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At least 19 recordsLinked to original sources

PubMed1975

[Electron therapy using wedge filters. I. Experimental studies using wedge filters made from polystyrol].

Based on dose measurements at the phantom, the dose distributions obtained during electron therapy by the use of wedge filters made of polystyrol are reported. Energy doses from 15 to 42 MeV were applied; angles of wedges amounted to 10 degrees, 30 degrees, 45 degrees, and 60 degrees. Only by wedge-angles larger than 45 degrees, it was possible to bring about significant changes in the dose distribution. The results obtained are presented diagrammatically. The influence exerted by the wedge-angle and by electron energy upon the inclination of the 50%-isodose to the axis of the useful beam is shown by tables.

Electrons↗

PubMedDate not supplied

Characteristics of Clinac-18 wedged fields for 10-MV x rays.

The characteristics of wedged fields which affect their clinical use have been examined for the 10-MV x-ray beam from the Clinac-18. The methods used for obtaining and analyzing the wedged-field data are discussed. These characteristics have been examined in terms of (a) the wedge angle, (b) the variation of the wedge angle with field size, (c) the variation in the angle through which isodose curves between the approximate depths of 5 and 15 cm are turned relative to the central axis as a function of depth, and (d) the variation of wedge central-axis transmission factor with field size. Analysis of the data pertinent to these categories is presented for the 15-, 30-, 45-, and 60-deg wedges. In addition, the effect of the 60-deg wedge upon the position of maximum dose on the central axis was determined.

Particle Accelerators↗

PubMed1978

The effect of Swan-Ganz catheter height on the wedge pressure-left atrial pressure relationships in edema during positive-pressure ventilation.

We have studied the effect of the ventrical height of the pulmonary wedge catheter in the lung on the pulmonary wedge pressure-left atrial relationship during positive end-expiratory pressure ventilation in oleic acid-induced pulmonary edema. Pulmonary wedge catheters were placed above and below the left atrium in normal dogs and in dogs with oleic acid-induced edema. Wedge pressure and left atrial pressure were measured simultaneously during positive end-expiratory pressure ventilation (range, 0 to 30 cm H2O positive end-expiratory pressure). Pulmonary wedge catheters below the left atrium correctly recorded left atrial pressure and change in left atrial pressure at all positive end-expiratory pressures studied. Pulmonary wedge catheters above the atrium consistently recorded pressures higher than the normal left atrial pressure. They did not correctly respond to increases in left atrial pressure until it was increased to a value higher than the initial upper pulmonary wedge pressure. Pulmonary arterial catheters, when properly placed, should be reliable indicators of left atrial pressure during positive-pressure ventilation in normal and edematous lungs.

Animals↗

PubMedDate not supplied

A theoretical analysis of cast wedging with practical applications.

Cast wedging using vector and geometrical analysis demonstrated that the open wedge produces distraction of the fracture, the closing wedge shortening, and that the opening--closing wedge can perfectly correct skeletal deformity. The level of wedging should lie at the axis intersection, i.e., at the intersection of the long axes of the 2 major fracture fragments. An open wedge at the axis intersection is recommended for tibial shaft fractures immobilized with long leg casts; an opening--closing wedge at the axis intersection, for fractures immobilized with "pins and plaster".

Bone Nails↗

PubMed1976

A comparison of wedge and segmental resection of the lung.

In the past few years there has been increasing use of limited resection for pulmonary carcinoma, especially in patients with restricted cardiorespiratory function. Because there is frequently a choice as to the type of limited resection, it was considered worth while to review the safety and efficiency of the two principal types. In total, 212 wedge resections and 281 segmental resections are reported. Despite certain theoretical advantages to segmentectomy, wedge resection carried a lower complication rate. Seventy-one per cent of wedge resections were free of complications compared to 54% of segmental resections. Minor complications were defined as apical air space and apical haematoma. The incidence of minor complications was similar for each group, 22% for wedge resections and 27% for segmentectomies. However, there was a significantly higher major complication rate in the segmental resection group (19%) compared to the wedge group (7%). This is understandable, considering the amount of raw lung surface exposed after segmental resection. It appears that where it is surgically feasible, wedge resection should be practised.

Hemoptysis↗

PubMed1978

Pulmonary arterial wedge pressure in hemorrhagic shock.

