Pressure transduction during NPWT. Measurements were performed with conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source. Negative pressures of -50, -70, and -120 mmHg were applied and the pressure transduction centrally, beneath the dressing and on the anterior abdominal wall was recorded. The results are shown as means ± the SEM of six experiments. Statistical analysis was performed using the Mann-Whitney test. Significance was defined as p < 0.05 (*), p < 0.01 (**), p < 0.001 (***) and p > 0.05 (not significant, n.s.).