Role of inspiratory capacity on dyspnea evaluation in COPD with or without emphysematous lesions: a pilot study

Figures & data

Table 1 Subjects’ clinical characteristics at baseline and second visits

Characteristics	Baseline visit	Second visit	P-value
Case	124
Age, years	62.08±8.36		NA
Sex, male/female	96/28		NA
Smoking history, pack-years	25.03±24.21		NA
BMI, kg/m^2	24.64±3.33		NA
GOLD
I	11
II	47
III	47
IV	19
CT-EI
LAA% −950, %	12.79±11.49		NA
mMRC scores	1.98±0.86	0.78±0.75	<0.001a
Pulmonary function
IC, L	2.08±0.63	2.41±0.65	<0.001a
VC, L	2.88±0.79	3.27±0.80	<0.001a
FVC, L	2.70±0.76	3.04±0.78	<0.001a
FEV1, L	1.33±0.57	1.62±0.64	<0.001a
FEV1%pred, %	50.09±18.83
FEV1/FVC, %	48.56±10.84	52.89±12.87	<0.001a
FEV1/VC, %	45.57±10.61	49.21±12.96	<0.001a
TLC, L	5.24±1.02	5.53±0.95	0.002a
RV/TLC, %	44.31±9.35	40.38±8.15	0.004a
DLCO, mL/mmHg/min	7.60±4.75	8.11±4.84	0.002a
Changes in IC and FEV1
ΔIC, L		0.33±0.40	NA
ΔFEV1, L		0.29±0.35	NA

Notes: Data are presented as mean ± SD.

a Analysis with paired t-test.

Abbreviations: NA, not applicable; BMI, body mass index; GOLD, Global Initiative for Chronic Obstructive Lung Disease; CT, computerized tomography; EI, emphysema index; LAA% −950, percentage of low attenuation areas less than −950 Hu; mMRC, modified Medical Research Council; IC, inspiratory capacity; VC, vital capacity; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; TLC, total lung capacity; RV, residual volume; DLCO, diffusing capacity of the lungs for carbon monoxide; ΔIC, increases in inspiratory capacity; ΔFEV₁, increases in forced expiratory volume in 1 second; SD, standard deviation; CT, computed tomography; Hu, Hounsfield units.

Table 2 Correlation analysis of ΔmMRC scores and changes in pulmonary function parameters

Parameters	ccsa of ΔmMRC score	P-value
ΔIC	−0.490	<0.001
ΔVC	−0.417	<0.001
ΔFVC	−0.393	<0.001
ΔFEV1	−0.305	0.001
ΔRV/TLC	0.420	0.004
ΔTLC	−0.317	0.034
ΔDLCO	−0.185	0.235

Note:

a Analysis with Pearson’s correlation test.

Abbreviations: ΔmMRC scores, decline in the modified Medical Research Council scores; ccs, correlation coefficients; ΔIC, increases in inspiratory capacity; ΔVC, increases in vital capacity; ΔFVC, increases in forced vital capacity; ΔFEV₁, increases in forced expiratory volume in 1 second; ΔRV/TLC, increases in the ratio of RV to TLC; ΔTLC, increases in total lung capacity; ΔDLCO, increases in diffusing capacity of the lungs for carbon monoxide; RV, residual volume; TLC, total lung capacity.

Table 3 Comparison of characteristics between subjects of the obvious-remission group and the non-remission group

Characteristics	Obvious-remission group	Non-remission group	P-value
Case	39	85
Absolute value of ΔmMRC	2.15±0.37	0.75±0.46	<0.001a
LAA% −950, %	13.32±8.47	12.59±12.49	0.817a
ΔIC, L	0.54±0.37	0.23±0.38	<0.001a
ΔFEV1, L	0.42±0.39	0.23±0.32	0.01a
Emphysema predominant, %	63.16	47.06	0.176b
Significant change in IC (ΔIC ≥300 mL), %	74.36	35.29	≤0.001b
Significant change in FEV1 (ΔFEV1 ≥300 mL), %	51.28	32.94	0.041b

Notes: Data are presented as mean ± SD.

a Analysis with paired t-test.

b Analysis with chi-squared test.

