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Esophagogastroduodenoscopy procedures are typically performed under conscious sedation. Drug-induced respiratory depression is a major cause of serious adverse effects during sedation. Capnographic monitoring of respiratory activity improves patient safety during procedural sedation. This bench study compares the performance of the nasal cannulas and oral bite blocks used to monitor exhaled CO2 during sedation. We used a spontaneously breathing mechanical lung to evaluated four CO2 sampling nasal cannulas and three CO2 sampling bite blocks. We placed pneumatic resistors in the mouth of the manikin to simulate different levels of mouth opening. We compared CO2 measurements taken from the sampling device to CO2 measurements taken directly from the trachea. The end tidal CO2 concentration (PETCO2) measured through the bite blocks and nasal cannulas was always lower than the corresponding PETCO2 measured at the trachea. The difference became larger as the amount of oxygen delivered through the devices increased. The difference was larger during normal ventilation than during hypoventilation. The difference became larger as the amount of oral breathing increased. The two nasal cannulas without oral cups failed to provide sufficient CO2 for breath detection when the mouth was fully open and oxygen was delivered at 10 L/min. Our simulation found that respiratory rate can be accurately monitored during the procedure using a CO2 sampling bite block or a nasal cannula with oral cup. The accuracy of PETCO2 measurements depends on the device used, the amount of supplement oxygen, the amount of oral breathing and the patient's minute ventilation.

A gas chromatographic method is described for the direct quantitative determination of the partial pressure of halothane (or isoflurane) in blood as well as the blood-gas partition coefficient. A head space technique and a flame ionization detector were used. Standard blood was obtained by equilibrating patients' blood with known gas concentrations in a tonometer. Using an infra-red analyser to measure the halothane gas concentration in the tonometer and within the anaesthetic system allowed for the direct comparison of the partial pressure in blood to the partial pressure in the inspired gas. Technical problems associated with this procedure, and with comparable methods, are discussed.

With the use of previously published data, new sevoflurane-remifentanil interaction models of various degrees of sedation were created and adapted to desflurane-fentanyl by using minimal alveolar concentration and opioid equivalencies. These models were used to predict return of responsiveness in patients undergoing scoliosis surgery during a wake-up test. Our hypothesis was that one of the interaction models would accurately predict return of responsiveness during a wake-up test.Three new sevoflurane-remifentanil interaction models were constructed from previous observations in volunteers by using the Observer's Assessment of Alertness/Sedation (OAA/S) scores. These models included predictions of OAA/S2 (unresponsive), OAA/S3, and OAA/S4 (sedation). Twenty-three patients scheduled for scoliosis surgery received a fentanyl-desflurane anesthetic. With the use of published pharmacokinetic models, predictions of fentanyl and desflurane effect-site concentrations were recorded throughout surgery and converted to equivalent remifentanil and sevoflurane effect-site concentrations. Data were recorded every 10 seconds from the time when desflurane was turned off until 10 minutes after the patients responded by moving their hands and toes. Model predictions were compared with observations with graphical and temporal analyses.The average difference between the time when a patient first responded and the time when the model predicted that there was a 50% probability that the patient would respond were -2.6 ± 3.6 minutes (mean ± SD) for the OAA/S2 model, 2.8 ± 5.6 minutes for the OAA/S3 model and 52.6 ± 32.3 minutes for the OAA/S4 model.The results confirmed our study hypothesis; a sevoflurane-remifentanil interaction model built from observations in volunteers and adapted to desflurane and fentanyl accurately predicted patient response during a wake-up test. These results were similar to our previous study comparing model predictions and patient observations after a sevoflurane-remifentanil/fentanyl anesthetic. The OAA/S2 model most accurately predicted the time patients would respond by moving their fingers and toes. This model may help anesthesiologists better predict return of responsiveness during a wake-up test in patients undergoing spine surgery.

Sedative anesthetic procedures outside the operating room may depend on cylinders as oxygen source. Cylinders have limited storage capacity and a low oxygen flow rate improves the durability. We conducted the bench study to evaluate the fraction of inspired oxygen (FiO2) in different oxygen entrainment devices under low oxygen flow rate. The purpose of the bench study was to provide information to choose appropriate oxygen entrainment devices in non-operating room sedative anesthetic procedures. We utilized a manikin head-test lung-ventilator model and evaluated eight oxygen entrainment devices, including four nasal cannulas, two oral bite blocks, and two masks. Two different minute volumes that defined as the normal ventilation and the hypoventilation group were evaluated. Three pneuflow resistors were placed in turn in the mouth represented ratio of the nasal/oral breathing. Each condition was sampled 70 times after a 3 min ventilation period. Most devices had few drop in FiO2 according to the increased oral breathing ratio in normal ventilation. Most devices had obvious drop in FiO2 related to the increased oral breathing ratio in hypoventilation. Oxygen reservoir units had little effect for accumulating oxygen in normal ventilation. In the hypoventilation group, oxygen reservoir units helped oxygen retention in local area and maintained a higher oxygen concentration. There were multiple factors lead to different oxygen fraction that we measured, such as different devices, respiratory patterns, and oxygen reservoir units. The result of our bench study provided some information for anesthesiologist to choose appropriate oxygen entrainment devices in various sedative anesthetic procedures.

Background Drug administration errors are frequent and are often associated with the misuse of IV infusion pumps. One source of these errors may be the infusion pump's user interface. Methods We used failure modes-and-effects analyses to identify programming errors and to guide the design of a new syringe pump user interface. We designed the new user interface to clearly show the pump's operating state simultaneously in more than 1 monitoring location. We evaluated anesthesia residents in laboratory and simulated environments on programming accuracy and error detection between the new user interface and the user interface of a commercially available infusion pump. Results With the new user interface, we observed the number of programming errors reduced by 81%, the number of keystrokes per task reduced from 9.2 ± 5.0 to 7.5 ± 5.5 (mean ± SD), the time required per task reduced from 18.1 ± 14.1 seconds to 10.9 ± 9.5 seconds and significantly less perceived workload. Residents detected 38 of 70 (54%) of the events with the new user interface and 37 of 70 (53%) with the existing user interface, despite no experience with the new user interface and extensive experience with the existing interface. Conclusions The number of programming errors and workload were reduced partly because it took less time and fewer keystrokes to program the pump when using the new user interface. Despite minimal training, residents quickly identified preexisting infusion pump problems with the new user interface. Intuitive and easy-to-program infusion pump interfaces may reduce drug administration errors and infusion pump-related adverse events.

