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Biomedical subjects

A Gottschalk

Publications and source records attributed to A Gottschalk.

At least 73 records · Page 4Linked to original sources
PubMed1996

Small perfusion defects in suspected pulmonary embolism.

UNLABELLED: The purpose of this investigation was to assess the diagnostic value of 1 to 3 versus > 3 small subsegmental defects on perfusion lung scans of patients with suspected acute pulmonary embolism (PE). METHODS: Data from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were evaluated from patients with suspected acute PE. Angiograms, follow-up data and outcome classifications were used to determine PE status. The perfusion scan of included patients showed only small subsegmental defects ( < 25% of a segment) in the presence of a regionally normal chest radiograph. Findings on the ventilation scan were irrelevant. RESULTS: The positive predictive value for PE of perfusion lung scans with 1-3 small subsegmental defects was 1% to 3%, depending on the group analyzed. The positive predictive value for the PE of perfusion lung scans with > 3 small subsegmental defects was 11% to 17% depending on the group analyzed. CONCLUSION: Perfusion lung scans with 1-3 small subsegmental defects satisfy the criterion for a very low probability ( < 10% positive predictive value) for PE and perfusion lung scans with > 3 small subsegmental defects satisfy the criteria for a low probability ( < 20% positive predictive value) for PE.

Acute Disease↗
PubMed1996

Matched ventilation, perfusion and chest radiographic abnormalities in acute pulmonary embolism.

UNLABELLED: This investigation assessed the positive predictive value of matched ventilation/perfusion (V/Q) and chest radiographic defects (triple-matched defects) for the detection of acute pulmonary embolism (PE). METHODS: Data are from the Prospective investigation of Pulmonary Embolism Diagnosis (PIOPED). Only patients randomized for obligatory pulmonary angiography were included. Lungs were excluded if they showed any mismatched V/Q defect or any pleural effusion. RESULTS: Positive predictive values of triple-matched defects in the upper plus middle zones, 1 of 27 (4%), were less frequent than in the lower zones, 13 of 57 (23%) (p < 0.05). Triple-matched defects that involved 25-50% of a zone showed PE in 12 of 38 (32%) which was a higher positive predictive value than with smaller or larger triple-matched defects, 2 of 46 (4%) (p < 0.001). CONCLUSION: Refinement of the PIOPED data by elimination of nonrandomized patients, elimination of lungs with mismatched perfusion defects and elimination of lungs with a pleural effusion indicate that triple matches with PE (radiographic pulmonary infarcts) are infrequent in the upper and middle lung zones. When a triple match with PE occurs, it is most likely to be 25-50% of a zone.

Acute Disease↗
PubMed1995

Evidence of chaotic mood variation in bipolar disorder.

BACKGROUND: Using long-term daily mood records obtained from patients with bipolar disorder and normal subjects, we sought to determine the temporal pattern of mood in bipolar disorder. METHODS: Time series of 1.0 to 2.5 years from seven rapid-cycling patients with bipolar disorder and 28 normal controls were obtained. These were evaluated with several techniques to identify whether the temporal pattern of mood originates from a periodic, a random, or a deterministic source. RESULTS: True cyclicity was not apparent in the power spectra of either the normal subjects or the patients with bipolar disorder. Instead, spectra with a broadband "l/f" shape were observed in both groups, and these spectra were significantly flatter in normal subjects (P = .02). Correlation dimension estimates are a measure of nonlinear deterministic structure, and convergent estimates could be obtained for six of the seven patients with bipolar disorder and none of the normal subjects (P < .001). Additional findings are consistent with these results. CONCLUSIONS: These studies indicate that mood in patients with bipolar disorder is not truly cyclic for extended periods. Nonetheless, self-rated mood in bipolar disorder is significantly more organized than self-rated mood in normal subjects and can be characterized as a low-dimensional chaotic process. This characterization of the dynamics of bipolar disorder provides a unitary theoretical framework that can accommodate neurobiologic and psychosocial data and can reconcile existing models for the pathogenesis of the disorder. Furthermore, consideration of the dynamical structure of bipolar disorder may lead to new methods for predicting and controlling pathologic mood.

Adult↗
PubMed1993

Stratification of patients according to prior cardiopulmonary disease and probability assessment based on the number of mismatched segmental equivalent perfusion defects. Approaches to strengthen the diagnostic value of ventilation/perfusion lung scans in acute pulmonary embolism.

