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Biomedical subjects

J H May

Publications and source records attributed to J H May.

10 recordsLinked to original sources
PubMed2000

Modeling the uncertainty of surgical procedure times: comparison of log-normal and normal models.

BACKGROUND: Medical institutions are under increased economic pressure to schedule elective surgeries efficiently to contain the costs of surgical services. Surgical scheduling is complicated by variability inherent in the duration of surgical procedures. Modeling that variability, in turn, provides a mechanism to generate accurate time estimates. Accurate time estimates are important operationally to improve operating room utilization and strategically to identify surgeons, procedures, or patients whose duration of surgeries differ from what might be expected. METHODS: The authors retrospectively studied 40,076 surgical cases (1,580 Current Procedural Terminology-anesthesia combinations, each with a case frequency of five or more) from a large teaching hospital, and attempted to determine whether the distribution of surgical procedure times more closely fit a normal or a log-normal distribution. The authors tested goodness-of-fit to these data for both models using the Shapiro-Wilk test. Reasons, in practice, the Shapiro-Wilk test may reject the fit of a log-normal model when in fact it should be retained were also evaluated. RESULTS: The Shapiro-Wilk test indicates that the log-normal model is superior to the normal model for a large and diverse set of surgeries. Goodness-of-fit tests may falsely reject the log-normal model during certain conditions that include rounding errors in procedure times, large sample sizes, untrimmed outliers, and heterogeneous mixed populations of surgical procedure times. CONCLUSIONS: The authors recommend use of the log-normal model for predicting surgical procedure times for Current Procedural Terminology-anesthesia combinations. The results help to legitimize the use of log transforms to normalize surgical procedure times before hypothesis testing using linear statistical models or other parametric statistical tests to investigate factors affecting the duration of surgeries.

Databases, Factual↗
PubMed2000

Surgeon and type of anesthesia predict variability in surgical procedure times.

BACKGROUND: Variability in surgical procedure times increases the cost of healthcare delivery by increasing both the underutilization and overutilization of expensive surgical resources. To reduce variability in surgical procedure times, we must identify and study its sources. METHODS: Our data set consisted of all surgeries performed over a 7-yr period at a large teaching hospital, resulting in 46,322 surgical cases. To study factors associated with variability in surgical procedure times, data mining techniques were used to segment and focus the data so that the analyses would be both technically and intellectually feasible. The data were subdivided into 40 representative segments of manageable size and variability based on headers adopted from the common procedural terminology classification. Each data segment was then analyzed using a main-effects linear model to identify and quantify specific sources of variability in surgical procedure times. RESULTS: The single most important source of variability in surgical procedure times was surgeon effect. Type of anesthesia, age, gender, and American Society of Anesthesiologists risk class were additional sources of variability. Intrinsic case-specific variability, unexplained by any of the preceding factors, was found to be highest for shorter surgeries relative to longer procedures. Variability in procedure times among surgeons was a multiplicative function (proportionate to time) of surgical time and total procedure time, such that as procedure times increased, variability in surgeons' surgical time increased proportionately. CONCLUSIONS: Surgeon-specific variability should be considered when building scheduling heuristics for longer surgeries. Results concerning variability in surgical procedure times due to factors such as type of anesthesia, age, gender, and American Society of Anesthesiologists risk class may be extrapolated to scheduling in other institutions, although specifics on individual surgeons may not. This research identifies factors associated with variability in surgical procedure times, knowledge of which may ultimately be used to improve surgical scheduling and operating room utilization.

Adolescent↗
PubMed1999

Surgical subspecialty block utilization and capacity planning: a minimal cost analysis model.

BACKGROUND: Operational inefficiencies in the use of operating rooms (ORs) are hidden by traditional measures of OR utilization. To better detect these inefficiencies, the authors defined two new terms, underutilization and overutilization, and illustrated how these measures might be used to evaluate the use of surgical subspecialty ORs. The authors also described capacity planning (optimizing surgical subspecialty block time allotments) using a minimal cost analysis (MCA) model. METHODS: The authors evaluated post hoc all surgeries performed over 6 yr at a large teaching hospital. To prepare utilization estimates, surgical records were categorized relative to budgeted OR block time for each subspecialty. Surgical cases beginning and ending during budgeted OR block time were categorized as budgeted utilization, budgeted time not used for surgery was underutilization, and cases beginning before/after budgeted block time were classified as overutilization. Cases that overlapped budgeted and nonbudgeted OR block time were parsed and the portions were assigned appropriately. Probability distributions were fitted to the historical patterns of surgical demand, and MCA block time budgets were estimated that minimized the costs of underutilization and overutilization for each subspecialty. To illustrate the potential savings if these MCA budgets were implemented, the authors compared actual operational costs to the estimated MCA budget costs and expressed the savings as a percentage of actual costs. RESULTS: The authors analyzed data from 58,251 surgical cases and 10 surgical subspecialty blocks. Classic utilization for each block-day by surgical subspecialty ranged from 44-113%. Average daily block-specific underutilization ranged from 16 to 60%, whereas overutilization ranged from 4 to 49%. CONCLUSIONS: Underutilization and overutilization are important measures because they may be used to evaluate the quality of OR schedules and the efficiency of OR utilization. Overutilization and underutilization also allow capacity planning using an MCA model This study indicated that the potential savings, if the MCA budgets were to be implemented, would be significant.