Objective Fatal errors can occur in intensive care units (ICUs). Researchers claim that information integration at the bedside may improve nurses' situation awareness (SA) of patients and decrease errors. However, it is unclear which information should be integrated and in what form. Our research uses the theory of SA to analyze the type of tasks, and their associated information gaps. We aimed to provide recommendations for integrated, consolidated information displays to improve nurses' SA. Materials and Methods Systematic observations methods were used to follow 19 ICU nurses for 38 hours in 3 clinical practice settings. Storyboard methods and concept mapping helped to categorize the observed tasks, the associated information needs, and the information gaps of the most frequent tasks by SA level. Consensus and discussion of the research team was used to propose recommendations to improve information displays at the bedside based on information deficits. Results Nurses performed 46 different tasks at a rate of 23.4 tasks per hour. The information needed to perform the most common tasks was often inaccessible, difficult to see at a distance or located on multiple monitoring devices. Current devices at the ICU bedside do not adequately support a nurse's information-gathering activities. Medication management was the most frequent category of tasks. Discussion Information gaps were present at all levels of SA and across most of the tasks. Using a theoretical model to understand information gaps can aid in designing functional requirements. Conclusion Integrated information that enhances nurses' Situation Awareness may decrease errors and improve patient safety in the future.

Preventable adverse events are one of the leading causes of patient mortality in hospitals. Many of these adverse events occur in Intensive Care Units (ICUs) where nurses often work under cognitive, perceptual, and physical overloads. One contributing factor to these overloads is the display of treatment orders, monitoring information, and equipment status on numerous, spatially separated information displays. If these separate displays were combined into a single integrated display at the bedside, the display could potentially reduce nursing workload and improve nurse awareness of the patients' treatment plans and physiological status. We performed a study with three parts. First, we observed ICU nurses at work and found that task-relevant information was often presented in a sub-optimal format, it was unavailable at the point of care and/or it was laborious to retrieve. Second, we designed an integrated information display that presents the information needed by nurses at the patient bedside in a more optimal format. Finally, we evaluated paper-based prototypes of both the integrated display and existing ICU displays with pilot participants. The results for participants in a pilot study showed that nurses using the integrated display could answer questions about the patient's status and treatment significantly faster and more accurately. Integrated displays could potentially reduce adverse events in ICUs and reduce cognitive overloads.

INTRODUCTION: We previously reported models that characterized the synergistic interaction between remifentanil and sevoflurane in blunting responses to verbal and painful stimuli. This preliminary study evaluated the ability of these models to predict a return of responsiveness during emergence from anesthesia and a response to tibial pressure when patients required analgesics in the recovery room. We hypothesized that model predictions would be consistent with observed responses. We also hypothesized that under non-steady-state conditions, accounting for the lag time between sevoflurane effect-site concentration (Ce) and end-tidal (ET) concentration would improve predictions. METHODS: Twenty patients received a sevoflurane, remifentanil, and fentanyl anesthetic. Two model predictions of responsiveness were recorded at emergence: an ET-based and a Ce-based prediction. Similarly, 2 predictions of a response to noxious stimuli were recorded when patients first required analgesics in the recovery room. Model predictions were compared with observations with graphical and temporal analyses. RESULTS: While patients were anesthetized, model predictions indicated a high likelihood that patients would be unresponsive (99%). However, after termination of the anesthetic, models exhibited a wide range of predictions at emergence (1%–97%). Although wide, the Ce-based predictions of responsiveness were better distributed over a percentage ranking of observations than the ET-based predictions. For the ET-based model, 45% of the patients awoke within 2 min of the 50% model predicted probability of unresponsiveness and 65% awoke within 4 min. For the Ce-based model, 45% of the patients awoke within 1 min of the 50% model predicted probability of unresponsiveness and 85% awoke within 3.2 min. Predictions of a response to a painful stimulus in the recovery room were similar for the Ce- and ET-based models. DISCUSSION: Results confirmed, in part, our study hypothesis; accounting for the lag time between Ce and ET sevoflurane concentrations improved model predictions of responsiveness but had no effect on predicting a response to a noxious stimulus in the recovery room. These models may be useful in predicting events of clinical interest but large-scale evaluations with numerous patients are needed to better characterize model performance. (Anesth Analg 2009;X:●●●‐●●●)

Background Part task training (PTT) focuses on dividing complex tasks into components followed by intensive concentrated training on individual components. Variable priority training (VPT) focuses on optimal distribution of attention when performing multiple tasks simultaneously with the goal of flexible allocation of attention. This study explored how principles of PTT and VPT adapted to anesthesia training would improve first-year anesthesiology residents' management of simulated adverse airway and respiratory events. The authors hypothesized that participants with PTT and VPT would perform better than those with standard training. Methods Twenty-two first-year anesthesia residents were randomly divided into two groups and trained over 12 months. The control group received standard didactic and simulation-based training. The experimental group received similar training but with emphasis on PTT and VPT techniques. Participant ability to manage seven adverse airway and respiratory events were assessed before and after the training period. Performance was measured by the number of correct tasks, making a correct diagnosis, assessment of perceived workload, and an assessment of scenario comprehension. Results Participants in both groups exhibited significant improvement in all metrics after a year of training. Participants in the experimental group were able to complete more tasks and answered more comprehension questions correctly. There was no difference in perceived workload or the number of correct diagnoses between groups. Conclusion This study in part confirmed the study hypotheses. The results suggest that VPT and PTT are promising adjuncts to didactic and simulation-based training for management of adverse airway and respiratory events.