To test the hypothesis that the position of a pulmonary arterial wedge catheter might affect its ability to measure left atrial pressure, we inserted 2 wedge catheters, one superiorly, and one dependently, in supine dogs. The position of the catheter tips and the zero level of the transducers were located on a lateral chest radiograph so that by referencing the transducers to the posterior surface of the lung and measuring the height of the catheter tip above that reference point, the zones in which the catheter tips were located were determined. When both catheters were in Zone III (pulmonary arterial pressure greater than left atrial pressure greater than alveolar pressure), the wedge pressures accurately reflected left atrial pressure. However, during hemorrhage, left atrial pressure decreased, and when the pulmonary arterial wedge catheter placed superiorly came under Zone II conditions (pulmonary arterial pressure greater than alveolar pressure greater than left atrial pressure), it recorded a constant pressure somewhat greater than left atrial pressure; the pulmonary arterial wedge catheter placed dependently, which remained in Zone III, continued to reflect left atrial pressure. We conclude that a pulmonary arterial wedge catheter measures left atrial pressure only when it is located in Zone III.

Animals↗

PubMed1978

Hormone levels following wedge resection in polycystic ovary syndrome.

A study of serum estradiol, progesterone, 17alpha-hydroxy-progesterone, testosterone, dihydrotestosterone, dehydroepiandrosterone (DHA), delta4-androstenedione (delta4-A), FSH, and LH was carried out in one of three sisters having polycystic ovarian disease for a period of 18 days before wedge resection, at the time of surgery, and for 24 days following wedge resection. The mean levels of 17alpha-hydroxyprogesterone, testosterone, DHA, delta4-A, and LH were remarkably elevated prior to wedge resection. There was considerable day-to-day variation. Serum LH varied from 12.5 to 70.5 mIU/ml with a mean of 41.03 +/- 3.55 mIU/ml. Serum estradiol and progesterone levels were generally higher than those found in the early follicular phage. Wedge resection resulted in a fall in serum estradiol, progesterone, 17alpha-hydroxyprogesterone, DHA, and delta4-A. Ovarian secretion of the last four steroids was confirmed by a study of the ovarian vein blood obtained at the time of surgery. An estradiol peak occurred on the 14th post wedge resection day with smaller increases in 17alpha-hydroxyprogesterone, DHA and delta4-A. An increase in serum LH occurred on the 15th post wedge resection day with a peak on Day 16 accompanied by increases in FSH and progesterone. The postovulatory rise of progesterone was accompanied by reduction of serum LH levels to those generally found in the early part of the menstrual cycle. Various hypotheses for the ovulatory failure are discussed.

Adolescent↗

PubMed1978

Variations in depth-dose data between open and wedge fields for 4-MV X-rays.

Central-axis depth-dose data for 4-MV x rays, including tissue-maximum ratios, were measured for wedge fields. Comparison with corresponding open-field data revealed differences in magnitude which increased with depth, field size, and wedge thickness. However, phantom scatter correction factors for the wedge fields differed less than 1% from corresponding open-field factors. The differences in central-axis per cent depth doses between the two types of fields indicate beam hardening by the wedge filter. This study also implies that the derivation of tissue-maximum ratios from central-axis per cent depth is as valid for wedge as for open fields.

Humans↗

PubMed1978

The validity of determinations of pulmonary wedge pressure during mechanical ventilation.

Changes in the mean pulmonary wedge pressure were measured during temporary disconnection from a ventilator in 29 patients to assess the effects of therapy with controlled-volume ventilation on determinations of pulmonary wedge pressure. In 16 observations performed during therapy with intermittent positive-pressure ventilation, the mean value for the pulmonary wedge pressure was the same (10.3 mm Hg) with the patients connected to or disconnected from the ventilator. Thirteen of the patients were also maintained on therapy with positive end-expiratory pressure (PEEP); the mean (+/- SD) of 17 measurements of pulmonary wedge pressure did not show a significant variation on cessation of mechanical ventilation (12.5 +/- 6.7 mm Hg vs 11.7 +/- 6.9 mm Hg; P greater than 0.05). We conclude that pulmonary wedge pressure can be measured accurately at the end of exhalation during the administration of positive-pressure ventilation with 10 cm H2O of PEEP. The suggested practice of discontinuing mechanical ventilation in order to obtain a more exact measurement is not warranted.

Blood Pressure↗

PubMed1978

[The diagnostic value of wedged hepatic vein pressure in chronic hepatitis and liver cirrhosis (author's transl)].

