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Biomedical subjects

D M Goodman

Publications and source records attributed to D M Goodman.

At least 19 recordsLinked to original sources
PubMed2003

Timed Pediatric Risk of Mortality Scores predict outcomes in pediatric liver transplant recipients.

More reliable methods are needed to identify children at risk for poor outcomes following liver transplantation. The Pediatric Risk of Mortality (PRISM) Score is a physiology-based scoring system used to quantify risk of mortality in pediatric intensive care unit (ICU) populations. We evaluated the PRISM Score as a predictor of outcomes including survival in the pediatric liver transplant (LT) population. We retrospectively reviewed the records of 67 consecutive LTs performed between August 1997 and February 2000 at an urban, tertiary children's hospital in Chicago, IL, USA. Four PRISM Scores were calculated to determine which periods were most meaningful. A Classic PRISM Score was calculated during first 24 h of ICU admission, and three PRISM Scores were timed with the patient's transplant: a pre-LT PRISM Score (24 h prior to transplant whether in ICU or not), a 24-h post-LT PRISM Score and a 48-h post-LT PRISM Score. These PRISM Scores and other predictors including transplant number, UNOS status and PELD Score were compared with outcomes including survival using univariate methods. The pre-LT, the 24- and the 48-h PRISM Score were associated with the post-LT number of ventilated days (p < 0.05), ICU days (p < 0.05) and with 1-yr survival (p < 0.04). The PRISM Scores were not related to the post-LT hospital length of stay (LOS) or to 1-yr re-transplantation. The PELD Score correlated with the post-LT hospital LOS, but was not associated with mortality or with the ICU LOS. A patient's UNOS status and Classic PRISM Score were not associated with any of the outcomes measured. PRISM Scores are valid predictors of outcome including survival in pediatric LT recipients. These findings help to demonstrate the importance in this population of a patient's general physiologic condition and its influence on the overall hospital course and survival.

Adolescent↗
PubMed2001

Non-contact measurement of thermal diffusivity in tissue.

We demonstrate the application of an infrared (IR) imaging technique for non-contact determination of thermal diffusivity in biological materials. The proposed method utilizes pulsed laser excitation to produce an initial three-dimensional temperature distribution in tissue, and records IR images of subsequent heat diffusion. The theoretical model assumes that the time-dependent temperature increase following pulsed laser exposure is due to independent heat diffusion in longitudinal and lateral directions. A nonlinear least-squares algorithm is used to compute the lateral thermal point spread function from a pair of recorded IR images and to determine the thermal diffusivity of a test specimen. The recorded time-sequence of IR images is used to compute thermal diffusivity as a function of increasing time interval between two IR emission images. Experimental application of the method was demonstrated using tissue phantoms, ex vivo samples of hydrated cartilage and in vivo epidermis.

Adult↗
PubMed2001

Routine chest radiographs in pediatric intensive care units.

OBJECTIVES: To determine whether interventions were performed based on portable routine morning chest x-rays (CXRs) in pediatric intensive care unit (PICU) patients and to identify patient subgroups for whom the routine CXR is most useful. DESIGN: Prospective multiinstitutional study. Setting. PICUs of 15 tertiary care hospitals. Patients. PICU patients who received a routine morning CXR were included in the study. OUTCOME MEASURES: Recorded data included: weight, diagnosis, presence of active cardiopulmonary problems, length of stay, and number and type of devices. The number and types of interventions based on the interpretation of the CXR were recorded. RESULTS: Five hundred twelve routine CXRs were evaluated. The majority of the routine chest radiographs were obtained on patients who were admitted for cardiovascular disease (195/512; 38%) or respiratory failure (186/512; 36%), and 465/512 of the routine CXRs (91%) were performed on patients with one or more devices. Two hundred thirty-one of the 512 routine CXRs (45%) resulted in 1 or more interventions. One hundred fifty-five of the 284 routine CXRs (55%) obtained in children </=10 kg resulted in one or more interventions, compared with 61/152 (40%) and 15/76 (20%) of routine CXRs obtained in children 10 to 40 kg and >/=40 kg, respectively. The frequency of interventions increased from 19% in children with no devices to >50% in children with 2 or more devices. One or more interventions were performed in 27% of routine CXRs when no active cardiopulmonary problems were present, compared with 51% of routine CXRs when active cardiopulmonary problems were present. Diagnosis and length of intensive care unit stay at the time the routine CXR was obtained did not affect the percentage of CXRs that resulted in interventions. CONCLUSIONS: Routine CXRs are more likely to result in interventions in the smaller, critically ill child with one or more devices and if active cardiopulmonary problems are present.

