Anatomical dead space was measured in 72 normal children aged from 5 to 16 years, using the single breath method. There was a linear increase in this measurement with height, weight, and end-inspiratory lung volume. Physiological dead space was measured in 52 normal children using the Bohr equation and substituting a rebreathing PCO2 for alveolar PCO2. There was a parallel increase in this meas...

BACKGROUND Anatomical dead space is usually measured using the Fowler equal area method. Alternative methods include the Hatch, Cumming, and Bowes methods, in which first, second, and third order polynomials, respectively, fitted to an expired CO2 volume vs expired volume curve, intercept the x-axis at the anatomical dead space. This study assessed systematic errors and susceptibility to noise ...

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 dea...

Why clinicians are slow to implement advances in diagnosis and treatment from well-designed clinical trials is a continuously debated question in critical care. For instance, prone positioning significantly improves mortality in patients with severe acute respiratory distress syndrome (ARDS), but the usefulness of recruitment measures in this population is still under debate. Nevertheless, a re...

When physiological dead space (Vd(p)) is calculated for a patient who has alveolar dead space, e.g., after pulmonary vascular occlusion, less than the full volume of attached mechanical dead space (Vd(m)) appears in the measured dead space (Vd(n)). Under these conditions the traditional subtraction of Vd(m) from Vd(n) leads to underestimation of Vd(p) and can give a falsely small ratio of Vd(p)...

The accuracy of the steady-state measurement of ventilation by means of a short-lived insoluble inert gas tracer rests with the validity of the steady-state flow equation. This has previously been applied to the qualitative assessment of regional ventilation using krypton-81m, but may potentially be used for the calculation of regional alveolar ventilation per unit alveolar gas volume--(VA/VA)c...

In a steady state the rate of removal of COz from the blood into the alveoli equals its rate of removal from alveoli to atmosphere. There is a gradient of COz concentration from mixed venous blood to alveolar gas or arterial blood and then to mixed expired gas. The mixed venous to alveolar (or arterial) difference depends upon cardiac output (Fick) and the alveolar (or arterial) to mixed expire...

Introduction Lung protective ventilation, LPV, is recommended for ever wider patient populations, even those without primary lung disease. Low tidal volume ventilation is a first-hand remedy for LPV that is facilitated by dead space reduction. Inspiratory flow pattern affects gas exchange. In ARDS patients, it was recently shown that a long period during which inspired tidal gas is in contact w...

UNLABELLED Using an original, validated, high-fidelity model of pulmonary physiology, we compared the arterial to end-tidal CO(2) gradient divided by the arterial CO(2) tension (Pa-E'CO(2)/PaCO(2)) with alveolar dead space expressed as a fraction of alveolar tidal volume, calculated in the conventional manner using Fowler's technique and the Bohr equation: (VDalv/VTalv)(Bohr-Fowler). We examine...