Andreas Kirschbaum1, Thomas M Surowiec2, Anika Pehl3, Andreas Gockel4, Detlef K Bartsch1, Nikolas Mirow5. 1. Department of Visceral, Thoracic and Vascular Surgery, University Hospital Marburg, Marburg, Germany. 2. Department of Mathematics and Computer Science, University of Marburg, Marburg, Germany. 3. Institute of Pathology, University Hospital Marburg, Marburg, Germany. 4. Department of Anesthesiology and Intensive Care Medicine, University Hospital Marburg, Marburg, Germany. 5. Department of Cardiac and Thoracic Vascular Surgery, University Hospital Marburg, Marburg, Germany.
Abstract
BACKGROUND: Lung metastases can be removed by an Nd:YAG laser to save lung parenchyma. At these sites, a coagulated lung surface remains. Airtightness was investigated in relation to the depth of resection on an ex vivo porcine lung model. METHODS: Freshly slaughtered porcine double lung preparations were connected to a ventilator via a tube. Non-anatomical laser resections were performed with an 800 µm laser fiber and the Nd:YAG laser LIMAX® 120 (power: 40 and 60 watts). The following resection depths (each n=12) from the lung surface were examined: 0.5, 1, 1.5 and 2.0 cm. After resection the lungs were submerged under water and ventilated (frequency 10/min, Pinsp =25 mbar, PEEP =5 mbar). Airtightness of resection surfaces was determined by a leakage score, as well as the measurement of the leakage volume (in mL) per respiration (Group 1). Afterwards, the resection areas were coagulated for 5 seconds with a laser power of 60 watts at a distance of approximately 1 cm from the surface. This was followed by a re-evaluation for airtightness (Group 2). Finally, the resection surface was closed by a suture (PDS USP 4-0) and re-tested for airtightness (Group 3). The individual groups were compared for their significance (P<0.05) using a nonparametric test. RESULTS: Up to a resection depth of 1.5 cm, the ventilated resection surfaces were completely airtight regardless of the laser power. From a depth of resection of 1.5 cm, a mean air volume loss of 28.9±5.3 mL/respiratory cycle at 40 watts and of 26.4±5.8 mL at 60 watts was found. Additional surface coagulation did not significantly reduce the leakage rate. In contrast, suturing significantly reduced (P<0.0001) to 7.2±3.7 mL/ventilation (40 watts) and 6.0±3.4 mL/ventilation. At a resection depth of 2 cm, the leakage volume was 42.9±3.3 mL/respiratory cycle (40 watt) and 46.3±6.4 mL/respiratory cycle (60 watt). Additional surface coagulation failed to significantly reduce leakage volume, but suture closure provided airtightness. CONCLUSIONS: In non-ventilated porcine lungs, Nd:YAG laser resection surfaces up to a resection depth of 1.5 cm are airtight after ventilation onset. From a depth of 1.5 cm, closure of resection surfaces by an additional suture is needed. Airtightness of resection surfaces was not increased by additional coagulation.
BACKGROUND: Lung metastases can be removed by an Nd:YAG laser to save lung parenchyma. At these sites, a coagulated lung surface remains. Airtightness was investigated in relation to the depth of resection on an ex vivo porcine lung model. METHODS: Freshly slaughtered porcine double lung preparations were connected to a ventilator via a tube. Non-anatomical laser resections were performed with an 800 µm laser fiber and the Nd:YAG laser LIMAX® 120 (power: 40 and 60 watts). The following resection depths (each n=12) from the lung surface were examined: 0.5, 1, 1.5 and 2.0 cm. After resection the lungs were submerged under water and ventilated (frequency 10/min, Pinsp =25 mbar, PEEP =5 mbar). Airtightness of resection surfaces was determined by a leakage score, as well as the measurement of the leakage volume (in mL) per respiration (Group 1). Afterwards, the resection areas were coagulated for 5 seconds with a laser power of 60 watts at a distance of approximately 1 cm from the surface. This was followed by a re-evaluation for airtightness (Group 2). Finally, the resection surface was closed by a suture (PDS USP 4-0) and re-tested for airtightness (Group 3). The individual groups were compared for their significance (P<0.05) using a nonparametric test. RESULTS: Up to a resection depth of 1.5 cm, the ventilated resection surfaces were completely airtight regardless of the laser power. From a depth of resection of 1.5 cm, a mean air volume loss of 28.9±5.3 mL/respiratory cycle at 40 watts and of 26.4±5.8 mL at 60 watts was found. Additional surface coagulation did not significantly reduce the leakage rate. In contrast, suturing significantly reduced (P<0.0001) to 7.2±3.7 mL/ventilation (40 watts) and 6.0±3.4 mL/ventilation. At a resection depth of 2 cm, the leakage volume was 42.9±3.3 mL/respiratory cycle (40 watt) and 46.3±6.4 mL/respiratory cycle (60 watt). Additional surface coagulation failed to significantly reduce leakage volume, but suture closure provided airtightness. CONCLUSIONS: In non-ventilated porcine lungs, Nd:YAG laser resection surfaces up to a resection depth of 1.5 cm are airtight after ventilation onset. From a depth of 1.5 cm, closure of resection surfaces by an additional suture is needed. Airtightness of resection surfaces was not increased by additional coagulation.
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