Preparation and Properties of Porous Bismuth Films

The use of chemical solution routes to form inorganic thin films is a relatively new method which represents an alternative to vapor phase routes. The present study involves the use of a chemical solution route, the decomposition of metal carboxylates, to prepare bismuth thin films of controlled porosity. Such morphologies offer the opportunity to disrupt phonon transport without greatly affecting electrical conductivity and bismuth represents a well known system in which to investigate these effects. Porous bismuth thin films have been prepared using bismuth 2-ethylhexanoate (Bi[OOCCH(C2H5)C4H9]3) as the precursor in a solvent of 2-methyl- 1-propanol. The solution is deposited on glass, Kapton, silicon, alumina or magnesia substrates by spin coating and heated to between 250 – 300°C in hydrogen. Heat treatment temperature and time are important for controlling film microstructure as both pore volume (25 to 50%) and preferred orientation depend upon heat treatment conditions. Bismuth films (62 nm thick) with 32% porosity exhibit conductivities in the range of 150 S/cm with Seebeck coefficients comparable to that of bulk materials.

Mass rearing Halotydeus destructor (Tucker) (Acari : Penthaleidae) for use in summer screening of Trifolium subterraneum (L.) for mite resistance

Summary. Controlled environment experiments were conducted to establish some of the requirements for successful mass rearing of Halotydeus destructor (redlegged earth mite). Numbers of mites reared on Vicia sativa (common vetch) cv. Blanchefleur grown alone or on a mixture of vetch with Trifolium subterraneum (subterranean clover) cv. Goulburn, were significantly higher than those on subterranean clover or Arctotheca calendula (capeweed) alone. Populations reared on vetch grown in a sandy soil were significantly higher than those reared on vetch grown in a loamy soil, pure sand or pure loam. Covering the soil surface with a natural pasture mulch increased mite numbers compared with leaving the soil bare or placing plant pots inside ventilated cages. Subsequent changes in rearing methodology produced enough mites to enable summer screening of subterranean clover lines for resistance to H. destructorfor the first time. Over 20 000 mites can be produced from vetch at one time for screening tests throughout the year.

Post-irradiation malignant mesothelioma

BACKGROUND

Approximately 30 patients with malignant mesothelioma following radiotherapy have been described. Population-based studies of this occurrence have not been reported.

METHODS

Patients with malignant mesothelioma of the pleura were collected. All of the patients had a prior cancer and had received radiotherapy to the region in which the malignant mesothelioma developed. Data from the National Cancer Institute's Surveillance, Epidemiology and End Results Program and the Connecticut Tumor Registry were evaluated for cases of malignant mesothelioma of the pleura occurring in patients with a previous cancer. The literature on post-irradiation malignant mesotheliomas was reviewed.

RESULTS

Eight patients (4 men, 4 women) with malignant mesothelioma occurring in sites of radiotherapy for a prior tumor were identified. The mean age at diagnosis of mesothelioma was 45 years (range: 22-78 years), and the average interval between radiotherapy and the mesothelioma was 21 years (range: 11-29 years). Three of the patients had also received chemotherapy. Histologically, the mesotheliomas were epithelial in five cases, biphasic in one, and sarcomatous in one. One hundred forty-two patients were identified in the epidemiologic survey. The majority were men (89%), with a mean age for all patients of 68.5 years (range: 35-86 years) and a median latency between first cancer and mesothelioma of 4.3 years (range: 2 months-29.9 years).

CONCLUSIONS

Mesotheliomas rarely develop as second malignant neoplasms. Within a large, population-based survey of patients with cancer, temporal patterns and demographic features of most second primary mesotheliomas were similar to asbestos-related tumors, although the late effects of cancer treatment might have contributed to the occurrence of cancer in some patients.

Reduced work of breathing after single lung transplantation for emphysema

BACKGROUND

Pulmonary emphysema, with or without chronic bronchitis, has emerged as the most common indication for successful single lung transplantation. Although gas exchange can be expected to improve after successful transplantation, such changes do not adequately explain the improvement in dyspnea experienced by these patients and resulting in improved quality of life.

METHODS

We prospectively studied the respiratory mechanics of 14 single lung transplantation recipients with pulmonary emphysema, of whom 10 have been followed up beyond 1 year. The mean age of the group was 48.8 years (range, 42 to 60 years) for the seven men and seven women. Average donor-predicted total lung capacity was 0.6 L (+0.2 [standard error]) greater than recipient-predicted total lung capacity. Comparison of pulmonary resistance, dynamic lung compliance, and static lung compliance were taken to examine the possible role of reduced airways resistance and of improved elastic recoil in the reduced work of breathing. Results were analyzed by means of a one-tailed paired Student t test and linear regression analysis (both stepwise and multivariate); results are tabulated by mean (+/- 1 [standard error]).

