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Peripheral lung resistance in normal and asthmatic subjects
E M Wagner1, M C Liu, G G Weinmann
1Department of Medicine, Johns Hopkins University, Baltimore, Maryland.
The American Review of Respiratory Disease
|March 1, 1990
Summary
Peripheral airway resistance in obstructive lung disease is difficult to measure with standard tests. This study directly measured peripheral lung resistance in normal and asthmatic subjects, finding it nondistensible.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Peripheral airways are a key site of pathology in obstructive lung disease.
- Standard pulmonary function tests may not detect small airway abnormalities due to low contribution to total resistance.
Purpose of the Study:
- To directly measure peripheral lung resistance in normal and mildly asthmatic subjects.
- To assess if peripheral lung resistance differs between normal and asthmatic individuals.
Main Methods:
- Used a fiberoptic bronchoscope wedged into a subsegmental bronchus.
- Employed a double-lumen catheter to measure pressures (PB) at various gas flow rates (V).
- Measurements were conducted at a constant lung volume (functional residual capacity).
Main Results:
- No significant differences in spirometry (FEV1, FVC) or specific airway conductance were found between groups.
- The pressure-flow relationship in peripheral airways was linear and approximated a straight line through the origin.
- Peripheral lung resistance (Rp) was calculated as PB/V.
Conclusions:
- Direct measurement of peripheral lung resistance is feasible.
- Peripheral airways demonstrated relatively nondistensible characteristics in both normal and asthmatic subjects.
- Routine pulmonary function tests may not adequately reflect peripheral airway status in mild disease.