Body Weight↗
PubMed2000

Combining two excitation wavelengths for pulsed photothermal profiling of hypervascular lesions in human skin.

When pulsed photothermal radiometry (PPTR) is used for depth profiling of hypervascular lesions in human skin, melanin absorption also heats the most superficial skin layer (epidermis). Determination of lesion depth may be difficult when it lies close to the epidermal dermal junction, due to PPTR's limited spatial resolution. To overcome this problem, we have developed an approximation technique, which uses two excitation wavelengths (585 and 600 nm) to separate the vascular and epidermal components of the PPTR signal. This technique permits a noninvasive determination of lesion depth and epidermal thickness in vivo, even when the two layers are in close physical proximity to each other. Such information provides the physician with guidance in selecting the optimal parameters for laser therapy on an individual patient basis.

Blood↗
PubMed1998

Accuracy of subsurface temperature distributions computed from pulsed photothermal radiometry.

Pulsed photothermal radiometry (PPTR) is a non-contact method for determining the temperature increase in subsurface chromophore layers immediately following pulsed laser irradiation. In this paper the inherent limitations of PPTR are identified. A time record of infrared emission from a test material due to laser heating of a subsurface chromophore layer is calculated and used as input data for a non-negatively constrained conjugate gradient algorithm. Position and magnitude of temperature increase in a model chromophore layer immediately following pulsed laser irradiation are computed. Differences between simulated and computed temperature increase are reported as a function of thickness, depth and signal-to-noise ratio (SNR). The average depth of the chromophore layer and integral of temperature increase in the test material are accurately predicted by the algorithm. When the thickness/depth ratio is less than 25%, the computed peak temperature increase is always significantly less than the true value. Moreover, the computed thickness of the chromophore layer is much larger than the true value. The accuracy of the computed subsurface temperature distribution is investigated with the singular value decomposition of the kernel matrix. The relatively small number of right singular vectors that may be used (8% of the rank of the kernel matrix) to represent the simulated temperature increase in the test material limits the accuracy of PPTR. We show that relative error between simulated and computed temperature increase is essentially constant for a particular thickness/depth ratio.

Algorithms↗
PubMed1997

Non-invasive determination of port wine stain anatomy and physiology for optimal laser treatment strategies.

The treatment of port wine stains (PWSs) using a flashlamp-pumped pulsed dye laser is often performed using virtually identical irradiation parameters. Although encouraging clinical results have been reported, we propose that lasers will only reach their full potential provided treatment parameters match individual PWS anatomy and physiology. The purpose of this paper is to review the progress made on the technical development and clinical implementation of (i) infrared tomography (IRT), optical reflectance spectroscopy (ORS) and optical low-coherence reflectometry (OLCR) to obtain in vivo diagnostic data on individual PWS anatomy and physiology and (ii) models of light and heat propagation, predicting irreversible vascular injury in human skin, to select optimal laser wavelength, pulse duration, spot size and radiant exposure for complete PWS blanching in the fewest possible treatment sessions. Although non-invasive optical sensing techniques may provide significant diagnostic data, development of a realistic model will require a better understanding of relevant mechanisms for irreversible vascular injury.

Blood Vessels↗
PubMed1996

Anesthetics modulate phospholipase C hydrolysis of monolayer phospholipids by surface pressure.

