Computerized ventilator data selection: artifact rejection and data reduction

OBJECTIVE

To determine acceptable strategies for automated data acquisition and artifact rejection from computerized ventilators using the Medical Information Bus.

DESIGN

Medical practitioners were surveyed to establish 'clinically important' ventilator events. A prospective study involving frequent data collection from ventilators was also conducted.

SUBJECTS

Data from 10 adult patients were collected every 10 seconds from a Puritan Bennett 7200A ventilator for a total of 617.1 hours.

INTERVENTIONS

Twelve different computerized data selection and artifact algorithms were tested and evaluated.

MEASUREMENTS AND MAIN RESULTS

Data derived from 12 data selection algorithms were compared with each other and with data manually charted by respiratory therapists into a computerized charting system. Ventilator setting data collected by the algorithms, such as FIO2, reduced the amount of data collected to about 25% compared to manually charted data. The amount of data collected for measured parameters, such as tidal volume, from the ventilator had large variability and many artifacts. Automated data capture and selection generally increased the amount of data collected compared to manual charting, for example for the 3 minute median the increase was a modest 1.2 times.

CONCLUSION

Computerized methods for collecting ventilator setting data were relatively straightforward and more-efficient than manual methods. However, the method for automated selection and presentation of observed measured parameters is much more difficult. Based on the findings and analysis presented here, the authors recommend recording ventilator setting data after they have existed for three minutes and measured parameters using a three minute median data selection strategy. Such an algorithm rejected most artifacts, required minimal computational time, had minimal time-delay, and provided clinically acceptable data acquisition. The results presented here are but a starting point in developing automated ventilator data selection strategies.

Perspectives on development of IEEE 1073: the Medical Information Bus (MIB) standard

Automated data capture from bedside patient medical devices is now possible using a new Institute of Electrical and Electronic Engineering (IEEE) and American National Standards Institute (ANSI) Medical Information Bus (MIB) data communications standard (IEEE 1073). The first two standard documents, IEEE 1073.3.1 (Transportation Profile) and IEEE 1073.4.1 (Physical Layer), define the hardware protocol for bedside device communications. With the above noted IEEE MIB standards in place, hospitals can now start designing customized applications for acquiring data from bedside devices such as bedside monitors, i.v. pumps, ventilators, etc. for multiple purposes. The hardware 'plug and play' features of the MIB will enable nurses and physicians to establish communications with these devices simply and conveniently by plugging them into a bedside data connector. No other action will be necessary to establish identification of the device or communications with the device. Presently to connect bedside devices, technical help from hardware and software experts are required to establish such communications links. As a result of standardization of communications, it will be easy to establish a highly mobile network of bedside devices and more promptly and efficiently collect patient related data. Collection of data automatically should lead to the design of new medical computing applications that will tie in directly with the emerging mission and operations of hospitals. The MIB will permit acquisition of patient data more efficiently with greater accuracy, more completeness and more promptly. The above noted features are all essential to the development of computerized treatment protocols and should lead to improved quality of patient care. This manuscript provides the rational and historical overview of the development of the MIB standard.

Medical Information Bus usage for automated IV pump data acquisition: evaluation of usage patterns

OBJECTIVE

To identify factors which influence the choice of nurses to use automated collection of i.v. pump data from a prototype Medical Information Bus.

DESIGN

Observational study for a duration of three and one-half months.

SETTING

Four intensive care units, each with different missions, in an adult hospital.

SUBJECTS

One hundred fifty-eight registered nurses including both full and part time.

MEASUREMENTS AND MAIN RESULTS

Data were collected from the hospital information system about infusion orders including the type of medication, the number of rate changes, the method of documenting rate changes and the infusion methods. The method of documentation for infusion rate changes was defined as either automated, using a prototype Medical Information Bus (MIB), or manual, using the keyboard at a bedside computer terminal. The method of infusion was defined as either straight gravity feed without an i.v. pump ('no pump'), infusion using a pump but without connection to the hospital information system ('pump only') and infusion using a pump which was connected to the hospital information system using a prototype Medical Information Bus ('automated'). A total of 22,199 rate changes were documented during the study period and of those, 22,055 (99.35%) used the 'automated' method. Medications with the highest average rate change per single container were; Nitroprusside Sodium (9.50), Epinephrine (9.08) and Epoprostenol (7.50).

CONCLUSIONS

The nurses used automated i.v. pump data acquisition with medications which required frequent rate changes.

A preliminary assessment of intra-oral lubricating systems for dry mouth patients

OBJECTIVE

To provide extended intra-oral delivery of a saliva substitute.

INTERVENTION

Three different types of prostheses containing saliva substitute were designed and assessed: a two-part device resembling a mandibular complete denture sealed by cobalt-samerium magnets, a one-part clear resin device for the edentate patients and a flexible mouth guard type of appliance containing a lubricant releasing bubble for the dentate patients.

SETTING

A teaching hospital Oral Medicine and Rheumatology Clinic.

SUBJECTS

8 edentate and 3 dentate Sjogren Syndrome sufferers.

OUTCOME MEASURES

Subjective dryness after a week of wearing the lubricating appliance.

