![]() ![]() This review revisits the physiological concepts and methods of measuring deadspace. Thus making it more accessible and easy to monitor and study in large groups of patients, factors which have perhaps resulted in its under-utilisation in critical care. ![]() Several indices have been described that either predict deadspace or track ventilatory efficiency at the bedside. Recently though there has been a resurgence of interest in ventilatory efficiency. Deadspace and with it ventilatory efficiency has been largely forgotten. Yet indices of oxygenation seem to be the mainstay when instigating or fine-tuning ventilatory strategies. Since its first description by Bohr in the late 19th century to the current use of single-breath test for volumetric CO 2, our understanding of the physiological deadspace has vastly improved. Measuring deadspace ventilation should be the most reliable method of monitoring ventilatory efficiency in mechanically ventilated patients. V d V t = P A C O 2 − P e C O 2 P A C O 2 Ī common step is to then presume that the partial pressure of carbon dioxide in the end-tidal exhaled air is in equilibrium with that gas' tension in the blood that leaves the alveolar capillaries of the lung.Problems with ventilatory efficiency results in abnormal CO 2 clearance. The original formulation by Bohr, required measurement of the alveolar partial pressure P A. The Bohr equation is used to quantify the ratio of physiological dead space to the total tidal volume, and gives an indication of the extent of wasted ventilation. It differs from anatomical dead space as measured by Fowler's method as it includes alveolar dead space. This is given as a ratio of dead space to tidal volume. The Bohr equation, named after Danish physician Christian Bohr (1855–1911), describes the amount of physiological dead space in a person's lungs. Not to be confused with the Bohr model or the Bohr effect.
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