Body-plethysmographic pressure-flow diagrams in chronic obstructive lung disease. I. Comparative measurements.

One hundred patients with various forms of chronic obstructive lung disease were allocated to groups according to their body-plethysmographic pressure-flow diagrams. Group I comprised 30 patients with resistance curves displaying linear relationship between pressure and flow. The second group (n = 30) was formed by patients who had a markedly pronounced hysteresis in the central parts of their resistance curves. Group III consisted of 30 patients who exhibited resistance curves with distended expiratory parts. Group IV's patients (n = 30) had eight-shaped resistance curves. The comparative measurements on these 4 types of body-plethysmographic pressure-flow diagrams included all kinds of airway resistances, as well as their components and ratios (Raw, Rpeak, R, Raw(in), Raw(ex), R(ex), R(in), Raw/R, Raw(ex)/R(ex), Raw(in)/R(in), Raw(ex)/Raw(in), R(ex)/R(in)). The analysis of the results shows that the quantitative criteria used in the assessment undergo the greatest change in the eight-shaped loops and in those resistance curves whose expiratory parts are considerably distended. The difference between the absolute values obtained by using the basic methods of calculating airway resistance is the greater the weaker is the linear relationship between pressure and flow.