The Inverted Case Study Technique: Changing the Traditional Case-Study Approach to Prioritize Physiological Mechanisms Over Correct Diagnosis and Treatment.

The traditional case study has been used as a learning tool for the past 100 years and in our program, graduate physiology students are presented with a real-world scenario and must determine the diagnosis and treatment of the patient. We found that students defaulted to memorization of disease with treatment and bypassed gaining an understanding of the mechanistic physiology behind disease and treatment. To adjust our student's approach, we developed a novel way to enhance student learning. In order to accomplish this shift from memorization to physiological mastery, we created the Inverted Case Study. This approach diverges from the traditional model in that students are given the diagnosis and treatment beforehand and are tasked with explaining the actual physiology of the case. In this way, students can no longer rely on the memorization of symptoms-disease-treatment, but rather gain a solid understanding of the physiological mechanisms of the disease since that is the focus of ICST. The inverted case study approach is an effective approach to apply and hone critical thinking skills.

Mechanosensitivity below Ground: Touch-Sensitive Smell-Producing Roots in the Shy Plant Mimosa pudica.

The roots of the shy plant Mimosa pudica emit a cocktail of small organic and inorganic sulfur compounds and reactive intermediates into the environment, including SO2, methanesulfinic acid, pyruvic acid, lactic acid, ethanesulfinic acid, propanesulfenic acid, 2-aminothiophenol, S-propyl propane 1-thiosulfinate, phenothiazine, and thioformaldehyde, an elusive and highly unstable compound that, to our knowledge, has never before been reported to be emitted by a plant. When soil around the roots is dislodged or when seedling roots are touched, an odor is detected. The perceived odor corresponds to the emission of higher amounts of propanesulfenic acid, 2-aminothiophenol, S-propyl propane 1-thiosulfinate, and phenothiazine. The mechanosensitivity response is selective. Whereas touching the roots with soil or human skin resulted in odor detection, agitating the roots with other materials such as glass did not induce a similar response. Light and electron microscopy studies of the roots revealed the presence of microscopic sac-like root protuberances. Elemental analysis of these projections by energy-dispersive x-ray spectroscopy revealed them to contain higher levels of K(+) and Cl(-) compared with the surrounding tissue. Exposing the protuberances to stimuli that caused odor emission resulted in reductions in the levels of K(+) and Cl(-) in the touched area. The mechanistic implications of the variety of sulfur compounds observed vis-à-vis the pathways for their formation are discussed.

Involvement of snapdragon benzaldehyde dehydrogenase in benzoic acid biosynthesis.

Benzoic acid (BA) is an important building block in a wide spectrum of compounds varying from primary metabolites to secondary products. Benzoic acid biosynthesis from L-phenylalanine requires shortening of the propyl side chain by two carbons, which can occur via a beta-oxidative pathway or a non-beta-oxidative pathway, with benzaldehyde as a key intermediate. The non-beta-oxidative route requires benzaldehyde dehydrogenase (BALDH) to convert benzaldehyde to BA. Using a functional genomic approach, we identified an Antirrhinum majus (snapdragon) BALDH, which exhibits 40% identity to bacterial BALDH. Transcript profiling, biochemical characterization of the purified recombinant protein, molecular homology modeling, in vivo stable isotope labeling, and transient expression in petunia flowers reveal that BALDH is capable of oxidizing benzaldehyde to BA in vivo. GFP localization and immunogold labeling studies show that this biochemical step occurs in the mitochondria, raising a question about the role of subcellular compartmentalization in BA biosynthesis.

Managing unnecessary variability in patient demand to reduce nursing stress and improve patient safety.

BACKGROUND: Increases in adverse clinical outcomes have been documented when hospital nurse staffing is inadequate. Since most hospitals limit nurse staffing to levels for average rather than peak patient census, substantial census increases create serious potential stresses for both patients and nurses. By reducing unnecessary variability, hospitals can reduce many of these stresses and thereby improve patient safety and quality of care. THE SOURCE AND NATURE OF VARIABILITY IN DEMAND: The variability in the daily patient census is a combination of the natural (uncontrollable) variability contributed by the emergency department and the artificial (potentially controllable) peaks and valleys of patient flow into the hospital fromelective admissions. Once artificial variability in demand is significantly reduced, a substantial portion of the peaks and valleys in census disappears; the remaining censsus variability is largely patient and disease driven. When artificial variability has been minimized, a hospital must have sufficient resources for the remaining patient-driven peaks in demand, over which it has no control, if it is to deliver an optimal level of care. DISCUSSION: Study of operational issues in health care delivery, and acting on what is learned, is critical. Al forms of artificial variation in the demand and supply of health care services should be identified, and pilot programs to test operational changes should be conducted.

