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. The last two of three consecutive measurements were used for analysis.


RESULTS
In healthy subjects but not patients with CF, Dlno, and Dlco differed significantly (p < 0.05 each) between breath-hold times. Differences primarily occurred at 4 s and 10 s, while at 6 s and 8 s alveolar volume (VA), Dlno, Dlco, and Dlno/Dlco were similar. Variability of consecutive measurements (either three or the last two measurements) did not depend on breath-hold time. At 8 s, mean variabilities of Dlno and Dlco in healthy subjects were 4.9% and 2.5%, respectively, and 4.2% and 3.2% at 6 s. At 8 s, mean variabilities of Dlno and Dlco in CF patients were 4.4% and 1.9%, and 7.4% and 3.3% at 6 s.


CONCLUSIONS
Single-breath determinations of dlno and dlco showed no difference between breath-hold times of 6 s and 8 s in subjects with or without airway obstruction, and reproducibility was acceptable. Standardization of breath-hold time for Dlno measurements seems important for clinical and research comparisons.
Dressel
Holger
H
Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University Munich, Ziemssenstrasse 1, D-80336 München, Germany. holger.dressel@med.uni-muenchen.de
Filser
Laura
L
Fischer
Rainald
R
de la Motte
Dorothea
D
Steinhaeusser
Werner
W
Huber
Rudolf M
RM
Nowak
Dennis
D
Jörres
Rudolf A
RA
D000280:Administration, Inhalation; D000328:Adult; D000402:Airway Obstruction / Q000209:etiology / Q000503:physiopathology; D001944:Breath Tests / Q000379:methods; D002248:Carbon Monoxide / Q000008:administration & dosage*; D003550:Cystic Fibrosis / Q000150:complications / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage*; D011379:Prognosis; D011653:Pulmonary Diffusing Capacity / Q000187:drug effects* / Q000502:physiology; D012119:Respiration / Q000187:drug effects*; D012720:Severity of Illness Index; D013147:Spirometry / Q000379:methods; D013997:Time Factors
D009569:Nitric Oxide; D002248:Carbon Monoxide