Submitted on March 25, 2005
Accepted on July 10, 2005
An Open Circuit Method for Determining Lung Diffusing Capacity during Exercise: Comparison to Rebreathe
Eric M. Snyder1, Bruce D. Johnson1*, and Kenneth C. Beck2
1 Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, MN, USA
2 Physiological Imaging, Department of Radiology, University of Iowa, Iowa City, IA, USA
* To whom correspondence should be addressed. E-mail: johnson.bruce{at}mayo.edu.
To avoid limitations associated with the use of single breath and rebreathe methods for assessing the lung diffusing capacity for carbon monoxide (DLCO) during exercise, we developed an open-circuit technique. This method does not require rebreathing or alterations in breathing pattern and can be performed with little cognition on the part of the patient. To determine how this technique compared to the traditional rebreathe
(RBDLCO) method we performed both the open circuit (OCDLCO) and the RBDLCO methods at rest and during exercise (25, 50, and 75% of peak work) in 11 healthy
subjects (mean age=34±11 yrs, mean ± SD). Both OCDLCO and RBDLCO increased linearly with cardiac output and external work. There was a good correlation between OCDLCO and RBDLCO for rest and exercise (mean of individual r2= 0.88, overall r2 = 0.69, slope = 0.97). OCDLCO and RBDLCO were similar at rest and during exercise
(e.g. rest=27.2±5.8 vs. 29.3±5.2, and 75% peak work=44.0±7.0 vs. 41.2±6.7
ml/min/mmHg, for OCDLCO vs. RBDLCO). The coefficient of variation for repeat measurements of OCDLCO was 7.9% at rest and averaged 3.9% during exercise. These data suggest that the OCDLCO method is a reproducible, well tolerated
alternative for determining DLCO, particularly during exercise. The method is linearly associated with cardiac output, suggesting increased alveolar-capillary recruitment, and values were similar to the traditional rebreathe method.