A categorical diagnosis of "high probability" or "intermediate probability" encompasses a spectrum of diagnostic probabilities of pulmonary embolism (PE) that is not communicated to the referring physician. The diagnostic value of ventilation/perfusion lung scans, in the present investigation, was strengthened by use of a table to determine the likelihood of PE in individual patients on the basis of the observed number of mismatched segmental equivalent perfusion defects. In addition, we tested the hypothesis that stratification of patients according to the presence or absence of prior cardiopulmonary disease may enhance the ventilation/perfusion scan assessment of the probability of PE among both of these clinical categories of patients. Data were derived from the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Ventilation/perfusion lung scans were evaluated in 378 patients with acute PE and 672 patients in whom suspected PE was excluded. Among patients with no prior cardiopulmonary disease, > or = 1.0 mismatched segmental equivalents was indicative of PE in 102 of 118 (86 percent) vs 113 of 155 (73 percent) among patients with prior cardiopulmonary disease (p < 0.02). Among patients with prior cardiopulmonary disease, > or = 2 mismatched segmental equivalents were required to indicate > or = 80 percent probability of PE. Stratification on the basis of the presence or absence of prior cardiopulmonary disease, therefore, enhanced the ability of ventilation/perfusion scan readers to assign an accurate positive predictive value and specificity to individual patients based on the observed number of mismatched segmental equivalent defects. Among patients with no prior cardiopulmonary disease, fewer mismatched segmental equivalent defects were required to indicate a high probability of PE than were required by PIOPED criteria. The findings from some of these patients, by PIOPED criteria, would have indicated intermediate probability. Some indeterminate probability readings, therefore, will be eliminated among patients stratified with no prior cardiopulmonary disease.

Acute Disease↗
PubMed1993

Mismatched vascular defects. An easy alternative to mismatched segmental equivalent defects for the interpretation of ventilation/perfusion lung scans in pulmonary embolism.

The purpose of this investigation was to test the hypothesis that ventilation/perfusion (V/Q) lung scans in patients with suspected acute pulmonary embolism (PE) can be evaluated on the basis of the total number of mismatched vascular defects, irrespective of whether such defects are moderate or large size segmental defects. Lung scan data from the national collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were assessed in 383 patients with acute PE and 681 patients in whom suspected PE was excluded. The predictive value of the cumulative number of mismatched moderate size segmental defects (irrespective of the number of mismatched large segmental defects) was nearly the same as that of mismatched large segmental defects (irrespective of the number of mismatched moderate size segmental defects). This suggests that the diagnostic value of mismatched moderate size segmental defects is the same as mismatched large segmental defects. Lung scans evaluated on the basis of the number of mismatched vascular defects (moderate and/or large segmental defects) were compared with V/Q scans evaluated on the basis of the number of mismatched segmental equivalents. The maximum likelihood estimates of the areas under the receiver operating characteristic (ROC) curves for the number of mismatched vascular defects and for mismatched segmental equivalents were similar (0.8512 vs 0.8530) (NS). Stratification according to the presence or absence of prior cardiopulmonary disease permitted a more accurate assessment of both clinical groups. Evaluation of V/Q scans by vascular defects and by segmental equivalents showed similar areas under the ROC curves. In conclusion, the number of mismatched vascular defects is as powerful for the assessment of V/Q scans as the number of mismatched segmental equivalents. The number of mismatched vascular defects, however, is easier to interpret, and permits a more objective evaluation.

Humans↗
PubMed1993

The addition of clinical assessment to stratification according to prior cardiopulmonary disease further optimizes the interpretation of ventilation/perfusion lung scans in pulmonary embolism.

The purpose of this investigation was to test the hypothesis that prior clinical assessment among patients stratified according to the presence or absence of prior cardiopulmonary disease enhances the accuracy of the predictive value of pulmonary embolism (PE) in the various categories. Diagnostic evaluation was made on the cumulative spectrum of mismatched defects, rather than a probability based on a preassigned number of mismatched segmental equivalent defects or mismatched vascular defects. Families of curves were derived that allowed an accurate assessment of the predictive value for each category of patients. The families of curves were comparable, irrespective of whether ventilation/perfusion scans were assessed on the basis of mismatched segmental equivalent defects or mismatched vascular defects, although the latter eliminated the necessity of estimating whether segmental defects were large or moderate in size. Clinical assessment was shown to prominently affect the predictive value of PE. Prior clinical assessment among patients stratified according to prior cardiopulmonary disease enhanced the accuracy of the predictive value of PE in the various groups of patients.

Heart Diseases↗
PubMed1993

Ventilation-perfusion scintigraphy in the PIOPED study. Part I. Data collection and tabulation.

The Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study of more than 700 patients is the largest existing study of the accuracy of lung scintigraphy in the diagnosis of acute pulmonary embolism. Perfusion scans were obtained in all patients and ventilation scans in almost all, using standardized techniques. Chest radiographs were obtained in all patients within 12 hr of the lung scan. Most patients underwent pulmonary arteriography. The images were interpreted according to a set of interpretive criteria which remained constant throughout the trial. A standardized, detailed description of each image set was derived by consensus of teams of two readers blinded to clinical and arteriographic findings. This communication reports the methods used to describe and categorize the ventilation-perfusion scintigrams obtained in patients who were enrolled in the PIOPED study. Scintigraphic technique is reviewed briefly, probability assessment is described and the scan description is reviewed in detail. The form used to describe the findings on ventilation-perfusion scans is reproduced. Use of this standardized description permits retrospective evaluation of the PIOPED interpretive criteria. In addition, it represents a rigorous approach to scan analysis which could facilitate application of formal interpretive schemes and enhance the reproducibility of lung scan interpretations in the clinical setting.

Data Collection↗
PubMed1993

Ventilation-perfusion scintigraphy in the PIOPED study. Part II. Evaluation of the scintigraphic criteria and interpretations.

This article presents an evaluation of the criteria used for categorical interpretation of the ventilation-perfusion (V/Q) scans performed in the PIOPED study. In addition, the correlation of percent probability estimates with the actual frequency of pulmonary embolism (PE) is presented. Cases which met the PIOPED criteria for various diagnostic categories were selected by computerized search of the detailed scan descriptions that had been done as part of the study. The process by which the scans were described was detailed in Part I of this report. Most of the criteria appropriately categorized V/Q scans which satisfied them. However, we recommend that three criteria should be reconsidered: 1. A single moderate perfusion defect is appropriately categorized as intermediate, rather than as low probability. 2. Extensive matched V/Q abnormalities are appropriate for low probability, provided that the chest radiograph is clear. On the other hand, single-matched defects may be better categorized as intermediate probability. Although due to the small number of cases with this finding, no definite, statistically founded recommendation can be made. 3. Two segmental mismatches may not be the optimum threshold for high probability, and in some cases should be considered for intermediate probability. However, due to the small number of cases with this finding, no definite, statistically founded recommendation can be made. We suggest that the revised criteria resulting from these adjustments should now be used for the interpretation of V/Q scans.

Evaluation Studies as Topic↗
PubMed1992

Prospective validation of the stripe sign in ventilation-perfusion scintigraphy.

The data base of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) was used to test the accuracy of the stripe sign for the exclusion of embolic perfusion defects on lung scintigrams. Lung scan readings showed the presence and location of this sign in 50 (4.7%) of 1,064 patients. Perfusion defects showing the stripe sign were not associated with pulmonary embolism in the same lung zone (upper, middle, or lower third of each lung) in 93% (79 of 85) of instances. Thirty-eight percent (n = 32) of lung zones with the stripe sign had associated chest radiographic abnormalities, and 69% (n = 59) had ventilation scan abnormalities. Formulation of the scan diagnosis according to PIOPED criteria showed fewer indeterminate readings in patients with the stripe sign and without pulmonary embolism when the stripe sign was used. Use of the sign changed diagnosis in less than 1% of the total population, however, because of its low overall prevalence. The stripe sign is a useful adjunct to standard criteria in the interpretation of pulmonary scintigrams for evaluation of suspected acute pulmonary embolism.

Humans↗
PubMed1992

A network model of respiratory rhythmogenesis.

A mathematical model of the three-phase respiratory network proposed by Richter et al. (News Physiol. Sci. 1: 109-112, 1986) is developed and its properties are examined. The model reproduces the experimentally determined trajectories of membrane potential for the five physiologically distinct types of neurons included. Stepwise parameter changes can produce a respiratory rhythm with only two separate electrophysiological phases, result in apnea, or produce more complex patterns of firing. The phase-resetting behavior of the model was obtained with perturbing stimuli and is comparable to experimentally determined phase-resetting data. There is reasonable agreement between model predictions and experimental results. In the model, the properties of the phase singularity make termination of the respiratory rhythm by an appropriately timed perturbation virtually impossible, which is in agreement with experimental observations. The rhythm can be stopped by alterations that simulate the effect of input from the superior laryngeal nerve; the rhythm is locked in the postinspiratory phase. We conclude that our results are consistent with the concept of a network oscillator as the source of the respiratory rhythm.

Animals↗