Noninvasive Monitoring of Arterial Pressure: Finger or Lower Leg As Alternatives to the Upper Arm: A Prospective Study in Three ICUs

OBJECTIVES: When the upper arm is inaccessible for measurements of arterial pressure (AP), the best alternative site is unknown. We performed a between-site comparison of the agreement between invasive and noninvasive readings of AP taken at the lower leg, the finger, and the upper arm. The risk associated with measurement errors and the trending ability were also assessed. DESIGN: Prospective observational study. SETTING: Three ICUs. PATIENTS: Patients having an arterial catheter and an arm circumference less than 42 cm. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Three triplicates of AP measurements were collected via an arterial catheter (reference AP), a finger cuff system (ClearSight; Edward Lifesciences, Irvine, CA), and an oscillometric cuff (at the lower leg then the upper arm). Trending ability was assessed through an additional set of measurements after a cardiovascular intervention. The default bed backrest angle was respected. Failure to measure and display AP occurred in 19 patients (13%) at the finger, never at other sites. In 130 patients analyzed, the agreement between noninvasive and invasive readings was worse at the lower leg than that observed at the upper arm or the finger (for mean AP, bias ± sd of 6.0 ± 15.8 vs 3.6 ± 7.1 and 0.1 ± 7.4 mm Hg, respectively; p < 0.05), yielding a higher frequency of error-associated clinical risk (no risk for 64% vs 84% and 86% of measurements, respectively, p < 0.0001). According to the International Organization for Standardization (ISO) 81060-2:2018 standard, mean AP measurements were reliable at the upper arm and the finger, not the lower leg. In 33 patients reassessed after a cardiovascular intervention, both the concordance rate for change in mean AP and the ability to detect a therapy-induced significant change were good and similar at the three sites. CONCLUSIONS: As compared with lower leg measurements of AP, finger measurements were, when possible, a preferable alternative to upper arm ones.