Comparison of pulmonary function in patients with COPD, asthma-COPD overlap syndrome, and asthma with airflow limitation

Figures & data

Table 1 Clinical characteristics of patients with COPD, ACOS, and asthma FL⁺

	COPD (n=118)	ACOS (n=32)	Asthma FL^+ (n=27)
Age, years	71.9±0.8	69.1±1.2	70.3±2.2
Sex
Male, n (%)	96 (88.9)	30 (93.8)	11 (40.7)*,**
Female, n (%)	12 (11.1)	2 (6.3)	16 (59.3)*,**
Body mass index, kg/m^2	22.4±0.3	23.1±0.6	22.4±0.4
Brinkman index, pack-years	51.88±2.88	47.47±6.02	2.39±1.11*,**
Peripheral eosinophil count, %	2.77±0.20	3.66±0.52	3.82±0.69
Peripheral eosinophil count, mm^3	168.12±11.53	232.96±40.04	227.71±46.24
Chest HRCT findings
LAA score	9.52±0.76	5.09±1.16*	0.00±0.00*,**
Bronchial wall thickening, n (%)	27 (25.0)	12 (37.5)	15 (55.6)*

Notes: Values are mean ± standard error of the mean.

* P<0.01 vs COPD.

** P<0.01 vs ACOS.

Abbreviations: COPD, chronic obstructive pulmonary disease; ACOS, asthma-COPD overlap syndrome; asthma FL⁺, asthma with airflow limitation; HRCT, high-resolution computed tomography; LAA, low attenuation area.

Table 2 Pulmonary function of patients with COPD, ACOS, and asthma FL⁺

	COPD (n=118)	ACOS (n=32)	Asthma FL^+ (n=27)
VC, % predicted	98.70±1.70	95.57±3.05	101.34±3.07
FVC, % predicted	97.72±1.88	90.82±3.26	99.53±3.55
FEV1, % predicted	69.84±1.85	63.43±3.22	76.28±2.54*
FEV1/FVC, %	56.97±1.01	55.98±1.66	61.06±1.28
PEFR, % predicted	69.67±2.09	61.08±3.54	74.40±3.16*
MMF, % predicted	25.56±1.01	23.03±1.78	27.67±1.59
FRC, % predicted	100.98±2.04	104.74±3.65	111.30±6.61
RV, % predicted	137.38±3.43	148.46±6.25	112.05±4.34**,***
TLC, % predicted	112.48±1.40	112.93±2.57	111.74±3.12
DLco, % predicted	64.93±2.15	70.67±3.68	85.70±3.19*,***
DLco/VA, % predicted	80.51±2.55	85.70±4.12	118.50±4.06**,***
Delta N2, % N2/L	3.21±0.20	2.63±0.35	2.35±0.24
CV/VC, %	20.41±1.28	18.23±1.95	16.76±2.12

Notes: Values are mean ± standard error of the mean. Delta N₂, slope of Phase III of the single breath nitrogen washout test.

*** P<0.01 vs COPD.

** P<0.01.

* P<0.05 vs ACOS.

Abbreviations: ACOS, asthma-COPD overlap syndrome; asthma FL⁺, asthma with airflow limitation; VC, vital capacity; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; PEFR, peak expiratory flow rate; MMF, maximum midexpiratory flow rate; FRC, functional residual capacity; RV, residual volume; TLC, total lung capacity; DLco, diffusing capacity for carbon monoxide; DLco/VA, diffusing capacity of lung for carbon monoxide corrected for alveolar volume; CV/VC, closing volume/vital capacity.

Figure 1 Response to short-acting β2 agonists in patients with COPD, ACOS, and asthma FL⁺.

Note: Values are mean ± standard error of the mean.
Abbreviations: ACOS, asthma-COPD overlap syndrome; asthma FL⁺, asthma with airflow limitation; FEV₁, forced expiratory volume in 1 second; ∆FEV₁, increases in FEV₁.

Table 3 Respiratory impedance in patients with COPD, ACOS, and asthma FL⁺

	COPD (n=118)	ACOS (n=32)	Asthma FL^+ (n=27)
Whole-breath
R5 (cmH2O/L/s)	3.41±0.14	3.65±0.22	4.29±0.30**
R20 (cmH2O/L/s)	2.68±0.10	3.03±0.15	3.50±0.24**
R5–R20 (cmH2O/L/s)	0.75±0.06	0.63±0.11	0.79±0.17
X5 (cmH2O/L/s)	−1.32±0.12	−1.51±0.23	−1.39±0.20
Fres (Hz)	13.21±0.52	13.66±0.96	14.18±1.00
ALX (cmH2O/L/s Hz)	10.15±1.27	10.75±2.08	10.34±1.95
Expiratory phase
R5 (cmH2O/L/s)	3.75±0.17	3.98±0.25	4.81±0.34**
R20 (cmH2O/L/s)	2.80±0.11	3.18±0.16	3.69±0.30**
R5–R20 (cmH2O/L/s)	0.95±0.07	0.80±0.14	1.03±0.18
X5 (cmH2O/L/s)	−1.78±0.20	−1.91±0.34	−1.67±0.28
Fres (Hz)	14.81±0.65	15.19±1.21	15.83±1.20
ALX (cmH2O/L/s Hz)	15.04±2.24	14.94±3.19	13.60±2.86
Inspiratory phase
R5 (cmH2O/L/s)	3.06±0.13	3.33±0.21	3.76±0.28*
R20 (cmH2O/L/s)	2.54±0.10	2.87±0.15	3.10±0.24**
R5–R20 (cmH2O/L/s)	0.52±0.06	0.46±0.10	0.55±0.17
X5 (cmH2O/L/s)	−0.84±0.06	−1.11±0.15	−1.11±0.14
Fres (Hz)	11.61±0.43	12.13±0.76	12.52±0.87
ALX (cmH2O/L/s Hz)	5.13±0.51	6.53±1.14	7.08±1.26
Differences between inspiratory and expiratory phases
R5 (cmH2O/L/s)	−0.69±0.11	−0.65±0.11	−1.05±0.20*
R20 (cmH2O/L/s)	−0.26±0.07	−0.31±0.07	−0.59±0.13*
R5–R20 (cmH2O/L/s)	−0.43±0.06	−0.34±0.07	−0.47±0.10
X5 (cmH2O/L/s)	0.95±0.17	0.80±0.24	0.55±0.21
Fres (Hz)	−3.19±0.41	−3.06±0.65	−3.32±0.64
ALX (cmH2O/L/s Hz)	−9.78±2.01	−8.42±2.38	−6.51±2.08

Notes: Values are mean ± standard error of the mean.

** P<0.01.

* P<0.05 vs COPD.

Abbreviations: ACOS, asthma and COPD overlap syndrome; asthma FL⁺, asthma with airflow limitation; R5 and R20, respiratory resistances at 5 Hz and 20 Hz frequencies; X5, respiratory reactance at 5 Hz frequencies; Fres, resonant frequency; ALX, low-frequency reactance area.