['Small arteries and veins up to 7 mm can be sealed safe and divided with a bipolar sealing instrument. The results for the safe sealing of larger vessels were unsatisfactory in the past. Using an ex vivo pulmonary artery model, we aimed to investigate, if a higher compression force and duration will improve the bursting pressures in case of vessels >7 mm.', 'Heart-lung preparations (from 90 kg pigs) were removed en bloc at a slaughterhouse. The whole pulmonary artery was exposed from the pulmonary valve up to the periphery of the left lung. In the laboratory, a digital pressure sensor was implanted in the central end of the blood vessel to measure the bursting pressure (in mbar). The vessels examined were divided into three groups by diameter: 1-6 mm, 7-12 mm and >12 mm. After bipolar sealing, bursting pressures were determined by pneumatic testing. Seals were made using three equal MARSEAL instruments (Gebrüder Martin GmbH & CoKG, Tuttlingen, Germany) with a SealSafe G3 electric current and different jaw compression forces of each 35 N, 45 N, and 55 N. Bursting pressures were also measured for different compression durations (0 s, 5 s, 10 s, and 20 s) with 35 N compression. Mean bursting pressures were calculated for each group (n = 15). Groups were compared using a nonparametric test (Mann-Whitney U test). The significance level was P < 0.05.', 'Mean bursting pressures in the 1-6 mm blood vessels were 290.5 ± 77.1 mbar (35 N), 323.0 ± 76.0 mbar (45 N) and 301.6 ± 69.9 mbar (55 N). The groups did not differ significantly. Mean bursting pressures in the 7-12 mm vessels were 108.1 ± 19.1 mbar (35 N), 154.3 ± 28.5 mbar (45 N), and 212.4 ± 45.3 mbar (55 N). In blood vessels >12 mm in diameter, we found mean bursting pressures of 77.7 ± 11.7 mbar (35 N), 117.6 ± 27.1 mbar (45 N), and 166.3 ± 56.6 mbar (55 N). The results for the groups with 55 N compression were significantly higher than for the other groups. A compression duration of 5 s led to significantly higher mean bursting pressures than a duration of 0 s but a duration of >5 s did not bring a further significant increase in mean bursting pressure. Histologic staining of the seal zone and microscopic examination did not reveal any differences relating to compression force.'] Does more compression improve sealing effect on larger pulmonary arteries?