Recent work in our laboratory has characterized the synergistic interaction between remifentanil and propofol in volunteers using surrogate and actual measures of sedation and analgesia[1]. In this prior study, a wide range of remifentanil and propofol effect site concentrations were achieved using target controlled infusions. Metrics of sedation (the Observers Assessment of Alertness/Sedation scale – OAA/S scale[2]) and analgesia (response to tetanic stimuli, pressure algometry, and laryngoscopy) were made at numerous remifentanil/propofol effect site concentration pairs with the intent of characterizing the synergistic relationship between these two intravenous anesthetics. From this data, using a response surface approach [3], interaction models were developed to predict the probability of loss of responsiveness and loss of response to tetanic stimuli, pressure algometry, and laryngoscopy. Electrical tetany consisted of applying a small current through electrodes over the posterior tibial nerve until subjects considered the pain intolerable up to 50 mA and pressure algometry consisted of 1 cm diameter piston that applied pressure to the anterior aspect of the mid shaft of the tibia until subjects considered the pain intolerable up to 50 lb-in−2 [4]. As has been reported by other authors [5, 6], results from this analysis revealed significant synergism between remifentanil and propofol for both sedation and analgesia. Specifically, the co-administration of remifentanil with propofol led to a more pronounced sedating effect at lower concentrations of propofol than with propofol alone. Similarly, the co-administration of propofol with remifentanil led to a more pronounced analgesic effect at lower remifentanil concentrations than with remifentanil alone. The aim of this present work is to explore how well these interaction models developed from human subject volunteers would predict pertinent events of anesthetic care in patients undergoing elective surgery. An assessment of loss of responsiveness and the presence or absence of a response to laryngoscopy are easily observed in patients undergoing elective surgery. By contrast, interaction model predictions of a response to electrical tetany and pressure algometry, as surrogates of surgical pain, are more difficult to interpret clinically[1]. Of note, in our prior work, pressure algometry was found to be significantly less stimulating than electrical tetany. For example, the remifentanil effect site concentrations at which 50% of the volunteers did not respond to maximal settings for pressure algometry and electrical tetany were 8.8 and 21.3 ng/mL respectively. Some investigators have suggested that electrical tetany is a surrogate stimulus to skin incision [7]. In this present study, we intended to explore how model predictions of no response to 50 lb-in−2 of pressure algometry and 50 mA of electrical tetany compared to the observed response of selected stimulating events during elective surgery to include skin incision, surgical stimulus 5 minutes after skin incision, at the start of wound closure, at the start of skin closure, and requirement for administration of analgesics in the post anesthesia care unit. One metric of anesthetic behavior that was not characterized by an interaction model in our prior work was a prediction of loss of responsiveness. In our prior work, we used a transition from an OAA/S score of 4 to 3 to represent the onset of sedation. [1] Of equal, or perhaps, even more interest to an anesthetist, is a prediction of the onset and offset of responsiveness during the delivery of an anesthetic. With this in mind, we developed an additional interaction model that characterized the transition from an OAA/S score from 2 to 1. Our hypotheses were that these set of response surface models would predict with high probability (i) loss and return of responsiveness, (ii) the presence or absence of a response to laryngoscopy and tracheal intubation, and (iii) the presence or absence of a no response to skin incision, wound closure, and painful stimuli in the post anesthesia care unit.

Background Hypercapnia with hyperventilation shortens the time between turning off the vaporizer (1 MAC) and when patients open their eyes after isoflurane anesthesia by 62%. Methods In the present study we tested whether a proportional shortening occurs with sevoflurane and desflurane. Results Consistent with a proportional shortening, we found that hypercapnia with hyperventilation decreased recovery times by 52% for sevoflurane and 64% for desflurane (when compared with normal ventilation with normocapnia). Conclusion Concurrent hyperventilation to rapidly remove the anesthetic from the lungs and rebreathing to induce hypercapnia can significantly shorten recovery times and produce the same proportionate decrease for anesthetics that differ in solubility.

Objective: To lay the foundation for a framework of just-in-time support (JITS) for novices dealing with urgent, unfamiliar tasks, and to evaluate a JITS system. Background: More than 350,000 people die annually of cardiac arrest in the United States. In response, automated defibrillators are advocated that, unfortunately, do not provide important respiratory support. This paper presents elements of a framework for a JITS system that instructs a lay responder to follow a treatment protocol for integrating respiratory support with the use of an automatic external defibrillator. Method: We simulated a medical emergency using a high-fidelity patient simulator and asked participants to care for the patient. Results: When using a paper-based NASA treatment protocol, participants made more errors and took longer to stabilize the injured person than when using the JITS system. Conclusion: These findings demonstrate the benefit of a JITS system to instruct novices in unfamiliar tasks. Application: The JITS system has the potential to improve the treatment outcome of victims of cardiac arrest. The JITS framework can be applied to many situations in which novices deal with urgent tasks without expertise available.

Background Opioids are commonly used in conjunction with sedative drugs to provide anesthesia. Previous studies have shown that opioids reduce the clinical requirements of sedatives needed to provide adequate anesthesia. Processed electroencephalographic parameters, such as the Bispectral Index (BIS; Aspect Medical Systems, Newton, MA) and Auditory Evoked Potential Index (AAI; Alaris Medical Systems, San Diego, CA), can be used intraoperatively to assess the depth of sedation. The aim of this study was to characterize how the addition of opioids sufficient to change the clinical level of sedation influenced the BIS and AAI. Methods Twenty-four adult volunteers received a target-controlled infusion of remifentanil (0-15 ng/ml) and inhaled sevoflurane (0-6 vol%) at various target concentration pairs. After reaching pseudo-steady state drug levels, the modified Observer's Assessment of Alertness/Sedation score, BIS, and AAI were measured at each target concentration pair. Response surface pharmacodynamic interaction models were built using the pooled data for each pharmacodynamic endpoint. Results Response surface models adequately characterized all pharmacodynamic endpoints. Despite the fact that sevoflurane-remifentanil interactions were strongly synergistic for clinical sedation, BIS and AAI were minimally affected by the addition of remifentanil to sevoflurane anesthetics. Conclusion Although clinical sedation increases significantly even with the addition of a small to moderate dose of remifentanil to a sevoflurane anesthetic, the BIS and AAI are insensitive to this change in clinical state. Therefore, during "opioid-heavy" sevoflurane-remifentanil anesthetics, targeting a BIS less than 60 or an AAI less than 30 may result in an unnecessarily deep anesthetic state.

Esophagogastroduodenoscopy procedures are typically performed under conscious sedation. Drug-induced respiratory depression is a major cause of serious adverse effects during sedation. Capnographic monitoring of respiratory activity improves patient safety during procedural sedation. This bench study compares the performance of the nasal cannulas and oral bite blocks used to monitor exhaled CO2 during sedation. We used a spontaneously breathing mechanical lung to evaluated four CO2 sampling nasal cannulas and three CO2 sampling bite blocks. We placed pneumatic resistors in the mouth of the manikin to simulate different levels of mouth opening. We compared CO2 measurements taken from the sampling device to CO2 measurements taken directly from the trachea. The end tidal CO2 concentration (PETCO2) measured through the bite blocks and nasal cannulas was always lower than the corresponding PETCO2 measured at the trachea. The difference became larger as the amount of oxygen delivered through the devices increased. The difference was larger during normal ventilation than during hypoventilation. The difference became larger as the amount of oral breathing increased. The two nasal cannulas without oral cups failed to provide sufficient CO2 for breath detection when the mouth was fully open and oxygen was delivered at 10 L/min. Our simulation found that respiratory rate can be accurately monitored during the procedure using a CO2 sampling bite block or a nasal cannula with oral cup. The accuracy of PETCO2 measurements depends on the device used, the amount of supplement oxygen, the amount of oral breathing and the patient's minute ventilation.

