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A Mock Circulation Flow Loop for Non-clinical Characterization of Pressure-Based Cardiac Output Monitoring Systems

Catalog of Regulatory Science Tools to Help Assess New Medical Devices 

 

This regulatory science tool is a lab method in the form of a physical mock circulation loop (MCL) used for simulating peripheral radial pressure waveforms.

 

Technical Description

The MCL is designed for characterizing the dynamic attributes of pressure-based cardiac output monitoring systems. This type of system applies an algorithm to intra-radial arterial blood pressure waveforms for cardiac output and related hemodynamic measurements (e.g., stroke volume variation).

The MCL is designed to simulate three hemodynamic states: cardiogenic shock, normovolemic state, and hyperdynamic state. Thus, it enables non-clinical generation of synchronized central flow (representative of aortic flow), central pressure (representative of aortic pressure), and peripheral pressure (representative of radial pressure) waveforms for each hemodynamic state.

A full description of the design and manufacturing details is described in the Instructions document. More details about the design, function, and characterization of the MCL are described in Farahmand et al., 2023.

Intended Purpose

This regulatory science tool, the mock circulation loop, is a physical bench setup for characterizing certain dynamic attributes of hemodynamic monitoring devices that apply an algorithm to an intra-radial arterial pressure waveform to monitor cardiac output (Farahmand et al., 2023). This tool is intended to be used during device development of intra-radial arterial pressure-based cardiac output monitoring devices as a non-clinical method to characterize certain performance aspects in a non-clinical setup where the underlying flow and pressure patterns can be configured and recorded with reference methods. Other applications of this tool may be during device development of applications that may use intra-radial arterial pressure-derived cardiac output measurements from these types of devices.

Testing

The MCL-generated relationships between central pressure and peripheral pressure and average hemodynamic values were verified against clinical data (Farahmand et al., 2023). The MCL reproducibility was verified through disassembling and assembling the MCL and demonstrating that each hemodynamic state could be reproduced by the system, as defined in Figure 1, Tables 1 and 2 of the Instructions document.

Limitations

While this MCL facilitates testing of certain characteristics that are challenging to address in clinical studies (Farahmand et al., 2023), it is not a replacement for accuracy testing in clinically relevant patient populations with appropriate clinical reference methods. The MCL is a bench-top model of cardiovascular components and therefore may not represent all physiological relationships. A known limitation of the current tool is that the MCL does not simulate the nonlinear relationship between arterial compliances and pressure, which can affect the testing of certain pressure-based cardiac output algorithms (Farahmand et al., 2023). The MCL also significantly attenuates spectral components above 4.5 Hz. For many applications the lost pressure contents in this spectral range may have negligible impact on the cardiac output measurement performance, but this limitation should be taken into consideration depending on the design of the algorithm the tool is intended to be applied to and the potential effects of higher frequency components in the arterial pressure waveform.

Supporting Documentation

A full description of the MCL design development details are provided in the instructions below:

More details about the MCL design, function, and characterization are available online:

  • Farahmand, M., Bodwell, E., D'Souza, G. A., Herbertson, L. H., & Scully, C. G. (2023). Mock circulatory loop generated database for dynamic characterization of pressure-based cardiac output monitoring systems. Computers in biology and medicine, 160, 106979. https://doi.org/10.1016/j.compbiomed.2023.106979

The following publications provide additional background on the approach to generate arterial pressure waveforms with a mock circulatory loop and application of arterial pressure waveforms to testing with a physical pressure pulse generator.

  • Packy, A., D'Souza, G. A., Farahmand, M., Herbertson, L., & Scully, C. G. (2022). Simulating Radial Pressure Waveforms with a Mock Circulatory Flow Loop to Characterize Hemodynamic Monitoring Systems. Cardiovascular engineering and technology, 13(2), 279–290. https://doi.org/10.1007/s13239-021-00575-2
  • Farahmand, M., Mirinejad, H., & Scully, C. G. (2021). Model-based approach to investigate equipment-induced error in pressure-waveform derived hemodynamic measurements. Physiological measurement, 42(11), 10.1088/1361-6579/ac38be. https://doi.org/10.1088/13616579/ac38be

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