RESULTS

The majority of the subjects wore the appliances for 6-12 hours during each 24 hours. The initial dryness severity diminished after wearing the lubricating prosthesis. The patients preferred to wear the appliance at night.

CONCLUSION

All criteria were fulfilled on designing a saliva substitute lubricating appliance and some of the subjects have worn this prosthesis successfully for up to 3 years. Particular benefit was obtained by night-time wear.

Misconceptions about classical psychophysics and the measurement of response bias

Misconceptions exist about the ability of classical psychophysical techniques to measure separately the sensory and nonsensory (response bias) factors in a discrimination task. The views of the early researchers in psychophysics are reviewed. The manner in which the method of constant stimuli gives separate measures of sensory sensitivity and response bias is illustrated. Modern derivatives of classical psychophysical techniques which estimates sensory and nonsensory components are described. Finally, data indicating a correspondence between sensory and nonsensory factors obtained with various psychological techniques are reviewed.

Current status of mechanical ventilation decision support systems: a review

Objectives of computerized decision support systems for mechanical ventilation are discussed. Questions considered are: Why is computerized decision support for mechanical ventilation important? What parameter(s) should be optimized? What are the differences between a single attribute and a multiattribute value function used for optimization? How is it possible to achieve optimization in clinical practice with existing ventilators? How does one solve the problem of acquiring measurement of data needed for closed loop control? The possibilities and limitations of three existing decision support systems are discussed. 1) Computerized protocols from LDS Hospital in Salt Lake City, Utah, USA. 2) Optimization Program (OPTPROG) developed jointly at the Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland and Medical Intensive Care Unit, Department of Medicine at Karolinska Institute, South Hospital, Stockholm, Department of Medical Informatics Linkoping University, Sweden. 3) Ventilator Therapy Planner (VENT-PLAN) from the Section on Medical Informatics at Stanford University, Palo Alto, California, USA. Strategies leading to an optimal computerized decision support system are proposed. These strategies include development of better measurement methods for blood gases and cardiac output, improvement of man-machine and machine-machine interaction and the selection of optimization criteria. Finally, research directed towards building quantitative, dynamic patient models based on computerized databases of mechanically ventilated patients are discussed.

Methodological issues in assessment of the perceptual component of body image disturbance

An individual's body image consists of both a perceptual and an attitudinal (subjective) component. Methodological issues relative to the measurement of the perceptual component of body image are discussed. Traditionally, research in body image has employed psychophysical techniques and analyses which confound these two components. Psychophysical techniques which allow for a separate measurement of these two components are discussed, including method of constant stimuli, signal detection theory and adaptive probit estimation. The results of research utilizing these techniques are described and the importance of separately measuring perceptual and attitudinal components is discussed.

Accuracy and reliability of disposable pressure transducers coupled with modern pressure monitors

OBJECTIVE

To determine the bedside accuracy of direct patient pressure monitoring when used with new and clinically used disposable blood pressure (BP) transducers.

DESIGN

Prospective study.

SETTING

Laboratory bench and critical care units in an adult and children's hospital.

SUBJECTS

Seventy-five bedside patient monitors (25 Marquette Electronics, 25 Spacelab Medical, and 25 Hewlett-Packard), and 100 disposable transducers (50 from Utah Medical Products and 50 from Abbott Critical Care Systems [25 new, 25 clinically used of each manufacturer]) were tested.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A +/- 2% accuracy requirement for bedside monitors and the +/- 3% American National Standards Institute accuracy standard for disposable BP transducers were used. To test the accuracy of the bedside monitors, a certified transducer simulator was used to apply 100 mm Hg to each bedside monitor. To test the accuracy of the disposable BP transducers, a very accurate (+/- 0.05%) pneumatic dead weight tester was used to apply pressures to the transducer. A digital power supply and a 6 1/2 digit voltmeter were used. The average output of the bedside monitors when 100 mm Hg was applied was 99.90 +/- 0.83 mm Hg, with the worst cases being 98 and 103 mm Hg. For all 100 disposable pressure transducers, the average output was 100.03 +/- 0.55 mm Hg, with the worst cases being 98.53 and 101.36 when 100 mm Hg was applied. There was no important difference in the accuracy of the transducers obtained from the two vendors nor whether the transducers had been used clinically.

CONCLUSIONS

All disposable BP transducers tested were much more accurate than the American National Standards Institute standard for accuracy. Even the worst case transducers were twice as accurate as required by the American National Standards Institute standard. Only one bedside monitor was outside the +/- 2% accuracy range (103 mm Hg). Based on these findings, this author recommends that fixed calibration disposable transducers and fixed calibration bedside pressure monitoring systems be used. The clinical risks of air embolism and infection from the calibrating mercury manometer and the complexity of the calibration task are the overriding factors for making these recommendations.

Equivalence of fast flush and square wave testing of blood pressure monitoring systems

BACKGROUND

The accurate recording of intraarterial pressure depends upon an appropriate dynamic response of the monitoring system. Generation of a square wave (SW) at the catheter tip is the engineering and in vitro laboratory gold standard. Fast flush (FF) testing is the clinical test of choice. Results from these two test methods have been assumed equal but have not been empirically confirmed.

