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).

Dead space ventilation perfusion ratio