To detect endobronchial intubation (EBI) noninvasively in real time, we developed a novel, automated, lumped model-based approach. The model uses routinely monitored airway pressure and flow as inputs. The specificity of the method in detecting EBI was determined by testing events of stiff chest wall (SCW) in the absence of EBI. EBI was induced in 10 anesthetized, paralyzed, and mechanically ventilated mongrel dogs (19-45 kg) by advancing the endotracheal tube into the right mainstem bronchus. The event of SCW was created by wrapping a pressure cuff around the chest. Airway pressure and flow were continuously recorded at the mouth, and respiratory impedance was estimated from these signals. Model parameters were iteratively identified until the root mean square error between the respiratory and model-predicted impedance was minimum. The change in model parameters during EBI from baseline was analyzed. In nine of 10 cases, it was determined that during EBI, the model's compliance element (C1) decreased > or =50% and model's resistance element (R2) changed < or =10-fold from baseline. Testing this rule on 40 cases of SCW, four false positives were obtained. During SCW, R1 and R2 increased, whereas C2 decreased significantly from baseline. This preliminary study is a promising step toward noninvasive, real-time detection of EBI to aid clinicians in decision making.

Background Combining a hypnotic and an analgesic to produce sedation, analgesia, and surgical immobility required for clinical anesthesia is more common than administration of a volatile anesthetic alone. The aim of this study was to apply response surface methods to characterize the interactions between remifentanil and sevoflurane. Methods Sixteen adult volunteers received a target-controlled infusion of remifentanil (0-15 ng/ml) and inhaled sevoflurane (0-6 vol%) at various target concentration pairs. After reaching pseudo-steady state drug levels, the Observer's Assessment of Alertness/Sedation score and response to a series of randomly applied experimental pain stimuli (pressure algometry, electrical tetany, and thermal stimulation) were observed for each target concentration pair. Response surface pharmacodynamic interaction models were built using the pooled data for sedation and analgesic endpoints. Using computer simulation, the pharmacodynamic interaction models were combined with previously reported pharmacokinetic models to identify the combination of remifentanil and sevoflurane that yielded the fastest recovery (Observer's Assessment of Alertness/Sedation score > or = 4) for anesthetics lasting 30-900 min. Results Remifentanil synergistically decreased the amount of sevoflurane necessary to produce sedation and analgesia. Simulations revealed that as the duration of the procedure increased, faster recovery was produced by concentration target pairs containing higher amounts of remifentanil. This trend plateaued at a combination of 0.75 vol% sevoflurane and 6.2 ng/ml remifentanil. Conclusion Response surface analyses demonstrate a synergistic interaction between remifentanil and sevoflurane for sedation and all analgesic endpoints.

As our civilization continues to dive deeper into the information age, making sense of complex data becomes critical. This work takes on this challenge by means of a novel method based on complete inter disciplinarity, design process and built-in evaluations. The result is the design, construction, testing and deployment of data environments supporting real-time decision-making in such diverse domains as anesthesiology and live art performance. Fundraising success, technology licensing, market implementation and many live art performances provide evidence of the great potential of committed interdisciplinary work for advancing science, art and technology while benefiting society at large.

Monitors that show intravenous drug and effect concentrations currently do not exist. However, using real-time displays of intravenous anesthetic concentrations and effects could significantly enhance intraoperative clinical decision-making and patient safety. Pharmacological models are available to estimate drug concentrations in the brain, and to predict the drug's associated physiological effects. An interdisciplinary research team developed a graphic display incorporating these models to show the predicted present and future concentrations and effects of anesthetic drugs in real-time. The results of this study show that anesthesiologists using the display controlled hemodynamic patient variables better than a control group. Additionally, when using the drug display the procedure was shorter than in the control group. Taken together, the availability of a drug display has the potential to increase patient safety significantly.

Pharmacokinetics plays an important role in the delivery of anesthesia. Their complex nature creates a challenging control task for anesthesiologists while delivering anesthesia. The anesthesia domain confronts many known control difficulties such as non-linearity, oscillations, and sub-optimal feedback. A clinician's understanding of pharmacokinetics plays an important role in tracking performance. Information about anesthesiologists' knowledge of pharmacokinetics was collected and analyzed. Effects of expertise and considerable variability, even within groups, were observed in the collected data. Reducing variability and supporting the tracking task in the administration of anesthesia could lead to improved patient outcomes.

More than 350,000 people die annually of cardiac arrest. In response to this epidemic, automated defibrillators are advocated, but they do not provide important respiratory support. However, adding respiratory support makes the system more complex and difficult to use. To solve this problem we developed a graphical computer based “just-in-time” training that instructs a responder to follow a standard treatment protocol. We simulated a medical emergency in a patient simulator and asked novice volunteers to care for the patient. When using a paper-based version of the treatment protocol (based on a NASA protocol), subjects took significant longer to remove an obstruction from the airway and stabilize the injured person than when using an animated graphic treatment protocol. These findings validate the potential of graphically based just-in-time training to instruct novices in tasks they have not performed before.

Objective: Data representations on today's medical monitors need to be improved to advance clinical awareness and prevent data vigilance errors. Simply building graphical displays does not ensure an improvement in clinical performance because displays have to be consistent with the user's clinical processes and mental models. In this report, the development of an original pulmonary graphical display for anesthesia is used as an example to show an iterative design process with built-in usability testing. Design: The process reported here is rapid, inexpensive, and requires a minimal number of subjects per development cycle. Three paper-based tests evaluated the anatomic, variable mapping, and graphical diagnostic meaning of the pulmonary display. Measurements: A confusion matrix compared the designer's intended answer with the subject's chosen answer. Considering deviations off the diagonal of the confusion matrix as design weaknesses, the pulmonary display was modified and retested. The iterative cycle continued until the anatomic and variable mapping cumulative test scores for a chosen design scored above 90% and the graphical diagnostic meaning test scored above 75%. Results: The iterative development test resulted in five design iterations. The final graphical pulmonary display improved the overall intuitiveness by 18%. The display was tested in three categories: anatomic features, variable mapping, and diagnostic accuracy. The anatomic intuitiveness increased by 25%, variable mapping intuitiveness increased by 34%, and diagnostic accuracy decreased slightly by 4%. Conclusion: With this rapid iterative development process, an intuitive graphical display can be developed inexpensively prior to formal testing in an experimental setting. j J Am Med Inform Assoc. 2003;10:363-372. DOI 10.1197/jamia.M1207.

Anaesthetic information displays have been shown to influence anaesthesiologists’ situation awareness. In study 1 an object display was compared with the traditional display currently used. Twelve anaesthesiologists (residents and faculty members) participated in a simulator evaluation of the displays. Reaction times for detection of critical events and situation awareness were measured. The object display improved situation awareness for one of four test scenarios. Low-level situation awareness was higher with the traditional display, and medium-level situation awareness was higher with the new display. In study 2, an integrated 3D display was compared to the traditional display. Twelve students participated in the evaluation. The new 3D display helped the observers to see changes more rapidly. In one scenario, situation awareness was higher with the new display than with the traditional display. In summary, during 63% of the simulated scenarios, reliable differences were found in favour of the new displays. Thus, by introducing integrated graphical displays in the operating room, anaesthesiologists’ performance may be improved.