METHODS

We studied three different 5.1 cm catheter sizes (16 G, 18 G, 20 G Becton Dickinson, Sandy, UT) attached to three different lengths of arterial pressure tubing (36 in, 91.4 cm; 72 in, 182.9 cm; 108 in, 274.3 cm). An arterial recording system was assembled in the standard fashion by attaching a catheter to arterial pressure tubing, which was attached to a transducer (TXX-R, Ohmeda, formerly Viggo-Spectramed, Oxnard, CA) whose signal was recorded by a strip chart recorder (Gould 2400, Rolling Meadows, IL). The system was attached to a pressurized saline flush. The catheter tip was inserted into one port of a pressure generator. With the other port of the pressure generator open to atmosphere, FF tests were performed by activating the flush device of the transducer. Subsequent step response signals from the FF tests were then recorded from which natural frequency (fn) and damping coefficient (zeta) were calculated. Next, square waves were generated by closing the port that was open to atmosphere and attaching a signal generator to a pressure generator. Square waves so generated were recorded as described above and natural frequency and damping coefficients calculated. These procedures were repeated after 0.05 cc of air was introduced in the transducer and repeated again in a system containing a damping device (R.O.S.E., Resonant OverShoot Eliminator, Viggo-Spectramed, Oxnard, CA).

RESULTS

There was no significant difference between fn and zeta as calculated from the step response generated from the FF test versus fn and zeta as calculated from the square wave (SW) test in systems without air. However, in systems containing air, fn by FF testing was always less than fn by SW testing for all catheter sizes and extension tubing lengths (p < 0.05). Damping was also always greater by FF testing than by SW testing in systems with air for all catheter sizes and extension tubing lengths (p < 0.05). The R.O.S.E device created marked qualitative differences, although exact fn and zeta could not be quantified.

CONCLUSIONS

For the characterization of dynamic response of invasive blood pressure monitoring systems, the FF test and SW test yield identical results. However, under certain conditions-air, R.O.S.E device-dynamic response as measured by FF testing was not equivalent to dynamic response as measured by the gold standard-the SW test. Specifically, small amounts of air in fluid-filled invasive blood pressure monitoring systems cause a slightly worse dynamic response as measured by FF testing versus the laboratory gold standard-the SW test.

The role of sensory and nonsensory factors in body size estimations of eating disorder subjects

Body size distortion of anorectic and bulimic subjects was compared to controls via a video-distortion technique. Subjects judged the whole body, chest, hips and stomach regions. A adaptive probit estimation (APE) methodology examined separately the sensory and nonsensory components of body image distortion. Eating disorder subjects overestimated body size more than control subjects. There were no significant differences between eating disorder groups, although there was more variability in eating disorder subjects. Subjects overestimated more on whole body as compared to body regions. There were no differences in sensory sensitivity to detecting size differences between groups. Results indicate that differences in body size distortion between eating disorder and control subjects are due exclusively to affective, nonsensory factors.

Comparison of three psychophysical techniques for estimating body-size perception

Perception of body size was recorded for 63 university students (M age = 25.3 yr., 41 women) who estimated their own body size using three methods. Using the method of adjustment, subjects over- or underestimated their body size. A signal-detection analysis indicated that subjects were sensitive to detecting a 4% distortion in body size and that there was no systematic bias for reporting distortion as present or absent. Scores on the adaptive probit estimation task were significantly correlated with values for point of subjective equality and the size judgements with the method of adjustment. Over-all, this experiment demonstrated adaptive probit estimation as a reliable indicator of perceived body size, sensitivity in detecting size distortion, and response bias in making body-size judgements.

Computers in critical care

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.

Integrating computerized anesthesia charting into a hospital information system

BACKGROUND

Systems for computerization of anesthesia records have typically been 'stand-alone' computers many times connected to monitoring devices in the operating theater. A system was developed and tested at LDS Hospital in Salt Lake City, Utah, USA that was an integral part of the Health Evaluation through Logical Processing (HELP) hospital information system.

METHODS

The system was evaluated using time and motion studies to assess impact of the system on the anesthesiologists use of time, an assessment for completeness of the anesthesia record was conducted, and a questionnaire was used to assess anesthesiologists attitudes. Timing studies were performed on 44 surgical cases before computerization and 41 surgical cases after computerization. For both before and after computerization, about 80% of procedures were D&C, vaginal hysterectomy, laparoscopy, tubal ligation, or A&P repair.

RESULTS

The study showed a major reduction in time required for charting from 20.4% to 13.4% which was statistically significant (p = 0.0001). Other significant factors were a reduction in the time spent scanning the entire area which dropped from 10.5% to 5.6% (p = 0.001), patient preparation time increased from 10.1% to 13.1% (p = 0.02), the time spent arranging equipment increased from 6.4% to 8.1%, and the average time spent on non-anesthesia activities increased from 6.3% to 11.3%. The computerized anesthesia record was more legible, and complete than the manual record. The overall assessment of computer charting by anesthesiologists questionnaire was positive. The computerized anesthesia charting was preferred by the anesthesiologists, who, after one or two training sessions, used the system on their own.

CONCLUSIONS

It appears that having a computerized anesthesia charting system that is an integral part of a hospital information system not only saves anesthesiologists charting time, but also improves the quality of the record and was well accepted by busy private practice anesthesiologists.

