Papers by J. Mark Ansermino
Heart Rate Variability (HRV), the variation of time in-tervals between heartbeats, is an indirect... more Heart Rate Variability (HRV), the variation of time in-tervals between heartbeats, is an indirect and noninvasive method for monitoring the autonomic activities that con-trol heart rate. Traditionally, HRV is measured from the electrocardiogram. In this study, we estimated HRV from the photoplethysmogram (PPG), called pulse rate vari-ability (PRV) and investigated the effects of sleep disor-dered breathing (SDB) and different sleep stages on it. We recorded the overnight PPG signals from 160 children us-ing the Phone Oximeter, an oximeter connected to a mo-bile phone, simultaneously with the other signals within standard polysomnography. We analysed the mean pulse-to-pulse intervals, the power of low (LF) and high fre-quency (HF) bands of PRV and also the ratio of LF power to HF power (LF/HF) in the children with SDB during non-rapid eye movement (non-REM) and rapid eye move-ment (REM) sleep. The results showed that the normal-ized LF increased in children with SDB (from 0.26±0.12 t...
Background: Recently, several control systems for closed-loop anesthesia have been demonstrated b... more Background: Recently, several control systems for closed-loop anesthesia have been demonstrated both in simulation and clinical studies. A set of performance measures, proposed by Varvel et al. , have constituted the standard means of comparing systems. Because Varvel measures were developed for Target-Controlled Infusion (TCI), their relevance to closed-loop control is debatable. It is also pertinent to use different measures of performance during the induction, maintenance, and emergence phase of anesthesia. Varvel measures currently report for maintenance phase only.
Cyberpsychology, behavior and social networking, Jan 16, 2016
Physical inactivity is increasing among children globally and has been directly linked to the gro... more Physical inactivity is increasing among children globally and has been directly linked to the growing problems of overweight and obesity. We aim to assess the impact of a new mobile exergame, MobileKids Monster Manor (MKMM), in a school-based setting. MKMM, developed with input from youth to enhance physical activity, is wirelessly connected to an accelerometer-based activity monitor. Forty-two healthy students (11.3 ± 1.2 years old and 0.28 ± 1.29 body-mass index [BMI] z-score) participated in a randomized 4-week crossover study to evaluate the game intervention. The two study arms consisted of week-long baseline, game intervention/control, washout, and control/game intervention phases. All participants were required to wear an activity monitor at all times to record steps and active minutes for the study duration. MKMM was used during each arm's respective intervention week, during which children were asked to play the game at their convenience. When children were exposed to t...
We introduce a method based on empirical mode decomposition (EMD) to estimate both respiratory ra... more We introduce a method based on empirical mode decomposition (EMD) to estimate both respiratory rate (RR) and heart rate (HR) from the photoplethysmographic (PPG) signal obtained from pulse oximetry. The spectral analysis of the EMD applied to the PPG signal was used to extract two signals, the respiratory and cardiac modulations respectively. On these modulated signals, an additional spectral analysis was applied to calculate their frequency peaks. To improve spectral resolution a parametric power spectral analysis based on autoregressive modelling was selected. The frequency peak found in the respiratory and cardiac signals reflects RR and HR, respectively. The PPG signals were analysed using a 1-min sliding window with 50% overlap. The RR and HR estimation accuracy was assessed using the unnormalized root mean square (RMS) error. Median errors (quartiles) were calculated to account for the non-normal RMS distribution. The test dataset consisted of 8-min PPG and capnometric signals...
Methods: To develop the PhoneOxR (Figure 1), we used an iterative process of design and informal ... more Methods: To develop the PhoneOxR (Figure 1), we used an iterative process of design and informal testing. PhoneOxR is comprised of: a) The display and recording of the i) plethysmogram and ii) heart rate (HR) and SpO2 trends. b) A Signal Quality Index (SQI) ...
2014 IEEE Healthcare Innovation Conference (HIC), 2014
Pediatric Anesthesia, 2013
Background: During closed-loop control, a drug infusion is continually adjusted according to a me... more Background: 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-loop control in optimizing the administration of intravenous anesthesia. Objective: To clinically evaluate a robustly tuned system for closed-loop control of the induction and maintenance of propofol anesthesia in children undergoing gastrointestinal endoscopy. Methods: One hundred and eight children, aged 6-17, ASA I-II, were enrolled. Prior to induction of anesthesia, NeuroSENSE TM sensors were applied to obtain the WAV CNS DoH index. An intravenous cannula was inserted and lidocaine (0.5 mgÁkg À1 ) administered. Remifentanil was administered as a bolus (0.5 lgÁkg À1 ), followed by continuous infusion (0.03 lgÁkg À1 Ámin À1 ). The propofol infusion was closed-loop controlled throughout induction and maintenance of anesthesia, using WAV CNS as feedback.