A multi-disciplinary team developed a graphical/object-based cardiovascular display to support anesthesiologist's decision-making in the operating room. The process of designing the display incorporated central findings from the areas of naturalistic decision-making and medical cognition and used rapid iterative prototyping. To evaluate their performance when using the cardiovascular display, 20 anesthesiologists participated in a study in a high fidelity simulator (METI). Half the subjects used the cardiovascular display, the other half received the same information presented in a numeric format. The anesthesiologists treated two critical events in two simulated patients. In one case the patient suffered from anaphylactic shock, in the other case, severe blood loss and myocardial infarction occurred. Measurements were taken for detection, diagnosis, and treatment time. The cardiovascular display improved performance across these different indicators when anesthesiologists were dealing with a cardiovascular event.

Monitors that show intravenous (IV) drug concentrations currently do not exist. However, using real-time displays of intravenous anesthetic concentrations and effects could significantly enhance intraoperative clinical decision-making. Pharmacokinetic models are available to estimate past, present and future drug concentrations in the brain, and pharmacodynamic models are available to predict the drug's associated physiological effects. An interdisciplinary research team developed a new graphic display incorporating these models to show the predicted concentrations and effects of anesthetic drugs in real-time. To evaluate the effectiveness of the display on the management of anesthesia, 15 anesthesiologists participated in a computer-based simulation study. Anesthesiologists maintained drug concentrations closer to an optimal target level when they used the prototype anesthesia drug display. Participants also reported lower levels of workload with the display and rated the display as a useful addition to anesthesia monitoring.

To evaluate the accuracy and precision of an advanced thoracic bioimpedance cardiac output monitor by comparing it with conventional thermodilution.Prospective data collected from 47 patients undergoing routine cardiac catheterization. The new bioimpedance system differs from its predecessors in electrode system configuration, advanced signal processing, use of a modified Kubicek equation, and a reliable estimate of left ventricular ejection time from the time derivative bioimpedance signals.A cardiac catheterization laboratory in a university affiliated teaching hospital.A series of 47 relatively homogenous patients undergoing routine cardiac catheterization for suspected cardiac disease.The data from the first 20 patients was used to determine optimal values for coefficients in the bioimpedance cardiac output equations. The coefficients found were used when the system was tested in the subsequent 27 patients. For the last 27 patients, a total of 80 simultaneous pairs of cardiac output measurements were made by conventional thermodilution and by thoracic bioimpedance. The mean difference between the two methods was -0.31 L/min and the standard deviation of the differences was (0.76 L/min). The correlation coefficient was r2 = .72 (p.001).The correlation between conventional thermodilution and thoracic bioimpedance cardiac output estimates was good and the standard deviation of the differences was lower than that reported for commercially available devices. The system can be used in the cardiac catheterization lab for reliable and continuous noninvasive measurement of cardiac output.

Objective.This study reports on the efficacy of using the anesthesia simulator to teach sedation and analgesia to nurses. This provision of sedation and analgesia to a patient is accomplished with the goal of maintaining the ability of the patient to respond purposefully to auditory ortactile stimuli. Methods.Nurses working in areas of the hospital where conscious sedation is performed were the participants in this sedation and analgesia training course. Prior to the training session, the participants read the American Society of Anesthesiology Practice guidelines for sedation and analgesia by non-anesthesiologists.At the time of the training session, each participant completed a written pretest, had an introduction to sedation and analgesia with four clinical crisis teaching scenarios using the anesthesia simulator, a practical exam using the simulator, and a written post-test. Each participant was also given the opportunity to complete an evaluation of the session. Results.Twenty nurses completed the training session. The written tests had a maximum possible score of 30. Mean score on the written pretest was 22.9 ±3.54, and mean score on the written post-test was 26.0 ± 4.24 (p< 0.001). Seventeen of the twenty subjects scored higher on the post-test. Mean practical exam score was 5.5 of a possible 6.0. Mean participant rating of the education session was 3.75 (1 = poor, 4 =excellent). All but one participant rated the length of the training sessionas “about right.” Conclusions.The anesthesia simulator provides an excellent tool for teaching conscious sedation skills to hospital nurses. The participants' test performance improved following the session, and they also rated the educational experience as excellent.

Objective.Evaluation in animals of a non-invasive and continuous cardiac output monitoring system based on partial carbon-dioxide (CO2) rebreathing indirect Fick technique. Methods.We have developed a non-invasive cardiac output (NICO) monitoring system, based on the partial rebreathing method. The partial rebreathing technique employs a differential form of the Fick equation for calculating cardiac output (QT) using non-invasive measurements. Changes in CO2 elimination (ΔVCO2) and partial pressure of end-tidal CO2 (Δ PETCO2) in response to a brief period of partial rebreathing are used to measure pulmonary capillary blood flow (QPCBF). A non-invasive estimate of anatomic and intrapulmonary shunt fraction (QS/QT), based on oxygen saturation from pulse oximetry (SpO2) and inspired oxygen concentration (FIO2), is added to compute total cardiac output [QT=QPCBF/(1−QS/QT)]. The performance of the NICO was compared with iced 5% dextrose bolus thermodilution cardiac output (TDco) measurements in 6 dogs. Cardiac output was varied using dobutamine, and halothane, and by clamping of the inferior vena cava. Two hundred and forty-six (n = 246) paired measurements of TDco and NICO over a range of cardiac outputs (TDco range = 0.60–8.87 l/min) were compared using Bland-Altman analysis and weighted correlation coefficient. Results.The Bland–Altman technique yielded a NICO precision of ± 0.70 l/min (13.8%) with a mean bias of −0.07 l/min (−1.4%) compared to TDco. The weighted correlation coefficient between TDco and NICO values was: r= 0.93 (n= 246). Conclusion.The partial CO2 rebreathing technique for measurement of cardiac output is non-invasive, automated, and based on the well accepted Fick principle. The limits of agreement between NICO and TDco is within the recommended value for NICO to be a clinically acceptable method for cardiac output measurement. The results of this canine study show that NICO performed as well, and in some cases better, than other currently available non-invasive cardiac output techniques over a wide range of cardiac outputs.

Objective. This study is an evaluation of a new thoracic bioimpedance cardiac output monitoring system which incorporates a modified form of the Kubicek equation and a method of estimating the left ventricular ejection time from the time derivative bioimpedance signals. Methods.The performance of the new system was compared with conventional thermodilution in a porcine model. One hundred and ninety nine (n = 199) paired measurements of thermodilution cardiac output (TDCO) (range 1.20–18.00 L/min) and thoracic bioimpedance cardiac output (BICO) were collected in 7 pigs. The bioimpedance measurements were adjusted for the animal's weight and chest circumference, thus compensating for the differences in the anatomy of pigs when compared to humans. Data were compared using weighted correlation coefficient and Bland–Altman analysis. Results. The weighted correlation coefficient between TDCO and BICO values was 0.87 (n = 199). The Bland–Altman technique yielded a precision of the device of ±1.69 L/min with a bias of 0.11 L/min. Conclusion. The results from the porcine study show that the new system performed well over a wide range of cardiac outputs, comparing favorably with data from other new bioimpedance cardiac output devices currently available in the market.

