Comparison of invasive and non-invasive measurements of continuous arterial pressure using the Finapres

A comparison was made of arterial pressures measured invasively from a radial arterial cannula and non-invasively from the middle finger using the 2300 Finapres (Ohmeda) during induction and maintenance of anaesthesia. Digital outputs of both pressures were captured directly onto computer hard disk; data recorded during flushing of the arterial line were excluded from analysis. We studied 53 patients undergoing cardiac, major vascular and neurosurgical procedures; 17705 comparisons of systolic, diastolic and mean pressure were analysed. Overall correlations between Finapres and invasive pressures were poor (r = 0.82, 0.68 and 0.78 for systolic, diastolic and mean pressures, respectively). The Finapres exhibited a high level of accuracy and precision in some recordings. However, patient data sets showed marked variability in average pressure differences (invasive minus Finapres) when examined individually or grouped by operation type. Unexplained variations in pressure difference with time and absolute pressure were observed also. Whilst providing useful beat-to-beat information on arterial pressure trends, the Finapres cannot be recommended as a universal substitute for invasive arterial pressure monitoring.