Efficacy of a new blood pressure monitor (inflationary non-invasive blood pressure, iNIBP™): a randomised controlled study.

The inflationary non-invasive blood pressure monitor (iNIBP™) uses a new measurement method, whereby the cuff is slowly inflated whilst simultaneously sensing oscillations, to determine the diastolic blood pressure first and then the systolic pressure. It may measure blood pressure more quickly than the conventional non-invasive blood pressure monitor. We studied 66 patients undergoing general anaesthesia, comparing the time taken to measure the blood pressure between the two monitors at times when there were marked changes (increases or decreases by 30 mmHg or greater) in the systolic blood pressure. The median (IQR) [range]) time was significantly longer for the non-invasive blood pressure monitor (38.8 (31.5-44.7) [18.0-130.0] s) than for the iNIBP (14.6 (13.7-16.4) [11.5-35.5] s), p = 0.001, 95%CI for difference 22-25 s). We also studied 30 volunteers to evaluate the accuracy of the iNIBP, comparing it with the mercury sphygmomanometer. There was good agreement between the two monitors, with a mean difference of 0 (95% limit of agreement -12 to 11) mmHg for the systolic blood pressure. We also compared the degree of pain during cuff inflation between the automated non-invasive blood pressure and iNIBP monitors. Pain was significantly more for the non-invasive blood pressure monitor (22 of 30 volunteers had less pain with the iNIBP). We have shown that the iNIBP measured the blood pressure quicker than the conventional non-invasive blood pressure monitor and the speed of measurement was not significantly affected by marked changes in the blood pressure.