Scatter diagram of mean arterial pressure (MAP) measurements done with the femoral arterial catheter and the high-fidelity upper arm cuff. In total, 550 measurements were taken in 110 patients having abdominal surgery or neurosurgery (five measurements per patient; Pearson correlation coefficient r = 0.96; P < 0.0001; 95% CI, 0.96 to 0.97).