The Impact of Homogeneous Versus Heterogeneous Emphysema on Dynamic Hyperinflation in Patients With Severe COPD Assessed for Lung Volume Reduction

Figures & data

Figure 1. (A) Upper slice (at the superior border of the aortic arch) transferred to the post-processing workstation, where quantitative lung density analysis was performed using the Pulmo CT program. (B) Histogram of distribution of lung attenuation values, measured in HU in the upper slice (at the superior border of the aortic arch) for several potential emphysema thresholds.

Table 1. Baseline characteristics of the study population

	Heterogeneous (n = 50)	Homogenous (n = 14)	P
Age	60.9 ± 7.5	62.5 ± 5.9	0.471
Gender (%)			0.936
-Male	62.7	61.5
-Female	37.3	38.5
BMI (kg/m^2)	24 ± 4.5	25.6 ± 3.6	0.243
FEV1%predicted	32.4 ± 11.4	28.1 ± 10.3	0.213
FEV1/FVC	29.1 ± 7	26.5 ± 6.4	0.216
rIC (lit)	2.2 ± 0.7	2.2 ± 0.5	0.932
rIC /TLC	0.18 ± 0.05	0.17 ± 0.05	0.660
rEELV (lit)	6.1 ± 1.4	6 ± 1.5	0.840
rEELV/TLC	0.73 ± 0.07	0.72 ± 0.06	0.660
TLC %predicted	137 ± 16.4	132.4 ± 9.4	0.198
RV %predicted	232.8 ± 44.6	220.7 ± 32	0.365
RV/TLC (%)	61.6 ± 8.5	60.8 ± 5.2	0.757
FRC %predicted	189.9 ± 31.5	168.8 ± 47.4	0.059
TLCOc %predicted	34.1 ± 10	33.3 ± 11.5	0.867
KCOc %predicted	45.8 ± 12	40 ± 12.1	0.300
PaO2 (kPa)	9.6 ± 1.3	9.2 ± 1	0.527
PaCO2 (kPa)	4.8 ± 0.7	5.1 ± 1.5	0.398

BMI: Body Mass Index; FEV₁: Forced Expiratory Volume in 1 second; FVC: Forced Vital Capacity; TLC: Total Lung Capacity; EELV: End-Expiratory Lung Volume; RV: Residual Volume; FRC: Functional Residual Capacity; TLco_c: Carbon monoxide transfer factor corrected for haemoglobin; Kco_c: Carbon monoxide transfer coefficient corrected for haemoglobin; PaO₂: arterial Oxygen Partial Pressure; PaCO₂: arterial Carbon Dioxide Partial Pressure.

Table 1. Baseline characteristics of the study population

	Heterogeneous (n = 50)	Homogenous (n = 14)	P
Age	60.9 ± 7.5	62.5 ± 5.9	0.471
Gender (%)			0.936
-Male	62.7	61.5
-Female	37.3	38.5
BMI (kg/m^2)	24 ± 4.5	25.6 ± 3.6	0.243
FEV1%predicted	32.4 ± 11.4	28.1 ± 10.3	0.213
FEV1/FVC	29.1 ± 7	26.5 ± 6.4	0.216
rIC (lit)	2.2 ± 0.7	2.2 ± 0.5	0.932
rIC /TLC	0.18 ± 0.05	0.17 ± 0.05	0.660
rEELV (lit)	6.1 ± 1.4	6 ± 1.5	0.840
rEELV/TLC	0.73 ± 0.07	0.72 ± 0.06	0.660
TLC %predicted	137 ± 16.4	132.4 ± 9.4	0.198
RV %predicted	232.8 ± 44.6	220.7 ± 32	0.365
RV/TLC (%)	61.6 ± 8.5	60.8 ± 5.2	0.757
FRC %predicted	189.9 ± 31.5	168.8 ± 47.4	0.059
TLCOc %predicted	34.1 ± 10	33.3 ± 11.5	0.867
KCOc %predicted	45.8 ± 12	40 ± 12.1	0.300
PaO2 (kPa)	9.6 ± 1.3	9.2 ± 1	0.527
PaCO2 (kPa)	4.8 ± 0.7	5.1 ± 1.5	0.398

BMI: Body Mass Index; FEV₁: Forced Expiratory Volume in 1 second; FVC: Forced Vital Capacity; TLC: Total Lung Capacity; EELV: End-Expiratory Lung Volume; RV: Residual Volume; FRC: Functional Residual Capacity; TLco_c: Carbon monoxide transfer factor corrected for haemoglobin; Kco_c: Carbon monoxide transfer coefficient corrected for haemoglobin; PaO₂: arterial Oxygen Partial Pressure; PaCO₂: arterial Carbon Dioxide Partial Pressure.

