Chest
Volume 107, Issue 3, Supplement, March 1995, Pages 148S-152S
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Session 9
Relationships Among Airway-Parenchymal Interactions, Lung Responsiveness, and Inflammation in Asthma: Giles F. Filley Lecture

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Volume History Measurements

Over a wide range of circumstances, the effects of a DI, whether expressed as an isovolumic ratio (M/P ratio) of maximal flows on successively performed partial (P—ie, maneuvers begun from functional residual capacity) and maximal (M—ie, maneuvers begun from total lung capacity) expiratory flow volume curves or the ratio of specific conductance measured immediately after a DI to that measured just before, give equivalent results1 (Fig 1). Therefore no special distinction will be made between

MECHANISMS

Is there a single, encompassing hypothesis that can account for all of these phenomena? Preferential emptying of a fast compartment at the beginning of both the P and M maneuvers could explain decreasing ratios with worsening obstruction as seen in cystic fibrosis,14 but would not explain the rising ratios seen with induced obstruction, nor would it be compatible with the equivalency of M/P and before and after DI conductance ratios. Diminished degrees of airway-parenchymal interdependence due

TESTING THE RELATIVE HYSTERESIS ANALYSIS

Since airway size is a dependent variable, no direct or indirect measurement of airway size can tell you whether a change in volume history response is predominantly the result of a change in parenchymal or in airway hysteresis. To test the appropriateness of the analysis, a direct assessment of parenchymal hysteresis is needed. We have used quasistatic lung volume-transpulmonary pressure curves to assess parenchymal hysteresis and its acute changes.8 This is based on the premise that overall

CONCLUSIONS

The relationships among lung responsiveness, sites and mechanisms of responses, and effects of a DI on airway caliber could make volume history ratio assessment an interesting and perhaps valuable physiologic tool in both clinical and epidemiologic studies of asthma. In addition, increased insight into the phlogistic and physiologic aspects of the phenomena described should enhance our understanding of airway-parenchymal interactions in health and disease.

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Supported by grants from the National Heart, Lung, and Blood Institute, Bethesda, Md.

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