Even though they are very relevant for accurate and optimal ventilation, flow mechanics and dead space are not within scope of this article.įirst, tidal volume is typically defined as the volume of gas that is being inspired and expired with each breath. We will discuss all four factors and how ventilators handle these factors in their tidal volume measurement and reporting. There are four major factors to consider when interpreting the measured tidal volumes that are reported by the ventilator: (1) the phase during which the tidal volume is measured (inspiration versus expiration) (2) the site of tidal volume measurement within the breathing circuit (3) the accuracy of the compliance compensation and (4) the conditions under which tidal volume is being measured. Whichever mode is being employed, an accurate measurement of tidal volume is essential to control the delivery of an optimal tidal volume.Ģ.1. When using the very popular volume-guaranteed modes, an algorithm controls the pressure to reach a volume that is set by the clinician. The ventilator displays the delivered inspiratory and the received expiratory tidal volume that it measures, at the pressure set by the clinician. In pressure modes, the clinician controls the tidal volume by setting the inspiratory pressure (either a peak inspiratory and an end-expiratory pressure or a delta pressure on top of the end-expiratory pressure). On the other hand, the tidal volume should not be excessive as it may damage the alveoli due to the large volumes and high pressures (volutrauma and barotrauma). On the one hand the tidal volume needs to be sufficiently large to ventilate the alveoli, deliver oxygen, and eliminate enough carbon dioxide. Tidal Volume in Pediatric Ventilation: Technical Challenges and Clinical ConsequencesĬontrol of the tidal volume is of critical importance in mechanical ventilation. Further, as research regarding the clinical impact of different solutions is lacking, we performed a small prospective cohort study to illustrate whether a software change in the ventilators at our PICU affected the administered tidal volumes in our patients.Ģ. First, we give an expert overview of the different approaches that are being used in ventilator devices to measure and control tidal volumes that are being administered. In this manuscript we aim to provide more insight into this question. Or, more specifically: do we really know what tidal volume we are administering to the lungs our patients, especially in our neonatal and infant populations? The advances in ventilator technology raise the question whether we, as clinicians, still understand how we are ventilating our patients. Multiple sensors and at least one computer processor is controlled by advanced software algorithms that deliver the breath air and oxygen that these devices deliver. The time of the iron lung or basic ventilators has passed and transitioned into an era of highly sophisticated ventilators on our pediatric intensive care units (PICUs). Mechanical ventilators are more and more frequently becoming computer-driven devices. In our search for the optimal TV for lung-protective ventilation, such choices should be taken into account. Design choices in both the hardware and software of mechanical ventilators can have a clinically relevant impact on the measurement of tidal volume. It showed, as example, a clinically significant impact of 8% difference in reported TV. A software change of the TV measuring algorithm of the SERVO-i ® (Getinge, Solna, Sweden) at the PICU of the University Medical Centre Utrecht was studied in a prospective cohort. Such choice may impact the measurement and subsequent display of TV. Ventilator manufacturers make various design choices regarding the phase, site and conditions of TV measurement as well as algorithmic processing choices. Tidal volume (TV) is one of the corner stones of ventilation: multiple technical factors influence the TV and, thus, influence clinical decision making. A good understanding of the design of mechanical ventilators can improve clinical care. These technical advancements have impact on clinical decisions in pediatric intensive care units (PICUs). Mechanical ventilators are increasingly evolving into computer-driven devices.
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