Time course and pattern of pulmonary flow distribution following unilateral airway occlusion in sheep

Safety and local efficacy of computed tomography-guided microwave ablation for treating early-stage non-small cell lung cancer adjacent to bronchovascular bundles

OBJECTIVES

To retrospectively evaluate the safety and efficacy of computed tomography (CT)-guided percutaneous microwave ablation in treating early-stage non-small cell lung cancer (NSCLC) adjacent to bronchovascular bundles.

METHODS

Two hundred and thirty-one patients with early-stage NSCLC who underwent CT-guided microwave ablation of the tumor were included for analysis. Among these, 66 lesions were located adjacent to the bronchovascular bundle. Achievement of the specific ablation range (defined as the ablation zone encompassing the tumor and the adjacent vessel) was assessed after ablation. Complications and tumor progression after treatment were examined and compared between the bronchovascular bundle and non-bronchovascular bundle groups.

RESULTS

A total of 231 patients were included. Overall, 1-, 2-, and 3-year local progression-free survival (LPFS) was 77.4%, 70.5%, and 63.8%, respectively. Bronchovascular bundle proximity, pure-solid tumor, tumor size, and ablation margin < 5 mm were independent risk factors for local progression in multivariate analysis. In the bronchovascular bundle group, the 1-, 2- and 3-year LPFS rates were 63.0%, 50.7%, and 43.4%, respectively; vessel proximity and specific ablation range failure were independent risk factors for local progression. Overall survival in the entire cohort was 93.0% at 1 year, 76.1% at 2 years, and 55.0% at 3 years. The incidence of postoperative complications did not significantly differ between the two groups (p > 0.05). The most common complication was pneumothorax. Severe hemoptysis did not occur.

CONCLUSION

Tumor location near the bronchovascular bundles was a significant risk factor for local progression after microwave ablation. Achieving a specific ablation range may increase LPFS for these lesions.

CLINICAL RELEVANCE STATEMENT

Achieving the specific ablation range may improve local efficacy for early-stage non-small cell lung cancer located adjacent to the bronchovascular bundle.

KEY POINTS

• Local efficacy of percutaneous microwave ablation in treating early-stage non-small cell lung cancer was affected by bronchovascular bundle proximity. • Achieving the specific ablation range may improve local efficacy for lesions located adjacent to the bronchovascular bundle.

Hypoxic pulmonary vasoconstriction

Hypoxic pulmonary vasoconstriction (HPV) continues to fascinate cardiopulmonary physiologists and clinicians since its definitive description in 1946. Hypoxic vasoconstriction exists in all vertebrate gas exchanging organs. This fundamental response of the pulmonary vasculature in air breathing animals has relevance to successful fetal transition to air breathing at birth and as a mechanism of ventilation-perfusion matching in health and disease. It is a complex process intrinsic to the vascular smooth muscle, but with in vivo modulation by a host of factors including the vascular endothelium, erythrocytes, pulmonary innervation, circulating hormones and acid-base status to name only a few. This review will provide a broad overview of HPV and its mechansms and discuss the advantages and disadvantages of HPV in normal physiology, disease and high altitude.

Pulmonary pathophysiology and lung mechanics in anesthesiology: a case-based overview

Anesthesia, surgical requirements, and patients' unique pathophysiology all combine to make the accumulated knowledge of respiratory physiology and lung mechanics vital in patient management. This article take a case-based approach to discuss how the complex interactions between anesthesia, surgery, and patient disease affect patient care with respect to pulmonary pathophysiology and clinical decision making. Two disparate scenarios are examined: a patient with chronic obstructive pulmonary disease undergoing a lung resection, and a patient with coronary artery disease undergoing cardiopulmonary bypass. The impacts of important concepts in pulmonary physiology and respiratory mechanics on clinical management decisions are discussed.

Thermal ablation of lung tumors

The 5-year survival for all stages of nonsmall cell lung cancer (NSCLC) remains bleak, having increased from 13% to just 16% over the past 30 years. Despite promising results in nonoperative patients with NSCLC and pulmonary metastatic disease, thermal ablation appears to be limited by large tumor size and proximity to large vessels. This article discusses the particular challenges of performing thermal ablation in aerated lung tissue and reviews important considerations in performing ablation including treatment complications and imaging follow-up. The article compares and contrasts the three major thermal ablation modalities: radiofrequency ablation, microwave ablation, and cryoablation.

