Key points are not available for this paper at this time.
Mechanical insufflation-exsufflation (MIE) is used to augment secretion clearance in individuals with respiratory muscle weakness. Direct visualisation and flow-wave analysis have demonstrated upper airway closure (UAC) during MIE, but its prevalence at different pressures is not well described. This study sought to determine the prevalence of UAC in response to changing exsufflation pressure. Patients with Duchenne muscular dystrophy receiving domiciliary MIE via facemask were included. MIE was delivered with insufflation (Pins)/exsufflation (Pexs) pressure:+40/-40cmH2O; +40/-50cmH2O; +40/-60cmH2O; +50/-50cmH2O; +50/-60cmH2O. Peak cough flow (PCF) was measured with a pneumotachograph. Flow-volume curves were used to identify absent flow, which was presumed to indicate UAC. 12 patients (31±6yr) were included. Unassisted PCF 98±55L/min. At Pins +40, increasing Pexs from -40 to -50 resulted in a negligible rise in PCF (mean difference 16-14,46L/min). At Pins of +40 and +50, increasing Pexs from -50 to -60 resulted in a negligible fall in PCF (mean difference -8-27,11L/min and -2-20,15L/min, respectively). Flow-volume analysis demonstrated UAC at all pressures, with an increase in prevalence with higher Pexs (70% of participants at +40/-40, compared with 90% at +40/-60 (Fisher's exact test p=0.0007)). The heterogeneous physiology of patients with respiratory muscle weakness does not foster a uniform, predictable response to MIE. UAC is an increasingly identified and common sequelae of MIE. Titrating MIE to PCF may not identify UAC, and other techniques such as direct visualisation or flow-volume curve assessment should be considered to deliver indiviualised settings.
Shah et al. (Thu,) studied this question.