Effects of foam or gauze on sternum wound contraction, distension and heart and lung damage during negative-pressure wound therapy of porcine sternotomy wounds☆

The study was performed to compare the effects of negative-pressure wound therapy (NPWT) using gauze and foam on wound edge movement and the macroscopic appearance of the heart and lungs after NPWT. Sternotomy wounds were created in 6×70 kg pigs. Negative pressures of -40, -70, -120 and -160 mmHg were applied and the following were evaluated: wound contraction, distension and the macroscopic appearance of the heart and lungs after NPWT. Wound contraction was greater when using foam than gauze (3.5±0.3 cm and 1.3±0.2 cm, respectively, P<0.01). The application of traction to the lateral edges of the sternotomy resulted in greater wound distention with foam than with gauze (5.3±0.3 cm and 3.6±0.2 cm, respectively, P<0.001). After using foam, the surface of the heart was red and mottled, and lung emphysema and sometimes, lung rupture were observed. After using gauze, the organ surface had no markings. The study shows that foam allows greater wound contraction and distension than gauze. This movement of the wound edges may cause damage to the underlying organs. There is less damage to the heart and lungs when using gauze than foam.