The nomenclature describing dead space can be quite confusing (see for in-depth reading). , where V̇CO 2 = CO 2 production by the body (units: cc/min) and V̇ A = alveolar ventilation. The alveolar ventilation controls CO 2 homeostasis according to the alveolar ventilation equation : Mathematically, V̇ A is total ventilation minus anatomical dead space ventilation. Its calculation requires exclusion of ventilation occurring in the anatomical dead space. in a passive mechanically ventilated patient on volume control (VC) mode, V̇ E = V T x RR.Īlveolar ventilation ( V̇ A the subscript ‘A’ denotes ‘alveolar’) is the amount of ventilation occurring in the alveoli in one minute. Minute ventilation ( V̇ E the subscript ‘E’ denotes ‘exhaled’) is the total ventilation in one minute (units: L/min). At this point, it is helpful to define minute ventilation and alveolar ventilation : V D /V T is a common way to quantify dead space. The fraction of the tidal volume that does not contribute to gas exchange is known as dead space fraction (V D /V T where V T = tidal volume and V D = dead space volume). A certain amount of dead space is normally present in every person (this is known as anatomical dead space: see below). This concept can be extended to include factors that cause a dead space effect. Some apparatus dead space may actually reduce total dead space, as an ETT bypasses the majority of anatomical dead space of the patient (nasopharynx).ĭead space from the patient.Simply put, dead space represents the volume of ventilated air that does not participate in gas exchange. Types of Dead Spaceĭead space from equipment, such as tubes ventilator circuitry. Glomerular Filtration and Tubular Functionĭead space is the proportion of minute ventilation which does not participate in gas exchange. Functional Anatomy and Control of Blood Flow
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