Factors impacting the success of computerized preadmission screening

Many approaches to controlling costs under managed care rely on the ability to prospectively identify the type or level of service a patient requires at the time of presentation. Although computers may effectively predict these factors, the impact of such a computer system is greatly dependent on its integration into the admission process. Three factors that influence the effectiveness of predictive screening using a computer were identified. They are detection, intervention and compliance. The effect of these factors was then measured in a prospective randomized trial evaluating the effectiveness of computerized preadmission screening for predicting the appropriateness of inpatient care. This paper examines the three factors and their impact on the effectiveness of the system. A mathematical model that relates the factors to the overall effectiveness of computerized preadmission screening is proposed and considered in a more general context.

Nurses, pagers, and patient-specific criteria: three keys to improved critical value reporting

At LDS Hospital, we have developed and evaluated a computerized critical value reporting system based on digital pagers. Criteria used to identify critical values are patient-specific. An evaluation of the system was conducted from October 23, 1993 to January 21, 1994. Results showed that 100% of all critical values (497 values in the form of 335 alerts) were reported to clinicians within an average of 38.6 minutes, and that 51% of all alerts were received within 12 minutes. Data also showed that 92% of the alerts were considered valid, that 76% were communicated directly to the primary care nurse, and that 67% of the time nurses were previously unaware of the critical value(s).

Decision support in medicine: examples from the HELP system

Computerized health information systems can contribute to the care received by patients in a number of ways. Not the least of these is through interactions with health care providers to modify diagnostic and therapeutic decisions. Since its beginning, developers have used the HELP hospital information system to explore computerized interventions into the medical decision making process. By their nature these interventions imply a computer-directed interaction with the physicians, nurses, and therapists involved in delivering care. In this paper we describe four different approaches to this intervention. These include: (1) processes that respond to the appearance of certain types of clinical data by issuing an alert informing caregivers of these data's presence and import, (2) programs that critique new orders and propose changes in those orders when appropriate, (3) programs that suggest new orders and procedures in response to patient data suggesting their need, and (4) applications that function by summarizing patient care data and that attempt to retrospectively assess the average or typical quality of medical decisions and therapeutic interventions made by health care providers. These approaches are illustrated with experience from the HELP system.

Challenges and opportunities for computerizing the anesthesia record

Most observers would agree that the goal of computerizing the anesthesia record is a worthy one. Despite the fact that several academic groups and vendors have attempted to develop and provide computerized anesthesia charting, the practice is not widespread. In this review article, we attempt to outline the reasons for this reluctance to use computers for anesthesia charting. Where there are problems to be solved, there also are opportunities. We discuss the development of strategies to solve these problems and thus present opportunities for medical informatics professionals and anesthesiologists to work toward joint solutions. Solving these problems includes the development of consensus standards and working out technical, social, and educational difficulties. Details of the approaches recommended are outlined.

Evaluation of user acceptance of a clinical expert system

OBJECTIVE

To measure the attitudes of physicians and nurses who use the Health Evaluation through Logical Processing (HELP) clinical information system.

DESIGN

Questionnaire survey of 360 attending physicians and 960 staff nurses practicing at the LDS Hospital. The physicians' responses were signed, permitting follow-up for nonresponse and use of demographic data from staff files. The nurses' responses were anonymous and their demographic data were obtained from the questionnaires.

MEASUREMENTS

Fixed-choice questions with a Likert-type scale, supplemented by free-text comments. Question categories included: computer experience; general attitudes about impact of the system on practice; ranking of available functions; and desired future capabilities.

RESULTS

The response rate was 68% for the physicians and 39% for the nurses. Age, specialty, and general computer experience did not correlate with attitudes. Access to patient data and clinical alerts were rated highly. Respondents did not feel that expert computer systems would lead to external monitoring, or that these systems might compromise patient privacy. The physicians and nurses did not feel that computerized decision support decreased their decision-making power.

CONCLUSION

The responses to the questionnaire and "free-text comments" provided encouragement for future development and deployment of medical expert systems at LDS Hospital and sister hospitals. Although there has been some fear on the part of medical expert system developers that physicians would not adapt to or appreciate recommendations given by these systems, the results presented here are promising and may be of help to other system developers and evaluators.

Representative charting of vital signs in an intensive care unit

An automatic vital signs charting system had been operational in the intensive care units of our hospital for over 10 years, but the system was susceptible to non-representative transients in the data. A median selection rule was implemented to make the system less susceptible to transients. After implementation of the median rule, we examined (1) the agreement of the resulting medians and the values that would have been reported using the previous "real-time" system and (2) the frequency of occurrence of "out-of-range" values for each system. The median value system was found to improve the representativeness of the recorded data. Improved representativeness will enhance the usefulness of reports, but more importantly will enable us to use the resulting data as inputs to computerized practice protocols and other computerized decision support applications.

Computerized detection of nosocomial infections in newborns

Hospital-acquired infections are responsible for an increase in patient mortality and costs. Their detection is essential to permit better infection control. We developed an expert system specifically to detect infections in pediatric patients. The expert system is implemented at LDS Hospital that has a level three newborn intensive care unit and well baby units. We describe how the knowledge base of the expert system was developed, implemented, and validated in a retrospective study. The results of the system were compared to manual reviewer results. The expert system had a sensitivity of 84.5% and specificity of 92.8% in detecting hospital-acquired infections when compared to a physician reviewer. The Cohen's kappa between the expert system and the physician reviewer was 0.62 (p < .001).

