Luis Vargas - Academia.edu (original) (raw)

Papers by Luis Vargas

Research paper thumbnail of Neuropsychophysiological Study of Children at Risk for Schizophrenia: A Preliminary Report

Journal of The American Academy of Child and Adolescent Psychiatry, 1995

Objective: This initial report, from an ongoing study, examines whether children who have symptom... more Objective: This initial report, from an ongoing study, examines whether children who have symptoms of schizophrenia spectrum disorder display neuropsychological or neuroanatomic abnormalities similar to those seen in adults with schizophrenia. Method: Experimental subjects were 12 children between 8 and 12 years of age who displayed symptoms of early-onset schizophrenia or schizotypal personality disorder, as assessed through the Schedule for Affective Disorders and Schizophrenia for School-Age Children. The experimental subjects were compared with 13 controls on neuropsychological test performance, magnetic resonance imaging measurements, and proton magnetic resonance spectroscopy results. Results: Findings from the first phase of this project reveal significant overall group differences for several morphometric magnetic resonance imaging measurements and all neuropsychological measures. Differences between the groups were found for amygdala volume, mesial temporal volume, callosal area, and anatomic asymmetry.

Research paper thumbnail of Brain abnormalities in schizophrenia-spectrum children: implications for a neurodevelopmental perspective

Psychiatry Research-neuroimaging, 1997

Children with symptoms of schizophrenia-spectrum disorder (N= 20) were compared to controls (N= 2... more Children with symptoms of schizophrenia-spectrum disorder (N= 20) were compared to controls (N= 20) matched for age and socioeconomic status. Structural brain abnormalities were assessed with magnetic resonance imaging and functional brain abnormalities with neuropsychological tests. Children with schizophrenia-spectrum disorder had smaller amygdala and temporal cortex volumes, along with reduced callosal areas and an unusual pattern of neuroanatomic asymmetries. No differences were noted in overall brain volume, ventricular volume, hippocampal volume, or frontal area. Schizophrenia-spectrum children were also characterized by deficits in all neuropsychological functions examined. Some types of verbal memory and frontal lobe skills were especially deficient. These results support the hypothesis that children with schizophrenia-spectrum disorder have significant brain abnormalities, similar in some ways to those seen in adult schizophrenics. In conjunction with recent primate studies, the current results draw attention to the role of the amygdala as one relevant factor in the pathogenesis of schizophrenia. © 1997 Elsevier Science Ireland Ltd.

Research paper thumbnail of A probabilistic study of preference structures in the analytic hierarchy process with interval judgments

Mathematical and Computer Modelling, 1993

Here we study the problem of determining the ranking of the alternatives that one should infer wh... more Here we study the problem of determining the ranking of the alternatives that one should infer when decision makers use interval judgments rather than point estimates in the Analytic Hierarchy Process. How many rankings could one infer from the matrix of interval judgments, and which is the most likely to be selected?

Research paper thumbnail of A probabilistic study of preference structures in the analytic hierarchy process with interval judgments

Mathematical and Computer Modelling, 1993

Here we study the problem of determining the ranking of the alternatives that one should infer wh... more Here we study the problem of determining the ranking of the alternatives that one should infer when decision makers use interval judgments rather than point estimates in the Analytic Hierarchy Process. How many rankings could one infer from the matrix of interval judgments, and which is the most likely to be selected?

Research paper thumbnail of The possibility of group welfare functions

International Journal of Information Technology and Decision Making, 2005

... RefMan, ProCite), ReDIF Handle: RePEc:wsi:ijitdm:v:04:y:2005:i:02:p:167-176. Contact details ... more ... RefMan, ProCite), ReDIF Handle: RePEc:wsi:ijitdm:v:04:y:2005:i:02:p:167-176. Contact details of provider: Web page: http://www.worldscinet.com/ijitdm/ijitdm.shtml. Order Information: Email: For technical questions regarding this item, or to correct its listing, contact: (Tai Tone Lim ...

Research paper thumbnail of Uncertainty and rank order in the analytic hierarchy process

European Journal of Operational Research, 1987

The Analytic Hierarchy Process uses paired comparisons to derive a scale of relative importance f... more The Analytic Hierarchy Process uses paired comparisons to derive a scale of relative importance for alternatives. We investigate the effect of uncertainty in judgment on the stability of the rank order of alternatives. The uncertainty experienced by decision makers in making comparisons is measured by associating with each judgment an interval of numerical values. The approach leads to estimating the probability that an alternative or project exchanges rank with other projects. These probabilities are then used to calculate the probability that project would change rank at all. We combine the priority of importance of each project with the probability that it does not change rank, to obtain the final ranking.

