Development and characterization of silicone-based tissue phantoms for pulse oximeter performance testing.

Significance: Pulse oximeter measurements are commonly relied upon for managing patient care and thus often require human testing before they can be legally marketed. Recent clinical studies have also identified disparities in their measurement of blood oxygen saturation by race or skin pigmentation.

Aim: The development of a reliable bench-top performance test method based on tissue-simulating phantoms has the potential to facilitate pre-market assessment and the development of more accurate and equitable devices.

Melanometry for objective evaluation of skin pigmentation in pulse oximetry studies.

Pulse oximetry enables real-time, noninvasive monitoring of arterial blood oxygen levels. However, results can vary with skin color, thus detecting disparities during clinical validation studies requires an accurate measure of skin pigmentation. Recent clinical studies have used subjective methods such as self-reported color, race/ethnicity to categorize skin.

Tissue mimicking materials and finger phantom design for pulse oximetry.

Pulse oximetry represents a ubiquitous clinical application of optics in modern medicine. Recent studies have raised concerns regarding the potential impact of confounders, such as variable skin pigmentation and perfusion, on blood oxygen saturation measurement accuracy in pulse oximeters. Tissue-mimicking phantom testing offers a low-cost, well-controlled solution for characterizing device performance and studying potential error sources, which may thus reduce the need for costly in vivo trials.

Hybrid Cathode Lithium Battery Discharge Simulation for Implantable Cardioverter Defibrillators Using a Coupled Electro-Thermal Dynamic Model.

This paper explores the effect of the load imposed by implantable cardioverter defibrillators (ICDs) on their lithium battery power sources longevity using a simulation approach that incorporates a coupled electro-thermal dynamic model. ICDs are one of the effective treatments available to significantly improve survival of patients with fatal arrhythmia (abnormal heart rhythm) disorders. Using a lithium battery power source, this life-saving device sends electrical shocks or pulses to regulate the heartbeat.

Evaluation of the robustness of cerebral oximetry to variations in skin pigmentation using a tissue-simulating phantom.

Clinical studies have demonstrated that epidermal pigmentation level can affect cerebral oximetry measurements. To evaluate the robustness of these devices, we have developed a phantom-based test method that includes an epidermis-simulating layer with several melanin concentrations and a 3D-printed cerebrovascular module. Measurements were performed with neonatal, pediatric and adult sensors from two commercial oximeters, where neonatal probes had shorter source-detector separation distances.

Usability Engineering Recommendations for Next-Gen Integrated Interoperable Medical Devices.

This article reports on the development of usability engineering recommendations for next-generation integrated interoperable medical devices. A model-based hazard analysis method is used to reason about possible design anomalies in interoperability functions that could lead to use errors. Design recommendations are identified that can mitigate design problems.

Applying Medical Device Informatics to Enable Safe and Secure Interoperable Systems: Medical Device Interface Data Sheets.

This article describes the concept of Medical Device Interface Data Sheets (MDIDSs) to document and characterize medical device interface data requirements, the processes for creating MDIDSs, and its role in supporting patient safety and cybersecurity of current systems while enabling innovation in the area of next-generation medical Internet of Things (IoT) platforms for integrating sensors, actuators, and applications (apps).

Cerebral oximetry performance testing with a 3D-printed vascular array phantom.

Cerebral oximetry based on near-infrared spectroscopy represents a unique noninvasive tool for real-time surgical monitoring, yet studies have shown a significant discrepancy in accuracy among commercial systems. Towards the establishment of a standardized method for performance testing, we have studied a solid phantom approach - based on a 3D-printed cerebrovascular module (CVM) incorporating an array of 148 cylindrical channels - that has several advantages over liquid phantoms. Development and characterization of a CVM prototype are described, including high-resolution imaging and spectrophotometry measurements.

Evaluation of Fluid Resuscitation Control Algorithms via a Hardware-in-the-Loop Test Bed.

Objective: This paper presents a hardware-in-the-loop (HIL) testing platform for evaluating the performance of fluid resuscitation control algorithms. The proposed platform is a cyber-physical system that integrates physical devices with computational models and computer-based algorithms.

Methods: The HIL test bed is evaluated against in silico and in vivo data to ensure the hemodynamic variables are appropriately predicted in the proposed platform.

Credibility Evidence for Computational Patient Models Used in the Development of Physiological Closed-Loop Controlled Devices for Critical Care Medicine.

Physiological closed-loop controlled medical devices automatically adjust therapy delivered to a patient to adjust a measured physiological variable. In critical care scenarios, these types of devices could automate, for example, fluid resuscitation, drug delivery, mechanical ventilation, and/or anesthesia and sedation. Evidence from simulations using computational models of physiological systems can play a crucial role in the development of physiological closed-loop controlled devices; but the utility of this evidence will depend on the credibility of the computational model used.