Queuing theory accurately models the need for critical care resources.

BACKGROUND: Allocation of scarce resources presents an increasing challenge to hospital administrators and health policy makers. Intensive care units can present bottlenecks within busy hospitals, but their expansion is costly and difficult to gauge. Although mathematical tools have been suggested for determining the proper number of intensive care beds necessary to serve a given demand, the performance of such models has not been prospectively evaluated over significant periods. METHODS: The authors prospectively collected 2 years' admission, discharge, and turn-away data in a busy, urban intensive care unit. Using queuing theory, they then constructed a mathematical model of patient flow, compared predictions from the model to observed performance of the unit, and explored the sensitivity of the model to changes in unit size. RESULTS: The queuing model proved to be very accurate, with predicted admission turn-away rates correlating highly with those actually observed (correlation coefficient = 0.89). The model was useful in predicting both monthly responsiveness to changing demand (mean monthly difference between observed and predicted values, 0.4+/-2.3%; range, 0-13%) and the overall 2-yr turn-away rate for the unit (21%vs. 22%). Both in practice and in simulation, turn-away rates increased exponentially when utilization exceeded 80-85%. Sensitivity analysis using the model revealed rapid and severe degradation of system performance with even the small changes in bed availability that might result from sudden staffing shortages or admission of patients with very long stays. CONCLUSIONS: The stochastic nature of patient flow may falsely lead health planners to underestimate resource needs in busy intensive care units. Although the nature of arrivals for intensive care deserves further study, when demand is random, queuing theory provides an accurate means of determining the appropriate supply of beds.

Variability in surgical caseload and access to intensive care services.

BACKGROUND: Variability in the demand for any service is a significant barrier to efficient distribution of limited resources. In health care, demand is often highly variable and access may be limited when peaks cannot be accommodated in a downsized care delivery system. Intensive care units may frequently present bottlenecks to patient flow, and saturation of these services limits a hospital's responsiveness to new emergencies. METHODS: Over a 1-yr period, information was collected prospectively on all requests for admission to the intensive care unit of a large, urban children's hospital. Data included the nature of each request, as well as each patient's final disposition. The daily variability of requests was then analyzed and related to the unit's ability to accommodate new admissions. RESULTS: Day-to-day demand for intensive care services was extremely variable. This variability was particularly high among patients undergoing scheduled surgical procedures, with variability of scheduled admissions exceeding that of emergencies. Peaks of demand were associated with diversion of patients both within the hospital (to off-service care sites) and to other institutions (ambulance diversions). Although emergency requests for admission outnumbered scheduled requests, diversion from the intensive care unit was better correlated with scheduled caseload (r = 0.542, P < 0.001) than with unscheduled volume (r = 0.255, P < 0.001). During the busiest periods, nearly 70% of all diversions were associated with variability in the scheduled caseload. CONCLUSIONS: Variability in scheduled surgical caseload represents a potentially reducible source of stress on intensive care units in hospitals and throughout the healthcare delivery system generally. When uncontrolled, variability limits access to care and impairs overall responsiveness to emergencies.

An in vitro study of the effect of in-folds on the durability of mammary implants.

We hypothesize that the presence of in-folding in a filled mammary shell leads to shortening of the time to failure under tensile fatigue. Specimens, cut from pristine shells, were mounted in S-folded, creased, and unfolded configurations. A characteristic change, occurring in a transmembrane capacitance-proportional alternating current (AC) signal, which was used to monitor working of each specimen, was chosen as a robust marker that preceded frank shell perforation. Subjecting all specimens to stringent, controlled conditions led to time-to-fatigue failure estimates that demonstrated an order-of-magnitude reduction in lifetime for the folded specimens when compared with that for pair-matched, unfolded specimens. Creases also reduced the fatigue lifetime, but not to the degree that folds did. Observations based on the experimental behavior of folded shell material provide possible mechanisms for the potential lifetime clinical reduction of in-folded implants as well as for the development of silicone-on-silicone abrasive wear and generation of debris.