Lung diffusing capacity for nitric oxide and carbon monoxide: dependence on breath-hold time.

Background: The combined measurement of diffusing capacity of the lung for nitric oxide (Dlno) and diffusing capacity of the lung for carbon monoxide (Dlco) is a simple, noninvasive tool, but methodologic factors might influence results and reproducibility. We thus quantified the influence of breath-hold time on Dlco and Dlno in subjects with or without airway disease.

Methods: Simultaneous single-breath measurements of Dlco and Dlno were performed in 10 patients with cystic fibrosis (CF) [mean +/- SD age, 33 +/- 9 years; FEV(1), 69 +/- 28% of predicted] and 10 healthy subjects (age, 31 +/- 9 years; FEV(1), 108 +/- 8% of predicted), using the Masterscreen PFT (Viasys/Jaeger; Höchberg, Germany), with 45 ppm of inspired nitric oxide (NO), and breath-hold times of 4 s, 6 s, 8 s, and 10 s.