Research paper thumbnail of Reply to "Remarks on the Analytic Hierarchy Process" by J. S. Dyer

Management Science, 1990

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, a... more JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

Research paper thumbnail of An overview of the analytic hierarchy process and its applications

European Journal of Operational Research, 1990

Research paper thumbnail of The allocation of intangible resources: the analytic hierarchy process and linear programming

Socio-economic Planning Sciences, 2003

An intangible is an attribute that has no scale of measurement. Intangibles such as effort and sk... more An intangible is an attribute that has no scale of measurement. Intangibles such as effort and skill arise in conjunction with resource allocation but are not usually included directly in a mathematical model because of the absence of a unit of measurement. However, intangibles can be quantified through relative measurement (priorities). Intangible resource allocation uses these priorities along with normalized

Research paper thumbnail of The Theory of Ratio Scale Estimation: Saaty's Analytic Hierarchy Process

Research paper thumbnail of The Seven Pillars of the Analytic Hierarchy Process

The Analytic Hierarchy Process (AHP) provides the objective mathematics to process the inescapabl... more The Analytic Hierarchy Process (AHP) provides the objective mathematics to process the inescapably subjective and personal preferences of an individual or a group in making a decision. With the AHP and its generalization, the Analytic Network Process (ANP), one constructs hierarchies or feedback networks, then makes judgments or performs measurements on pairs of elements with respect to a controlling element to derive ratio scales that are then synthesized throughout the structure to select the best alternative.

Research paper thumbnail of Experiments on rank preservation and reversal in relative measurement

Mathematical and Computer Modelling, 1993

We show through simulation that three methods of scaling, distributive (uniqueness is important),... more We show through simulation that three methods of scaling, distributive (uniqueness is important), ideal (uniqueness is not important), and utility (use of interval scales for the ideal) modes, yield the same ranking of alternatives with surprisingly high frequency, except for the case of copies or near copies of an alternative in which the distributive mode always reverses rank, which is legitimate when the uniqueness of the most preferred alternative is important.

Research paper thumbnail of The legitimacy of rank reversal

Omega-international Journal of Management Science, 1984

Research paper thumbnail of Modeling the Uncertainty of Surgical Procedure Times: Comparison of Log-normal and Normal Models

Anesthesiology, 2000

Medical institutions are under increased economic pressure to schedule elective surgeries efficie... more 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. 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. 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. 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.

Research paper thumbnail of Surgical Suite Utilization and Capacity Planning: A Minimal Cost Analysis Model

Journal of Medical Systems, 1997

In this paper, we are concerned with cost reduction, operating suite utilization, and capacity pl... more 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.

Research paper thumbnail of Fitting the Lognormal Distribution to Surgical Procedure Times

Decision Sciences, 2000

Minimum surgical times are positive and often large. The lognormal distribution has been proposed... more Minimum surgical times are positive and often large. The lognormal distribution has been proposed for modeling surgical data, and the three-parameter form of the lognormal, which includes a location parameter, should be appropriate for surgical data. We studied the goodness-of-fit performance, as measured by the Shapiro-Wilk p-value, of three estimators of the location parameter for the lognormal distribution, using a large data set of surgical times. Alternative models considered included the normal distribution and the two-parameter lognormal model, which sets the location parameter to zero. At least for samples with n > 30, data adequately fit by the normal had significantly smaller skewness than data not well fit by the normal, and data with larger relative minima (smallest order statistic divided by the mean) were better fit by a lognormal model. The rule “If the skewness of the data is greater than 0.35, use the three-parameter lognormal with the location parameter estimate proposed by Muralidhar & Zanakis (1992), otherwise, use the two-parameter model” works almost as well at specifying the lognormal model as more complex guidelines formulated by linear discriminant analysis and by tree induction.

Research paper thumbnail of Surgical Subspecialty Block Utilization and Capacity Planning: A Minimal Cost Analysis Model

Anesthesiology, 1999

Operational inefficiencies in the use of operating rooms (ORs) are hidden by traditional measures... more 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. 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. 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%. 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.

Research paper thumbnail of Surgeon and Type of Anesthesia Predict Variability in Surgical Procedure Times

Anesthesiology, 2000

Variability in surgical procedure times increases the cost of healthcare delivery by increasing b... more 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. 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. 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. 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.

