Respiratory impedance following bronchoscopic or surgical lung volume reduction for emphysema

BACKGROUND: Bronchoscopic methods for achieving lung volume reduction (BLVR) are presently undergoing clinical trials, and will soon be clinically available. Understanding the differential effects of surgical volume reduction therapy (LVRS) and BLVR on lung and chest wall physiology will assist physicians in selecting an optimal approach for patients. OBJECTIVES: Determine whether LVRS adversely affects lung or chest wall physiology at 3-month follow-up relative to BLVR in an experimental model of sheep emphysema. METHODS: Twelve mixed-breed sheep were treated with papain to produce experimental emphysema, and were divided into control, LVRS, and BLVR treatment groups. Lung and chest wall impedance was measured at 0, 5, and 10 cm H2O positive end-expiratory pressure at baseline and 3-month follow-up. RESULTS: Emphysema was associated with increased airway resistance, decreased lung tissue resistance and elastance, and increased chest wall tissue resistance. Following treatment, equivalent increases in lung elastance occurred in the LVRS and BLVR groups compared to controls. LVRS did not adversely affect chest wall impedance despite causing extensive pleural scarring. CONCLUSIONS: (1) Experimental emphysema following prolonged papain exposure progresses after cessation of treatment. (2) BLVR and LVRS produced equivalent lung and chest wall impedance responses at 3-month follow-up. (3) LVRS did not adversely affect chest wall impedance despite being associated with extensive pleural scarring.