Objective. To evaluate the VIA V-ABG (VIA Medical Corp.) point-of-care blood gas and chemistry monitor in healthy human volunteers, with particular emphasis on the measurement of blood gases. Methods. Experimental conditions were varied by intermittently subjecting volunteers to either isocapnic hypercapnia (end-tidal (ET), PETCO2 = 50 ± 2 mmHg, ETPO2 = 130 ± 5 mmHg) or isocapnic hypoxia (PETCO2 = 42 ± 2, PETO2 + 45 ± 2 mmHg) in addition to room air breathing. Measurements by the VIA V-ABG device were compared with paired samples and measurements performed by two ABL Radiometers (505 and 500). Analysis of results includes bias and precision plots and comparison of results with minimal performance criteria as established by CLIA. Results. Nineteen volunteers yielded 222 matched samples. The range of values were 7.32-7.61 for pH, 20.9–51.6 mmHg for PCO2, 27.9–184.5 mmHg for PO2, 134-141 mmol/l for Na, 3.1–4.1 mmol/l for K, and 30.0–50.4% for hematocrit. Bias and precision (± 2 sd) for pH was 0.01 and 0.04, for PCO2 was 0.4 and 4.8, for PO2 was 1.0 and 17.0, for Na was −0.3 and 5.2, for K was 0.1 and 0.2, and for Hct was 2.0 and 5.4. Conclusions. Over the range of blood gas values assessed, blood gas measurements by the VIA V-ABG device were clinically acceptable and met minimal performance criteria utilizing current Medicare CLIA proficiency standards. Performance criteria were also met by the VIA V-ABG device for Na, K, and Hct measurements but the range of values was too narrow to allow characterization of clinical acceptability. The VIA V-ABG device appears to perform well compared with the results which have been published for other point-of-care devices. Comparison between different studies investigating point-of-care devices is difficult due to several factors (range of values measured, comparison device, population studied, etc.). Some of these instruments, including the VIA V-ABG device, may serve quite well as point-of-care devices to perform certain tests at the bedside. Whether or not any of these devices can substitute for traditional laboratory blood gas and chemistry measurements remains an issue that is not adequately studied.

In previous studies, oscillometric blood pressure measured from the supraorbital artery has been shown to agree quite well with pressure measured from the brachial artery in normal subjects. In this study, surgical patients whose conditions warranted the use of invasive blood pressure monitoring during the surgery were chosen. We compared systolic and diastolic blood pressure measured oscillometrically from the supraorbital artery with intraarterial blood pressures, measured invasively from the radial artery. A pressure bladder was attached to the forehead of each patient. The bladder was connected to a forehead blood pressure monitor. A catheter was inserted in a radial artery, and connected to a pressure monitor. Forehead blood pressure was measured every 5 min. Radial arterial pressure was averaged over the same period during which the forehead measurement was made. Blood pressures measured with the two methods were compared. For the systolic pressure, the difference between the two methods was -9.9 +/- 17.9 mm Hg (mean +/- SD). For diastolic pressure, the difference was -8.0 +/- 10.9 mm Hg. There was a significant difference between the two methods in the patient population chosen in this study.

Objective. Air flow through an endotracheal tube causes a pressure drop across the tube. This pressure drop creates a difference between air pressure measured in the trachea and the pressure measured in the breathing circuit, which can lead to errors when calculating pulmonary mechanics and when setting ventilators. We have developed a method of estimating tracheal pressure from the pressure in the endotracheal tube cuff and tested this system in clinical trials. Methods. Pressure measurement ports were placed between the Y piece of the ventilator circuit and the ETT connector, in the trachea at the carinal end of the ETT, and in the ETT cuff inflation line. Tracheal pressures and cuff pressures were found at end-inspiration and end-expiration (no flow states) and used to define a linear relationship between cuff pressure and tracheal pressure. Using the estimated tracheal pressure (Ptrach) and the measured pressure at the Y piece of the breathing circuit (PY), the pressure drop across the ETT was found as a function of flow through the tube. Tracheal pressure was then calculated from the flow-dependent pressure drop and PY. Tests of this system were performed in six patients in the operating room and six patients in the intensive care unit. Results. The flow-based tracheal pressure estimates were within 0.7 ± 0.4 cm H2O of actual tracheal pressure (mean ± SD). At peak inspiratory pressure the difference averaged 0.5 ± 0.3 cm H2O. The difference between our estimate of tracheal pressure and actual tracheal pressure was always less than 1 cm H2O. Conclusion. The flow-based tracheal pressure estimates were accurate during intermittent spontaneous breathing, but not during spontaneous breathing or with a poorly inflated cuff. The estimates were more immune to noise than the cuff-based estimates of tracheal pressure. The estimates of tracheal pressure measured from the ETT cuff should be accurate enough for clinical use in the operating room.

Summary statement: Processed digitized Doppler signals abstracted from recordings during continuous air infusion in dogs were used to train a neural network to estimate air embolism infusion rates. Background: Precordial Doppler is a sensitive technique for detecting venous air embolism during anesthesia, but it requires constant attentive listening. Since neural networks are particularly well suited to the task of pattern recognition, we sought to investigate this technology for detection and grading of air embolism. Methods: Air was infused into peripheral veins of four anesthetized dogs at rates of 0.025, 0.05, 0.10, 0.25, 0.50 and 1.0 ml−1·kg−1·min−1 while digital recordings of the precordial Doppler ultrasound signal were collected. The frequency content of the recordings was determined by Fourier analysis. The output of the Fourier transform was the input to a neural network. The network was then trained to estimate the air infusion rate. Results: The correlation coefficient between the size of the air embolism and the air infusion rate was greater than r2 = 0.93 for each of the four animals in the study when the network was trained using the data for all four dogs. When the data from a dog was withheld from the training set and used only for testing the correlation coefficients ranged from r2 = 0.75 to r2 = 0.27. For frequencies below 250 Hz, the acoustic energy tended to fall as the air infusion rate increased. The opposite occurred at frequencies above 325 Hz. Conclusions: Neural network processing of the precordial Doppler signal provides a quantitative estimate of the size of an air embolism.

