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Marieke L Duiverman,1 Anouk S Huberts,2 Leo A van Eykern,3 Gerrie Bladder,1 Peter J Wijkstra1 1Department of Pulmonary Diseases and Home Mechanical Ventilation, University Medical Centre Groningen, 2Faculty of Medical Sciences, University of Groningen, 3Inbiolab B.V., Groningen, the Netherlands Introduction: High-intensity noninvasive ventilation (NIV) has been shown to improve outcomes in stable chronic obstructive pulmonary disease patients. However, there is insufficient knowledge about whether with this more controlled ventilatory mode optimal respiratory muscle unloading is provided without an increase in patient–ventilator asynchrony (PVA). Patients and methods: Ten chronic obstructive pulmonary disease patients on home mechanical ventilation were included. Four different ventilatory settings were investigated in each patient in random order, each for 15 min, varying the inspiratory positive airway pressure and backup breathing frequency. With surface electromyography (EMG), activities of the intercostal muscles, diaphragm, and scalene muscles were determined. Furthermore, pressure tracings were derived simultaneously in order to assess PVA. Results: Compared to spontaneous breathing, the most pronounced decrease in EMG activity was achieved with the high-pressure settings. Adding a high breathing frequency did reduce EMG activity per breath, while the decrease in EMG activity over 1 min was comparable with the high-pressure, low-frequency setting. With high backup breathing frequencies less breaths were pressure supported (25% vs 97%). PVAs occurred more frequently with the low-frequency settings (P=0.017). Conclusion: High-intensity NIV might provide optimal unloading of respiratory muscles, without undue increases in PVA. Keywords: electromyography, high-intensity NIV, chronic obstructive pulmonary disease, ineffective efforts

Question High-intensity non-invasive ventilation (NIV) has been shown to improve outcomes in stable COPD. However, it is not known whether this ventilatory mode provides optimal respiratory muscle unloading without increasing patient-ventilator asynchrony (PVA). Patients and methods In 10 COPD patients on chronic NIV, 4 ventilatory settings were investigated in random order each for 10 minutes varying inspiratory pressures (high (HP, median 30 cm H 2 O) and low pressure (LP, median 18 cm H 2 O) and back-up frequencies (high (HF, median 22 breaths/min) and low frequency (LF, 10 breaths/min)). With surface electromyography (EMG), activity of the diaphragm, intercostal and scalene muscles were derived. The EMG activity ratio (EMGAR), which is the ratio between EMG activity during NIV and during spontaneous breathing, was used to express change in EMG activity with NIV. Pressure tracings were derived to assess PVA. Results Compared to spontaneous breathing, with HP settings, EMG activity decreased most (lower EMGAR, *P Adding a HF did further reduce EMG activity/ breath, while the decrease over 1 minute was comparable with the HPLF setting. With HF, less breaths were pressure supported (25% vs. 97%, P Answer High-intensity NIV provides optimal unloading of respiratory muscles, without undue increases in PVA.