Comparison of Four Mechanical Insufflation-Exsufflation Devices: Effect of Simulated Airway Collapse on Cough Peak Flow

Abstract

Background: Mechanical insufflation-exsufflation (MI-E) devices are used to improve airway clearance in individuals with acute respiratory failure. Some MI-E devices measure cough peak flow (CPF) during MI-E to optimize pressure adjustments.The aim was to compare CPF and effective cough volume (ECV: volume expired/coughed above 3 L/sec) measurements between four MI-E devices under simulated conditions of stable versus collapsed airway.Methods: Four MI-E devices were tested on the bench. Each device was connected via a standard circuit to a collapsible tube placed in an airtight chamber that was attached to a lung model with adjustable compliance and resistance. Pressure was measured upstream and downstream the collapsing tube; airflow was measured between the chamber and the lung model. Each device was tested in two conditions: collapse condition (0 cmH 2 O) and nocollapse condition (-70 cmH 2 O). For each condition, 6 combinations of inspiratory/expiratory pressures were applied. CPF was measured at the "mouth level" by the device built-in flow meter and at the "tracheal level" by a dedicated pneumotachograph.Comparisons were performed with non-parametric tests.Results: CPF values measured at the "tracheal level" and ECV values differed between devices for each inspiratory/expiratory pressure in the collapse and no-collapse conditions (P<.0001). CPF values were significantly lower at the "tracheal" level in the collapse as compared with the no-collapse condition (P<.0001 for each device), whereas they were higher at the "mouth" level (P<.05) for three of the four devices.Conclusions: CPF values differed significantly across MI-E devices, highlighting limitation(s) of using only CPF values to determine cough effectiveness: in situations of airway collapse, CPF increases at the "mouth" whereas it decreases at the "tracheal" level.

Waves of Precision: A Practical Guide for Reviewing New Tools to Evaluate Mechanical In-Exsufflation Efficacy in Neuromuscular Disorders

“…In recent years it has been widely used both in chronic [19] and in acute settings [20], with significant positive clinical outcomes. Different devices have been commercialized [21,22] with diverse characteristics, like the possibility to see or download waveform data. In our review, we provide some guidance on technologies to assist titration and on how to analyze waveform graphics to help clinicians tailor MI-E in the real world.…”

“…These are not because each manufacturer measures flows with different components that are not calibrated and therefore give an indication of the MI-E assisted expiratory flow, but when air is sucked out of the device with negative pressure it gives an MI-E assisted CPF reading regardless of what the patient is doing or if the upper airway is patent. Indeed, Terzi and co-workers [21] showed that in a lung model when there was upper airways collapse, the MI-E assisted CPF can be paradoxically high. CPF measurements on MI-E devices have their limitations.…”