![]() Scalars on conventional mechanical ventilators are representations of specific respiratory parameters over time. The first of these graphics are termed scalars. Now that we have reviewed the basic ways breaths are delivered from a ventilator, it is important to understand how those breaths are represented in graphical form. Any combination of the above variables can define the type of breath delivered by the machine. The delivery of the breath is stopped when a certain amount of time has elapsed, a goal amount of volume has been inspired, or the ventilator senses a decrease in the flow taken in by the patient. The two main target variables are either a specific inspiratory flow rate or a pressure goal. This is also referred to as the target variable. ![]() After the breath is started, the gas is delivered to the patient in a set pattern that is sustained throughout the course of inspiration. This variable is also referred to as the trigger. A breath can be started by either the patient (referred to as a supported or assisted breath) or by the machine (referred to as a controlled breath). A mechanical breath is classified based on three main variables-how the breath starts, how the breath is delivered by the machine, and how the breath is stopped. Thorough understanding of both scalars and loops, and their characteristic appearances, is essential to being able to evaluate a patient’s respiratory mechanics and interaction with the ventilator.īefore reviewing the graphics associated with mechanical ventilation, it is important to understand the concepts of how ventilators can deliver breaths. These include three scalars (flow versus time, volume versus time, and pressure versus time) and two loops (pressure-volume and flow-volume). Ventilator waveforms are graphical descriptions of how a breath is delivered to a patient. Identification of PVA is possible with a thorough knowledge of ventilator waveforms. ![]() PVA is associated with worse outcomes including increased length of mechanical ventilation, increased length of stay, and increased mortality. Patient-ventilator asynchrony (PVA) is a common finding in pediatric patients and observed in approximately one-third of ventilator breaths. This review covers the basics of how to interpret and use data from ventilator waveforms in the pediatric intensive care unit. Knowledge of ventilator waveforms is important for clinicians working with children requiring mechanical ventilation.
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