Longitudinal changes in lung hyperinflation in COPD

Figures & data

Table 1 Baseline patient characteristics

Characteristics	Value
Age, years	65±7
Male sex, n (%)	166 (94.3)
BMI, kg/m^2	23.5±3.3
Smoking status
Current smoker, n (%)	54 (30.7)
Smoking history, pack-year	42.0 (25.0, 54.0)
Exacerbations during the year prior to enrollment
Experience of exacerbation, n (%)	30 (17.1)
Frequency of exacerbation	2 (1, 5)
mMRC dyspnea scale	2 (1, 2)
SGRQ score	28.76 (20.43, 41.71)
6MWD, m	456.8±74.2
Post-bronchodilator FEV1
Value, L	1.70±0.53
Percentage of predicted value	64.0±17.6
Post-bronchodilator FVC
Value, L	3.45±0.78
Percentage of predicted value	92.5±17.7
Post-bronchodilator FEV1/FVC, %	49.3±10.2
GOLD stage
I, n (%)	34 (19.3)
II, n (%)	106 (60.2)
III, n (%)	33 (18.8)
IV, n (%)	3 (1.7)
DLCO
Value, mL/mmHg/min	16.15±6.00
Percentage of predicted value	84.9±25.7

Notes: Data are shown as mean ± SD for normally distributed data, medians (with IQRs) for non-normally distributed data, and number (%) for categorical variables. Abbreviations: BMI, body mass index; mMRC, modified Medical Research Council; SGRQ, St George’s Respiratory Questionnaire; 6MWD, 6-minute walk distance; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; DLCO, diffusing capacity for carbon monoxide; SD, standard deviation; IQR, interquartile range.

Table 2 Results of baseline lung volume measurement

Parameters	Value
RV
Value, L	2.80±0.96
Percentage of predicted value	131.8±44.3
FRC
Value, L	4.10±0.98
Percentage of predicted value	128.1±27.2
TLC
Value, L	6.21±1.09
Percentage of predicted value	112.7±16.9
IC
Value, L	2.10±0.53
Percentage of predicted value	83.4±18.8
VC
Value, L	3.40±0.75
Percentage of predicted value	92.9±16.8
IC/TLC ratio, %	34.2±7.7
RV/TLC ratio, %	44.7±11.2
VC/TLC ratio, %	55.3±11.2

Notes: Data are shown as mean ± SD.

Abbreviations: RV, residual volume; FRC, functional residual capacity; TLC, total lung capacity; IC, inspiratory capacity; VC, vital capacity; SD, standard deviation.

Figure 1 Correlation between the RV/TLC ratio and the percentage of predicted value of post-bronchodilator FEV₁ at baseline measurement.

Abbreviations: RV, residual volume; TLC, total lung capacity; FEV₁, forced expiratory volume in 1 second.

Figure 2 Distribution of estimated annual rate of change in the RV/TLC ratio.

Abbreviations: RV, residual volume; TLC, total lung capacity.

Figure 3 Distribution of estimated annual rate of change in the IC/TLC ratio.

Abbreviations: IC, inspiratory capacity; TLC, total lung capacity.

Table 3 Effect of exacerbation and treatment on the change in RV/TLC ratio and IC/TLC ratio

Characteristics	Adjusted annual rate of change in RV/TLC	P-value	Adjusted annual rate of change in IC/TLC	P-value
Exacerbations during the year prior to enrollment		0.083		0.261
No (n=146)	−0.48±0.18		−0.75±0.11
Yes (n=30)	0.31±0.42		−0.44±0.25
Exacerbations during follow-up		0.007		0.014
Infrequent (<2/year; n=149)	−0.54±0.18		−0.59±0.11
Frequent (≥2/year; n=27)	0.67±0.41		−1.21±0.23
Use of long-acting beta agonist		0.666		0.582
No (n=39)	−0.48±0.36		−0.59±0.22
Yes (n=137)	−0.31±0.19		−0.73±0.11
Use of long-acting muscarinic antagonist		0.440		0.002
No (n=51)	−0.14±0.32		−0.21±0.19
Yes (n=125)	−0.43±0.20		−0.89±0.12
Use of inhaled corticosteroid		0.694		0.545
No (n=39)	−0.48±0.36		−0.58±0.22
Yes (n=137)	−0.31±0.19		−0.73±0.11

Notes: Data are shown as mean ± standard error. Mixed-effect linear regression analysis was performed, which included the following covariates: age, sex, current smoking status, smoking pack-year, exacerbations before and after enrollment, BMI, GOLD stage, diffusing capacity, treatments, and interaction of each covariate with time.

Abbreviations: RV, residual volume; TLC, total lung capacity; IC, inspiratory capacity; BMI, body mass index; GOLD, Global Initiative for Chronic Obstructive Lung Disease.

Figure 4 The negative correlation between the rates of change in FEV₁ and RV/TLC ratio.

Abbreviations: FEV₁, forced expiratory volume in 1 second; RV, residual volume; TLC, total lung capacity.