Noninvasive continuous versus intermittent arterial pressure monitoring: evaluation of the
vascular unloading technique (CNAP device) in the emergency department
Sammanfattning
BACKGROUND:
Monitoring cardiovascular function in acutely ill patients in the emergency department (ED) is of
paramount importance. Arterial pressure (AP) is usually monitored using intermittent oscillometric
measurements with an upper arm cuff. The vascular unloading technique (VUT) allows continuous
noninvasive AP monitoring. In this study, we compare continuous AP measurements obtained by VUT
with intermittent oscillometric AP measurements in ED patients. In addition, we aimed to investigate
whether continuous noninvasive AP monitoring allows detection of relevant hypotensive episodes
that might be missed with intermittent AP monitoring.
METHODS:
In a German university hospital, 130 ED patients who required AP monitoring were analyzed in this
prospective method comparison study. Continuous AP monitoring was performed using VUT (CNAP
technology; CNSystems Medizintechnik AG, Graz, Austria) over a 2-hour period. The oscillometric AP
values were recorded simultaneously every 15 minutes for the comparison of both methods. For
statistical evaluation, Bland-Altman plots accounting for repeated AP measurements per individual
were used.
RESULTS:
The mean difference (±standard deviation) between AP measurements obtained by VUT and
oscillometric AP measurements was -5 mmHg (±22 mmHg) for systolic AP (SAP), -2 mmHg (±15
mmHg) for diastolic AP (DAP), and -6 mmHg (±16 mmHg) for mean AP (MAP), respectively. In the
interval between two oscillometric measurements, the VUT device detected hypotensive episodes (?4
minutes) defined as either SAP <90 mmHg or MAP <65 mmHg in 30 patients and 16 patients,
respectively. In 11 (SAP <90 mmHg) and 6 (MAP <65 mmHg) of these patients, hypotension was also
detected by the subsequent intermittent oscillometric AP measurement.
CONCLUSIONS:
VUT using the CNAP system for noninvasive continuous AP measurement shows reasonable
agreement with intermittent oscillometric measurements in acutely ill ED patients. Continuous AP
monitoring allows immediate recognition of clinically relevant hypotensive episodes, which are
missed or only belatedly recognized with intermittent AP measurement.