In 38 patients with chronic hepatitis and 53 patients with liver cirrhosis the portal vein pressure was determined by wedged hepatic vein pressure (WHVP). There were significant differences among chronic persistent, chronic active hepatitis and liver cirrhosis. The wedged hepatic vein pressure increased in chronic active hepatitis according to the rate of hepatic connective tissue. The platelet count and the thromboplastin time were correlated to the values of wedged hepatic vein pressure not only in chronic active hepatitis but in liver cirrhosis as well. The correlation among serum albumin level, bromsulphalein retention and systolic blood pressure after Riva-Rocci and wedged hepatic vein pressure was significant in liver cirrhosis exclusively. Even if the determination of wedged hepatic vein pressure does not permit an absolute statement on the risk of hemorrhage of esophageal varicosis it is nevertheless suited for follow-up controls in chronic hepatitis and liver cirrhosis and renders possible an outlook on the progress of the disease.

Blood Pressure Determination↗

PubMed1977

Pulmonary artery wedge pressures in congenital heart disease.

The bilateral measurement of pulmonary artery wedge pressure is essential in the cardiac catheterization evaluation of all patients with pulmonary artery hypertension. Five cases of pulmonary venous obstruction are presented, 4 of whom had additional intracardiac defects. The pulmonary artery hypertension in these 4 patients was initially attributed to the associated cardiac anomalies and because the left atrium had been entered directly with the catheter in each case, pulmonary artery wedge to the left atrium pressure gradients were initially either not obtained or were discounted as being artificial. Pulmonary venous obstruction was recognized in all 5 cases on the basis of an elevated pulmonary artery wedge pressure, and the anatomic site of the obstruction was successfully documented. Unless bilateral pulmonary artery wedge pressures are measured in all patients with pulmonary artery hypertension regardless of the presence of additional cardiac anomalies, a surgically correctable cause of pulmonary hypertension may be overlooked.

Blood Pressure↗

PubMed1977

Use of a wedge cuvette in thin layer photometry and its application to oximetry.

A wedge cuvette was constructed by fixing 2 glass plates at a known angle with a spacer at one end. This resulted in a thin layer with thickness varying from 0 to 250 micrometer. By measuring the intensity of a beam of light through the thin layer as a function of distance along the wedge (and thus layer thickness), the absorption coefficient at the light wavelength used could be obtained without a separate measurement of I0, the reference light intensity. In addition, the difficult problem of determining accurate layer thickness as encoutered in conventional thin layer photometry has been avoided. Tests of the wedge cuvette method with Evans Blue and Malachite Green serial dilutions as well as with haemoglobin solutions at several oxygen saturations demonstrate that accuracy of the order of 1% can be obtained. Application of the wedge cuvette in experiments on oxygen uptake by layers of haemoglobin solution are discussed.

Hemoglobins↗

PubMed1976

Pulmonary arterial wedge and left atrial pressures and the site of hypoxic pulmonary vasoconstriction.

The pulmonary vascular response to breathing 5% oxygen in nitrogen was studied in anesthetized, artificially ventilated dogs. The pulmonary arterial (Pa), pulmonary arterial wedge (PW), left atrial (LAP) pressures and pulmonary blood flow (Q) were monitored. The pulmonary arterial catheter was wedged at the mid-lung level. At 10 min of hypoxia, Pa-PW pressure gradient increased while the PW-LAP gradient did not change significantly. The PW and LAP were significantly correlated during room air breathing (r=0.832) and during hypoxia (r=0.980). The calculated resistance from the pulmonary artery to the wedged catheter (Pa-Pa/Q) increased and the calculated resistance from the wedged catheter (Pa-Pw/Q) did not change significantly. These findings indicate that the mean LAP and PW pressures are not significantly different during severe hypoxia, and that the increase in pulmonary vascular resistance during hypoxia is due to constriction of the large precapillary vessels.

Animals↗

PubMed1975

Pulmonary edema related to changes in colloid osmotic and pulmonary artery wedge pressure in patients after acute myocardial infarction.

