Why does it matter?īecause if you take lots of rapid shallow breaths, you will be moving air in and out of your dead space, without sending any meaningful ventilation to the areas of your lung that can engage in gas exchange. It is composed of anatomical and alveolar dead space. The total dead space is called the physiological dead space. These areas therefore do not undertake gas exchange with the blood. If the air and the blood are being sent to different alveoli, then clearly the system isn't going to work very well, and this is called a ventilation/perfusion mismatch.ĭead space refers to the areas of the respiratory tract that are ventilated but not perfused. Not only does the air need to be drawn successfully into the alveoli, but blood needs to be pumped to those same alveoli in order to pick up the oxygen. The lungs represent an interface between ventilation and perfusion. This is why you start assessing your patient with an airway, breathing, circulation approach, because that's the most life-threatening order in which problems present. To survive, we need to get oxygen from the air into our blood, in order to supply the tissues. Dead space is important to think about, especially in paediatrics.Ventilation/Perfusion matching is everything (sort of).Hopefully the components of that volume of air will be clearer after reviewing the following illustrations. And then real quick before we dive in: if you’re not familiar with the idea of dead space in general, it’s the concept that there is a difference between the quantity of air breathed in during a breath (tidal volume) and the volume of air that actually participates in gas exchange at the alveolar level (clinically relevant tidal volume). Dead space is a concept that we generally discuss in the context of mechanical ventilation – this short series of graphics won’t get into too much detail on that, but we can point you towards our free book on the idea: The goal here is simply to review the different types of dead space, demonstrate them graphically, and point out specific interventions for each of the various types. The series of illustrations in this post demonstrate the different types of dead space encountered in clinical practice and interventions to address them.
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