S. Blake Wachter

Beta-Adrenergic Receptors, from Their Discovery and Characterization through Their Manipulation to Beneficial Clinical Application

β-Adrenergic receptors (β-AR) are central to the overall regulation of cardiac function. From the first proposed receptor/transmitter concept to the latest clinical β-blocker trials β-AR have been shown to play an important role in cardiac disease and heart failure in particular. This study provides a historical perspective, reviews the latest discoveries and beliefs, and discusses the current clinical practices of β-AR and their modulation with their associated guanine-nucleotide regulatory protein/adenylylcyclasesignal transduction pathways.

The Employment of an Iterative Design Process to Develop a Pulmonary Graphical Display

OBJECTIVE Data representations on todays 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 users 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 designers intended answer with the subjects 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.

The Evaluation of a Pulmonary Display to Detect Adverse Respiratory Events Using High Resolution Human Simulator

OBJECTIVE Authors developed a picture-graphics display for pulmonary function to present typical respiratory data used in perioperative and intensive care environments. The display utilizes color, shape and emergent alerting to highlight abnormal pulmonary physiology. The display serves as an adjunct to traditional operating room displays and monitors. DESIGN To evaluate the prototype, nineteen clinician volunteers each managed four adverse respiratory events and one normal event using a high-resolution patient simulator which included the new displays (intervention subjects) and traditional displays (control subjects). Between-group comparisons included (i) time to diagnosis and treatment for each adverse respiratory event; (ii) the number of unnecessary treatments during the normal scenario; and (iii) self-reported workload estimates while managing study events. MEASUREMENTS Two expert anesthesiologists reviewed video-taped transcriptions of the volunteers to determine time to treat and time to diagnosis. Time values were then compared between groups using a Mann-Whitney-U Test. Estimated workload for both groups was assessed using the NASA-TLX and compared between groups using an ANOVA. P-values < 0.05 were considered significant. RESULTS Clinician volunteers detected and treated obstructed endotracheal tubes and intrinsic PEEP problems faster with graphical rather than conventional displays (p < 0.05). During the normal scenario simulation, 3 clinicians using the graphical display, and 5 clinicians using the conventional display gave unnecessary treatments. Clinician-volunteers reported significantly lower subjective workloads using the graphical display for the obstructed endotracheal tube scenario (p < 0.001) and the intrinsic PEEP scenario (p < 0.03). CONCLUSION Authors conclude that the graphical pulmonary display may serve as a useful adjunct to traditional displays in identifying adverse respiratory events.

Evaluation of a pulmonary graphical display in the medical intensive care unit: an observational study

We developed a pulmonary graphic display that depicts pulmonary physiological variables for intubated, mechanically ventilated patients in a graphical format. The pulmonary graphical display presents multiple respiratory variables and changes are depicted by alterations in shape and color. Learning how this new technology will be integrated and accepted by users is an important step before it is introduced into the clinical arena. This study observed use and acceptance of the pulmonary graphical display by health care providers in an intensive care unit. Investigators noted that physicians, respiratory therapists, and nurses observed the pulmonary graphical display on average six, three, and one times, respectively, per patient room entry. Based on questionnaires, the pulmonary graphical display was perceived as useful, a desirable addition to current ICU monitors, and an accurate representation of respiratory variables.

Carvedilol Produces Sustained Long-Term Benefits: Follow-Up at 12 Years

The authors measured long-term outcomes of patients who initiated carvedilol between 1990 and 1992 to test the hypothesis that carvedilol produces sustained benefits in heart failure patients. The study population consisted of 57 patients who completed a carvedilol placebo-controlled phase II trial. Patients were given open-label carvedilol and were titrated to the maximum dose. Patients were assessed by serial multigated acquisition, echocardiography, and symptom scores. Survival was assessed for all patients and censored as of January 1, 2004. Survival for ischemic vs nonischemic patients was compared using the log-rank test and further compared using Cox regression, controlling for covariates. Etiology of heart failure was ischemic in 15 patients and nonischemic in 42 patients. Median follow-up was 12.9 years. Resting left ventricular ejection fraction (LVEF) and heart failure symptom scores improved at 4 months of treatment and were sustained at 24 months. Left ventricular internal diameter in systole (LVIDS) and left ventricular internal diameter in diastole decreased significantly at 4 and 8 months, respectively, and LVIDS continued to improve at 24 months. Overall mortality was 43% in nonischemic patients and 73% in ischemic patients. In a multivariate analysis, ischemic etiology and baseline LVEF were significant predictors of mortality. Carvedilol produces sustained improvements in left ventricular remodeling and symptoms. Long-term survival is good, particularly in nonischemic patients.

Design and Evaluation of a Graphical Pulmonary Display for Anesthesia

A multi-disciplinary team developed and evaluated a graphical pulmonary display to support anesthesiologists 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.

Elevated resting heart rate in heart transplant recipients: innocent bystander or adverse prognostic indicator?

The elevated baseline heart rate (HR) of a heart transplant recipient has previously been considered inconsequential. However, we hypothesized that a resting HR above 100 beats per minute (bpm) may be associated with morbidity and mortality.