Chris Petersen

• PhD
• Fellow at ESS Technology Inc.

Many aspects of modern medicine, including the administration of anesthetic agents during general surgery, remain unautomated and reliant on the vigilance of the attending clinicians. In other fields where failures can have catastrophic consequences, such as the aviation and nuclear power industry, automated control regimens have been adopted to re...

A new push-based mechanism of information exchange between medical devices using the MQ Telemetry Transport (MQTT) protocol for the Internet of Things (IoT) is presented. The proposed implementation allows any medical device to become interoperable without knowledge of the existence of other devices, and provides a simple, scalable solution to the...

Infectious diseases such as pneumonia take the lives of millions of children in low- and middle-income countries every year. Many of these deaths could be prevented with the availability of robust and low-cost diagnostic tools using integrated sensor technology. Pulse oximetry in particular, offers a unique non-invasive and specific test for an inc...

A modular framework for the development of medical applications that promotes deterministic, robust and correct code is presented. The system is based on the portable Gambit Scheme program-ming language and provides a flexible cross-platform environment for developing graphical applications on mobile devices as well as medical instrumentation inter...

Introduction of the EEG simulation and replay plugin of the MapleQuest EEGstudio free open-source application, https://eegstudio.maplequestlabs.com , with demonstrated replay to both the BIS (Covidien, MA) and SedLine (Masimo, CA) pEEG monitors.

Introduction and demonstration of the EEG sonification plugin to the free open source MapleQuest EEGstudio application, https://eegstudio.maplequestlabs.com

Background: The WHO-WFSA International Standards for a Safe Practice of Anesthesia describe delivery systems for volatile anesthetics and infusion pumps as “suggested” equipment to deliver safe anesthesia. However, delivering total intravenous anesthesia using a battery-powered syringe pump may be more robust in remote settings, easier to transport...

Current commercial depth-of-hypnosis anesthesia monitors report proprietary depth-of-hypnosis indices that purportedly represent how deeply anesthetized the patients are, based on encephalography (EEG) acquired intraoperatively. However, depth-of-hypnosis indices can be influenced by many factors such as medications (i.e. ketamine) and external int...

A self-clocking (or self-oscillating) modulator in signal processing, similar to a ΣΔ modulator, with particular application in the design of neural networks based on such modulators is described. A system of multiple self-clocking modulators and supporting structures may be configured to perform a calculation similar to that of an analog computer,...

A multiport memory in which one of the ports is analog rather than digital is described. In one embodiment, the analog port functions as a read-only port and the digital port functions as a write only port. This allows the data in the core memory to be applied to an analog signal, while retaining a digital port having access to the core memory for...

Ketamine may affect the reliability of electroencephalographic (EEG) depth-of-hypnosis indices as it affects power in high-frequency EEG components. The purpose of this study was to compare the effects of ketamine on three commonly-used depth-of-hypnosis indices by extending our EEG simulator to allow replay of previously-recorded EEG. Secondary an...

A system and method for passively balancing electroacoustic transducers so that sounds other than the transducer's output can be detected. A transducer producing audio output based upon an input audio signal can operate in reverse to produce a signal in response to the impact of external sound upon the transducer from another source. This "reverse"...

A framework using semidefinite programming is proposed to enable the design of sigma delta modulator loop filters at the transfer function level. Both continuous-time and discrete-time, low-pass and band-pass designs are supported. For performance, we use the recently popularized Generalized Kalman–Yakubovič–Popov (GKYP) lemma to place constraints...

Background: Deep diaphragmatic breathing, also called belly breathing, is a popular behavioral intervention that helps children cope with anxiety, stress, and their experience of pain. Combining physiological monitoring with accessible mobile technology can motivate children to comply with this intervention through biofeedback and gaming. These inn...

Described herein is an apparatus for the recovery of asynchronous data into a fixed clock domain. A phase-locked loop (PLL) of the known art is replaced by a modified quadrature resolver, and the output from the resolver re-creates the selected frequency component of the input asynchronous data. The zero-crossings of this re-created data clock are...

An improved system and method for quickly calculating Fourier transforms without multiplication is disclosed. A combinatorial unit circuit that contains only adders and scaling elements is used to calculate each sine wave value that is summed to create the Fourier transform. A real-time Fourier transform (RTFT) can be implemented using only a numbe...

BACKGROUND Deep diaphragmatic breathing, also called belly breathing, is a popular behavioral intervention that helps children cope with anxiety, stress, and their experience of pain. Combining physiological monitoring with accessible mobile technology can motivate children to comply with this intervention through biofeedback and gaming. These inno...

