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Changes in total lung capacity during acute spontaneous asthma.
S P Blackie1, S al-Majed, C A Staples
1UBC Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, British Columbia, Canada.
The American Review of Respiratory Disease
|July 1, 1990
Summary
Asthma exacerbations can cause acute, reversible increases in total lung capacity (TLC). Radiographic planimetry, a reliable method, detected these changes, unlike traditional lung volume assessments in obstructive lung disease.
Area of Science:
- Pulmonary Medicine
- Radiology
- Respiratory Physiology
Background:
- Traditional methods for measuring total lung capacity (TLC) like helium dilution and plethysmography are unreliable in obstructive lung disease.
- Previous reports suggest increased TLC during asthma exacerbations, but assessment methods were flawed.
Purpose of the Study:
- To accurately measure changes in TLC during asthma exacerbations using a reliable radiographic method.
- To compare radiographic TLC measurements with traditional methods at recovery.
Main Methods:
- Total lung capacity (TLC-XR) was measured using radiographic planimetry from chest X-rays during exacerbations (E) and recovery (R) in 12 asthma patients.
- TLC was also measured by plethysmography or helium dilution at recovery for comparison.
- Radiologists assessed lung hyperinflation using independent radiographic variables.
Main Results:
- Mean TLC-XR during exacerbations (6.01 L) was significantly greater than at recovery (5.44 L).
- Radiographic TLC measurements at recovery strongly correlated with plethysmography/helium dilution (r=0.94).
- Increased lung height was the only radiographic variable distinguishing exacerbations from recovery.
Conclusions:
- Acute, reversible increases in TLC occur during asthma exacerbations.
- Radiographic planimetry is a reliable method for detecting these TLC changes, which are missed by traditional lung volume assessments in obstructive disease.