Anesthetics are believed to produce anesthesia through the reversible inhibition of synaptic transmission but how this is accomplished is unknown. Based on earlier studies of anesthetic-enzyme-phospholipid interaction, we surmised that anesthetics may inhibit synaptic transmission by increasing synaptic membrane lateral pressure thereby inhibiting phospholipid hydrolysis, membrane transduction and synaptic transmission. As a first approximation towards investigating this concept, we hypothesized that anesthetics modulate the rate of phospholipase C hydrolysis of a lipid monolayer through its effects on surface pressure. The relationship between the hydrolysis rate of a monolayer of dipalmitoylphosphatidylcholine [14C-choline] (DPPC) by phospholipase C (Plase C) and monolayer surface pressure (SP) as altered by either halothane, isoflurane, or by physical compression at 37 degrees C was studied. The decline in surface 14C-activity as the [14C]choline diffuses into the Krebs-Ringer bicarbonate buffer aqueous subphase is estimated as the rate of DPPC hydrolysis measured by the initial slope method. DPPC hydrolysis was about 300 cpm/min and constant between SP of 0 to 20 dynes/cm. Higher SP between 25 and 30 dyne/cm, whether induced by halothane, isoflurane or physical compression, increased the rate of hydrolysis by 5-fold to a peak rate of about 1600 cpm/min at 25-30 dynes/cm. At a SP above 32 dynes/cm, DPPC hydrolysis abruptly ceased. We conclude that anesthetics can reversibly inhibit synaptic transmission through their effects on synaptic membrane lateral pressure. We also speculate that membrane lateral pressure may be a highly sensitive means of controlling membrane function through alteration in membrane lipid composition, membrane enzyme activity, receptor affinity and ion channel permeability.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1996

Imaging laser heated subsurface chromophores in biological materials: determination of lateral physical dimensions.

We describe a non-contact method using infrared radiometry to determine lateral physical dimensions of laser heated subsurface chromophores in biological materials. An imaging equation is derived that relates measured radiometric temperature change to the reduced two-dimensional temperature increase of laser heated chromophores. From measured images of radiometric temperature change, the lateral physical dimensions of chromophores positioned in an in vitro model of human skin are determined by deconvolution of the derived imaging equation using a non-negative constrained conjugate gradient algorithm. Conditions for optimum spatial resolution are found by analysis of a derived radiometric transfer function and correspond to superficial chromophores and/or weak infrared absorption in a laser irradiated biological material. Analysis indicates that if the infrared attenuation coefficient is sufficiently small (i.e., less than 10mm-1), infrared radiometry in combination with a deconvolution algorithm allows estimation of lateral physical dimensions of laser heated subsurface chromophores in human skin.

Algorithms↗
PubMed1995

Holographic methods in X-ray crystallography. IV. A fast algorithm and its application to macromolecular crystallography.

The holographic method makes use of partially modeled electron density and experimentally measured structure-factor amplitudes to recover electron density corresponding to the unmodeled part of a crystal structure. This paper describes a fast algorithm that makes it possible to apply the holographic method to sizable crystallographic problems. The algorithm uses positivity constraints on the electron density and can incorporate a 'target' electron density, making it similar to solvent flattening. The potential for applying the holographic method to macromolecular X-ray crystallography is assessed using both synthetic and experimental data.

Algorithms↗
PubMed1995

Probability of survival after prolonged extracorporeal membrane oxygenation in pediatric patients with acute respiratory failure. Extracorporeal Life Support Organization.