An improved system and method for reducing the ambient noise experienced by a user listening to an earpiece without the use of a microphone is disclosed. An “ambient noise signal” created by the sound pressure wave of the ambient noise acting on the earpiece transducer is obtained. In some embodiments, the ambient noise signal is inverted and fed b...

Background: In the perioperative environment, a multidisciplinary clinical team continually observes and evaluates patient information. However, data availability may be restricted to certain locations, cognitive workload may be high, and team communication may be constrained by availability and priorities. We developed the remote Portable Operatin...

BACKGROUND In the perioperative environment, a multidisciplinary clinical team continually observes and evaluates patient information. Data availability may be restricted to certain locations, cognitive workload may be high, and team communication constrained by availability and priorities. We developed the remote Portable Operating Room Tracker ap...

Today almost 6 billion people around the world live in countries where access to adequate medical care resources and facilities is limited. Portable optical technologies can potentially improve health care delivery in emerging countries. Medical optical devices can non-invasively determine the composition of tissue and their function, as well as be...

Background: Conventional pulse oximetry uses light absorption to detect volumetric changes in arterial blood over time, captured in the photoplethysmogram (PPG) [1]. Complementary data, from a change in blood pressure, will allow for the exploration of the pressure-volume relationships in the cardiac cycle. We previously reported how a brass disk w...

ntroduction: Globally, one of the biggest health inequalities is the lack of access to essential surgical services in low resource settings [1]. Safe delivery of anesthesia is crucial to address the need for increased surgical services. Intravenous administration of agents such as ketamine requires less complicated equipment (i.e. syringe pumps) th...

Background: Processed electroencephalogram (EEG) monitors provide clinical information by deriving a single depth-of-hypnosis (DoH) index from a complex EEG signal comprising a multitude of frequency components. The reliability of DoH indices can be influenced by many factors, including the unanticipated EEG effects of co-administered drugs. Ketami...

Background: Closed-loop control of anesthesia involves continual adjustment of drug infusion rates according to measured clinical effect. The NeuroSENSE monitor provides an electroencephalographic measure of depth of hypnosis (wavelet-based anesthetic value for central nervous system monitoring [WAVCNS]). It has previously been used as feedback fo...

Obstructive sleep apnea (OSA), characterized by cessations of breathing during sleep due to upper airway collapse, can affect the healthy growth and development of children. The gold standard for OSA diagnosis, polysomnography (PSG), is expensive and resource intensive, resulting in long waiting lists to perform a PSG. Previously, we investigated t...

Proof of the Stone - von Neumann theorem

Background: Recent research and advances in the automation of anesthesia are driving the need to better understand electroencephalogram (EEG)-based anesthesia end points and to test the performance of anesthesia monitors. This effort is currently limited by the need to collect raw EEG data directly from patients. Methods: A procedural method to...

A method for contactless detection of the lateral electrical transport properties of semiconductor surfaces and thin films is presented. Small changes in the electrical response of a capacitive transmission line are used to extract information about the local sheet resistance at the sample surface. Measurements on undoped GaAs demonstrate excellent...

A low power digital device for electrical impedance measurements has been developed. It is intended for embedded high precision sensor interface applications, but will also operate as a general purpose phase sensitive detector. It integrates an automatic least mean square (LMS) AC bridge with a digital dual phase lock-in amplifier, and is capable o...

Background:Commercially available Depth of Hypnosis (DoH) monitors are based on the processing of electroencephalography (EEG) data. Each manufacturer uses different signal processing algorithms, and for most monitors the details of implementation are not fully disclosed. Little is known about how these DoH indices compare with respect to bias and...

Background: Commonly used electroencephalogram (EEG) based anesthesia monitors rely on EEG measurements to determine a Depth of Hypnosis (DoH) index, a dimensionless number between 100 (awake) and 0 (comatose). The algorithms used in these monitors differ greatly and it is possible that the same EEG episodes can lead to quite different DoH values,...

Background: Trusted timestamps [1] are digital markers that can be used to prove the existence of data before a specific time and preventing the owner from modifying the data at a later time without invalidating the timestamp. Trusted timestamps are issued by a third party, typically a certificate authority. Their integrity is based on the applicat...

Background: Pulse oximetry is an important monitor in anesthesia , as it provides an early indicator of hypoxemia. Pulse oximetry is also being increasing used in other monitoring and screening applications. . Many new devices are coming to market, and the challenges of calibration and testing are are a significant barrier to implementation. Regula...

