Oscillometric versus invasive blood pressure measurement in patients with shock: a prospective observational study in the emergency department

Abstract

In emergency medicine, blood pressure is often measured by an oscillometric device using an upper arm cuff. However, measurement accuracy of this technique in patients suffering from hypotensive shock has not been sufficiently evaluated. We designed a prospective observational study investigating the accuracy of an oscillometric device in hypotensive patients admitted to the resuscitation area of the emergency department. Patients admitted to the resuscitation area of a university hospital, who were equipped with an arterial catheter and found to be hypotensive (mean arterial pressure (MAP) < 60 mmHg) were eligible for the study. Blood pressure was measured simultaneously via upper arm cuff and invasively under routine clinical conditions. After data extraction, Bland-Altman analysis, correlation coefficient and percentage error of mean and systolic blood pressure pairs were performed. We analysed 75 simultaneously obtained blood pressure measurements of 30 patients in hypotension, 11 (37%) were female, median age was 76.5 years (IQR 63-82). Oscillometric MAP was markedly higher than invasive MAP with a mean of the differences of 13 ± 15 mmHg (oscillometric-invasive), 95% limits of agreement - 16 to 41 mmHg, percentage error was 76%. In 64% of readings, values obtained by the upper arm cuff were not able to detect hypotension. Oscillometric blood pressure measurement is not able to reliably detect hypotension in emergency patients. Therefore, direct measurement of blood pressure should be established as soon as possible in patients suffering from shock.

Keywords: Emergency medicine; Hypotension; Oscillometric blood pressure; Resuscitation area; Shock.

Fig. 1

Flow chart of patient inclusion in the study

Fig. 2

Modified Bland–Altman-Plot of oscillometric and invasive mean arterial pressure in mmHg. Invasive pressure values on the x-axis are plotted against the bias (oscillometric—invasive) of each pair on the y-axis. The bold line corresponds to the mean difference, dashed lines show 95% limits of agreement, the dotted lines indicate the corresponding 95% confidence intervals. Radial, brachial and femoral measurements are black, blue and red, respectively

Fig. 3

Error grid for mean arterial pressure in mmHg. Invasive pressure (x-axis, reference method) is plotted against noninvasive pressure (y-axis, test method), the colours indicate the continuous risk level from green (zone A, no risk) to dark red (zone E, dangerous risk), based on experts’ clinical judgement [10]

Fig. 4

Modified Bland–Altman-Plot of oscillometric and invasive systolic arterial pressure in mmHg. Invasive pressure values on the x-axis are plotted against the bias (oscillometric—invasive) of each pair on the y-axis. The bold line corresponds to the mean difference, dashed lines show 95% limits of agreement, the dotted lines indicate the corresponding 95% confidence intervals. Radial, brachial and femoral measurements are black, blue and red, respectively

Fig. 5

Error grid for systolic arterial pressure in mmHg. Invasive pressure (x-axis, reference method) is plotted against noninvasive pressure (y-axis, test method), the colours indicate the continuous risk level from green (zone A, no risk) to dark red (zone E, dangerous risk), based on experts’ clinical judgement [10]