Percutaneous radiofrequency lung ablation combined with transbronchial saline injection: an experimental study in swine

To evaluate the efficacy of radiofrequency lung ablation with transbronchial saline injection. The bilateral lungs of eight living swine were used. A 13-gauge bone biopsy needle was inserted percutaneously into the lung, and 1 ml of muscle paste was injected to create a tumor mimic. In total, 21 nodules were ablated. In the saline injection group (group A), radiofrequency ablation (RFA) was performed for 11 nodules after transbronchial saline injection under balloon occlusion with a 2-cm active single internally cooled electrode. In the control group (group B), conventional RFA was performed for 10 nodules as a control. The infused saline liquid showed a wedge-shaped and homogeneous distribution surrounding a tumor mimic. All 21 RFAs were successfully completed. The total ablation time was significantly longer (13.4 +/- 2.8 min vs. 8.9 +/- 3.5 min; P = 0.0061) and the tissue impedance was significantly lower in group A compared with group B (73.1 +/- 8.8 Omega vs. 100.6 +/- 16.6 Omega; P = 0.0002). The temperature of the ablated area was not significantly different (69.4 +/- 9.1 degrees C vs. 66.0 +/- 7.9 degrees C; P = 0.4038). There was no significant difference of tumor mimic volume (769 +/- 343 mm(3) vs. 625 +/- 191 mm(3); P = 0.2783). The volume of the coagulated area was significantly larger in group A than in group B (3886 +/- 1247 mm(3) vs. 2375 +/- 1395 mm(3); P = 0.0221). Percutaneous radiofrequency lung ablation combined with transbronchial saline injection can create an extended area of ablation.

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 cm(3) on CT and 3.01 +/- 0.94 cm(3) on gross examinations in G1, 6.56 +/- 2.47 cm(3) and 5.22 +/- 0.85 cm(3) in G2, 10.93 +/- 2.17 cm(3) and 9.97 +/- 2.91 cm(3) in G3, and 13.81 +/- 3.03 cm(3) and 11.06 +/- 3.27 cm(3) 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.

Paradoxical redistribution of pulmonary blood flow in prone and supine humans exposed to hypergravity

We hypothesized that exposure to hypergravity in the supine and prone postures causes a redistribution of pulmonary blood flow to dependent lung regions. Four normal subjects were exposed to hypergravity by use of a human centrifuge. Regional lung perfusion was estimated by single-photon-emission computed tomography (SPECT) after administration of (99m)Tc-labeled albumin macroaggregates during normal and three times normal gravity conditions in the supine and prone postures. All images were obtained during normal gravity. Exposure to hypergravity caused a redistribution of blood flow from dependent to nondependent lung regions in all subjects in both postures. We speculate that this unexpected and paradoxical redistribution is a consequence of airway closure in dependent lung regions causing alveolar hypoxia and hypoxic vasoconstriction. Alternatively, increased vascular resistance in dependent lung regions is caused by distortion of lung parenchyma. The redistribution of blood flow is likely to attenuate rather than contribute to the arterial desaturation caused by hypergravity.

Lung radiofrequency ablation with and without bronchial occlusion: experimental study in porcine lungs

PURPOSE

This study was undertaken to compare the thermal lesion volumes in normal pig lungs when radiofrequency (RF) ablation is performed with and without airway occlusion.

MATERIALS AND METHODS

RF ablation was performed in six pigs. A straight 17-gauge internally cooled-tip electrode with a 2-cm exposed tip was inserted into the center of the lower lobe of the lung under biplane fluoroscopic guidance. In each animal, RF ablation was performed for 12 minutes with balloon occlusion of the main bronchus in one lung and without balloon occlusion in the contralateral lung. The tissue temperature around the electrode tip was measured immediately after RF application. The volumes of the thermal lesions were compared by histologic examination of the groups of lungs ablated with and without airway occlusion.

RESULTS

Tissue temperature was significantly higher in the bronchial occlusion group than in the group with normal ventilation (51 degrees C +/- 7 vs. 44 degrees C +/- 2; P < .05). RF ablation with bronchial occlusion resulted in the creation of a significantly greater thermal lesion volume compared with RF ablation with normal ventilation (6,535 mm(3) +/- 1,114 vs 3,368 mm(3) +/- 676; P < .03).

CONCLUSION

Prevention of ventilation in the normal swine lung via bronchial balloon occlusion during RF ablation increases the thermal ablation lesion volume, suggesting that active ventilation is a significant cause of in vivo heat loss.