Alveolar Volume Determined by Single-Breath Helium Dilution Correlates with the High-Resolution Computed Tomography-Derived Nonemphysematous Lung Volume.
Respiration 2006;
73:468-73. [PMID:
16205050 DOI:
10.1159/000088711]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Accepted: 05/19/2005] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND
The alveolar volume (V(A)), determined by single-breath helium dilution, is a measure for the total lung capacity (TLC) that is very sensitive to ventilatory disturbances. In chronic obstructive pulmonary disease (COPD), the emphysematous lung parts are less accessible to test gas; therefore, the V(A) is smaller than TLC measured by multiple-breath helium dilution (TLC(He)).
OBJECTIVES
The aim of this study was to investigate whether the V(A) represents the nonemphysematous lung parts.
METHODS
We measured V(A) as part of the diffusing capacity for carbon monoxide (DL(CO)), TLC(He) and spirometry in 50 patients with COPD. High-resolution computed tomography (HRCT) scans of all subjects were analyzed with the density mask method, where parts with an attenuation of less than -950 Hounsfield units were considered as emphysematous.
RESULTS
A strong correlation was observed between the V(A) (mean 5.2 liters) and nonemphysematous HRCT lung volume (mean 5.2 liters, r(2) = 0.9) and between the TLC(He) (mean 6.6 liters) and total HRCT lung volume (mean 6.4 liters, r(2) = 0.9). Bland-Altman plots showed considerable disagreement between the V(A) and the nonemphysematous HRCT lung volume. A weak correlation between the forced expiratory volume in 1 s (mean 46% predicted) and DL(CO) (mean 46% predicted) versus the HRCT emphysema ratio (nonemphysematous/total HRCT lung volume) was observed (r(2) = 0.3 and 0.3, respectively).
CONCLUSION
We concluded that the V(A) correlates with the nonemphysematous HRCT lung volume, although the two measurements are not equivalent, possibly due to technical factors.
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