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Biomedical subjects

P Vernon

Publications and source records attributed to P Vernon.

At least 19 recordsLinked to original sources
PubMed1991

Modelling length bias in a longitudinally-linked record system of HIV cases.

We compare numbers of hospital admissions for intravenous drug using (IVDU) HIV patients and other HIV patients in acute-care facilities in New York State. Data consist of routinely collected hospital-discharge reports from New York's Statewide Planning and Research Cooperative System, linked into longitudinal case histories. Because recognition of an IVDU depends on an opioid diagnosis on any record in the case history, the observed distribution of the number of admissions per case for recognized IVDU's is biased towards greater numbers of admissions. We develop and apply a model to overcome this biasing. Our findings reveal that the mean numbers of admissions for the two groups differ significantly, but less so than without recognition of the length biasing.

Bias↗
PubMed1991

Validation of the cause of renal failure of patients in the Medicare end-stage renal disease program.

Studies addressing the epidemiological issues of end-stage renal disease (ESRD) and the implications for health resource allocations are valuable, especially because the Medicare ESRD program is expected to continue growing during the next decade. Studies on trends in the causes of renal failure have benefited from Medicare's extensive data files on ESRD patients. However, no studies have been published that validate the cause of renal failure field in the Medicare files. The primary disease causing renal failure for over 10,000 New York State patients in the Medicare ESRD program was compared with their hospital discharge diagnoses. Of these patients, 8,730 (83%) had a known cause of renal failure in the Health Care Financing Administration (HCFA) data files. Eighty-nine percent of these patients' primary cause of renal failure was matched with the same major hospital diagnostic code. Patients with diabetes and glomerulonephritis had the highest overall match rates (96% to 97%). Patients with polycystic kidney disease and causes of renal failure other than the four major causes had the lowest match rates (75% to 76%), but these match rates increased to 84% to 87% for patients hospitalized more than five times. Some differences in match rate by age and race were found. These findings suggest that HCFA data on the causes of renal failure of ESRD patients are reasonably accurate and can be used successfully to study a variety of issues related to the diseases leading to chronic renal failure.

Adult↗
PubMed1990

Transluminal angioplasty performed by the surgeon in lower limb arterial occlusive disease: one hundred fifty cases.

From February 1985 through November 1988, we performed 159 transluminal angioplasty in 135 patients with arterial occlusive disease of the lower limb. The indications were claudication, 114 cases (72%) and limb salvage, 45 cases (28%). Lesions consisted of one or more critical stenoses in 142 cases (61 iliac, 69 femoropopliteal, and 12 following surgical revascularization) and single segmental occlusion in 17 cases (one iliac and 16 femoropopliteal). Angioplasty failed because the guidewire could not be inserted in nine (5.7%) cases. Angioplasty was performed intraoperatively in 44 (29%) cases and as an isolated procedure in 106 cases (71%). When performed as an isolated procedure, the percutaneous approach was preferred in 34 of the iliac lesions (73%), 28 of the femoropopliteal lesions (50%), and four of the postsurgical lesions (50%). Early postoperative mortality was 3.3% (five patients). Eight early occlusions (5.3%) were observed, two after iliac and six after femoropopliteal angioplasty. Secondary clinical surveillance and hemodynamic and venous digital angiographic follow-up detected 35 instances of stenosis (25%), 18 of which were equal to or greater than 60%. Nine occlusions occurred (6.5%), six after iliac angioplasty and three after femoropopliteal angioplasty. At 24 months, primary cumulative patency of all transluminal angioplasties was 84% and secondary patency was 89%. Transluminal angioplasty performed by the surgeon in the operating room provides good results whether performed as an isolated procedure or as a complement to surgery. The study of secondary deteriorations confirms the value of morphologic surveillance by arteriograms. Arteriography appears to be of paramount importance in the evaluation of results and the codification of indications.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Transluminal angioplasty in a surgical setting. 150 cases].