The presence of a biophase compartment in a pharmacokinetic model indicates that the response to an administered dose of drug is damped such that the time to peak effect occurs after the peak concentration in the bloodstream. This phenomenon, which is common to most intravenous anesthetic agents, can be exploited by a drug delivery method that administers minibolus doses of drug rather than a continuous infusion. Through analysis of the frequency response behavior of the biophase compartment, a bolus magnitude and dose frequency or interval (1/frequency) can be chosen such that the oscillation in drug effect is minimized even though the plasma concentration may be changing significantly with each supplemental dose. A pharmacokinetic and pharmacodynamic based method for calculating the bolus dose size and dosing interval is presented. The trade-off between dose interval and change in drug effect is exemplified through computer simulation of this strategy applied to delivery of the neuromuscular blocking agent pancuronium. The method provides a repetitive perturbation to the pharmacokinetic and pharmacodynamic system that can aid in model parameter identification during closed loop applications.

OBJECTIVE: To show that an integrated graphic data display can shorten the time taken to detect and correctly identify critical events during anesthesia. METHODS: We developed a graphic display which presents 30 anesthesia-related physiologic variables as shapes and colors, rather than traditional digits and waveforms. To evaluate the new display, we produced four critical events on a computer-based anesthesia simulator and asked two groups of five anesthesiologists to identify the events as quickly as possible. One group observed the new display while the other group viewed a traditional cardiovascular monitor with digital and waveform displays. RESULTS: The group which observed the integrated graphic display saw changes caused by inadequate paralysis 2.4 min sooner, and changes caused by a cuff leak 3.1 min sooner than those observing the traditional display. The integrated display group correctly identified the reason for the change 2.8 min sooner for inadequate paralysis, 3.1 min sooner for cuff leak and 3.1 min sooner for bleeding. These differences were all statistically significant. CONCLUSIONS: The results show that some simulated critical events are detected and correctly identified sooner, when an anesthesiologist views an integrated graphic display, rather than a traditional digital/waveform monitor.

Background:Undetected apnea can lead to severe hypoxia, bradycardia, and cardiac arrest. Tracheal sounds entropy has been proved to be a robust method for estimating respiratory flow, thus maybe a more reliable way to detect obstructive and central apnea during sedation.Methods:A secondary analysis of a previous pharmacodynamics study was conducted. Twenty volunteers received propofol and remifentinal until they became unresponsive to the insertion of a bougie into the esophagus. Respiratory flow rate and tracheal sounds were recorded using a pneumotachometer and a microphone. The logarithm of the tracheal sound Shannon entropy (Log-E) was calculated to estimate flow rate. An adaptive Log-E threshold was used to distinguish between the presence of normal breath and apnea. Apnea detected from tracheal sounds was compared to the apnea detected from respiratory flow rate.Results:The volunteers stopped breathing for 15 s or longer (apnea) 322 times during the 12.9-h study. Apnea was correctly detected 310 times from both the tracheal sounds and the respiratory flow. Periods of apnea were not detected by the tracheal sounds 12 times. The absence of tracheal sounds was falsely detected as apnea 89 times. Normal breathing was detected correctly 1,196 times. The acoustic method detected obstructive and central apnea in sedated volunteers with 95% sensitivity and 92% specificity.Conclusions:We found that the entropy of the acoustic signal from a microphone placed over the trachea may reliably provide an early warning of the onset of obstructive and central apnea in volunteers under sedation.

Objective. Noninvasive blood pressure measured from the superficial temporal artery bas been shown to correlate well with pressure in the brachial artery. The supraorbital artery may be an even better site for monitoring blood pressure on the forehead because it originates from the internal carotid artery, and it is easier to locate anatomically. This study compares mean pressure measured oscillometrically over the supraorbital artery and at the upper arm.Methods. Oscillometric signals from the supraorbital artery were recorded in 20 surgical patients under general anesthesia using a 2.5- × 1-cm bladder attached to the forehead with a self-adhesive pad. Blood pressure was measured simultaneously from the arm using a Dinamap 1846 blood pressure monitor, and the resulting data compared with the supraorbital artery measurements.Results. The mean difference between 219 pairs of blood pressure measurements, from the forehead and the arm, was 3.8 mm Hg. The standard deviation of the differences was 7.4 mm Hg. The linear regression equation for the data wasy = 0.98x + 3.25, with a standard error of estimate of 7.31 mm Hg. The correlation coefficient between the two measurements was 0.82.Conclusions. The results show that mean blood pressures measured oscillometrically from the supraorbital and brachial arteries agree and correlate well with each other. The supraorbital artery should be a good alternative site for blood pressure measurement.

A multi-disciplinary team developed and evaluated a graphical pulmonary display to support anesthesiologist's treatment of pulmonary complications. The design process incorporated central findings from the areas of naturalistic decision-making and medical cognition, and used rapid iterative prototyping. To evaluate performance when using the pulmonary display, 19 anesthesiologists participated in a study in a high fidelity simulator. 10 subjects used the graphical pulmonary display; 9 received the same information presented numerically. The anesthesiologists treated five critical events and one “non-event”. Measurements were taken for effective treatment time. The pulmonary display tended to improve overall performance. In addition, we found effects of expertise, with experts treating faster than the two less experienced groups.

Objective. Blood pressure is usually measured noninvasively with a cuff on the arm or the leg. Circumstances exist, however, when an alternative site for blood pressure measurement is desirable. This study is designed to identify a location on the forehead where blood pressure can be reliably measured noninvasively.Methods. We mapped the superficial temporal artery and/or the supraorbital artery in 65 volunteers and found a rectangular area where an adhesive pressure pad could be placed over each artery. Oscillometric signals were recorded from four different locations over the forehead in 19 of the 65 volunteers to compare the amplitude of the signal and mean blood pressure between locations.Results. The course of the supraorbital artery is quite consistent. It passed through a 2.5-×1-cm rectangular area on the forehead in all volunteers in which it was mapped. The medial border of the rectangle is 0.5-cm medial and 1-cm above the medial corner of the left eyebrow. The course of the superficial temporal artery differed remarkably from person to person. We could not find an area of reasonable size to cover the artery in all volunteers. Mean blood pressures were the same in all forehead locations. The signal was the weakest on the center of the forehead and strongest directly over the superficial temporal artery.Conclusions. Our results show that the supraorbital artery, an end-artery of the internal carotid artery, which emerges through the supraorbital foramen and crosses the forehead near the center, is the preferred site to monitor blood pressure noninvasively on the forehead with an adhesive pressure bladder.

