A new functional method to choose the target lobe for lung volume reduction in emphysema – comparison with the conventional densitometric method

Figures & data

Table 1 Baseline characteristics of the patients

Characteristics	N=36 (100%)
Age – years
Mean ± SD	63.3±6.4
Gender – n (%)
Male	21 (58.3)
Female	15 (41.7)
Smoking state – n (%)
Nonsmoker	1 (2.8)
Current smoker	9 (25.0)
Ex-smoker	24 (66.7)
Unknown	2 (5.5)
Height – cm
Mean ± SD	167.9±9.4
Weight – kg
Mean ± SD	61.5±12.8

Note: Data presented as mean ± SD or n (%).

Table 2 Lung volumes and densitometry of the patients

Spirometric/bodyplethysmographic determined lung function/volumes	N=36 (100%)
FEV1 − liter
Absolute volume ± SD	0.75±0.22
Percentage of predicted value ± SD	27.1±7.7
FVC − liter
Absolute volume ± SD	2.29±0.85
Percentage of predicted value ± SD	62.5±19.7
RV − liter
Absolute volume ± SD	5.88±1.46
Percentage of predicted value ± SD	264.7±71.7
TLC – liter
Absolute volume ± SD	8.21±1.68
Percentage of predicted value ± SD	134.9±24.5
VC/TLC − %
Mean ± SD	0.28±0.09
Carbon monoxide diffusion capacity − mL/min/mmHg
Absolute value ± SD	2.79±0.86
Percentage of predicted value ± SD	32.66±8.86
CT-based determined lung volumina (based on all lobes of all patients)
LVC/LTC − %
Mean ± SD	0.19±0.10
CT-based lung densitometry (based on all lobes of all patients)	Inspiration	Expiration
MLD − HU
Mean ± SD	−880±15.5	−853±25.4
LAV − percent <−950 HU
Mean ± SD	25.2±9.4	17.9±9.3
15%P − HU
Mean ± SD	−961±12.4	−951±20.9

Note: Data presented as mean ± SD.

Abbreviations: 15%P, 15th percentile of Hounsfield units; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; HU, Hounsfield unit; LAV, low attenuation value; LTC, lobar total capacity; LVC, lobar vital capacity; MLD, mean lung density; RV, residual volume; TLC, total lung capacity; VC, vital capacity.

Figure 1 Example of a sagittal reconstruction of corresponding planes of the left lung in inspiration (In 1, In 2) and expiration (Ex 1, Ex 2).

Notes: Although densitometric parameters in inspiration indicate a slightly higher degree of destruction in the UL in comparison to the LL (UL vs LL: MLD [HU] −889 vs −881; LAV [% <−950 HU] 18.4 vs 15.3; 15%P [HU] −949 vs −945) there is a higher deflation during expiration in the UL compared to the LL (UL vs LL: LVC/LTC 0.43 vs 0.25). This example illustrates a huge diversity of volume changes between lobes with almost equal inspiratory densitometric parameters. Based on inspiratory densitometric parameters the target for lung volume reduction would have been the upper lobe. In contrast the lower deflation of the LL indicates to treat this lobe.
Abbreviations: 15%P, 15th percentile of Hounsfield units; HU, Hounsfield unit; LAV, low attenuation value; LL, lower lobe; LVC/LTC, lobar vital capacity/lobar total capacity; MLD, mean lung density; UL, upper lobe.

Figure 2 Correlation coefficients (cc) between LVC/LTC and iMLD, iLAV, and i15%P [HU] in different shading, indicating the grade of correlation.

Notes: Every dot represents one lobe. Parameters of all four measured lobes (right UL, right LL, left UL, and left LL) of every patient are given.
Abbreviations: HU, Hounsfield unit; i15%P, inspiratory 15th percentile of Hounsfield units; iLAV, inspiratory low attenuation value; iMLD, inspiratory mean lung density; LL, lower lobe; LVC/LTC, lobar vital capacity/lobar total capacity; UL, upper lobe.

Figure 3 cc between LVC/LTC and eMLD, eLAV, and e15%P [HU] in different shading, indicating the grade of correlation.

Notes: Every dot represents one lobe. Parameters of all four measured lobes (right UL, right LL, left UL, and left LL) of every patient are given.
Abbreviations: cc, correlation coefficient; e15%P, expiratory 15th percentile of Hounsfield units; eLAV, expiratory low attenuation value; eMLD, expiratory mean lung density; HU, Hounsfield unit; LL, lower lobe; LVC/LTC, lobar vital capacity/lobar total capacity; UL, upper lobe.

Figure 4 Pathophysiology of emphysema.

Note: ↓ means decrease and ↑ means increase.
Abbreviations: COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in the first second; TLC, total lung capacity; VC, vital capacity.