Pulmonary artery wedge and plasma colloid osmotic pressures and their relationship to pulmonary edema were investigated in 26 patients with acute myocardial infarction of whom 14 developed pulmonary edema. In the absence of pulmonary edema, both the pulmonary artery wedge pressure and plasma colloid osmotic pressure were in normal range; after onset pulmonary edema, a moderate increase in pulmonary wedge pressure and reduction in plasma colloid osmotic pressure were observed. When the gradient between the plasma colloid osmotic pressure and the pulmonary artery wedge pressure was calculated, highly significant differences were demonstrated (P less than 0.002). In the absence of pulmonary edema, this gradient averaged 9.7 (plus or minus 1.7 SEM) torr; following appearance of pulmonary edema, it was reduced to 1.2 (plus or minus 1.3) torr. During therapy with digoxin and furosemide, reversal of pulmonary edema was closely related to a concomitant change in the colloid osmotic-hydrostatic pressure gradient. These observations indicate that both increases in pulmonary capillary pressure and decreases in colloid osmotic pressure may follow the onset of pulmonary edema. Such decline in colloid osmotic pressure and especially the reduction in colloid osmotic-hydrostatic capillary pressure gradient may favor transudation of fluid into the lungs.

Adult↗

PubMed1977

Peripheral pulmonary wedge angiography in chronic obstructive pulmonary disease. Relationship to pulmonary function, chest x-ray film, and hemodynamic data.

Peripheral pulmonary wedge angiographic studies can investigate only limited areas of the pulmonary vascular bed; nevertheless, this technique is very useful in emphasizing the morphologic changes of small vessels (less than 1 mm in diameter) in pulmonary emphysema. The aim of this work is to determine the relationship between peripheral wedge angiographic appearances and pulmonary function, the chest x-ray film, and hemodynamic data in patients with chronic obstructive pulmonary disease. Three healthy subjects, four patients with type-A chronic obstructive pulmonary disease, and eight patients with type-B chronic obstructive pulmonary disease were studied. Among the tests of pulmonary function, only a marked reduction (less than 60 percent of predicted) of the diffusing capacity for carbon monoxide is always indicative of severe widespread emphysema. No relationship was found between hemodynamic data and peripheral wedge angiographic findings. Some agreement resulted between the chest x-ray film and peripheral wedge angiographic abnormalities only in patients with type-A chronic obstructive pulmonary disease; on the contrary, in patients with type-B chronic obstructive pulmonary disease, both false-positives and false-negatives were noted.

Angiography↗

PubMed1978

Colloid osmotic and pulmonary wedge pressures in acute respiratory failure following hemorrhage.

Acute respiratory failure evolved in five patients following hypovolemic shock related to trauma or surgical operation, or both. A reduction in colloid osmotic pressure, increases in pulmonary artery wedge pressure and reductions in colloid osmotic pressure-pulmonary artery wedge pressure gradient to levels which are likely to account for pulmonary edema were observed. Accordingly, reduction in the colloid hydrostatic pressure gradient may, in part, explain the development of acute respiratory failure after acute blood loss. In one instance, however, the absence of such reduction in the colloid osmotic pressure-pulmonary artery wedge pressure gradient together with increases in pulmonary vascular resistance showed that colloid osmotic pressure and pulmonary artery wedge pressure are not exclusively operative in the pathogenesis of the clinical syndrome of acute respiratory failure.

Acute Disease↗

PubMed1978

Relationship between colloid osmotic pressure and pulmonary artery wedge pressure in patients with acute cardiorespiratory failure.

Close relationships between progressive respiratory failure, roentgenographic signs of pulmonary opacification and decreases in the difference between colloid osmotic pressure of plasma and the pulmonary artery wedge pressure (colloid-hydrosatic pressure gradient) were demonstrated in 49 critically ill patients with multisystem failure, in patients in shock. The potential importance of this relationship is underscored by the observation that fatal progression of pulmonary edema was related to a critical reduction in the colloid-hydrostatic pressure gradient to levels of less than 0 mm Hg. More often, reduction in colloid osmotic pressure rather than increases in left ventricular filling pressure (pulmonary artery wedge pressure) accounted for the decline in colloid-hydrostatic pressure gradient. Routine measurement of colloid osmotic pressure, preferably in conjunction with pulmonary artery wedge pressure, is likely to improve understanding of the mechanisms of acute pulmonary edema.

Acute Disease↗

PubMed1975

A wedge filter interlock system for 4 MV linear accelerators.

The wedge filter interlock system on a 4 MV linear accelerator was modified to ensure proper selection and placement of filter. By using a series of microswitches to replace the two-pin connection for each wedge, proper placement of the wedge in the treatment beam was ensured. Both the chain and plug were eliminated by using a 6 pole, 6 position sub-miniature rotary switch to produce the remaining connections.

Filtration↗