Non-invasive ventilation during sleep: time to define new tools in the systematic evaluation of the technique.

Non-invasive ventilation (NIV) has been remarkably effective in the management of chronic respiratory failure, despite initially rudimentary equipment and limited understanding of what was actually happening, minute by minute when ventilation was applied. Modern ventilators, controlled by complex algorithms, and with integrated monitoring allow for sophisticated customisation of ventilatory support to an individual. However, if problems with ventilation are not recognised, and their significance understood, they cannot be fixed. Experience of monitoring during sleep from patients predominantly with sleep apnoea can be transferred and extended to patients receiving NIV. This article, the first in a series, explores the rationale for NIV and how its application to an individual patient can be monitored using simple tools and, when problems are identified, the causes can be identified using sophisticated interpretation of more detailed monitoring. This requires a detailed understanding of how different modes of ventilation work and some knowledge of the algorithms that control each machine. These themes are explored in this article and developed in subsequent articles in the series.