Accuracy and reliability of noninvasive continuous finger blood pressure measurement in critically ill patients

Objective: To evaluate the accuracy and reliability of noninvasive continuous finger blood pressure measurement in critically ill patients. Design: Prospective data collection. Setting: Emergency department in a 2,000-bed hospital. Patients: Thirty-nine patients admitted to the emergency department requiring invasive arterial blood pressure monitoring were enrolled to the study protocol. Interventions: Continuous noninvasive blood pressure measurement was performed on the middle phalanx of the second and third finger, using a test instrument which provides continuous arterial waveform display with the use of a finger cuff. Invasive mean arterial blood pressure measurement was done by cannula tion of the radial artery and direct transduction of the systemic arterial pressure waveform. Measurements and Main Results: Three thousand one hundred eighteen pairs of simultaneous finger cuff and intra-arterial blood pressure measurements were collected in 1-min intervals from 39 patients over a total of 51.8 hrs. The overall discrepancy between both measurements was 0.10 mm Hg. The standard deviation of the differences was +/-5.02 mm Hg. The mean bias in patients treated with catecholamines was 0.01 mm Hg and was not different from the bias observed in patients without catecholamines (mean bias: 0.23 mm Hg; p > .22). Whereas 95% of all comparisons between finger cuff and intra arterial measurement had a discrepancy less than or equal to+/-10 mm Hg, 4.7% had a discrepancy between +/-10.1 to 15 mm Hg and 0.3% exhibited a discrepancy >+/-15 mm Hg. In 29 (74%) patients, the duration of errors >10 mm Hg was less than or equal to 1 min. In seven (18%) patients, the duration of errors >10 mm Hg was between 2 to 3 mins and in three (8%) patients, the errors lasted for >3 mins. Conclusions: Our data provide a guide to the accuracy and reliability of noninvasive finger blood pressure measurements in critically ill patients. Although most test instrument measurements were reliable, in 8% of all patients large discrepancies (>10 mm Hg) between both measurements with a duration of >3 mins were noted. Concerning the considerable risk for arterial cannulation, our preliminary data demonstrate that the test instrument (PORTAPRES(R) TNO Biomedical Instrumentation Research Unit; The Netherlands) is an advance in noninvasive monitoring of critically ill patients and may be useful in most emergency clinical settings.