Abbreviations: ΔmMRC scores, decline in the modified Medical Research Council scores; LAA% −950, percentage of low attenuation areas less than −950 Hu; ΔIC, increases in inspiratory capacity; ΔFEV₁, increases in forced expiratory volume in 1 second; IC, inspiratory capacity; FEV₁, forced expiratory volume in 1 second; SD, standard deviation; CT, computed tomography; Hu, Hounsfield units.

Table 4 Comparison of characteristics between the emphysema-predominant group and the non-emphysema-predominant group

Characteristics	Emphysema-predominant group	Non-emphysema-predominant group	P-value
Case	36	34
Sex, male/female	33/3	24/10	0.023a
Age, years	64.33±6.88	61.03±9.57	0.100b
Smoking history, pack-years	29.32±26.13	19.79±19.08	0.088b
BMI, kg/m^2	23.69±3.06	25.37±2.86	0.020b
LAA% −950, %	21.10±10.28	3.99±2.94	<0.001b
mMRC score	2.39±0.77	1.68±0.73	<0.001b
IC, L	2.01±0.68	2.18±0.62	0.283b
FEV1, L	1.27±0.53	1.48±0.63	0.131b
FEV1%pred, %	46.92±19.71	56.33±17.11	0.037
FEV1/FVC, %	45.78±10.60	53.37±10.69	0.004b
FVC, L	2.71±0.65	2.75±0.91	0.807b
DLCO, mL/mmHg/min	6.90±4.10	8.40±5.41	0.324b

Notes: Data are presented as mean ± SD.

a Analysis with chi-squared test.

b Analysis with independent-sample t-test.

Abbreviations: BMI, body mass index; LAA% −950, percentage of low attenuation areas less than −950 Hu; mMRC, modified Medical Research Council; IC, inspiratory capacity; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; DLCO, diffusing capacity of the lungs for carbon monoxide; SD, standard deviation; CT, computed tomography; Hu, Hounsfield units.

Table 5 Correlation analysis of ΔIC and ΔFEV₁ with ΔmMRC in the emphysema-predominant group and the non-emphysema-predominant group

Parameters	Emphysema-predominant group		Non-emphysema-predominant group
	cca	P-value	cca	P-value
ΔIC and ΔmMRC	−0.459	0.005	−0.465	0.006
ΔFEV1 and ΔmMRC	−0.061	0.723	−0.335	0.053

Note:

a Analysis with Pearson’s correlation test.

Abbreviations: ΔIC, increases in inspiratory capacity; ΔFEV₁, increases in forced expiratory volume in 1 second; ΔmMRC, decline in the modified Medical Research Council scores; cc, correlation coefficient.

Table 6 Regression analysis for dyspnea remission in terms of ΔIC and ΔFEV₁

Variable	ORa	95% CI	P-value
Emphysema-predominant group (remission, absolute ΔmMRC ≥ 1)
ΔIC ≥300 mL	2.29	1.54–3.39	0.034
ΔFEV1 ≥300 mL	1.39	1.12–1.73	0.221
Non-emphysema-predominant group (obvious remission, absolute ΔmMRC >1)
ΔIC ≥300 mL	10.20	1.07–97.41	0.044
ΔFEV1 ≥300 mL	3.64	0.60–22.23	0.162
ΔFEV1 ≥400 mL	7.143	1.12–45.52	0.037

Note:

a Analysis of bivariate logistic regression.

Abbreviations: ΔIC, increases in inspiratory capacity; ΔFEV₁, increases in forced expiratory volume in 1 second; OR, odds ratio; CI, confidence interval; ΔmMRC, decline in the modified Medical Research Council scores.