Individuals with sleep disordered breathing (SDB) can experience changes in automatic cardiac regulation as a result of frequent sleep fragmentation and disturbance in normal respiration and oxygenation that accompany most apnea/hypopnea events. In adults, these changes are reflected in enhanced sympathetic and reduced parasympathetic activity. In...

The University of British Columbia's Pediatric Anesthesia Research Team (PART) has developed mobile applications for data collection and analysis using the REDCap API. It is being used for 12 clinical studies in 9 countries with 100,000 subjects with objectives of a) Creating predictive risk models for pneumonia, sepsis, and pre-eclampsia in low an...

The photoplethysmogram (PPG) obtained from pulse oximetry shows the local changes of blood volume in tissues. Respiration induces variation in the PPG baseline due to the variation in venous blood return during each breathing cycle. We have proposed an algorithm based on the synchrosqueezing transform (SST) to estimate instantaneous respiratory rat...

and reducing overall drug volumes. However, the development of such systems carries significant risk, and particularly requires extensive testing of all devices used for closed-loop feedback. This includes the EEG-based Depth of Hypnosis (DoH) measure. Objectives: To build a system that simulates EEG-based DoH feedback dynamics, with the purpose of...

Virtual shunt describes the overall loss of O2 content between the alveolar gas and arterial blood. Clinicians indirectly estimate the magnitude of the virtual shunt by monitoring peripheral blood oxygen saturation (SpO2) using non-invasive pulse oximetry. An inherent limitation of this method is the variable precision of pulse oximeters and the no...

Background: Clinical environments such as intensive care units, operating rooms, and increasingly general wards, are full of technically advanced monitoring (and therapy) devices. Unfortunately, and to the detriment of patient safety, many of these devices are unable to communicate with one another because of vendor incompatibilities and closed com...

The development of mobile applications for the diagnosis and management of pregnant women with pre-eclampsia is described. These applications are designed for use by community-based health care providers (c-HCPs) in health facilities and during home visits to collect symptoms and perform clinical measurements (including pulse oximeter readings). Th...

Introduction: Closed-loop controlled anesthesia continually adjusts drug infusion rates using depth of hypnosis feedback. This method has been shown to effectively control anesthetic drug administration during induction and maintenance of anesthesia [1]. We previously speculated [2] that a higher remifentanil effect site concentration [3] (CeRemi)...

Introduction: Feasibility of closed-loop control of propofol anesthesia with a simple, robustly tuned Proportional-Integral-Derivative (PID) controller has been shown in adults1 and children2. Interpatient variability was taken into account in the design of these robust controllers, resulting in a system expected to provide adequate control of anes...

The fluctuation of heartbeat intervals is irregular and erratic in healthy young individuals. Sleep disordered breathing (SDB) influences the fluctuation of heart rate. In this study, we investigated the effects of SDB on heart rate fluctuations by analyzing the short- and long-range correlation of photoplethysmogram pulse to pulse intervals (PPIs)...

Introduction: Closed-loop control of anesthesia involves automated administration of anesthetic agents, according to feedback obtained from a measure of clinical effect, such as a processed EEG signal [1]. One potential benefit of closed-loop control is improved hemodynamic stability [2]. The purpose of the present study is to develop a robust cont...

This paper describes the design of a robust proportional-integral derivative (PID) controller for propofol infusion in children and presents the results of clinical evaluation of this closed-loop system during endoscopic investigations in children age 6–17. The controller design is based on a set of models that describes the interpatient variabilit...

Introduction: Low-cost smartphone-based medical devices, e.g. mobile pulse oximeters, hold great promise as diagnostic tools in low- and middle-income countries [1]. The artifact rejection capability of mobile oximeters is a key aspect of their performance, as their main users are likely inexperienced healthcare workers unfamiliar with plethysmogra...

Background: Closed loop control of total intravenous anesthesia involves the continuous adjustment of drug infusion rates according to measured clinical effect [1]. Depth of Hypnosis (DoH) measures, such as the WAVCNS index [2], can provide feedback suitable for closed loop control. A study that will culminate in the design of a robustly tuned cont...

Background: telePORT, the remote Portable Operating Room Tracker, was developed by the Pediatric Anesthesia Research Team at BC Children’s Hospital to improve information exchange, and simplify communication between anesthesia team members1. It combines a real-time feed of waveforms and vital signs from the operating rooms with messaging and paging...

