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Total dead space (also known as physiological dead space) is the sum of the anatomical dead space and the alveolar dead space. Benefits do accrue to a seemingly wasteful design for ventilation that includes dead space. [1] Carbon dioxide is retained, making a bicarbonate-buffered blood and interstitium possible.
In respiratory physiology, the ventilation/perfusion ratio (V/Q ratio) is a ratio used to assess the efficiency and adequacy of the ventilation-perfusion coupling and thus the matching of two variables: V – ventilation – the air that reaches the alveoli; Q – perfusion – the blood that reaches the alveoli via the capillaries
In medicine, the ratio of physiologic dead space over tidal volume (V D /V T) is a routine measurement, expressing the ratio of dead-space ventilation (V D) to tidal ventilation (V T), as in physiologic research or the care of patients with respiratory disease. [1]
The Bohr equation, named after Danish physician Christian Bohr (1855–1911), describes the amount of physiological dead space in a person's lungs. This is given as a ratio of dead space to tidal volume. It differs from anatomical dead space as measured by Fowler's method as it includes alveolar dead space.
It is generally only observed when a person is ventilated with positive pressure or hemorrhage. In these circumstances, blood vessels can become completely collapsed by alveolar pressure (PA) and blood does not flow through these regions. They become alveolar dead space. Zone 2 is the part of the lungs about 3 cm above the heart.
In anatomy, a potential space is a space between two adjacent structures that are normally pressed together (directly apposed). Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realization being dynamic according to physiologic or pathophysiologic events).
Physiologic dead space cannot change as it is ventilation without perfusion. A shunt is a perfusion without ventilation within a lung region. [citation needed] Low tidal volume ventilation was the primary independent variable associated with reduced mortality in the NIH-sponsored ARDSNet trial of tidal volume in ARDS.
In anatomy, a spatium or anatomic space is a space (cavity or gap). Anatomic spaces are often landmarks to find other important structures. When they fill with gases (such as air) or liquids (such as blood) in pathological ways, they can suffer conditions such as pneumothorax, edema, or pericardial effusion.