Accuracy of Real-Time Data Provided by Mechanical Insufflation-Exsufflation Devices

Background: Mechanical insufflation-exsufflation (MI-E) is crucial to assist patients with impaired cough, especially those with neuromuscular diseases. Despite recent advancements that enable real-time display of peak expiratory flow (PEF) and inspiratory volume, accurately monitoring these parameters with MI-E devices during treatment can still present challenges. Methods: A bench study that used a mechanical lung connected to 3 MI-E devices (EOVE-70; E-70 and Comfort Cough II) was conducted to evaluate PEF and inspiratory volume monitoring accuracy. Two clinical conditions were tested, low and normal compliance, with 6 different MI-E settings tested: +20/-20, +30/-30, +40/-40, +40/-50, +40/-60, and +40/-70 cm H₂O. PEF (L/min) and inspiratory volume (mL) displayed on the screen were recorded cycle by cycle, while a pneumotachograph connected to the mechanical lung was used to measure the actual PEF and inspiratory volume for data comparison. Flow bias was assessed by calculating the difference (PEF - peak inspiratory flow) and ratio (PEF to peak inspiratory flow) between flows. Results: All devices systematically underestimated PEF, with device A showing the smallest estimation error (-7.4 [-10.1; -6] %). Devices B and C exhibited larger errors (-26.5 [-29.2; -25.6] and (-29.9 [-30.7; -28.7] %, respectively). All the devices underestimated inspiratory volume, with device B showing the smallest estimation error (-15.1 [-21.2; -12.3] %). Device A exhibited a significantly larger error (-26.9 [-30.3; -24.8] %). The error from device C (-17.7 [-34.5; -13.8] %) was not statistically different from device B. Device type, high pressure settings (>+40/-40 cm H₂O), and a lung model compliance of 60 mL/cm H₂O were the main contributors to error in estimating PEF and inspiratory volume. Finally, we observed differences of PEF-to-peak inspiratory flow ratio and PEF minus peak inspiratory flow differences achieved. Conclusions: Our study highlighted consistent underestimation of PEF and inspiratory volume across MI-E devices. Improving device monitoring is essential for guiding MI-E therapy and ensuring patient safety.