Validation of the Next-Generation Caretaker Continuous Physiological Monitor Using Invasive Intra-Arterial Pressures in Abdominal Surgery Patients

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Irwin Gratz Martin Baruch Isabel Elaine Allen Julia Seaman Magdy Takla Brian McEniry Edward Deal




The reliable detection and, ultimately, prediction of hypotensive events in post-operative settings remains an unsolved problem, as patients are currently only monitored intermittently because of the lack of validated, non-invasive/non-intrusive and continuous physiological monitoring technologies.

With this goal in mind, the aim of this study was to validate a next-generation platform version of the currently FDA-cleared non-invasive Caretaker (CT) physiological monitor in the hemodynamically challenging environment of abdominal surgeries in comparison with blood pressures obtained from arterial catheters, evaluated against ANSI/AAMI/ISO 81060–2:2019 standards as well as against current non-invasive standard of care measurements provided by clinical-grade automatic oscillometric cuffs.


Comparison data from 41 major abdominal surgery patients at Cooper Hospital (Camden NJ) were analyzed in this IRB approved study. Each patient was monitored with a radial arterial catheter and CT using a finger cuff applied to the contralateral middle finger. Systolic and diastolic blood pressures continuously collected from the arterial catheter and CT were compared using Pearson correlation coefficients and Bland-Altman analysis.  In addition, a trend analysis using 4Q plots was performed. Both the CT’s continuous BP tracking and the CT’s self-calibration capability were analyzed.


The continuous data comparisons were performed with and without taking the CT recalibrations into account. With the recalibrations the mean differences and standard deviations (STDs) for systole and diastole were, respectively, -1.14 mmHg (13.82 mmHg) and -2.49 mmHg (9.42 mmHg), while the correlations were 0.80 and 0.78. Mean differences and STDs for an initial calibration and no subsequent recalibrations were, respectively for systole and diastole, -0.42 mmHg (16.73 mmHg) and -2.57 mmHg (10.36 mmHg), while the correlations were 0.64 and 0.67. For the CT’s self-calibrations alone, correlations for systole and diastole were, respectively, 0.83 and 0.75, while corresponding mean differences (STD) were -3.19 mmHg (10.86 mmHg) and -2.41 mmHg (8.18 mmHg). For 41% of total surgery time, both systole and diastole were within 8 mmHg of the arterial catheter Gold Standard. The concordances for systolic and diastolic blood pressure changes on a 30-second time scale were 0.87 and 0.86. The same comparison analysis for the automatic cuff and the arterial catheter data yielded: correlations for systole and diastole: 0.69 and 0.61, mean differences and STDs: 2.48 mmHg (15.82 mmHg) and 0.65 mmHg (10.68 mmHg).


The results of this study are significant in that they validate the future use of the CT physiological monitor, which utilizes Pulse Decomposition Analysis (PDA), in the post-operative monitoring scenario both as a monitor to detect hypotensive events to facilitate clinical intervention as well as provide signal inputs that could enable anticipatory measures.



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GRATZ, Irwin et al. Validation of the Next-Generation Caretaker Continuous Physiological Monitor Using Invasive Intra-Arterial Pressures in Abdominal Surgery Patients. Medical Research Archives, [S.l.], v. 9, n. 7, july 2021. ISSN 2375-1924. Available at: <>. Date accessed: 19 may 2022. doi:
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