Partitioning of dead space ‐ a method and reference values in the awake human

Abstract

Although dead space is often increased in disease, it is not frequently measured in the clinic. This may reflect that an adequate method as well as reference values are missing. Healthy males and females, n=38, age 20-61 yrs, were connected to a pneumotachograph and a fast CO2 analyser after radial artery catheterization. The physiological dead space was partitioned into airway and alveolar dead space using a delineation principle denoted the pre-interface expirate. Physiological dead space was 201+/-41 mL in males and 150+/-34 mL in females. Dead space values were depending upon parameters reflecting lung size (predicted total lung capacity), breathing pattern and age. After multiple correlation the variation decreased and differences between males and females disappeared. The residual SD was then for physiological dead space 18.9 mL. The clinical use of the new method for determination of dead space can be based upon reference values, with a more narrow range than previous data.

Effects of positive end-expiratory pressure on dead space and its partitions in acute lung injury

“…Airway VD distal to the CO 2 sensor (VD aw,dist ) was determined according to an algorithm of Wolff and Brunner [18] that was modified to correct for a sloping alveolar plateau [19] in accordance with principles previously described [20].…”

“…The alveolar plateau was described in an equation [19] from which the slope of the alveolar plateau (SLOPE) at the volume halfway between VD aw,dist and VT was calculated (Fig. 2).…”

“…The difference may be of a methodological nature. We applied the principle of Wolff and Brunner [18] that is considered to give "the smallest possible of determinable values of airway dead space" [19]. Fletcher used the original principle of Fowler [25] that probably gives higher values because correction for the alveolar slope, that decreases the airway dead space calculated [20], was not performed.…”

Gas exchange with a reflecting system for inhalational anaesthesia

“…84 Their algorithm was modified by Åström et al to be more robust in the presence of a sloping plateau. 61 At the end of expiration a certain volume of CO 2 has been expired. At the start of inspiration a part of that volume is re-inspired.…”

“…All subjects, even those with healthy lungs, have some ventilation/perfusion mismatch. 61 Physiological dead space is the sum of airway and alveolar dead space. Physiological dead space is typically 30% of tidal volume in healthy individuals.…”