Table 2. Comparison of exercise parameters between patients with heterogeneous and homogeneous emphysema

	Heterogeneous (n = 50)	Homogenous (n = 14)	p
eIC (lit)	1.5 ± 0.5	1.3 ± 0.3	0.240
eIC/TLC	0.18 ± 0.05	0.17 ± 0.05	0.385
ΔIC %	31.2 ± 13	39.8 ± 9.8	0.031
eEELV (lit)	6.8 ± 1.4	6.9 ± 1.5	0.833
eEELV/TLC	0.82 ± 0.05	0.83 ± 0.05	0.385
ΔEELV/TLC	0.079 (0.01–0.21)	0.119 (0.06–0.15)	0.035
eIRV (lit)	0.4 ± 0.3	0.3 ± 0.3	0.352
rBorg	1(0–5)	2(0–2)	0.441
pBorg	7(4–10)	7(5–7)	0.807
ΔBorg	5(1–9)	5(3-7)	0.852
Peak VE (lit/min)	34(15–47)	32(18–84)	0.593
Peak Vt (lit/min)	1.1(0.5–2.1)	1(0.7–1.4)	0.739
Peak VO2 (ml/kg/min)	13.3(7.9–26.2)	12.5(7.8–26)	0.349
Peak VO2%predicted	49(13–99)	44(14–67)	0.246
Peak WR %predicted	26(5–73)	34(12–59)	0.361
Peak VCO2 (ml/min)	780.6(404–2023.4)	934.6(361–1025)	0.944
RER	0.9(0.4–1.3)	0.9(0.4–1.5)	0.662
Peak HR %predicted	75.5(42–106)	75.5(65–86)	0.802
PETO2 (kPa)	14.9(13–18)	14.9(11.4–16)	0.441
PETCO2 (kPa)	4.7(2.3–6.7)	4.6(3.6–8.3)	0.687
Peak VE/VCO2	39.4(26.9–72.2)	41.6(21–48.3)	0.834
Peak VO2/HR %predicted	66.6(14.4–112.3)	59(20.4–82)	0.131
RR (breaths/min)	32.9 ± 8.9	31.2 ± 9.4	0.545
rSPO2 (%)	94.5(88–99)	96(91–98)	0.323
pSPO2 (%)	89(79–98)	89(80–95)	0.869
ΔSPO2 (%)	6(0–12)	6.5(3–11)	0.674

e: end-exercise values; IC: Inspiratory Capacity; EELV: End-Expiratory Lung Volume; TLC: Total Lung Capacity; IRV: Inspiratory Residual Volume; rBorg: rest Borg scale score; pBorg: peak Borg scale score; VE: Minute ventilation; Vt: Tidal Volume; VO₂: Oxygen Consumption; WR: Work Rate; VCO₂: Carbon Dioxide Production; RER: Respiratory Exchange Ratio; HR: Heart Rate; PETO₂: End Expiratory Oxygen partial pressure; PETCO2: End Expiratory Carbon Dioxide partial pressure; VE/VCO₂: Ventilatory Equivalent for Carbon Dioxide; VO₂/HR: Oxygen Pulse; rSPO₂: rest arterial Oxygen Saturation; pSPO₂: peak arterial Oxygen Saturation.

Table 3. Correlations between emphysema distribution and exercise parameters, for both emphysema thresholds

Exercise parameter	950 UM/L	960 UM/L
ΔIC %	-0.264*	-0.246*
rBorg	-0.018	0.016
pBorg	0.096	0.068
ΔBorg	0.078	0.030
Peak VE (lit/min)	0.186	0.040
Peak Vt (lit/min)	0.025	0.053
Peak VO2 (ml/kg/min)	0.050	0.033
Peak VO2%predicted	0.340**	0.341**
Peak WR %predicted	0.087	0.040
Peak VCO2 (ml/min)	0.130	0.128
RER	0.075	0.110
Peak HR %predicted	-0.074	-0.086
Peak PETO2 (kPa)	0.193	0.197
Peak PETCO2 (kPa)	-0.097	-0.109
Peak VE/VCO2	-0.006	0.010
Peak VO2/HR %predicted	0.398**	0.390**
Peak RR (breaths/min)	0.300*	0.266*
rSPO2 (%)	0.046	0.030
pSPO2 (%)	0.079	0.069
ΔSPO2 (%)	-0.099	-0.091

Emphysema distribution is expressed as the UM/L ratio of emphysema score for both the 950 and 960 emphysema thresholds; a high ratio represents upper lobe predominance. IC: Inspiratory Capacity; rBorg: rest Borg scale score; pBorg: peak Borg scale score; VE: Minute ventilation; Vt: Tidal Volume; VO₂: Oxygen Consumption; WR: Work Rate; VCO₂: Carbon Dioxide Production; RER: Respiratory Exchange Ratio; HR: Heart Rate; PETO2: End Expiratory Oxygen partial pressure; PETCO₂: End Expiratory Carbon Dioxide partial pressure; VE/VCO₂: Ventilatory Equivalent for Carbon Dioxide; VO₂/HR: Oxygen Pulse; rSPO₂: rest arterial oxygen saturation; pSPO₂: arterial oxygen saturation at peak exercise.

* Significant correlation at 0.05 level.

**Significant correlation at 0.01 level.