Effects of Blood Flow and/or Ventilation Restriction on Radiofrequency Coagulation Size in the Lung: An Experimental Study in Swine

The purpose of this study was to investigate how the restriction of blood flow and/or ventilation affects the radiofrequency (RF) ablation coagulation size in lung parenchyma. Thirty-one RF ablations were done in 16 normal lungs of 8 living swine with 2-cm LeVeen needles. Eight RF ablations were performed as a control (group G1), eight with balloon occlusion of the ipsilateral mainstem bronchus (G2), eight with occlusion of the ipsilateral pulmonary artery (G3), and seven with occlusion of both the ipsilateral bronchus and pulmonary artery (G4). Coagulation diameters and volumes of each ablation zone were compared on computed tomography (CT) and gross specimen examinations. Twenty-six coagulation zones were suitable for evaluation: eight in G1, five in G2, seven in G3, and six in G4 groups. In G1, the mean coagulation diameter was 21.5 ± 3.5 mm on CT and 19.5 ± 1.78 mm on gross specimen examination. In G2, the mean diameters were 26.5 ± 5.1 mm and 23.0 ± 2.7 mm on CT and gross specimen examination, respectively. In G3, the mean diameters were 29.4 ± 2.2 mm and 27.4 ± 2.9 mm on CT and gross specimen examination, respectively, and in G4, they were 32.6 ± 3.33 mm and 28.8 ± 2.6 mm, respectively. The mean coagulation volumes were 3.39 ± l.52 cm³ on CT and 3.01 ± 0.94 cm³ on gross examinations in G1, 6.56 ± 2.47 cm³ and 5.22 ± 0.85 cm³ in G2, 10.93 ± 2.17 cm³ and 9.97 ± 2.91 cm³ in G3, and 13.81 ± 3.03 cm³ and 11.06 ± 3.27 cm³ in G4, respectively. The mean coagulation diameters on gross examination and mean coagulation volumes on CT and gross examination with G3 and G4 were significantly larger than those in G1 (p < 0.0001, p < 0.0001, p < 0.0001, respectively) or in G2 (p < 0.05, p < 0.005, p < 0.005, respectively). Pulmonary collapse occurred in one lung in G2 and pulmonary artery thrombus in two lungs of G3 and two lungs of G4. The coagulation size of RF ablation of the lung parenchyma is increased by ventilation and particularly by pulmonary artery blood flow restriction. The value of these restrictions for potential clinical use needs to be explored in experimentally induced lung tumors.