Computerized decision support for concurrent utilization review using the HELP system

OBJECTIVE

Development and evaluation of computerized concurrent utilization review (UR) support taking advantage of a clinically rich computerized patient database.

DESIGN

The Automated Support System for Utilization Review (ASSURE) applies the Appropriateness Evaluation Protocol (AEP) Day of Care criteria to computerized patient data in the HELP hospital information system. This paper reports the development, verification, and validation of ASSURE.

MEASUREMENTS

Implementation correctness was verified by measuring agreement with a nurse reviewer, using separate sample sets for all 20 criteria for a total of 560 current inpatients. Usefulness in detecting inappropriate days of care was validated by two nurse reviewers who were crossed with manual and computer-assisted review methods in a blocked design for 168 current inpatients. Agreement with reviewers, sensitivity, specificity, positive predictive value, and negative predictive value were measured.

RESULTS

Agreement was very good for satisfaction of criteria, and good for appropriateness of day of care. A patient day identified by ASSURE as potentially inappropriate would be twice as likely to be judged inappropriate by a reviewer as a randomly selected patient day. Review of the 10% of patient days identified as potentially inappropriate by ASSURE would identify approximately 21% of the inappropriate days of care.

CONCLUSION

ASSURE is a clinically useful tool for screening adult acute care patients for inappropriate days of care, and promises to make a major contribution to reducing health care costs. The prognosis for successful routine clinical use is good.

Fundamentals of physiologic monitoring

For centuries, medical practitioners had no electronic medical instruments and had to rely on their senses of sight, hearing, smell, taste, and touch to obtain physiologic measurements. Although it is possible to estimate blood pressure by palpating the pulse at the radial or brachial artery, such estimates are not accurate. Determining arterial oxygen saturation of hemoglobin is more complex: how "blue" a patient appears depends on skin coloration, lighting, and the examiner's sense of color. Finally, using radiographic images to validate pulmonary edema when clinicians suspect that there is an elevated left atrial or pulmonary artery wedge pressure also challenges human senses. However, today's medical instruments use transducers and signal processors to convert patient information into a form that clinicians can easily perceive and understand. This article defines terms used with biomedical instrumentation and discusses the components of ideal physiologic patient monitoring systems.

Decision support for concurrent utilization review using a HELP-embedded expert system

Utilization Review is the process of evaluating the efficiency of medical care, based on examination of the patient record. At LDS Hospital, the electronic patient record is in an advanced state. This paper describes the development and knowledge base verification of ASSURE (Automated Support System for Utilization Review), an application within the HELP hospital information system. ASSURE applies the Appropriateness Evaluation Protocol (AEP) Day of Care criteria to the electronic patient record, concurrent with the patient's stay. In blinded trials, an experienced Utilization Manager agreed with 92% of ASSURE's decisions on single AEP criteria for 560 acute care patients. Agreement was statistically significant, with kappa = 0.84, P < 0.0001.

Computerized detection of arterial oxygen desaturations in an intensive care unit

Automatic detection of arterial oxygen desaturations was investigated by collecting pulse oximeter saturation data through an MIB. Two algorithms, one based on a threshold principle and the other based on moving median calculations, performed the detection. The median algorithm detected fewer "unimportant" events than did the threshold algorithm, but also did not detect some "important" events that the threshold algorithm detected. Successful detection algorithms will likely need to incorporate into their decision-making other patient information in addition to saturation. A proposed recording algorithm is described.

Computers, quality, and the clinical laboratory: a look at critical value reporting

The reporting of critical values is an important function of the clinical laboratory. The success of critical value reporting depends on laboratory personnel recognizing critical values and effectively communicating them to clinicians, and on clinicians correctly interpreting and using the critical values to provide appropriate patient care. At LDS Hospital, we have conducted a study of the critical value reporting process. Results of the study indicate that few critical values are actually reported by the clinical laboratory (only 28 of 294 critical values during November 24-30, 1992). Data on the quality of critical value documentation showed that 19 of 124 (15%) patient charts audited during January-February, 1993 contained no documentation that clinicians were ever aware of the critical value, or that corrective actions were taken. Other data on the quality of critical value reporting were also collected and analyzed. Study results have been used to design and implement a computerized critical value reporting system to improve the quality of critical value reporting at our hospital.

Using a hospital information system to assess the effects of adverse drug events

The most common adverse events experienced by hospitalized patients are drug related. While numerous studies have described the incidence and types of adverse drug events (ADEs), the actual effect of these events on patient outcomes have only been estimated. The studies that have described the effects of ADEs on patient outcomes have not stratified patients by severity of illness and hospital costs were estimated based on a percent of hospital charges. We designed a study to utilize the resources of our hospital information system to assess the attributable effects of ADEs on hospital length of stay and cost of hospitalization. This approach emphasized the difference between study patients and their matched control patients rather than overall differences between patients with and without ADEs. In addition, we used nursing acuity data to help adjust severity of illness within DRG groups and actual hospital costs were used instead of estimated costs. This study found that while the average length of stay for patients with ADEs was 8.19 days compared to 4.36 days for matched control patients, the attributable difference due to the ADEs was 1.94 days. Similar methods found that patients with ADEs had an average cost of hospitalization of $10,584 compared to $5,350 for those without and the attributable difference due to ADEs was $1,939. This indicates that the 569 ADEs at our hospital during 1992 resulted in an additional 1,104 extra patient days at a cost of $1,103,291.

