Mechanical Insufflation-Exsufflation: Considerations for Improving Clinical Practice

Abstract

The provision of mechanical insufflation-exsufflation (MI-E) devices to enhance cough efficacy is increasing. Typically, MI-E devices are used to augment cough in patients with neuromuscular disorders but also in patients who are weak in an acute care setting. Despite a growing evidence base for the use of these devices, there are barriers to the provision of MI-E, including clinician lack of knowledge and confidence. Enhancing clinician education and confidence is key. Individualized or protocolized approaches can be used to initiate MI-E. Evaluation of MI-E efficacy is critical. One method to evaluate effectiveness of MI-E is the MI-E-assisted cough peak flow (CPF). However, this should always be considered alongside other factors discussed in this review. The purpose of this review is to increase the theoretical understanding of the provision and evaluation of MI-E and provide insight into how this knowledge can be applied into clinical practice. Approaches to initiation and titration can be selected based on the clinical situation, patient diagnosis (including and beyond neuromuscular disorders), and clinician's confidence.

Keywords: MI-E; airway clearance techniques; bulbar insufficiency; cough; cough assist; cough peak flow; neuromuscular disease.

Figure 1

Shows the components that occur within a normal cough. Blue represents the gastric pressure, red is the esophageal pressure, and black is the transdiaphragmatic pressure. Superimposed on this in grey are the flow changes that are seen during a cough. Arrow 1 indicates the start of the deep inspiration. Arrow 2 is the forced expiration against a closed glottis. Arrow 3 is the sudden opening of the glottis and Arrow 4, compression of the intra-thoracic airways. Cough peak flow (CPF) is measured as the peak expiratory flow that occurs during a cough. For anyone over the age of 12 years old, a CPF that exceeds 360 L/min is deemed to be normal. There are reference values for children [9].

Figure 2

Shows one approach to assessing the efficacy of a patient’s cough.

Figure 3

Shows a suggested algorithm for a standard approach to MI-E initiation in adult patients.

Figure 4

Shows a suggested algorithm for personalized approach to titration of mechanical insufflation-exsufflation (MI-E) devices in adult patients. This algorithm is modified from Chatwin and Simonds [57], taking into account more recent evidence around MI-E times and also MI-E-assisted cough peak flow (CPF). Inspiratory time (Ti), expiratory time (Te).

Figure 5

Shows pressure (red) and flow (blue) traces during a cycle of mechanical insufflation exsufflation with a patient coughing. The first negative flow point is artifact as it is the compressible volume. The second peak is the true cough peak flow (CPF). With thanks to Manuel Lujan.

Figure 6

Shows the flow, pressure, and inspiratory tidal volumes (Vti) download for a patient using an E70 (Philips Respironics, Murrysville, PA, USA). The blue line shows the device assisted cough peak flow (CPF) of around 350 L/min. Clinicians would normally be very pleased with this reading as it is at a level that would indicate an effective assisted CPF. However, after the initial CPF, there is flattening of the exsufflation curve, indicating an obstructed airway. With thanks to Tiago Pinto.