The effect of intravenous anesthetic drugs is traditionally modeled using pharmacokinetic (PK) an... more The effect of intravenous anesthetic drugs is traditionally modeled using pharmacokinetic (PK) and pharmacodynamic (PD) models. However, a physiological meaningful set of PD parameters is not required for controller design and is not essential for prediction of closed-loop performance provided that the experimental conditions for identification and closed-loop control are similar 1 . In this study, a set of models describing the effect of propofol in children is identified specifically for the design of a robust linear closed-loop controller.
Mobile phones offer huge potential as platforms for clinical decision making in resource-poor and... more 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 systems and is optimized for small phone screens. It displays vital physiological parameters in the corresponding clinical colours. Combined with an easily identifiable icon, this guarantees that accessibility is language-independent. To evaluate the acceptance and usability of the initial prototype of the Phone Oximeter, the Think Aloud process while completing a specific Task List, followed by the Mobile Phone Usability Questionnaire (MPUQ) were tested on 20 subjects with varying medical and mobile phone experience. The acceptance rate of 81.9 % from the MPUQ questionnaire clearly demonstrates the usability of the Phone Oximeter. The incorporation of the most relevant errors and complaints into the design of the next iteration of the Phone Oximeter prototype enhanced its capabilities further.
Games for Health Journal, 2015
Objective: The majority of children in North America are not meeting current physical activity gu... more Objective: The majority of children in North America are not meeting current physical activity guidelines. The purpose of this study was to evaluate the impact of a mobile phone game (''MobileKids Monster Manor'') as a tool to promote voluntary physical activity among children. Materials and Methods: The game integrates data from an accelerometer-based activity monitor (Tractivity Ò ; Kineteks Corp., Vancouver, BC, Canada) wirelessly connected to a phone and was developed with the involvement of a team of young advisors (KidsCan Initiative: Involving Youth as Ambassadors for Research). Fifty-four children 8-13 years old completed a week of baseline data collection by wearing an accelerometer but receiving no feedback about their activity levels. The 54 children were then sequentially assigned to two groups: One group played ''MobileKids Monster Manor,'' and the other received daily activity feedback (steps and active minutes) via an online program. The physical activity (baseline and intervention weeks) was measured using the activity monitor and compared using two-way repeated-measures analysis of variance (intervention · time). Results: Forty-seven children with a body mass index (BMI) z-score of 0.35 -1.18 successfully completed the study. Significant (P = 0.01) increases in physical activity were observed during the intervention week in both the game and feedback groups (1191 and 796 steps/day, respectively). In the game group, greater physical activity was demonstrated in children with higher BMI z-score, showing 964 steps/day more per BMI z-score unit (P = 0.03; 95 percent confidence interval of 98 to 1829). Conclusions: Further investigation is required to confirm that our game design promotes physical activity.
Background: Pediatric pharmacokinetic (PK) models [1,2] used for target-controlled infusion (TCI)... more Background: Pediatric pharmacokinetic (PK) models [1,2] used for target-controlled infusion (TCI) of propofol, frequently employ an effect site equilibration rate constant, k e0 , that is derived from adult studies. Pharmacodynamic (PD) differences between adults and children, however, dictate that it is unacceptable to extrapolate available adult PD data to pediatric models. Although pediatric PK data on intravenous anesthetics are available, the availability of pediatric PD data is relatively limited. Previous pediatric PD studies investigating propofol administration in children have described PD models based on the Bispectral Index (BIS) [3] and auditory evoked potential (AEP) monitors. In this work we have identified a pediatric PD model of propofol in children, based on the State Entropy [4] (SE) (M-entropy® module; GE Healthcare, Helsinki, Finland) and respiratory responses as clinical end-points.
Anaesthesia, 2013
In this prospective observational study we investigated the changes in cardiac index and mean art... more In this prospective observational study we investigated the changes in cardiac index and mean arterial pressure in children when positioned prone for scoliosis correction surgery. Thirty children (ASA 1-2, aged 13-18 years) undergoing primary, idiopathic scoliosis repair were recruited. The cardiac index and mean arterial blood pressure (median (IQR [range])) were 2.7 (2.3-3.1 [1.4-3.7]) l.min(-1).m(-2) and 73 (66-80 [54-91]) mmHg, respectively, at baseline; 2.9 (2.5-3.2 [1.7-4.4]) l.min(-1).m(-2) and 73 (63-81 [51-96]) mmHg following a 5-ml.kg(-1) fluid bolus; and 2.5 (2.2-2.7 [1.4-4.8]) l.min(-1).m(-2) and 69 (62-73 [46-85]) mmHg immediately after turning prone. Turning prone resulted in a median reduction in cardiac index of 0.5 l.min(-1).m(-2) (95% CI 0.3-0.7 l.min(-1).m(-2), p=0.001), or 18.5%, with a large degree of inter-subject variability (+10.3% to -40.9%). The changes in mean arterial blood pressure were not significant. Strategies to predict, prevent and treat decreases in cardiac index need to be developed.
