Agreement between continuous noninvasive finger cuff-derived and invasive arterial blood pressure measurements: Effect of data sampling and data processing

BACKGROUND The effect of different methods for data sampling and data processing on the results of comparative statistical analyses in method comparison studies of continuous arterial blood pressure (AP) monitoring systems remains unknown. OBJECTIVE We sought to investigate the effect of different methods for data sampling and data processing on the results of statistical analyses in method comparison studies of continuous AP monitoring systems. DESIGN Prospective observational study. SETTING University Medical Center Hamburg-Eppendorf, Hamburg, Germany, from April to October 2019. PATIENTS 49 patients scheduled for neurosurgery with AP measurement using a radial artery catheter. MAIN OUTCOME MEASURES We assessed the agreement between continuous noninvasive finger cuff-derived (CNAP Monitor 500; CNSystems Medizintechnik, Graz, Austria) and invasive AP measurements in a prospective method comparison study in patients having neurosurgery using all beat-to-beat AP measurements (Method all ), 10-s averages (Method avg ), one 30-min period of 10-s averages (Method 30 ), Method 30 with additional offset subtraction (Method 30off ), and 10 30-s periods without (Method iso ) or with (Method iso-zero ) application of the zero zone. The agreement was analysed using Bland-Altman and error grid analysis. RESULTS For mean AP, the mean of the differences (95% limits of agreement) was 9.0 (−12.9 to 30.9) mmHg for Method all , 9.2 (−12.5 to 30.9) mmHg for Method avg , 6.5 (−9.3 to 22.2) mmHg for Method 30 , 0.5 (−9.5 to 10.5) mmHg for Method 30off , 4.9 (−6.0 to 15.7) mmHg for Method iso , and 3.4 (−5.9 to 12.7) mmHg for Method iso-zero . Similar trends were found for systolic and diastolic AP. Results of error grid analysis were also influenced by using different methods for data sampling and data processing. CONCLUSION Data sampling and data processing substantially impact the results of comparative statistics in method comparison studies of continuous AP monitoring systems. Depending on the method used for data sampling and data processing, the performance of an AP test method may be considered clinically acceptable or unacceptable.