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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. |
