Optimizing expiratory flows during mechanical cough in a pediatric neuromuscular lung model

Abstract

Mechanical insufflation‐exsufflation (MI‐E) is recommended for subjects of all ages with neuromuscular disorders (NMDs) and weak cough. There is a lack of knowledge on the optimal treatment settings for young children. This study aims to determine the MI‐E settings providing high expiratory airflow while using safe inspiratory volumes, and to identify possible limits where the benefit of incrementing the MI‐E settings to achieve a higher expiratory airflow, decreased. Using an MI‐E device and a lung model imitating a 1‐year‐old child with NMD, we explored the impact of 120 combinations of MI‐E pressure and time settings on maximal expiratory airflow and inspiratory volume. High expiratory airflows were achieved with several pressure and time combinations where the exsufflation pressure, followed by insufflation pressure and time, had the greatest impact. The benefit of incrementing the settings to increase the expiratory airflow leveled off for the insufflation pressure and time, but not for the exsufflation pressure. Given exsufflation pressure of −40 or −50 cmH2O and insufflation time longer than 1 second, a plateau in the expiratory airflow curve was present at insufflation pressures from 25 cmH2O, whereas a plateau in the inspired volume curve occurred at insufflation pressures from 35 cmH2O. The present neuromuscular pediatric lung model study showed that expiratory pressure impacts expiratory airflow more than inspiratory pressure and time. An inspiratory and expiratory pressure set between 20 to 30 and −40 cmH2O, respectively, and an inspiratory time longer than 1 second may be considered as a basis when titrating MI‐E settings in young children with NMD. The findings must be confirmed in clinical trials.

Tailoring NIV by dynamic laryngoscopy in a child with spinal muscular atrophy type I

“…The application of TFL during NIV treatment enabled us to adjust MI‐E settings directly, by titrating insufflation pressures and flow to the most optimal levels of laryngeal opening, partly alluded to in a previous model 6 . The procedure led to immediate changes in treatment.…”

Mechanical Insufflation-Exsufflation: Considerations for Improving Clinical Practice

“…An alternative option is for the clinician to gain confidence with a more protocolized approach and once they have been successful, to individualize. Reasons for suggesting a more individualized approach include that bench [ 60 ] and clinical case series [ 57 , 59 ] have highlighted a greater negative to positive pressure that has been clinically effective. When it comes to the insufflation pressure, Mellis and Goebel [ 61 ] showed that it is not necessarily the deepest breath in that produces the highest CPF.…”

Upper Airway Assessment and Responses During Mechanically Assisted Cough

“…86 Lachal et al 87 enhance our understanding of airflow dynamics, and a wide range of MI-E settings may be systematically applied to suggest possible combinations to be applied subsequently in patients. 52,88 The dogma that upper airway collapse during exsufflation causes MI-E treatment failure, highly influenced former evaluation methods, assessing the exsufflation phase alone. Sancho et al's CT-scannings 25 and Lacombe's flow-curve shapes 84 confirmed Bach's postulate that exsufflation caused upper airway collapse in subjects with bulbar dysfunction.…”

“…Increasing inspiratory time may be necessary to achieve required insufflation volume prior to exsufflation. 23,88,103 A prolonged inspiration seems to be physiological in inducing cough. 68 Several rapid MI-E cycles may be challenging or impossible to handle for individuals with bulbar dysfunction.…”