The first phase has no nitrogen, the second phase nitrogen concentration increases and third phase is plateau phase. The subject breathes out and deeply inhales from 0% nitrogen gas mixture and exhales into the equipment that measures nitrogen and gas volume. Physiological dead space is calculated as follows:Īlveolar dead space is calculated as follows:

Slowly the expirate is switched to Douglas bag once the respiration became steady. The rate of respiration and minute volume are recorded. The expirate is passed through the dry gas meter and into the atmosphere via two-way tap. The latter is firmly supported in the mouth by the standard mouth piece. A nose clip is applied and the subject is asked to breathe in and out through Ruben non-return valve. The examination is carried out by subject lying on the bed supported by pillow. However, differences in the exact way of measuring this space result in clinically significant different results and, therefore, debate remains about the true value of this measured parameter.Ĭopyright © 2023, StatPearls Publishing LLC.The anatomic dead space is measured by Fowler’s method.

Indeed, it may serve as a prognostic factor in patients with acute repository distress syndrome (ARDS) who require ventilation.

This phenomenon has clinical significance because, both in healthy and impaired lungs, properly calculating and accounting for this non-physiological space is important for the proper respiratory care of ventilated patients. This is therefore termed anatomical dead space as it serves no respiratory function.

Anatomic dead space is an important phenomenon in respiratory physiology whereby, owing to the fact that upper airways do not function as locations for gas exchange, and because of the tidal nature of ventilation, there is always a fraction of the inspired air that does not perform a physiologic function of exchanging carbon dioxide for oxygen.

Define dead space in lungs