Novel method for measuring anatomical dead space as a potential means of assessing airway distensibility

This thesis describes the development and application of a new, noninvasive method for providing in-vivo measurements of anatomical dead space (VD), and its components in cooperative human subjects. It also investigates their relationships with changing lung volume (airway distensibility, AVD) in normal versus asthmatic subjects. The computerised method for measuring VD was based on CO₂ washout, with tidal breathing, at discrete, or progresnively increasing or decreasing lung volumes between TLC or RV. Absolute lung volume (TLC or RV), determined by body plethysmography, was used in the computer calculation of AVD as the reference volume to obtain end-inspiratory lung volume for each measurement of anatomical VD. This new method provided rapid measurements of VD, with duplicate measurements taking 10-15 minutes to complete, even in untrained subjects.[…]