Since 1985, 150 transluminal angioplasty operations have been performed by surgical teams, in the operating theater, for treatment of atheromatous lesions of the lower extremities, either as a complement to or in replacement of direct surgical repair. 150 angioplasties were carried out on patients with severe stage II lesions (72%). There was one or several significant stenosis in 140 of cases, and one short segmental thrombosis in 10 cases (1 common iliac and 9 superficial femoral or popliteal). These angioplasties fell into the following categories: 60 iliac, 78 femoral-popliteal and 12 angioplastic repairs of stenosis to iliac or distal femoral surgery (anastomosis, grafting, endarterectomy...). Angioplasty was combined with revascularization or lumbar sympathectomy in 29% of cases. It was performed singly in most cases (71%) and carried out percutaneously (45%) or by limited superficial proximal femoral approach under local anesthesia (26%), either directly or when the percutaneous approach failed. Eight cases of thrombosis (5.3%) developed during the first month: 2 cases after iliac angioplasty and 6 cases after femoral-popliteal angioplasty. Five deaths occurred consecutively to myocardial infarction. At long term, 4 cases of iliac thrombosis and 3 cases of thrombosis complicating femoral-popliteal angioplasty were detected. The overall cumulative permeability rate was 89% at 30 months, and there was no significant difference at one year's time between iliac and femoral-popliteal angioplasty patients (90% and 86%, respectively). Data collected from digital angiographic monitoring allowed to detect 9 cases of residual or recurrent stenosis (2 iliac, 6 femoral-popliteal and 1 postoperative lesions). Two repeat femoral-popliteal angioplasties were successfully performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1987

Dynamic modifications of the popliteal arterial axis in the sagittal plane during flexion of the knee.

The authors have studied, on the basis of purely radiologic data, the modifications of the popliteal arterial axis during flexion of the knee. They note the appearance in the sagittal plane of very marked flexures of the upper part of the artery, while the lower part describes a harmonious curve. These modifications take place between two fixed points: a cranial fixed point, represented by the origin of the descending artery of the knee, and a caudal fixed point represented by the origin of the anterior tibial artery. The pathologic importance of these modifications of the course of the artery should not be underestimated when obtaining revascularization by means of an arterial prosthesis.

Humans↗
PubMed1987

Measurement of lung tissue mass, thoracic blood and interstitial volumes by transmission/emission scanning using [99mTc]pertechnetate.

1. We have developed a method for non-invasive measurement of lung tissue mass, thoracic blood and interstitial volumes by a combination of transmission and emission scanning with technetium isotope (99mTc). 2. In a lung model we demonstrated that emission counts could be successfully corrected for attenuation with data obtained by transmission scanning, despite an uneven distribution of radioactivity and attenuation in the model. 3. In dogs we compared regional transthoracic tissue thickness, measured by transmission scanning, and regional 'thickness' of blood measured by transmission/emission scanning with direct gravimetric measurements made post mortem. Scanning and direct measurements correlated significantly. 4. In man we used a [99mTc]pertechnetate (99mTcO4) flood source to obtain antero-posterior transmission scans with a gamma-camera. The thickness of attenuating tissue was estimated in each pixel. Scans were obtained of thoracic blood (by labelling erythrocytes with 99mTcO4) and of interstitium (with 99mTc-labelled diethylenetriaminepenta-acetic acid and subtraction of the blood image). We used a computer program to correct the emission scans for attenuation using the transmission scan derived tissue thickness, pixel by pixel. Finally we took a lateral chest radiograph to estimate chest wall thickness. 5. In normal man lung tissue thickness at hilar level was 3.1 +/- 0.5 cm (n = 8). Thoracic blood thickness increased from the apex downwards in the upright lung, being 1.2 +/- 0.1 cm at the hilar level and 2.0 +/- 0.3 cm at the lung base. Interstitial thickness was 0.8 +/- 0.3 cm at the hilum and 0.85 +/- 0.2 at the base. These values compare well with data in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Geographic variations in elderly hospital and surgical discharge rates, New York State.

Hospital and surgical discharges for 1981, as recorded by the uniform hospital discharge data of New York State, were aggregated by county of residence and converted into age-sex adjusted rates. Elderly hospital discharge and surgery rates in New York State, 1981, varied 2.4- and 2-fold, respectively. Discharge rates of elderly with specific surgical procedures showed even greater variation. However, proportions of highly complex and non-elective procedures performed on the elderly were similar in counties with high and low surgical rates. A multiple regression model consisting of independent dimensions of county demographic and medical resources characteristics plus a proxy variable for surgical practice styles was applied to hospital and surgery rates. Variations in elderly surgical discharge rates were found to be related to the supply of medical resources and to surgical practice styles.

Aged↗
PubMed1986

Lung scan abnormalities in asthma and their correlation with lung function.