Objective. Our objective was to overcome the limitations of linear models of oscillometric blood pressure determination by using a nonlinear technique to model the relationship between the oscillometric envelope and systolic and diastolic blood pressures, and then to use that technique for near-continuous arterial pressure monitoring at the supraorbital artery.Methods. An adhesive pressure pad and transducer were used to collect oscillometric data from the supraorbital artery of 85 subjects. These data were then used to train an artificial neural network (ANN) to report diastolic or systolic pressure. Arterial pressure measurements defined by brachial artery auscultation were used as a reference. ANN results were compared with those obtained using a standard oscillometric algorithm that determined pressures based on fixed percentages of the maximum oscillometric amplitude.Results. The ANN produced better estimates of reference blood pressures than the standard oscillometric algorithm. Mean difference between target and actual output for the ANN was 0.50±5.73 mm Hg for systolic pressures, compared to the mean difference of the standard algorithm of 2.78±19.38 mm Hg. For diastolic pressures, the ANN had a mean difference of 0.04±4.70 mm Hg, while the mean difference of the standard algorithm was −0.34±9.75 mm Hg.Conclusions. The ANN produced a better model of the relationship between the oscillometric envelope and reference systolic and diastolic pressures than did the standard oscillometric algorithm. Noninvasive blood pressure measured from the supraorbital artery agreed with pressure measured by auscultation in the brachial artery, and may sometimes be more clinically useful than an arm cuff device.

This article reviews the current state-of-the-art and future applications of computers in critical care, with particular attention to ventilator and drug-delivery applications. Automated charting, alerts and alarms, and tools for decision support (such as expert systems and closed-loop control) are discussed also.

The study measured whether nurses' situation awareness would increase and task completion time decrease when they used an integrated information display compared to traditional displays for medication management, patient awareness and team communication.The Burn Trauma Intensive Care Unit (BTICU) at the University Hospital, University of Utah Health Science Center, Salt Lake City, Utah, USA.12 experienced BTICU nurses.Situation awareness (accuracy of the participants' answer) and task completion time (response time from seeing the question to submitting the answer) were measured using paper prototypes of both displays.Counter-balanced (on display order), repeated-measures design.Nurses had a higher situation awareness when using the integrated display, with an overall accuracy of 85.3% compared to 61.8% with the traditional displays (odds ratio 3.61, P.001, 95% CI=2.34…5.57). Task completion times were nearly half with integrated displays compared to traditional displays (median 26.0 and 42.1s, hazard ratio 2.31, P.001, CI=1.83…2.93).An integrated ICU information display increased nurses' situation awareness and decreased task completion time. Information integration has the potential to decrease errors, increase nurses' productivity and may allow nurses to react faster to a patient's clinical needs. Bidirectional device communication is needed for these displays to achieve full potential in improving patient safety.

Objective. The objectives of our study were (1) to implement intelligent respiratory alarms with a neural network; and (2) to increase alarm specificity and decrease false-alarm rates compared with current alarms.Methods. We trained a neural network to recognize 13 faults in an anesthesia breathing circuit. The system extracted 30 breath-to-breath features from the airway CO2, flow, and pressure signals. We created training data for the network by introducing 13 faults repeatedly in 5 dogs (616 total faults). We used the data to train the neural network using the backward error propagation algorithm.Results. In animals, the trained network reported the alarms correctly for 95.0% of the faults when tested during controlled ventilation, and for 86.9% of the faults during spontaneous breathing. When tested in the operating room, the system found and correctly reported 54 of 57 faults that occurred during 43.6 hr of use. The alarm system produced a total of 74 false alarms during 43.6 hr of monitoring.Conclusion. Neural networks may be useful in creating intelligent anesthesia alarm systems.

In the past two far-view displays, which showed vital signs, trends, alarms, infusion pump status, and therapy support indicators, were developed and assessed by critical care nurses (Gorges et al. in Dimens Crit Care Nurs. 30(4):206–17, 2011). The aim of the current study is to assess the generalizability of these findings to physicians. The first aim is to test whether an integrated far-view display, designed to be readable from 3 to 5 m, enables critical care physicians to more rapidly and accurately (1) recognize a change in patient condition; (2) identify alarms; and (3) identify near-empty infusion pumps, than a traditional patient monitor and infusion pump. A second aim is to test if the new displays reduce the mental workload required for this decision making. Fifteen critical care fellow physicians (median age of 34 years, with 2–8 years of ICU experience) were asked to use the three displays to compare the data from two patients and decide which patient required their attention first. Each physician made 60 decisions: 20 with each of the two far-view displays and 20 decisions with a standard patient monitor next to an infusion pump. A 41 and 26 % improvement in decision accuracy was observed with the bar and clock far-view displays, respectively. Specifically, the identification of near empty infusion pumps, a task normally performed by nurses, and patients with a single alarm were better with the new displays. Using the bar display physicians made their decision 12 % faster than when using the control display, a median improvement of 2.1 s. No significant differences were observed in measured workload. Displays that present patient data in a redesigned format enables critical care clinicians to more rapidly identify changes in patient conditions and to more accurately decide which patient needs their attention. In a clinical setting, this could improve patient safety. In future work, an evaluation of the display using live patient data from an ICU should be performed.

This paper shows experimentally that standard wireless networks which measure received signal strength (RSS) can be used to reliably detect human breathing and estimate the breathing rate, an application we call "BreathTaking". We show that although an individual link cannot reliably detect breathing, the collective spectral content of a network of devices reliably indicates the presence and rate of breathing. We present a maximum likelihood estimator (MLE) of breathing rate, amplitude, and phase, which uses the RSS data from many links simultaneously. We show experimental results which demonstrate that reliable detection and frequency estimation is possible with 30 seconds of data, within 0.3 breaths per minute (bpm) RMS error. Use of directional antennas is shown to improve robustness to motion near the network.

Although nurses perform the majority of the clinical tasks in an intensive care unit, current patient monitors were not designed to support a nurse's workflow. Nurses constantly triage patients, deciding which patient is currently in the most need of care. To make this decision, nurses must observe the patient's vital signs and therapeutic device information from multiple sources. To obtain this information, they often have to enter the patient's room. This study addresses 3 hypotheses. Information provided by far-view monitoring displays (1) reduces the amount of time to determine which patient needs care first, (2) increases the accuracy of assigning priority to the right patient, and (3) reduces nurses mental workload. We developed 2 far-view displays to be read from a distance of 3 to 5 m without entering the patient's room. Both display vital signs, trends, alarms, infusion pump status, and therapy support indicators. To evaluate the displays, nurses were asked to use the displays to decide which of 2 patients required their attention first. They made 60 decisions: 20 with each far-view display and 20 decisions with a standard patient monitor next to an infusion pump. Sixteen nurses (median age of 27.5 years with 2.75 years of experience) participated in the study. Using the 2 far-view displays, nurses more accurately and rapidly identified stable patients and syringe pumps that were nearly empty. Median decision times were 11.3 and 12.4 seconds for the 2 far-view displays and 17.2 seconds for the control display. The 2 far-view displays reduced median decision-making times by 4.8 to 5.9 seconds, increased accuracy in assignment of priority in 2 of 7 patient conditions, and reduced nurses' frustration with the triaging task. In a clinical setting, the proposed far-view display might reduce nurses' mental workload and thereby increase patient safety.