Applying a Computational Model Credibility Framework to Physiological Closed-loop Controlled Medical Device Testing.

Physiological closed-loop controlled medical devices are safety-critical systems that combine patient monitors with therapy delivery devices to automatically titrate therapy to meet a patient's current need. Computational models of physiological systems can be used to test these devices and generate pre-clinical evidence of safety and performance before using the devices on patients. The credibility, utility, and acceptability of such model-based test results will depend on, among other factors, the computational model used.

Regulatory Considerations for Physiological Closed-Loop Controlled Medical Devices Used for Automated Critical Care: Food and Drug Administration Workshop Discussion Topics.

Part of the mission of the Center for Devices and Radiological Health (CDRH) at the US Food and Drug Administration is to facilitate medical device innovation. Therefore, CDRH plays an important role in helping its stakeholders such as manufacturers, health care professionals, patients, patient advocates, academia, and other government agencies navigate the regulatory landscape for medical devices. This is particularly important for innovative physiological closed-loop controlled (PCLC) devices used in critical care environments, such as intensive care units, emergency settings, and battlefield environments.

The Importance of State and Context in Safe Interoperable Medical Systems.

This paper describes why "device state" and "patient context" information are necessary components of device models for safe interoperability. This paper includes a discussion of the importance of describing the roles of devices with respect to interactions (including human user workflows involving devices, and device to device communication) within a system, particularly those intended for use at the point-of-care, and how this role information is communicated. In addition, it describes the importance of clinical scenarios in creating device models for interoperable devices.

The Need to Apply Medical Device Informatics in Developing Standards for Safe Interoperable Medical Systems.

Medical device and health information technology systems are increasingly interdependent with users demanding increased interoperability. Related safety standards must be developed taking into account these systems' perspective. In this article, we describe the current development of medical device standards and the need for these standards to address medical device informatics.

Capturing Essential Information to Achieve Safe Interoperability.

In this article, we describe the role of "clinical scenario" information to assure the safety of interoperable systems, as well as the system's ability to deliver the requisite clinical functionality to improve clinical care. Described are methods and rationale for capturing the clinical needs, workflow, hazards, and device interactions in the clinical environment. Key user (clinician and clinical engineer) needs and system requirements can be derived from this information, therefore, improving the communication from clinicians to medical device and information technology system developers.

Optical-thermal characterization of cutaneous transilluminators.

In recent years, there has been an increase in the popularity of light-emitting diode (LED)-based, battery-powered transilluminators (BPTs) for facilitating transdermal vascular access in adults and neonates. BPTs are believed to have lower potential for inducing skin burns than prior devices based on high-power broadband lamps; however, the optical and thermal outputs of BPTs are not well documented and safety limits for these devices are not well established. In this study, we characterize and assess the optical and thermal outputs of six BPTs that incorporate red, orange and white LEDs.

Effective standards and regulatory tools for respiratory gas monitors and pulse oximeters: the role of the engineer and clinician.

Developing safe and effective medical devices involves understanding the hazardous situations that can arise in clinical practice and implementing appropriate risk control measures. The hazardous situations may have their roots in the design or in the use of the device. Risk control measures may be engineering or clinically based.

Development of a standardized method for motion testing in pulse oximeters.

Background: Pulse oximeter performance in the presence of motion varies among devices and manufacturers because of variations in hardware, software, testing, and calibration. Compounding these differences is a lack of uniform characterization of motion, and the consequential effects of motion upon the wide range of normal and abnormal human physiology. Traditional motion testing attempts to standardize motion into a reproducible form by using a mechanical jig to produce passive motion of a known amplitude and frequency.

Fetal pulse oximetry and cesarean delivery.

Background: Knowledge of fetal oxygen saturation, as an adjunct to electronic fetal monitoring, may be associated with a significant change in the rate of cesarean deliveries or the infant's condition at birth.

Methods: We randomly assigned 5341 nulliparous women who were at term and in early labor to either "open" or "masked" fetal pulse oximetry. In the open group, fetal oxygen saturation values were displayed to the clinician.

Designing a pulse oximeter safety standard.

The development of a safety standard is a time-consuming and complex task. Many factors influence the stringency of the requirements, including history with the products and test methods, safety records, and the intended use of the standard and device. Four primary issues are used to illustrate the complexity of developing a safety standard for today's complicated software-controlled pulse oximeters: Can a patient simulator be used to assess performance? What is meant by motion artifact resistance? What is a safe surface temperature limit for the probe? What default low SpO2 limit should be required? Under ASTM's new standards development paradigm, ASTM may achieve consensus on the 2001 draft of ASTM F1415 but not publish it, electing instead to submit the standard to ISO for consideration as the internationally harmonized pulse oximeter safety standard.