Accuracy of the CNAP™ monitor, a noninvasive continuous blood pressure device, in providing beat-to-beat blood pressure readings in pediatric patients weighing 20-40 kilograms

Abstract

Background: During perioperative care, the continuous measurement of blood pressure (BP) provides superior physiologic monitoring to intermittent techniques. However, such monitoring requires placement of an intraarterial catheter, which may be time-consuming or associated with adverse events and technical difficulty. A noninvasive, continuous BP monitoring device has been studied in the adult population. This study prospectively assesses its accuracy in pediatric patients, weighing 20-40 kg.

Methods: The technology evaluated is the CNAP™ Monitor 500, developed by CNSystems AG (Graz, Austria). The study cohort included pediatric patients weighing between 20 and 40 kg, scheduled for surgery for which arterial line (AL) placement was planned. Systolic (sBP), diastolic (dBP), and mean arterial (MAP) blood pressure readings were captured from the AL and the CNAP™ device every minute during anesthetic care.

Results: The study cohort consisted of 20 patients (11 weighing between 30 and 40 kg and 9 weighing between 20 and 29.9 kg) with a mean age of 9.8 ± 3.4 years (range, 6-16 years) and weight of 29.8 ± 6.1 kg (range, 20.9-38.7 kg). There were a total of 1076 pairs each of sBP, dBP, and MAP values in the 20-29.9 kg group. The absolute difference between the sBP, dBP, and MAP was 9.8 ± 8.5, 6.8 ± 5.3, and 6.7 ± 6.2 mmHg, respectively. The correlation coefficient between the AL and the CNAP™ device was 0.48, 0.60, and 0.64 for the sBP, dBP, and MAP, respectively. The CNAP™ values (sBP, dBP, MAP) were ≤5 mmHg from the AL values in 38.6%, 48.5%, and 55.0% of the values, respectively. In the 30-40 kg group, there were a total of 2737 pairs of sBP, dBP, and MAP values. The absolute difference between the sBP, dBP, and MAP was 11.5 ± 9.3, 7.5 ± 5.3, and 7.9 ± 6.6 mmHg, respectively. The correlation coefficient between the arterial cannula and the CNAP™ device was 0.48, 0.45, and 0.51 for the sBP, dBP, and MAP, respectively. CNAP™ readings were ≤5 mmHg from the AL values (sBP, dBP, MAP) in 29.0%, 41.9%, and 40.5% of the values, respectively.

Conclusion: Although some variation in its accuracy was noted, the CNAP™ device provides a noninvasive and continuous blood pressure reading which appears to be within clinically useful limits. It may be that modification of the finger cuffs is needed to improve its absolute accuracy as our clinical experience demonstrated that achieving an effective fit with the cuffs was at times difficult.

Keywords: arterial blood pressure; blood pressure monitors; pediatrics.