Research paper thumbnail of Amplitude Channel A/B Channel B Rotation Output circuit

Research paper thumbnail of Neuropsychophysiological Study of Children at Risk for Schizophrenia: A Preliminary Report

Journal of The American Academy of Child and Adolescent Psychiatry, 1995

Objective: This initial report, from an ongoing study, examines whether children who have symptom... more Objective: This initial report, from an ongoing study, examines whether children who have symptoms of schizophrenia spectrum disorder display neuropsychological or neuroanatomic abnormalities similar to those seen in adults with schizophrenia. Method: Experimental subjects were 12 children between 8 and 12 years of age who displayed symptoms of early-onset schizophrenia or schizotypal personality disorder, as assessed through the Schedule for Affective Disorders and Schizophrenia for School-Age Children. The experimental subjects were compared with 13 controls on neuropsychological test performance, magnetic resonance imaging measurements, and proton magnetic resonance spectroscopy results. Results: Findings from the first phase of this project reveal significant overall group differences for several morphometric magnetic resonance imaging measurements and all neuropsychological measures. Differences between the groups were found for amygdala volume, mesial temporal volume, callosal area, and anatomic asymmetry.

Research paper thumbnail of Brain abnormalities in schizophrenia-spectrum children: implications for a neurodevelopmental perspective

Psychiatry Research-neuroimaging, 1997

Children with symptoms of schizophrenia-spectrum disorder (N= 20) were compared to controls (N= 2... more Children with symptoms of schizophrenia-spectrum disorder (N= 20) were compared to controls (N= 20) matched for age and socioeconomic status. Structural brain abnormalities were assessed with magnetic resonance imaging and functional brain abnormalities with neuropsychological tests. Children with schizophrenia-spectrum disorder had smaller amygdala and temporal cortex volumes, along with reduced callosal areas and an unusual pattern of neuroanatomic asymmetries. No differences were noted in overall brain volume, ventricular volume, hippocampal volume, or frontal area. Schizophrenia-spectrum children were also characterized by deficits in all neuropsychological functions examined. Some types of verbal memory and frontal lobe skills were especially deficient. These results support the hypothesis that children with schizophrenia-spectrum disorder have significant brain abnormalities, similar in some ways to those seen in adult schizophrenics. In conjunction with recent primate studies, the current results draw attention to the role of the amygdala as one relevant factor in the pathogenesis of schizophrenia. © 1997 Elsevier Science Ireland Ltd.

Research paper thumbnail of A probabilistic study of preference structures in the analytic hierarchy process with interval judgments

Mathematical and Computer Modelling, 1993

Here we study the problem of determining the ranking of the alternatives that one should infer wh... more Here we study the problem of determining the ranking of the alternatives that one should infer when decision makers use interval judgments rather than point estimates in the Analytic Hierarchy Process. How many rankings could one infer from the matrix of interval judgments, and which is the most likely to be selected?

Research paper thumbnail of A probabilistic study of preference structures in the analytic hierarchy process with interval judgments

Mathematical and Computer Modelling, 1993

Here we study the problem of determining the ranking of the alternatives that one should infer wh... more Here we study the problem of determining the ranking of the alternatives that one should infer when decision makers use interval judgments rather than point estimates in the Analytic Hierarchy Process. How many rankings could one infer from the matrix of interval judgments, and which is the most likely to be selected?

Research paper thumbnail of The possibility of group welfare functions

International Journal of Information Technology and Decision Making, 2005

... RefMan, ProCite), ReDIF Handle: RePEc:wsi:ijitdm:v:04:y:2005:i:02:p:167-176. Contact details ... more ... RefMan, ProCite), ReDIF Handle: RePEc:wsi:ijitdm:v:04:y:2005:i:02:p:167-176. Contact details of provider: Web page: http://www.worldscinet.com/ijitdm/ijitdm.shtml. Order Information: Email: For technical questions regarding this item, or to correct its listing, contact: (Tai Tone Lim ...

Research paper thumbnail of Uncertainty and rank order in the analytic hierarchy process

European Journal of Operational Research, 1987

The Analytic Hierarchy Process uses paired comparisons to derive a scale of relative importance f... more The Analytic Hierarchy Process uses paired comparisons to derive a scale of relative importance for alternatives. We investigate the effect of uncertainty in judgment on the stability of the rank order of alternatives. The uncertainty experienced by decision makers in making comparisons is measured by associating with each judgment an interval of numerical values. The approach leads to estimating the probability that an alternative or project exchanges rank with other projects. These probabilities are then used to calculate the probability that project would change rank at all. We combine the priority of importance of each project with the probability that it does not change rank, to obtain the final ranking.

