Single-Breath Continuous Carbon Dioxide Analysis

Abstract

MEASUREMENTS of inequalities in alveolar ventilation and of physiological dead space give an estimate of the under-ventilated and under-perfused volumes of diseased lungs. Comroe and Fowler¹ described the use of a nitrogen meter to detect uneven alveolar ventilation during a single expiration. Dubois et al. ² showed how the physiological dead space could be assessed by measuring the carbon dioxide content of expired air with a rapid infra-red gas-analyser, and Dornhorst et al. ³ described the pattern produced, with similar apparatus, by emphysematous patients. This method relates the carbon dioxide content of expired air to time, and the records produced are sometimes difficult to interpret because the carbon dioxide content is also influenced by the volume of air expired. Marshall et al. ⁴ demonstrated the relation between volume and carbon dioxide content of expired air by fractional analysis and applied their method to normal and diseased subjects.