title: [Single-breath and rebreathing methods for measurement of pulmonary diffusing function: a comparative study].
abstract: OBJECTIVE
  To compare the difference of pulmonary diffusing capacity measured by single-breath (SB) and re-breathing (RB) in normal subjects, patients with interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  We enrolled a cohort of subjects from the Guangzhou Institute of Respiratory Disease between September 2011 and February 2012: control group 29 (male 9, female 20, 42-74 y), ILD group 32 (male 15, female 17, 41-72 y), COPD group 32 (male 28, female 4, 40-75 y). All subjects underwent pulmonary diffusing capacity test using SB or RB method according to random figures order list. Diffusing capacity of carbon monoxide per predicted measured by SB method (SB-DLCO%pred) of the normal group was used as the standard to adjust the diffusing capacity of carbon monoxide per predicted measured by RB method (RB-DLCO%pred) and diffusing capacity of carbon monoxide per liter of VA per predicted measured by RB (RB-DLCO/VA%pred) in the 3 groups, respectively. Comparisons between 2 groups were performed by using the independent-sample t test, among more than 2 groups by using the One-Way ANOVA test, while the ROC curve was used to calculate the area under curve (AUC) and its 95%CI.
  
  
  RESULTS
  In the control group, 15 subjects' RB-DLCO%pred was lower than 80%, and the mean value (78.8 ± 2.1)% was also lower than 80%. Using SB-DLCO%pred of the normal group as a standard to adjust the RB-DLCO%pred, the corrected value was 1.097, and then this value was used to adjust RB-DLCO/VA%pred in the 3 groups, respectively. Before correction DLCO%pred [the control group: (91.2 ± 1.9)% vs (78.8 ± 2.1)%; the ILD group: (45.8 ± 2.6)% vs (60.0 ± 1.9)%;the COPD group: (66.3 ± 2.9)% vs (56.6 ± 1.6)%]and DLCO/VA%pred [the control group: (99.8 ± 2.3)% vs (84.6 ± 4.5)%; the ILD group: (75.9 ± 3.0)% vs (88.5 ± 5.4)%; the COPD group: (80.2 ± 3.7)% vs (50.6 ± 2.5)% ] between the SB and RB were statistically different among the 3 groups. After correction, only the DLCO%pred [(45.8 ± 2.6)% vs (65.8 ± 2.1)%], DLCO/VA%pred [ (75.9 ± 3.0)% vs (102.2 ± 6.2)%] of the ILD group and the DLCO/VA%pred [(80.2 ± 3.7) vs (58.3 ± 2.8)%] of the COPD group had significant difference between the 2 methods (t = -6.00-4.68, all P < 0.01) . The test time of re-breathing in the COPD group (106 ± 5) s was significant longer than that of the ILD group (73 ± 4) s and the control group (79 ± 5) s (F = 11.99, P < 0.01), and the correlation between DLCO/VA%pred and the test time(r = -0.661, P < 0.01) was higher than the relationship between DLCO%pred and the test time (r = -0.391, P < 0.01). Furthermore, in the ILD group, the area of RB-DLCO%pred under ROC was 0.893, 95%CI being 0.817-0.970. In the COPD group, the area of RB-DLCO/VA%pred under ROC was 0.895, 95%CI being 0.811-0.979.
  
  
  CONCLUSIONS
  There were differences between re-breathing and single-breath in measuring diffusing capacity. The present predicted value of the re-breathing method needed further study to confirm its applicability. Re-breathing method was more consistent with the respiratory physiology, and might be a better method to detect diseased states.
authors.affiliation: The First Affiliated Hospital of Guangzhou Medical College, Guangzhou 510120, China.
authors.forename: Qing-xia
authors.initials: QX
authors.lastname: Liu
authors.forename: Jin-ping
authors.initials: JP
authors.lastname: Zheng
authors.forename: Yan-qing
authors.initials: YQ
authors.lastname: Xie
authors.forename: Wei-jie
authors.initials: WJ
authors.lastname: Guan
authors.forename: Cai-yu
authors.initials: CY
authors.lastname: Jiang
authors.forename: Jia-ying
authors.initials: JY
authors.lastname: An
authors.forename: Xin-xin
authors.initials: XX
authors.lastname: Yu
authors.forename: Wen-Ting
authors.initials: WT
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Gao
mesh_terms: D000328:Adult; D000368:Aged; D002248:Carbon Monoxide / Q000378:metabolism*; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology; D017563:Lung Diseases, Interstitial / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011650:Pulmonary Alveoli / Q000502:physiology; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000503:physiopathology*; D012119:Respiration; D012129:Respiratory Function Tests / Q000379:methods*
chemical_list: D002248:Carbon Monoxide