Research paper thumbnail of Reply to "Remarks on the Analytic Hierarchy Process" by J. S. Dyer

Management Science, 1990

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, a... more JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

Research paper thumbnail of An overview of the analytic hierarchy process and its applications

European Journal of Operational Research, 1990

Research paper thumbnail of The allocation of intangible resources: the analytic hierarchy process and linear programming

Socio-economic Planning Sciences, 2003

An intangible is an attribute that has no scale of measurement. Intangibles such as effort and sk... more An intangible is an attribute that has no scale of measurement. Intangibles such as effort and skill arise in conjunction with resource allocation but are not usually included directly in a mathematical model because of the absence of a unit of measurement. However, intangibles can be quantified through relative measurement (priorities). Intangible resource allocation uses these priorities along with normalized

Research paper thumbnail of The Theory of Ratio Scale Estimation: Saaty's Analytic Hierarchy Process

Research paper thumbnail of The Seven Pillars of the Analytic Hierarchy Process

The Analytic Hierarchy Process (AHP) provides the objective mathematics to process the inescapabl... more The Analytic Hierarchy Process (AHP) provides the objective mathematics to process the inescapably subjective and personal preferences of an individual or a group in making a decision. With the AHP and its generalization, the Analytic Network Process (ANP), one constructs hierarchies or feedback networks, then makes judgments or performs measurements on pairs of elements with respect to a controlling element to derive ratio scales that are then synthesized throughout the structure to select the best alternative.

Research paper thumbnail of Experiments on rank preservation and reversal in relative measurement

Mathematical and Computer Modelling, 1993

We show through simulation that three methods of scaling, distributive (uniqueness is important),... more We show through simulation that three methods of scaling, distributive (uniqueness is important), ideal (uniqueness is not important), and utility (use of interval scales for the ideal) modes, yield the same ranking of alternatives with surprisingly high frequency, except for the case of copies or near copies of an alternative in which the distributive mode always reverses rank, which is legitimate when the uniqueness of the most preferred alternative is important.

Research paper thumbnail of The legitimacy of rank reversal

Omega-international Journal of Management Science, 1984

Research paper thumbnail of Modeling the Uncertainty of Surgical Procedure Times: Comparison of Log-normal and Normal Models

Anesthesiology, 2000

Medical institutions are under increased economic pressure to schedule elective surgeries efficie... more 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. 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. 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. 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.

Research paper thumbnail of Surgical Suite Utilization and Capacity Planning: A Minimal Cost Analysis Model

Journal of Medical Systems, 1997

In this paper, we are concerned with cost reduction, operating suite utilization, and capacity pl... more 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.

Research paper thumbnail of Fitting the Lognormal Distribution to Surgical Procedure Times

Decision Sciences, 2000

Minimum surgical times are positive and often large. The lognormal distribution has been proposed... more Minimum surgical times are positive and often large. The lognormal distribution has been proposed for modeling surgical data, and the three-parameter form of the lognormal, which includes a location parameter, should be appropriate for surgical data. We studied the goodness-of-fit performance, as measured by the Shapiro-Wilk p-value, of three estimators of the location parameter for the lognormal distribution, using a large data set of surgical times. Alternative models considered included the normal distribution and the two-parameter lognormal model, which sets the location parameter to zero. At least for samples with n > 30, data adequately fit by the normal had significantly smaller skewness than data not well fit by the normal, and data with larger relative minima (smallest order statistic divided by the mean) were better fit by a lognormal model. The rule “If the skewness of the data is greater than 0.35, use the three-parameter lognormal with the location parameter estimate proposed by Muralidhar & Zanakis (1992), otherwise, use the two-parameter model” works almost as well at specifying the lognormal model as more complex guidelines formulated by linear discriminant analysis and by tree induction.

Research paper thumbnail of Surgical Subspecialty Block Utilization and Capacity Planning: A Minimal Cost Analysis Model

Anesthesiology, 1999

Operational inefficiencies in the use of operating rooms (ORs) are hidden by traditional measures... more 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. 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. 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%. 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.

Research paper thumbnail of Surgeon and Type of Anesthesia Predict Variability in Surgical Procedure Times

Anesthesiology, 2000

Variability in surgical procedure times increases the cost of healthcare delivery by increasing b... more 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. 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. 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. 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.

Research paper thumbnail of Amplitude Channel A/B Channel B Rotation Output circuit