Lung Hyperinflation and Its Reversibility in Patients with Airway Obstruction of Varying Severity

Figures & data

Table 1.  Subject characteristics

	Healthy Controls (n = 128)	GOLD I (n = 620)	GOLD II (n = 1,129)	GOLD III/IV (n = 516)
Sex, %male	50.0	59.4	58.4	68.0
Age, years	63 ± 10	65 ± 10	65 ± 9	65 ± 9
Height, cm	168 ± 9	166 ± 9	166 ± 9	167 ± 9
Body mass index, kg/m^2	26.4 ±3.8	27.9 ± 5.3 ^a	28.0 ± 6.1 ^a	26.4 ± 6.2 ^b
Post-bronchodilator FEV1, L	—	2.33 ± 0.61 ^a	1.63 ± 0.43 ^b	1.00 ± 0.28 ^c
Post-bronchodilator FEV1, %predicted	—	93 ± 10 ^a	65 ± 8 ^b	39 ± 8 ^c
Post-bronchodilator FEV1/FVC, %	—	64 ± 5 ^a	58 ± 8 ^b	45 ± 10 ^c
Pre-bronchodilator pulmonary function:
FEV1, %predicted	114 ± 16	91 ± 9 ^a	60 ± 10 ^b	35 ± 8 ^c
FEV1/FVC, %	75 ± 5	64 ± 6 ^a	58 ± 8 ^b	46 ± 10 ^c
FEF25–75, %predicted	91 ± 32	44 ± 14 ^a	28 ± 10 ^b	15 ± 6 ^c
FEF50, %predicted	84 ± 36	39 ± 13 ^a	23 ± 10 ^b	11 ± 5 ^c
TLC, %predicted	103 ± 11	111 ± 13 ^a	107 ± 17 ^b	116 ± 22 ^c
SVC, %predicted	112 ± 14	100 ± 12 ^a	78 ± 13 ^b	62 ± 13 ^c
IC, %predicted	105 ± 18	99 ± 18 ^a	77 ± 17 ^b	57 ± 16 ^c
IC/TLC, %	47 ± 8	41 ± 8 ^a	33 ± 8 ^b	24 ± 7 ^c
FRC, %predicted	102 ± 19	119 ± 24 ^a	132 ± 30 ^b	166 ± 40 ^c
RV, %predicted	95 ± 19	135 ± 32 ^a	162 ± 43 ^b	218 ± 62 ^c
RV/TLC, %	34 ± 7	45 ± 8 ^a	55 ± 9 ^b	67 ± 8 ^c
ERV, %predicted	123 ± 55	89 ± 47 ^a	70 ± 38 ^b	61 ± 34 ^c
sRaw, %predicted	148 ± 55	250 ± 122 ^a	383 ± 183 ^b	643 ± 321 ^c
SVC-FVC difference, L	0.16 ± 0.21	0.14 ± 0.18 ^a	0.18 ± 0.20 ^b	0.25 ± 0.24 ^c
DLCO, %predicted	106 ± 21	89 ± 23 ^a	77 ± 21 ^b	60 ± 19 ^c
DLCO/VA, %predicted	113 ± 17	94 ± 25 ^a	96 ± 27 ^a	86 ± 32 ^b
VA, % predicted TLC	89 ± 11	90 ± 12 ^a	76 ± 13 ^b	64 ± 14 ^c
TLC-VA difference, L	0.84 ± 0.51	1.15 ± 0.61 ^a	1.79 ± 0.86 ^b	3.10 ± 1.23 ^c

Values are means ± SD unless otherwise specified.

*p < 0.05 difference across GOLD groups by chi-square analysis.

^a,b,c,d GOLD group means with different letters are significantly different from each other after Bonferroni adjustment for multiple comparisons (p < 0.05).

Abbreviations: D_LCO, diffusing capacity of the lung for carbon monoxide; ERV, expiratory reserve volume; FEF_25–75, forced mid-expiratory flow; FEF50, forced expiratory flow at 50% of forced vital capacity; FEV₁, forced expiratory volume in 1 s; FRC, functional residual capacity; FVC, forced vital capacity; IC, inspiratory capacity; RV, residual volume; sRaw, specific airway resistance; SVC, slow vital capacity; TLC, total lung capacity; VA, alveolar volume.

