Systolic (SBP), diastolic (DBP), and mean (MAP) arterial blood pressure measurements frequently guide management in intensive care. Direct readings, commonly from a major artery, are considered to be the gold standard. Since arterial cannulation is associated with risks, alternative non-invasive blood pressure (NIBP) measurements are routinely used. However, the accuracy of NIBP in overweight patients in the outpatient setting is variable and little is known about critically ill patients. This study was performed to compare direct intra-arterial BP (IABP) to NIBP measurements obtained using auscultatory and oscillometric methods in overweight critically ill patients.
After obtaining informed consent, patients with a BMI > 25 and a functional arterial line (assessed by the rapid flush test) were enrolled in the study. IABP measurements were compared to those obtained non-invasively. A calibrated aneroid manometer with arm-cuffs compatible with arm sizes and a NIBP monitor (M1008B Hewlett Packard, Inc., CA) were used for NIBP measurements. Agreement between methods was assessed using Bland-Altman analysis.
Sixty seven patients (27 males) with a mean (± SD) age of 58 ± 18 years were included in the study. Mean BMI was 33.7 ± 9.7. IABP readings were obtained from the radial artery in 54 (81%) patients. Only 9 patients were receiving vasoactive medications during the study.
Oscillometric BP measurements underestimated IABP readings regardless of patient BMI. Auscultatory measurements were also inaccurate tending to underestimate SBP and overestimate MAP and DBP.
NIBP can be inaccurate amongst overweight critically ill patients and lead to erroneous interpretations of IABP. Direct intra-arterial measurements are preferred in this patient population when therapies are targeted to a certain BP goal. Mean bias (mm Hg)AuscultatoryOscillometricAuscultatory (BMI ≤30) n = 30Oscillometric (BMI ≤30) n = 30Auscultatory (BMI > 30) N = 37Oscilometric (BMI > 30) N = 37SBP−6.1 ± 32.3−14.9 ± 28.8−16.0 ± 38.8−18.2 ± 34.41.4 ± 24.8−12.3 ± 23.5DBP9.7 ± 15.6−4.9 ± 15.29.4 ± 14.8−0.01 ± 11.410.0 ± 16.4−8.9 ± 16.7MAP6.8 ± 19.2−5.6 ± 17.23.0 ± 21.5−4.0 ± 17.610.1± 17.0−12.6 ± 10.1
A. Araghi, None.