Dynamic parameters like pulse pressure Variation (PPV) , synonymous: difference in pulse pressure (dPP), can predict fluid responsiveness reliably (Marik PE et al, Crit Care Med 2009; 37:2642-7). An arterial line is required for assessment of dPP. On a modified Penaz technique, a non-invasive measurement device is now available commercially. In this study, the reference technique based on arterial measurement and a respiratory variation monitor (Pestel G et al, Anesth Analg 2009; 108:1823-9) was compared to the non-invasive device a clinical setting. At defined time points, systolic, diastolic, mean arterial blood pressure and dPP were compared using Bland-Altmann Analysis (Bland JM, Altman DG, Lancet 1986; 1: 307-10)