Figure 1.  Pre- and post-bronchodilator static lung volumes are shown for each GOLD stage group compared with an age-matched healthy control group. Residual volume (RV) and functional residual capacity (FRC) increased progressively as GOLD stage worsened. Total lung capacity increased in GOLD stage I in conjunction with a preserved inspiratory capacity (IC), vital capacity (VC) and expiratory reserve volume (ERV). IC and VC then decreased progressively in GOLD stages II and III/IV.

Figure 2.  Relationships between forced vital capacity (FVC), residual volume (RV), diffusing capacity of the lung (D_LCO) and specific airway resistance (sRaw) are shown against FEV₁ (all measurements expressed as% of predicted normal values). FVC changed linearly with FEV₁, RV and sRaw both increased exponentially as FEV₁ decreased, and D_LCO decreased as FEV₁ decreased.

Table 2.  Bronchodilator reversibility: pre- to post-bronchodilator changes

	GOLD I (n = 620)	GOLD II (n = 1,129)	GOLD III/IV (n = 516)	ANOVA p-value
ΔFEV1, L	0.15 ± 0.18	0.14 ± 0.16	0.10 ± 0.12
%	7 ± 9	11 ± 12	13 ± 14	<0.0005
%predicted	5.8 ± 6.8 ^a	5.5 ± 6.0 ^a	3.9 ± 4.1 ^b
ΔFEV1/FVC,%	0.4 ± 3.7	0.0 ± 4.0	-1.4 ± 4.4
%predicted	1 ± 5 ^a	0 ± 6 ^a	-2 ± 6 ^b	<0.0005
ΔFEF50, L/s	0.13 ± 0.32	0.07 ± 0.22	0.03 ± 0.11
%predicted	3 ± 8 ^a	2 ± 6 ^b	1 ± 3 ^c	<0.0005
ΔTLC, L	-0.06 ± 0.25	-0.12 ± 0.30	-0.15 ± 0.36
%predicted	-1 ± 4 ^a	-2 ± 5 ^b	-2 ± 5 ^b	<0.0005
ΔSVC, L	0.15 ± 0.21	0.20 ± 0.25	0.27 ± 0.27
%predicted	4 ± 6 ^a	6 ± 7 ^b	7 ± 7 ^c	<0.0005
ΔIC, L	0.13 ± 0.26	0.16 ± 0.26	0.20 ± 0.26
%predicted	5 ± 10 ^a	6 ± 9 ^a,b	7 ± 9 ^b	0.002
ΔFRC, L	-0.18 ± 0.29	-0.28 ± 0.34	-0.33 ± 0.43
%predicted	-6 ± 9 ^a	-9 ± 11 ^b	-10 ± 13 ^c	<0.0005
ΔRV, L	-0.21 ± 0.33	-0.32 ± 0.38	-0.42 ± 0.47
%predicted	-6 ± 10 ^a	-15 ± 18 ^b	-19 ± 22 ^c	<0.0005
ΔsRaw, mmHg/L/s * L	-3.0 ± 3.6	-4.4 ± 4.8	-5.7 ± 7.0
%predicted	-71 ± 85 ^a	-105 ± 115 ^b	-137 ± 185 ^c	<0.0005

Values are means ± SD.

Δ = post- minus pre-bronchodilator change.

^a,b,c,d means with different letters are significantly different from each other after Bonferroni adjustment for multiple comparisons (p < 0.05).

Figure 3.  Bronchodilator-induced changes in lung volumes are shown as (A) measured changes expressed as % of predicted normal and (B) frequencies of a positive response defined as at least a 10 % of predicted improvement in that measurement. As GOLD stage worsened, the FEV₁ response became less important while other lung volume responses increased progressively.

Figure 4.  The frequency of a significant bronchodilator response (change of at least 10% predicted) is shown when only spirometric measurements are taken into account (FEV₁ alone, FVC alone or combination of FEV₁ and FVC) (top). By considering plethysmographic lung volume (RV and SVC) improvements in addition to spirometric FEV₁, greater rates of reversibility were uncovered (bottom). When volumes were taken into account, the frequency of a positive bronchodilator response increased with worsening GOLD stage.