We have used asthma as a model of airways disease to test how well an automated, quantitative method of analysis of lung scans correlates with physiological measurements of disturbed lung function and gas exchange. We studies 25 asthmatics (age 16-73) of widely differing severity (forced expiratory volume in 1-s (FEV1) 22%-123% of predicted value), who had airways tests, arterial blood gas analysis, and krypton-technetium lung scans within a short time of each other. In all patients with airways obstruction and in some with normal function during remission, scans showed the typical appearances of multiple defects of ventilation and perfusion. The severity of ventilation defects was computed from the posterior view of the krypton scan compared to an age- and sex-matched normal range to yield an underventilation score. This correlated closely with the severity of airways obstruction as measured by forced expiratory manoeuvres. Ventilation and perfusion defects were usually imperfectly matched; the severity of this was computed using a subtraction method applied to the counts on the posterior krypton and technetium scans. The degree of mismatch was inversely related to the arterial partial pressure of oxygen (r = -0.86). The results suggest that computer scan analysis can provide useful functional information about the lung in airways disease.

Adolescent↗
PubMed1985

Changes in the subcellular distribution of calmodulin-kinase II during brain development.

Subcellular fractions prepared from rodent forebrain at different postnatal ages were examined for calmodulin-binding proteins using [125I]calmodulin and a gel overlay technique. Synaptic junction (SJ) fractions from newborn brain, which display purity comparable to adult SJ fractions, contain low but detectable amounts of 60 and 50 kdalton calmodulin-binding polypeptides; the latter being the major postsynaptic density protein. These polypeptides have recently been shown to be the calmodulin-binding protein subunits of calmodulin-dependent protein kinase II (CaM-kinase II). CaM-kinase II polypeptides represented the predominent calmodulin-binding proteins in nearly every subcellular fraction examined, regardless of postnatal age. Large increases were observed in the CaM-kinase II content of every subcellular fraction throughout postnatal development. During development, a striking shift in the subcellular distribution of CaM-kinase Ii was observed. Over 4 times as much CaM-kinase II was cytosolic relative to particulate in newborn brain while this ratio was completely reversed in adult brain. Large age-dependent increases in particulate-associated CaM-kinase II were observed in highly purified synaptic plasma membrane (5-fold) and SJ (14-fold) fractions. The CaM-kinase II content of SJ fractions increased approximately 70% between days 24 and 90, a period in development that follows the most active stages of synapse formation in situ. In adult brain, approximately 60% of CaM-kinase II in crude synaptosomal fractions (P2-INT) was recovered in SJ fractions. The CaM-kinase II in SPM fractions from all developmental ages resists solubilization in Triton X-100 and greater than 90% is recovered in SJ fractions. These studies indicate that during brain development the accumulation of SJ-associated CaM-kinase II represents an important process in the molecular and enzymatic maturation of CNS postsynaptic structures.

Age Factors↗
PubMed1985

Computer analysis of ventilation-perfusion scans for detection and assessment of lung disease.

A previously reported computer analysis has been used to provide numerical ventilation-perfusion lung scan data, for comparison with tests of airways function and results of arterial blood gas analysis in 11 patients with pulmonary embolism, 18 with asthma, and 37 with chronic obstructive lung disease. In pulmonary embolism an index of underperfusion showed high sensitivity, and an index of ventilation-perfusion mismatching correlated well with severity (hypoxaemia). In asthma an index of underventilation was sensitive and correlated well with severity of airways obstruction. In chronic obstructive lung disease the same index was sensitive but correlated poorly with severity. This was attributed to heterogeneity of the lung disease (airways obstruction plus emphysema) in chronic obstructive lung disease. Ventilation-perfusion mismatching was frequently present in airways disease, and was often of great severity in chronic obstructive lung disease. Discrimination between pulmonary embolism and either type of airways disease was possible by using a combination of underfusion and underventilation indices. The technique offers the prospect of increasing the information derived from lung scans and of automating the reporting of scans.

Adult↗
PubMed1972

Gastric emptying of solid meals after truncal vagotomy and pyloroplasty in human subjects.

Gastric emptying of isotopically labelled solid meals was studied in normal human subjects and in patients at different intervals after truncal vagotomy and Heineke-Mikulicz pyloroplasty. One to four weeks after vagotomy and pyloroplasty gastric emptying was delayed grossly in some patients regardless of the completeness of vagotomy. Patients with gross delay had symptoms of gastric retention. Eight weeks later emptying had returned towards normal and one or more years after vagotomy and pyloroplasty emptying was within the normal range.A subthreshold dose of carbachol injected during the course of emptying of a meal in some of the postvagotomy patients had no detectable influence on the rate of emptying of the meal.

Carbachol↗