Accuracy of real-time data provided by mechanical insufflation-exsufflation devices

Mechanical in-exsufflation (MIE) aims to generate cough peak expiratory flows (PEF) similar to those of normal cough. Currently, these devices display PEF and inspiratory volume (Vti) in real time, but there is no data on whether these values correspond to the actual values generated. A bench study was conducted using a Michigan mechanical lung connected to 3 different MIE devices. We simulated normal and reduced compliance (60 and 30 ml/cmH2O). MIE settings were +20/-20, +30/-30, +40/-40, +40/-50, +40/-60, and +40/-70cmH2O. Values displayed on the screen were recorded cycle by cycle, while a pneumotachograph connected to the mechanical lung measured actual PEF and Vti. All devices underestimated PEF, with error being statistically higher for devices B and C (A -20.6 ± 4.9 L/min vs B -68.4 ± 10.8 L/min vs C -70.6 ± 18.9; p < 0.0001 both). Similarly, all devices underestimated Vti by an average of 410 mL. <fig><object-id>erj;64/suppl_68/PA1435/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> Multivariate analysis showed that reasons for PEF (adjr2=0.86; p<0.0001) and Vti (adjr2=0.70; p<0.0001) estimation error were type of device, high pressure levels and compliance. <fig><object-id>erj;64/suppl_68/PA1435/F2</object-id><object-id>F2</object-id><object-id>F2</object-id><graphic></graphic></fig> Real time monitoring displayed on MIE devices underestimates the PEF and Vti.