Waveform analysis during noninvasive ventilation

Mechanical ventilators are equipped with a variety of graphical displays to enhance the monitoring of the patient while undergoing mechanical ventilation. One of those displays are waveforms or ventilator graphics. In a similar fashion to an electrocardiogram reflects the electrical activity of the heart, ventilator graphics reflect the interaction between patient and the ventilator. Therefore, interpretation of ventilator waveforms is an important skill in the continuous assessment of patient-ventilator interaction. Traditionally, waveform interpretation has been considered an essential tool in the management of endotracheally intubated and mechanically ventilated patients. However, it has become more important during the implementation of non-invasive ventilation (NIV) and the assessment of ventilator parameters. Most modern ventilators offer non-invasive ventilation as an alternative mode. Therefore, interpretation of ventilator graphics during NIV should be an extension of the skills learned for invasive mechanical ventilation. Close observation of the ventilator graphics during NIV is critical in reducing failure, unplanned intubations, and optimizing clinical outcomes. This chapter has been designed to describe the most common waveforms seen when NIV is used. A detailed review of scalars and loops, along with a description of common abnormalities are displayed in a fashion that allows the reader to get a solid knowledge of waveforms in general. Each section of the chapter starts with a depiction of general concepts of each scalar and loops to quickly embark into recognition of common abnormalities. Clinical conditions that are included in this chapter are airway obstruction, air trapping, air leak, and changes in pulmonary mechanics. Finally, the ventilator mode section displays basic principles for recognition of non-invasive modes and parameters on the scalar graphics.