiratory frequency and the inspiration time to prevent dynamic hyperinflation under Non-Invasive Ventilation in patients exhibiting persistent late expiratory flow.
Objective: To evaluate the ventilation quality and lung hyperinflation with and without AirTrap mode at varying degrees of obstruction in the test lung. Methods: Recording of pressure and flow curves with the Michigan test lung (5600i, Michigan Instruments, Grand Rapids, MI/USA) in a series of tests with increasing airway resistance levels. Analyses were made of respiratory frequency, tidal volume, minute ventilation, pre-inspiratory pressure (=PEEPi), inspiration time. Test conditions: respiratory frequency 20, IPAP 25 and EPAP 4 cmH2O, outgoing Ti 35%, lung compliance 30 ml/cmH2O). Results: Under the ventilator settings describe above, the AirTrap function reduced the respiratory frequency (Figure 1 A) and the inspiration time (Figure 1 B) starting at an airway resistance of 15 cmH2 O/liters/second (Figure 1, vertical dotted line). Intrinsic PEEP was first observed, however, at a resistance of 35 cmH2 O/liters/second (Figure 1 C). In the adjustment range of the AirTrap Control function, the respiratory minute volume was significantly reduced by 1.98±0.9 liters (Figures 1 D and Figure 2). The reduction of PEEPi was not statistically significant.
Conclusion: In the test the AirTrap Control function reduced the respiratory frequency and inspiration time before PEEPi arose. As a result, there was a reduction in respiratory minute volume in a non-critical range, which would be equivalent to a CO2 increase in vivo. The AirTrap Control function could be improved with a somewhat less sensitive or adjustable algorithm.
