Patient–ventilator discordance commonly occurs in patients receiving noninvasive ventilation (NIV). Unintentional leaks contribute to trigger and cycle asynchrony. Historically, ventilators designed for NIV with an intentional leak circuit compensated for unintentional leaks better than critical care ventilators. However, many critical care ventilators now have NIV settings for leak compensation. Per bench studies and some clinical studies, NIV settings for leak compensation variably improve synchrony related to leak. Some interfaces, such as the helmet, can contribute to asynchrony. Ventilator modes such a neurally adjusted ventilatory assist might improve synchrony but might not lead to better patient outcomes. Adaptive pressure control modes have the potential to remove support with increased patient effort, resulting in work shifting from the ventilator to the patient. Moreover, these modes are complicated if the ventilator does not correctly estimate tidal volume during NIV. Adding flow to the circuit, such as adding oxygen to increase FIO2, can also contribute to asynchrony. This article addresses issues related to discordance with NIV and strategies to improve patient–ventilator interactions during NIV.
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