BACKGROUND: Recent efforts to reduce hardware expenses and thereby increase global availability of pulse oximetry have led to the emergence of mobile phone based devices [1]. These new oximeters rely on consumer electronics to deliver clinical information. Systematic verification of their performance is needed; in particular with respect to low per...

INTRODUCTION: Closed-loop controlled anesthesia, which continually adjusts drug infusion rates using depth of hypnosis feedback, has been shown to effectively control drug administration during induction and maintenance of anesthesia1. However, little is known about its effectiveness in minimizing physiologic responses to specific noxious stimuli....

A modular framework for the development of medical applications that promotes deterministic, robust and correct code is presented. The system is based on the portable Gambit Scheme programming language and provides a flexible cross-platform environment for developing graphical applications on mobile devices as well as medical instrumentation interf...

An ultra-low-cost pulse oximeter is presented that interfaces a conventional clinical finger sensor with a mobile phone through the headset jack audio interface. All signal processing is performed using the audio subsystem of the phone. In a preliminary volunteer study in a hypoxia chamber, we compared the oxygen saturation obtained with the audio...

Introduction: iControl v3 is a system for closed-loop control of propofol and remifentanil anesthesia in adults. It includes a touch-screen user interface, the NeuroSENSE EEG monitor, two Alaris infusion devices and speakers for audible alarms. Previous versions of the system have been clinically evaluated [1]. The system has been designed for inve...

During closed-loop control, a drug infusion is continually adjusted according to a measure of clinical effect (e.g., an electroencephalographic depth of hypnosis (DoH) index). Inconsistency in population-derived pediatric pharmacokinetic/pharmacodynamic models and the large interpatient variability observed in children suggest a role for closed-loo...

We have previously designed a pulse oximeter connected to a mobile phone, called the Phone Oximeter, for clinical decision making based on photoplethysmography. The limited battery and computational resources demand efficient and low-power algorithms for the Phone Oximeter to be effective in resource-poor and remote areas. We present two new algori...

To increase the use of pulse oximetry by capitalise on the wide availability of mobile phones, we have designed, developed and evaluated a prototype pulse oximeter interfaced to a mobile phone. Usability of this Phone Oximeter was tested as part of a rapid prototyping process. Phase 1 of the study (20 subjects) was performed in Canada. Users perfor...

To address the need for clinical monitoring devices in low and middle income countries we are leveraging the ubiquitous mobile phone to deliver low cost pulse oximetry by interfacing a standard clinical finger sensor directly to the headset jack. Previous calibration against a Nonin oximeter showed good preliminary agreement. In the present paper w...

The first study with a PID controller based automatic drug delivery system for propofol anesthesia in children is presented. It is shown that a robustly tuned PID controller is capable of delivering safe and adequate anesthesia. The design process of the control system is reviewed. Results are discussed and compared to those of two previous studies...

The variations induced by mechanical ventilation in the arterial pulse pressure and pulse oximeter plethysmograph waveforms have been shown to correlate closely and be effective in adults as markers of volume responsiveness. The aims of our study were to investigate: (1) the feasibility of recording plethysmograph indices; and (2) the relationship...

Conventional methods for peak detection involve complicated filter banks and/or frequency domain analysis. We present a much simpler and computationally efficient method using an iterative function fractal. The simple nature of such functions and their ability to operate on complex unfiltered data could potentially provide a useful trade-off betwee...

Pulse oximetry is critically important in anesthesia as an early indicator of hypoxemia. Conventional pulse oximetry is widely used in the developed world, but many developing regions do not have access to this life saving technology due to lack of infrastructure (such as electricity) and the prohibitive cost of devices. The use of the ubiquitous c...

Background: Capturing vital signs for research activities, such as measuring heart rate variability [1], obtaining data to design, or testing novel medical displays [2] or alarm algorithms [3] is traditionally done by directly connecting a data capture device to the patient monitor. A novel method and device that allow researchers to retrospectivel...

Mobile phones offer huge potential as platforms for clinical decision making in resource-poor and remote areas. We present methods for the development of a human-centered interface for anesthesia monitoring that is targeted to remote operating rooms in developing countries. The Phone Oximeter is compatible with major PC and mobile phone operating s...

Mobile phones offer huge potential as platforms for clinical decision making in resource-poor and remote areas. We present methods for the development of a human-centered interface for anesthesia monitoring that is targeted to remote operating rooms in developing countries. The Phone Oximeter is compatible with major PC and mobile phone operating s...