ABSTRACT BACKGROUND: For a posterior surgical approach to scoliosis repair, patients are placed i... more ABSTRACT BACKGROUND: For a posterior surgical approach to scoliosis repair, patients are placed in the prone position. This can be associated with immediate significant decreases in blood pressure [1]. Changes in cardiac index when turning adult patients to the prone position for spinal surgery are well documented [2, 3], whilst pilot data are available in children [4]. Targeted preload optimization, with the goal of achieving a stroke volume variation of less than 14%, was reported to be effective in preventing significant cardiac index decreases induced by positioning adults prone [5]. We investigated the ability of using stroke volume variability to predict cardiac index changes in children during prone positioning in an observational study. METHODS: Following REB approval and written informed parental consent, with subject assent where appropriate, 29 ASA I-II patients, aged 12-18 years undergoing primary scoliosis repair, were recruited into this observational study. A standardized total intravenous anesthetic technique with propofol and sufentanil was used. In addition to routine monitoring, including an arterial line, an age appropriate transesophageal doppler probe (CardioQ DP240 or CardioQ KDP72, Deltex Medical Limited, West Sussex, UK) was positioned post induction of anesthesia [6, 7]. Cardiac index (CI) and stroke volume (SV) were recorded for a minute at three time points: post induction of anesthesia, following a 5ml/kg crystalloid fluid bolus, and immediately after the patient was turned prone. Data were plotted and analyzed using MATLAB (The Mathworks Inc, Natick, MA). RESULTS: Stroke volume variability (SVV) after a 5ml/kg crystalloid fluid bolus and immediately prior to positioning the patient prone, had a median of 12.7 % (range 5.3 to 36.9%), with 17/29 (59%) having a SVV<14%. Prone positioning caused a median decrease in CI of 19.3% (range -10.3 to 40.9 %) and produced a median SVV of 18.0% (range 4.1 to 42.8 %). Both changes with prone positioning are statistically significant (p=7.78x10-6, χ2=19.99 for SVV and p=1.2x10-3, χ2=10.51 for CI respectively). The CI drop in patients with SVV <14% did not significantly differ from patients with higher SVV (p=0.29, χ2=1.08). Figure 1 shows the temporal relationships of CI and SVV for all 29 patients. There was no correlation between SVV and the change in cardiac index (r2=0.047, see scatterplot in Figure 2). CONCLUSIONS: Prone positioning produced significant drop in CI and increase in SVV. SVV before prone positioning does not predict the magnitude of CI change when positioning children prone, and minor fluid loading (5cc/kg) does not prevent prominent drops in CI, even when it reduces SVV to less than 14% before prone positioning. Future work is needed to identify predictors of CI change with prone positioning as well as strategies to mitigate the decrease in CI to improve safety of positioning children prone. REFERENCES: [1] Can J Anaesth 2011;58:451-5; [2] Spine 2006;31:1388-93; [3] Acta Anaesthesiol Scand 1991;35:741-4; [4] Proc CAS Annual Meeting 2012; #1341754; [5] Anaesthesia 2012; doi: 10.1111/j.1365-2044.2012.07116.x; [6] Intensive Care Med 2001;27:201-5; [7] J Clin Monit Comput 2008;22:299-307
Alerting systems used by current physiological monitors are designed to detect changes in the lev... more Alerting systems used by current physiological monitors are designed to detect changes in the levels of vital signs, but they tend to be very sensitive to artifacts. This paper proposes a method to detect changes in the direction of trend and generate multilevel alerts according to the statistical significance of the detection. One-point-ahead signal predictions are calculated by averaging the historical data with the weights decreasing in the past. The two-sided cumulative sums (Cusum) of the prediction errors are tested against multiple thresholds to detect change points with two levels of certainty. The temporal shapes of the detected changes are analyzed using heuristics to determine whether to trigger an alert. The method was tested offline using 20 cases collected during surgery at a local hospital. The detection results were evaluated by two experienced anesthesiologists. The direction of trend was correctly detected in 90.2% of the annotated changes for end-tidal carbon dioxide, 89.4% for expiratory minute volume, 91.8% for peak airway pressure, and 95.4% for noninvasive blood pressure. The certainty levels of the true-positive alerts estimated by the algorithm have a high ratio of agreement with the anesthesiologists' evaluations.
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010
This paper presents an empirical model of end-tidal CO(2) (P(ET)CO(2)) response to minute ventila... more This paper presents an empirical model of end-tidal CO(2) (P(ET)CO(2)) response to minute ventilation (MV) for use in the closed-loop control of artificial respiration. An affine model structure consisting of a linear dynamic system followed by an affine transform is presented. It is proposed that this derives a low-order, high-fidelity representation of the respiratory process that can describe the positive and inversely proportional relationship between P(ET)CO(2) and MV. The efficacy of the model is evaluated using experimental respiratory data from 18 human subjects. The model performed well with a root-mean-squared error (RMSE) of 0.22+/-0.15mmHg and a coefficient of determination (r(2)) of 0.81+/-0.18 (mean+/-SD) when a 2(nd)-order rational transfer function was used as the linear component of the model. The physiologic implication of the model is analyzed by comparison with a traditional compartment model that is widely used in pharmacological modeling.
Uploads
Papers by J. Mark Ansermino