Computerized continuous quality improvement methods used to optimize blood transfusions

Blood transfusion, although common, is not without risk and expense. Recently there has been a national focus on both overtransfusion and undertransfusion. To provide the best quality of patient care, there must be a balance between both over and undertransfusion. We used a computer system to minimize overtransfusion by prompting physicians when orders that did not meet accepted criteria were made. Continuous quality improvement methods were used to optimize blood transfusions. We also evaluated undertransfusions by assessing patients who did not receive a red cell transfusion when the Hemoglobin or Hematocrit showed it was clearly indicated. Using our computerized alerting system we are able to promptly notify physicians when such conditions exist. Results of the blood ordering show that overtransfusions of red cells have been minimized. Reductions in both mean Hematocrit and the standard deviation have occurred as predicted by continuous quality improvement theory. Assessment of undertransfusions showed that it was a minimal problem, but one that can be easily addressed with our laboratory alerting system.

The fast flush test measures the dynamic response of the entire blood pressure monitoring system

The fast flush test (FT) is the only test that allows clinicians to determine in vivo the natural frequency (fn) and damping coefficient (zeta) of an invasive blood pressure monitoring system. The underlying assumption to the validity of the FT is that it activates the whole system including the distal catheter. We devised an in vitro model of a typical invasive blood pressure monitoring system to determine whether this assumption was true. The model consisted of a conventional transducer with a flush device attached to various lengths of connecting tubing (91.4, 182.9, and 274.3 cm) terminated by four different diameter catheters (5.1 cm 14 G, 16 G, 18 G, and 20 G). A microtipped transducer catheter was inserted into the distal catheter tubing system. A FT was performed and the fn and zeta were recorded from the conventional transducer and simultaneously from the microtipped transducer catheter. Similar studies were conducted using the ROSE damping device as well as with systems including 0.1 ml of air near the conventional transducer. These studies utilized 18- and 20-G catheters with each of the three lengths of connecting tubing. All measurements of fn and zeta at the proximal conventional transducer were identical to those measurements as recorded by the distal microtipped transducer catheter. We conclude that the FT activates the whole monitoring system and that fn and zeta are the same throughout the system including the distal catheter.

Familiarity and anticipation of negative life events as moderator variables in predicting illness

A 10-month longitudinal study with 79 university students examined the role of positive and negative life experiences on the subsequent development of health problems. The Life Experiences Survey (LES; Sarason, Johnson & Siegel, 1978) was modified to measure the potential role of five moderating variables on illness. Students gave monthly reports of life events experienced, as well as health status, on the Seriousness of Illness Rating Scale (Wyler, Masuda & Holmes, 1968). Results indicated that both positive and negative life events were predictors of subsequent health problems. Negative life events that were familiar to the students and were unanticipated proved to be significant moderator variables; both factors were significant predictors of the number of health problems subsequently experienced.

Digital electronic communication between ICU ventilators and computers and printers

Although many modern ICU ventilators offer the option of electronic communication, most of these systems are not used because there is a huge communication gap between the ventilator and the computer it might be connected to. When such systems are now used, a large part of what is communicated is artifactual and misleading. We need to overcome both legal and knowledge barriers in the effort to provide seamless communication between ventilators and computers. With regard to the specific issues raised in this paper, here are our answers. Issue #1: Is it essential to have a digital electronic communication port on an ICU ventilator?

ANSWER

No, it is not essential. The purpose of the mechanical ventilator is to support pulmonary ventilation by supplying gas and pressure. There is no vital role for digital communication in the gas-delivery function of the ventilator; however, in the future it will be essential to have effective electronic communication in order to guarantee accurate and timely charting. Issue #2: What impact does electronic communication between a ventilator and a computer have on patient outcome?

ANSWER

Our preliminary data show that electronic communication can reduce the number of charting errors and can improve the timeliness of data entry. However, there is little evidence, other than anecdotal, that this has any impact on patient outcome. Automated charting has been shown to reduce the time spent on charting. This time-savings could be used to increase time spent in direct patient care, but there is no conclusive evidence that this occurs. In fact, one report on computerized charting systems indicates that the result is less time spent in direct patient care. Issue #3: If electronic communication is to be effective in the future, how should these interfaces be configured for mechanical ventilation?

ANSWER

We recommend an optimal algorithm for automated respiratory care charting that has been suggested. Sampling frequency: Sample data from the ventilator every 10 seconds. Ventilator-setting changes: Report every new setting if change lasts more than 3 minutes. Measured respiratory care data: Filter raw MIB-collected data with a 3-minute moving-median filter. Report one filtered value every hour for each variable. In addition, use a threshold table (Table 3) to define significant events. Report changes that remain above threshold more than 3 minutes. Report all measured respiratory-care data 1 minute following any ventilator-mode changes.

