AUTHOR=Valipour Arschang , Kramer Mordechai , Stanzel Franz , Kempa Axel , Asadi Sherwin , Fruchter Oren , Eberhardt Ralf , Herth Felix , Ingenito Edward 

TITLE=Physiological Modeling of Responses to Upper Versus Lower Lobe Lung Volume Reduction in Homogeneous Emphysema

JOURNAL=Frontiers in Physiology

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2012.00387

DOI=10.3389/fphys.2012.00387

ISSN=1664-042X

ABSTRACT=<p><bold>Rationale:</bold> In clinical trials, homogeneous emphysema patients have responded well to upper lobe volume reduction but not lower lobe volume reduction. <bold>Materials/Methods:</bold> To understand the physiological basis for this observation, a computer model was developed to simulate the effects of upper and lower lobe lung volume reduction on RV/TLC and lung recoil in homogeneous emphysema. <bold>Results:</bold> Patients with homogeneous emphysema received either upper or lower lobe volume reduction therapy based on findings of radionucleotide scintigraphy scanning. CT analysis of lobar volumes showed that patients undergoing upper (<italic>n</italic> = 18; −265 mL/site) and lower lobe treatment (LLT; <italic>n</italic> = 11; −217 mL/site) experienced similar reductions in lung volume. However, only upper lobe treatment (ULT) improved FEV<sub>1</sub> (+11.1 ± 14.7 versus −4.4 ± 15.8%) and RV/TLC (−5.4 ± 8.1 versus −2.4 ± 8.6%). Model simulations provided an unexpected explanation for this response. Increases in transpulmonary pressure subsequent to volume reduction increased RV/TLC in upper lobe alveoli, while caudal shifts in airway closure decreased RV/TLC in lower lobe alveoli. ULT, which eliminates apical alveoli with high RV/TLC values, lowers the average RV/TLC of the lung. Conversely, LLT, which eliminates caudal alveoli with low RV/TLC values, has less effect. <bold>Conclusion:</bold> LLT in homogeneous emphysema is uniformly less effective than ULT.</p>