Costs and Cost Analysis↗
PubMed1997

Surgical suite utilization and capacity planning: a minimal cost analysis model.

In this paper, we are concerned with cost reduction, operating suite utilization, and capacity planning in surgical services. We studied 58,251 computerized surgical records from a teaching hospital to determine a model for measuring operating suite utilization, analyzing the quality of surgical schedules, and allocating surgical suite budgets (capacity planning). The classical definition of operating suite (OR) utilization, encountered in the literature is the ratio of the total OR time used to the total OR time allocated or budgeted. To create a better measure of utilization, we measured underutilization and overutilization providing a more complete description of the overall use of resources. Because the costs of under and overutilization of operating suites are high, they are attractive potential targets for cost minimization and the magnitude of the potential savings are such that attempts to measure and eliminate this inefficiency could be financially rewarding.

Algorithms↗
PubMed1996

Maternal serum amylase and lipase profiles in pregnancy: determinations in both once-sampled and multisampled patient cohorts.

The objective of this study was to determine the effect(s) of pregnancy and of advancing gestation on maternal serum amylase and lipase levels. Thus, serum amylase and lipase concentrations were quantitated in three groups of women. Groups included (1) 118 pregnant women whose serum amylase and lipase levels were measured once at various gestational ages ranging from 5 to 40 weeks, (2) 35 women comprising a multisampled patient cohort whose levels were measured sequentially at regular intervals throughout their pregnancy, and (3) 20 nonpregnant women of reproductive age whose levels were measured once. Results were statistically analyzed and trends in serum protein profiles with advancing gestation were charted. No significant differences were detected in either serum amylase or lipase concentrations as a result of pregnancy, nor were progressive changes noted with advancing gestation in either once-sampled or multisampled populations of pregnant patients. Therefore, contrary to the conclusions reached in some previous reports, no effects of pregnancy or of advancing gestation on maternal serum protein profiles were detected.

Amylases↗
PubMed1991

Investigation of an expert systems approach to bacterial identification.

An investigation was carried out to assess the feasibility of using an expert systems approach to assist in the identification of unknown isolates of bacteria. A system was developed using Lisp which utilized the knowledge stored in standard bacteriological texts. A comparison of the expert systems approach and the probabilistic approach based on Bayes Theorem was made together with the advantages and disadvantages of each approach.

Algorithms↗
PubMed1991

Knowledge-based schedule formulation and maintenance under uncertainty.

This paper is concerned with the dual sequential problems of (1) determining an acceptable personnel schedule over a specified time period, and (2) adjusting that schedule during the course of its execution in reaction to daily changes in both demand and available personnel. The first problem is schedule formulation; the second sequential problem is schedule execution. A rule-based, hierarchical system has been developed for first modeling and then solving both the schedule formulation and the schedule execution problems as a two-phase dependent process. The system is applied to the scheduling and staffing of nurses. A double-blind evaluation was conducted, which ascertained the quality of the resultant schedules in terms of maintainability, coverage, and personal satisfaction. The evaluation indicates that for units on which personnel changes have occurred, the prototype appears to perform as well as human schedulers.

Humans↗
PubMedDate not supplied

The assessment of the mutagenic potential of vehicle engine exhaust in the Ames Salmonella assay using a direct exposure method.

A method for the assessment of the mutagenic activity of vehicle engine exhaust in the Ames assay is described in which the bacterial strains used (TA98 and TA98/DNP) are exposed to the freshly produced engine exhaust using a "Cassella' slit sampler. The method is found to be effective both in the presence and absence of metabolic activation, using Aroclor-1254-induced rat liver S9 fractions. A comparison is made between the direct exposure method and the standard methods involving the collection of particulate samples on glass fibre filters and the testing of various extracts of these samples. Possible uses of the direct exposure testing method are suggested and the effect of sampling techniques on the results obtained in the Ames assay is also discussed.

Biotransformation↗
PubMedDate not supplied

Design of RCSS: Resource Coordination Systems for Surgical Services using distributed communications.

The plans for Resource Coordination for Surgical Services system (RCSS) incorporate a distributed objectbase with a coordinating server. User-centered information screens are customized for each geographic location in surgical services. User interfaces are designed to mimic paper lists and worksheets used by health care providers. Patient-specific and site-specific data will be entered and maintained by providers at each geographic location, but also rebroadcast and displayed for all providers. Although RCSS is primarily a communications system, it will also support review of surgical utilization and operative scheduling.

Cost Control↗