Effect of estriol on the structure and organization of collagen in the lamina propria of the immature rat uterus

Estradiol produces both hypertrophic and hyperplastic changes in the uterus, and these changes are associated with alterations in the structure of collagen in the lamina propria. Estriol induces only hypertrophic responses in the immature rat uterus; its effects on collagen structure were characterized in this study. Light micrographs of Masson's trichrome-stained sections revealed that the intensity of the collagen stain in the lamina propria of the rat uterus was profoundly reduced, relative to that in controls, 4 h after estriol (40 micrograms/kg) administration. These changes were not evident 24 h after estriol administration. In control uteri, transmission electron micrographs revealed that the collagen fibers surrounding stromal cells formed dense collections of bundles that were seen throughout the extracellular matrix, whereas in tissues exposed to estriol 4 h earlier, large regions of the extracellular spaces were devoid of collagen bundles. The 4-h changes in collagen were eliminated when animals were pretreated with actinomycin D (8 mg/kg) or cycloheximide (4 mg/kg). Dense collections of collagen bundles were present in tissues 24 h after estriol treatment, and their appearance was not altered by actinomycin D or cycloheximide treatment. Alterations in collagen 4 h after hormone administration appeared to be estrogen-specific since dexamethasone (600 micrograms/kg) and dihydrotestosterone (400 micrograms/kg) had no effect. These data provide evidence that the changes in collagen structure in the uterus are associated with events that function during the hypertrophic growth responses induced by estrogens.

Evaluation of accuracy and reproducibility of peak flowmeters at 1,400 m

Peak flow meters provide physicians and patients with objective measures about changes in pulmonary obstruction. We evaluated eight models of peak flowmeters and measured their accuracy and reproducibility with methods recently recommended by the National Asthma Education Program (NAEP). Waveforms from the American Thoracic Society's spirometer testing set were used to drive a computer-controlled syringe. Testing was done at Salt Lake City at an altitude 1,400 m. It appears that the original Wright peak flowmeter has been used as the "de facto" standard. We found that the original Wright peak flowmeter overestimated flows in its midrange; and, as a consequence, most of the other peak flowmeters also overestimated peak flows. The overestimation of peak flows may have been understated because of the 1,400-m altitude testing site. To the credit of the instrument manufacturers, we were pleasantly surprised with the quality, accuracy, and reproducibility of presently available peak flowmeters; however, as a result of our testing, we suspect that with little effort, manufacturers of peak flowmeters could improve the accuracy of their devices. Standardized testing methods and equipment should make the task of peak flowmeter design, manufacture, and testing even easier. We trust that manufacturers of peak flowmeters will respond appropriately and improve their instruments.

Improving blood transfusion practice: role of a computerized hospital information system

The recent focus on medical risk and financial cost has prompted a need for better guidelines for prescribing the transfusion of blood components. In 1987, to respond to the issues of quality transfusion practice and accurate evaluation, LDS Hospital (Salt Lake City, UT) began using a computerized, knowledge-based blood-ordering system. Each transfusion request was reviewed and flagged by the computer when it did not meet the criteria established by the medical staff. The study reviewed the use of red cells, platelets, and fresh-frozen plasma in 13,082 transfusion orders for 5847 consecutive patients from July 1, 1988, through June 30, 1989. The evaluation assessed, first, the adherence of physicians to computerized criteria and, second, their adherence to the quality of transfusion practice. A high percentage of the blood units ordered met the established criteria: 91.2 percent for the red cell transfusions, 72.9 percent for platelets, and 81.7 percent for fresh-frozen plasma. From the July 1, 1987, implementation date through June 1989, the mean hematocrit of persons being transfused dropped from 28.6 to 27.7 percent (0.29 = 0.28) (p less than 0.005) and the number of orders requiring review by the quality assurance department dropped from 100 to 14 percent; moreover, there was a true-exception rate of only 0.37 percent. The use of the computer system effected the implementation of the following measures: 1) identification of the indications and establishment of clear clinical and biologic parameters for every transfusion, and 2) measurement and improvement of institutional transfusion practice. These results demonstrated the efficacy of a computerized hospital information system in implementing continuous quality improvement for transfusion practice.(ABSTRACT TRUNCATED AT 250 WORDS)

Computerized identification of patients at high risk for hospital-acquired infection

Surveillance for hospital-acquired infections is required in U.S. hospitals, and statistical methods have been used to predict the risk of infection. We used the HELP (Health Evaluation through Logical Processing) Hospital Information System at LDS Hospital to develop computerized methods to identify and verify hospital-acquired infections. The criteria for hospital-acquired infection are standardized and based on the guidelines of the Study of the Efficacy of Nosocomial Infection Control and the Centers for Disease Control. The computer algorithms are automatically activated when key items of information, such as microbiology results, are reported. Computer surveillance identified more hospital-acquired infections than did traditional methods and has replaced manual surveillance in our 520-bed hospital. Data on verified hospital-acquired infections are electronically transferred to a microcomputer to facilitate outbreak investigation and the generation of reports on infection rates. Recently, we used the HELP system to employ statistical methods to automatically identify high-risk patients. Patient data from more than 6000 patients were used to develop a high-risk equation. Stepwise logistic regression identified 10 risk factors for nosocomial infection. The HELP system now uses this logistic-regression equation to monitor and determine the risk status for all hospitalized patients each day. The computer notifies infection control practitioners each morning of patients who are newly classified as being at high risk. Of 605 hospital-acquired infections during a 6-month period, 472 (78%) occurred in high-risk patients, and 380 (63%) were predicted before the onset of infection. Computerized regression equations to identify patients at risk of having hospital-acquired infections can help focus prevention efforts.