OBJECTIVE: Extracorporeal membrane oxygenation (ECMO) has been used with increasing frequency for respiratory failure that is unresponsive to conventional therapy. We examined the relationship between duration of ECMO and outcome to understand whether prolonged ECMO (duration of the procedure for > 14 days) was more commonly associated with futile therapy or eventual recovery. DESIGN: A cohort study of all patients reported to the Pediatric ECMO Registry for Acute Respiratory Failure of the Extracorporeal Life Support Organization. SETTING: Tertiary hospitals (n = 83) capable of providing extracorporeal support for pediatric patients. PATIENTS: Children (n = 382) between the ages of 1 wk and 18 yrs of age with severe respiratory failure. INTERVENTIONS: Extracorporeal membrane oxygenation. MEASUREMENTS AND MAIN RESULTS: The death or live hospital discharge of ECMO-treated patients, together with the post-ECMO mechanical ventilation course, were examined as a function of duration of ECMO and of pre-ECMO respiratory status. The occurrence of complications and the causes of death were also noted. The criteria used to initiate ECMO, as well as the determination of the futility of further ECMO, were determined by local practice at individual centers. There were 382 patients treated with ECMO, of whom 184 (48%) survived. The proportional survival in the patients treated for the longest duration was similar to the overall group. The cause of death was given for 168 patients: 32 neurologic deaths; nine deaths due to ECMO complications; and 30 deaths due to nonpulmonary organ failure. There were 97 deaths due to elective ECMO termination; 80 of these deaths occurred after the determination of the futility of anticipating pulmonary recovery. The latter deaths occurred at widely varying durations of ECMO, with a median of 282 hrs. However, at that same duration, 47 eventual survivors (26% of all survivors) continued to receive ECMO. By discriminant analysis, the survival rate was independently related (r2 = .18; p < .0001) to peak ventilator inspiratory pressure before ECMO and duration of intubation before ECMO, patient age, and the occurrence of several complications. CONCLUSIONS: While the survival rate in pediatric patients receiving ECMO appears related to the severity of lung disease and to the occurrence of ECMO complications, the survival rate in patients treated with ECMO courses of > 2 wks was similar to the survival rate of patients treated for shorter periods of time. ECMO was terminated in some patients for pulmonary futility at durations of ECMO associated with survival in substantial numbers of patients in whom ECMO was continued.

Acute Disease↗
PubMed1995

Depth profiling of laser-heated chromophores in biological tissues by pulsed photothermal radiometry.

A solution method is proposed to the inverse problem of determining the unknown initial temperature distribution in a laser-exposed test material from measurements provided by infrared radiometry. A Fredholm integral equation of the first kind is derived that relates the temporal evolution of the infrared signal amplitude to the unknown initial temperature distribution in the exposed test material. The singular-value decomposition is used to demonstrate the severely ill-posed nature of the derived inverse problem. Three inversion methods are used to estimate solutions for the initial temperature distribution. A nonnegatively constrained conjugate-gradient algorithm using early termination is found superior to unconstrained inversion methods and is applied to image the depth of laser-heated chromophores in human skin.

Absorption↗
PubMed1984

Demographic characteristics of the patient population in a Veterans Administration day hospital.

In order to better serve the clients in a Veterans Administration day-hospital program, the veterans' social and demographic characteristics were tabulated and correlations were calculated to investigate the existent of any interrelationships among the variables. The typical patient was in his mid-thirties; had a history of familial mental illness; had been hospitalized eight times previously, with the first hospitalization in his late twenties; had been unemployed for the previous 4 years; had completed at least 1 year of college; and had been married at some point in time, if not at the time of admission. One particularly interesting result was that acting-out behavior and the presence of substance abuse were related less to diagnosis (unless the diagnosis was itself substance abuse) and more to social class.

Adult↗
PubMed1980

Detection of cerebral lateralization of function using EEG alpha-contingent visual stimulation.

Lateralized functional specialization of cortical processing of linguistic and spatial information and anatomical lateralization of processing of hemiretinal stimuli were investigated with a randomized factorial design in 14 right-handed male undergraduates using EEG alpha-contingent visual stimulation. Words or geometric designs of equal luminosity and size were presented by computer to randomly selected visual half-fields contingent on the occurrence of alpha at one of 4 placements (left and right occipital and left and right temporal). The replicative reliability of alpha block and, by implication, the control of each stimulus type over different cortical sites, was assessed with the alpha control ratio (mean alpha duration/standard deviation of alpha durations). The alpha control ratio was significantly greater for alpha-contingent vs. random (non-contingent) stimulation. Within alpha-contingent data alone, cerebral lateralization was significantly demonstrated in the 2-way interactions of EEG hemisphere X visual field of stimulation, and of EEG hemisphere X type of stimulus (verbal or spatial). The alpha control ratio was higher for contralateral visual half-field stimulation compared to ipsilateral stimulation. Control was also significantly higher for cognitively appropriate stimulus-hemisphere combinations (verbal stimuli and left cerebral hemisphere, or spatial stimuli and right hemisphere) vs. inappropriate combinations (verbal, right hemisphere, or spatial, left hemisphere). These electrophysiological data corroborate in normal subjects the previous conceptions of hemispheric specialization ascertained with brain-damaged patients.

Adolescent↗