Elsevier

Respiratory Medicine

Volume 100, Issue 1, January 2006, Pages 101-109
Respiratory Medicine

Pattern of diffusion disturbance related to clinical diagnosis: The KCO has no diagnostic value next to the DLCO

https://doi.org/10.1016/j.rmed.2005.04.014Get rights and content
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Summary

Aim of the study

The diffusion capacity of the lung for carbon monoxide (DLCO) is an important tool in the diagnosis and follow-up of patients with pulmonary diseases. In case of a decreased DLCO the KCO, defined as DLCO/VA (VA is alveolar volume), can differentiate between normal alveolocapillary membrane (normal KCO) and abnormal alveolocapillary membrane (low KCO). The latter category consists of decreased surface of the membrane, increased thickness or decreased perfusion of ventilated alveoli. The VA/TLC (TLC is total lung capacity determined by whole body plethysmography) can partially differentiate between these categories. The aim of this study was to investigate the diagnostic value of the specific diffusion disturbances, which can be constructed by combining the DLCO, KCO and VA/TLC.

Methods

In 460 patients the diagnosis made by clinicians were fitted into five diagnostic categories: asthma, chronic obstructive pulmonary disease (COPD), treatment effects of haematologic malignancies, heart failure and diffuse parenchymal lung diseases (DPLD). These categories were linked to the pattern of diffusion disturbance.

Results

Almost all patients with asthma have a normal DLCO, most patients in the other groups do not have the expected pattern of diffusion disturbance, especially in the group with DPLD a bad match is observed.

Conclusion

In this study the pattern of diffusion disturbance is of limited use in establishing a diagnosis. The use of the KCO next to the DLCO has no additional diagnostic value. Regional ventilation–perfusion inequality probably forms an important underlying mechanism of decreased DLCO.

Keywords

Pulmonary diffusing capacity
Alveolar volume
Whole body plethysmography
COPD
Diffuse parenchymal lung disease

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