Integration of a stand-alone expert system with a hospital information system

A stand-alone PC expert system for evaluating the appropriateness of inpatient admissions has been integrated with an existing hospital information system. The expert system supports preadmission screening for appropriateness of inpatient admissions. The HIS provides extensive clinical data in a coded electronic form, permitting high-level decision support. The integrated system was developed for a 20 week randomized clinical trial to evaluate the effects of preadmission screening on inappropriate inpatient admissions. Three factors of the integration are considered: programmatic integration of the expert system, seamless presentation of mixed platform applications, and integration of coded data from the stand-alone application into the HIS data structure.

Real time data acquisition: recommendations for the Medical Information Bus (MIB)

Care of the acutely ill patient requires rapid acquisition, recording and communications of data. In the modern hospital it is not unusual for a patient to be connected to several monitoring and recording devices simultaneously. Each of these devices is typically made by a different manufacturer who may specialize in one sort of measurement, for example, pulse oximetry. Most of the modern monitoring and recording devices are micro-processor based and have communication capabilities. Unfortunately, there is no operable standard communication technology available from all devices. In addition different clinical staff (physicians, nurses, or respiratory therapists) may be responsible for collecting data. As a result there is a need to develop methods, standards, and strategies for timely and automatic collection of data from these monitoring and recording devices. We report on more than 5 years of clinical experience of automated ICU data collection using a prototype of the Medical Information Bus (MIB).

Performance of computerized protocols for the management of arterial oxygenation in an intensive care unit

Computerized protocols were created to direct the management of arterial oxygenation in critically ill ICU patients and have now been applied routinely, 24 hours a day, in the care of 80 such patients. The protocols used routine clinical information to generate specific instructions for therapy. We evaluated 21,347 instructions by measuring how many were correct and how often they were followed by the clinical staff. Instructions were followed 63.9% of the time in the first 8 patients and 92.3% in the subsequent 72 patients. Instruction accuracy improved after the initial 8 patients, increasing from 71.5% of total instructions to 92.8%. Instruction inaccuracy was primarily caused by software errors and inaccurate and untimely entry of clinical data into the computer. Software errors decreased from 7.2% in the first 8 patients to 0.8% in subsequent patients, while data entry problems decreased from 7.5% to 4.2%. We also assessed compliance with the protocols in a subset of 12 patients (2637 instructions) as a function of 1) the mode of ventilatory support, 2) whether the instruction was to increase or decrease the intensity of therapy or to wait for an interval of time and 3) whether the instruction was 'correct' or 'incorrect'. The mode of ventilatory support did not affect compliance with protocol instructions. Instructions to wait were more likely to be followed than instructions to change therapy. Ninety-seven percent of the correct instructions were followed and 27% of the incorrect instructions were followed.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical informatics in the intensive care unit: state of the art 1991

Intensive care medicine requires timely, accurate, and integrated patient records to provide the highest quality patient care. Computerized patient records offer the best method to achieve these needs. The expectations of society for medical progress through increased use of computers is growing. For optimal use of computers in the ICU there must be a harmonious collaboration between medical informaticists, physicians, nurses, therapists, and administrators. The future use of computers in ICU care will be evolutionary rather than revolutionary. We are on the frontier of some exciting times in the next decade as computers become commonplace in the clinical care process rather than an unusual event. This paper discusses the progress and challenges of computers in the ICU.

Innovations and research review: the impact of the HELP computer system on the LDS Hospital paper medical record

This study sought to answer the question: What percentage of an LDS Hospital patient's chart is contained in the HELP system? Using the number of pages in the record as the criteria, the answer is about 26 percent overall, but between 35 percent and 40 percent for patients in nursing divisions where computerized nurse charting is used. Although this fraction is likely to rise in the near future, the critical factor driving computerization is the desire for data usable in computerized decision making rather than the need to computerize the entire chart per se. The medical record at LDS Hospital will probably be a hybrid of computerized and paper data for some time to come.

Body-size judgments and eye movements associated with looking at body regions in obese and normal weight subjects

Eye movements of 20 male and 20 female obese and nonobese subjects were monitored during two body-size estimation tasks using a computer-based video technology. Analysis indicated no differences in body-size estimation between subjects using the staircase method. All subjects slightly underestimated body size; however, obese subjects were more sensitive than normal-weight subjects in detecting size distortion when a signal-detection task was employed. Eye-movement data indicated subjects looked longest at the chest, followed by waist, head, thighs, and calves/feet, in both the staircase and the signal-detection methods. Women viewed the waist region longer than men. On a signal-detection task subjects were better at detecting body-size distortion when viewing the body from the back than from front or profile.