The Reliability of the Pulmonary Diffusing Capacity Determination

Abstract

The test-retest reliability of the ten second breath-holding method for the determination of pulmonary diffusing capacity of carbon monoxide was studied in a series of 151 men and women, including patients, normal subjects and athletes.

The mean and standard deviation of the D_LCO was 28.2 ± 10.09 ml × min⁻¹ × mmHg⁻¹. The standard deviation of the difference of duplicate determinations made on the same day (32 pairs) was 1.260, of those made at an interval of 10–99 days (98 pairs) 2.915, and of those made at an interval of 100–999 days (74 pairs) 2.637. The intra-individual variation was correspondingly 12, 29 and 26 per cent of that between individuals. It is concluded that “physiological” factors cause variations in the diffusing capacity over periods longer than a day; even so the tendency to individual constancy is marked.

The results are compared with those of other investigators.

The authors express their thanks to Dr. J. E. Cotes, of the Medical Research Council Pneumoconiosis Research Unit at Cardiff, on whose initiative the study was carried out.