TY - JOUR T1 - Physiological consequence of lower vs upper lobe lung volume reduction in patients with advanced emphysema JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p3528 AU - Edward Ingenito AU - Larry Tsai Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p3528.abstract N2 - Objective(s): Lower lobe lung volume reduction in patients with advanced emphysema is associated with less benefit that upper lobe therapy. We present computer modeling results that explain these observations, and can help direct treatment site selection in patients undergoing lung volume reduction therapy.Methods: The model considers alveoli as discrete units with an exponential pressure-volume relationship of the form (V(Ptp) = Vmax – Ae-kPtp). Gravitational effects on transpulmonary pressure (Ptp), the extent of tissue destruction, airway closure effects, and extent of heterogeneity were incorporated as independent variables for predicting RV and RV/TLC.Results: Gravitational effects on Ptp are the major determinant of regional RV and overall RV/TLC. In upper lobe heterogeneous emphysema, changes in Ptp from volume reduction distend the remaining alveoli at end exhalation. However, RV and RV/TLC are reduced due to a decrease in the total number of diseased alveoli following treatment. In lower lobe heterogeneous emphysema, volume reduction distends already stretched upper lobe alveoli attenuating treatment effects on gas trapping. This phenomenon was more pronounced in homogeneous disease. Potential benefits of lower lobe volume reduction could be completely negated by upper lobe alveolar distention, resulting in no improvement, or even worsening of RV and RV/TLC despite alveolar resection.Conclusions: Gravitational effects largely explain why lower lobe volume reduction therapy is less therapeutic than upper lobe therapy. In patients with homogeneous emphysema, lower lobe therapy can actual worsen gas trapping despite resection of diseased tissue. ER -