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Table 4 Chronic respiratory symptom, spirometry, impulse oscillometry, and computed tomography results of 1862 subjects stratified by small airway dysfunction status based on impulse oscillometry and computed tomography diagnosis

From: Comparing spirometry, impulse oscillometry with computed tomography for assessing small airway dysfunction in subjects with and without chronic obstructive pulmonary disease

Variable

No SAD with IOS and CT‡

(n = 1010)

Combined IOS and CT-defined SAD§

(n = 274)

Only IOS-defined SAD¶

(n = 330)

Only CT-defined SAD#

(n = 248)

Mean difference (95% CI)*

P value*

Adjusted mean difference (95% CI)*†

Adjusted P value*†

Chronic respiratory symptom

        

 mMRC score

0.24 ± 0.51

0.83 ± 0.78

0.33 ± 0.58

0.40 ± 0.59

-0.07 (-0.17 to 0.03)

0.162

-0.04 (-0.16 to 0.09)

0.553

 CAT score

3.10 ± 3.76

7.15 ± 6.42

3.73 ± 4.43

4.63 ± 4.71

-0.90 (-1.65 to -0.15)

0.019

-0.79 (-1.75 to 0.18)

0.110

Prebronchodilator spirometry

        

 FEV1, % predicted

92.9 ± 14.8

53.0 ± 17.6

81.8 ± 16.4

79.9 ± 17.2

2.0 (-0.8 to 4.7)

0.165

-3.7 (-7.1 to -0.4)

0.030

 FVC, % predicted

102.9 ± 15.7

85.7 ± 18.4

95.3 ± 15.7

102.3 ± 17.4

-7.0 (-9.7 to -4.3)

< 0.001

-10.8 (-14.2 to -7.4)

< 0.001

 FEV1/FVC, %

73.4 ± 8.2

48.2 ± 10.8

69.8 ± 9.8

61.7 ± 10.2

8.0 (6.4 to 9.7)

< 0.001

3.9 (1.9 to 5.8)

< 0.001

 MMEF, % predicted

54.5 ± 23.5

16.3 ± 9.0

41.2 ± 20.9

34.9 ± 18.5

6.3 (3.0 to 9.6)

< 0.001

1.2 (-2.9 to 5.2)

0.574

 FEF50, % predicted

62.6 ± 25.3

16.5 ± 9.9

46.9 ± 23.7

37.0 ± 20.3

9.8 (6.2 to 13.5)

< 0.001

2.5 (-2.0 to 7.0)

0.268

 FEF75, % predicted

41.0 ± 23.1

15.6 ± 8.1

32.0 ± 19.7

31.8 ± 19.9

0.3 (-3.0 to 3.5)

0.876

-0.5 (-4.6 to 3.6)

0.812

Impulse oscillometry

        

 R5, kPa/L/s

0.30 ± 0.07

0.46 ± 0.11

0.43 ± 0.10

0.28 ± 0.06

0.15 (0.14 to 0.17)

< 0.001

0.11 (0.09 to 0.13)

< 0.001

 R20, kPa/L/s

0.27 ± 0.07

0.29 ± 0.06

0.31 ± 0.07

0.25 ± 0.06

0.06 (0.05 to 0.07)

< 0.001

0.02 (0.01 to 0.04)

< 0.001

 R5-R20, kPa/L/s

0.03 ± 0.02

0.17 ± 0.08

0.12 ± 0.05

0.03 ± 0.03

0.09 (0.09 to 0.10)

< 0.001

0.09 (0.08 to 0.10)

< 0.001

 X5, kPa/L/s

-0.09 ± 0.03

-0.23 ± 0.13

-0.15 ± 0.06

-0.10 ± 0.03

-0.06 (-0.06 to -0.05)

< 0.001

-0.06 (-0.07 to -0.05)

< 0.001

 AX, kPa/L

0.27 ± 0.16

2.04 ± 1.33

1.08 ± 0.73

0.31 ± 0.20

0.77 (0.68 to 0.86)

< 0.001

0.77 (0.65 to 0.89)

< 0.001

 Fres, Hz

12.0 ± 2.8

23.7 ± 4.6

19.2 ± 3.8

12.8 ± 3.9

6.3 (5.7 to 7.0)

< 0.001

6.8 (6.0 to 7.6)

< 0.001

Computed tomography

        

 Expiratory LAA− 856, %

6.4 ± 6.1

44.7 ± 19.3

7.6 ± 6.6

36.3 ± 14.4

-28.8 (-30.5 to -26.9)

< 0.001

-24.3 (-26.4 to -22.1)

< 0.001

 Inspiratory LAA− 950, %

1.0 ± 1.9

9.1 ± 9.7

1.1 ± 2.4

5.1 ± 6.8

-3.9 (-4.7 to -3.1)

< 0.001

-2.1 (-3.1 to -1.1)

< 0.001

 PRMfSAD, %

4.0 ± 4.0

36.3 ± 14.5

5.0 ± 4.4

30.1 ± 13.0

-25.1 (-26.6 to -23.5)

< 0.001

-22.6 (-24.5 to -20.7)

< 0.001

 PRMEmph, %

0.5 ± 1.4

8.8 ± 9.6

0.7 ± 1.8

4.5 ± 6.3

-3.8 (-4.5 to -3.1)

< 0.001

-2.3 (-3.2 to -1.4)

< 0.001

 Pi 10, mm

3.6 ± 0.7

4.4 ± 0.9

4.1 ± 0.8

3.7 ± 0.7

0.4 (0.3 to 0.5)

< 0.001

0.2 (0.1 to 0.4)

0.005

  1. Data are shown as mean ± standard deviation or median (interquartile range). * Comparing Only IOS-defined SAD with Only CT-defined SAD. † Adjusted for age, sex, BMI, smoking status, pack-years, biomass exposure, occupation exposure, family history of respiratory diseases. ‡ No SAD diagnosed by both IOS and CT. § SAD diagnosed by both IOS and CT. ¶ SAD diagnosed by only IOS but not CT.# SAD diagnosed by only CT but not IOS. Abbreviations: IOS, impulse oscillometry; CT, computed tomography; SAD, small airway dysfunction; mMRC, modified Medical Research Council dyspnea score; CAT, chronic obstructive pulmonary disease assessment test; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; MMEF, maximal mid-expiratory flow; FEF50, forced expiratory flow 50%; FEF75, forced expiratory flow 75%; R5, resistances at 5 Hz; R20, resistances at 20 Hz; R5-R20, resistances at 5 and 20 Hz; X5, reactance at 5 Hz; AX, reactance area; Fres, resonant frequency in Hz; LAA− 856, the low-attenuation area below − 856 Hounsfield units on full-expiration computed tomography; LAA− 950, the low-attenuation area below − 950 Hounsfield units on full-inspiration computed tomography; PRM, parametric response mapping; fSAD, functional small airway disease; Emph, emphysema; Pi 10, the square root of the airway wall area for a theoretical airway with 10 mm internal perimeter
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BMC Pulmonary Medicine

ISSN: 1471-2466

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