RESULTS

Between preoperative measurements and 12 months postoperatively, maximum lung elastic recoil increased from 8.1 (+/- 0.7) to 11.3 (+/- 1.0) cm H2O, p < 0.01; pulmonary resistance fell from 8.3 (+/- 0.8) to 5.4 (+/- 0.7) cm H2O sec/L, p < 0.01. Dynamic lung compliance fell from 0.23 (+/- 0.04) to 0.12 (+/- 0.02) L/cm H2O, p < 0.02, and static lung compliance fell from 0.66 (+/- 0.13) to 0.22 (+/- 0.05) L/cm H2O, p < 0.001.

CONCLUSIONS

The decline in lung compliance after single lung transplantation reflects the importance of improvement in elastic recoil and reduced chest wall distention, improving the work of breathing. The 67% decline in static lung compliance (300% increase in elastic recoil) is probably the single most important mechanical factor leading to reduced dyspnea after single lung transplantation for emphysema.

Unexplained dyspnea

Dyspnea is a common symptom that is difficult to define and can result from a wide variety of causes. This complex sensation that arises from multiple stimuli involves both subjective perceptions and objective reactions. In the assessment of patients with dyspnea, use of a systematic approach to determine the precipitating factors and the degree of breathlessness is important. Although many diseases may produce dyspnea, two thirds of the cases result from a pulmonary or cardiac disorder. Neuromuscular and psychogenic causes should also be considered. A comprehensive history, physical examination, and basic laboratory tests are important in the initial assessment; however, the diagnosis may depend on specialized testing, the results of which may differ from the initial clinical impression. Initial testing should include electrocardiography, chest roentgenography, hemoglobin determination, thyroid function, and spirometry with use of a bronchodilator. More specialized evaluation includes detailed pulmonary function testing and echocardiography. As shown in our illustrative case, cardiopulmonary exercise testing is important for evaluation of unexplained dyspnea when initial test results are nondiagnostic. Accurate diagnostic data are critical for choosing appropriate treatment.

Primary mediastinal neoplasms (other than thymoma)

Primary mediastinal neoplasms encompass a long list of histologically diverse lesions that can arise from a wide variety of mediastinal structures. Recent advances in diagnostic techniques have considerably enhanced the evaluation of the mediastinum with use of noninvasive or minimally invasive procedures. In adults, most primary mediastinal neoplasms can be classified in one of four categories: thymus-derived neoplasms, neurogenic tumors, lymphomas, or germ cell neoplasms. In children, neurogenic tumors (especially neuroblastomas) and lymphomas are most frequently encountered. Because of the presence of many vital structures in the confined thoracic cavity, even benign mediastinal neoplasms can cause severe symptoms from the mass effect and therefore warrant a carefully planned management strategy. With modern therapeutic and surgical interventions, associated morbidity and mortality can often be substantially decreased.

Prevention of infection in critically ill patients by selective decontamination of the digestive tract

OBJECTIVE

To determine whether selective decontamination of the digestive tract using oral and nonabsorbable antimicrobial agents and parenteral cefotaxime prevents infection in critically ill patients.

DESIGN

Randomized, controlled trial without blinding.

SETTING

Surgical trauma and medical intensive care units in a tertiary referral hospital.

PATIENTS

One hundred fifty patients admitted to surgical trauma and medical intensive care units during a 3-year interval, whose condition suggested a prolonged stay (greater than 3 days).

INTERVENTION

Patients were randomly allocated to an experimental group (n = 75) that received cefotaxime, 1 g intravenously every 8 hours for the first 3 days only, and oral, nonabsorbable antibiotics (gentamicin, polymyxin, and nystatin by oral paste and oral liquid) for the entire stay in the intensive care unit. Control patients (n = 75) received usual care.

MEASUREMENTS

The number of infections, total hospital days, and deaths, as well as the number of days in intensive care unit, were recorded.

RESULTS

Control patients experienced more infections (36 compared with 12, P = 0.04), including bacteremias (14 compared with 4, P = 0.05) and pulmonary infections (14 compared with 4, P = 0.03). Although total hospital days, days in intensive care, and the overall death rate all were lower in the treatment group, these differences were not statistically significant. Clinically important complications of selective decontamination of the digestive tract were not encountered.

CONCLUSIONS

Selective decontamination of the digestive tract decreases subsequent infection rates, especially by gram-negative bacilli, in selected patients during long-term stays in the intensive care unit.

Morphology and distribution of species in the Medicago murex complex

Morphological, cytological, and agronomic characteristics are reported for 560 accessions of the Medicago murex Willd. complex collected from countries bordering the Mediterranean and grown in field plots in Western Australia. All plants of the 2n = 16 taxon were shown to have white flecks on the leaves, a mean number of florets on each peduncle of < 2.5, and usually no ridges on the edge of the pod coils. Plants of the 2n = 14 taxon never had white leaf flecks, 99% of accessions had a mean number of florets > 2.5, and most had three distinct ridges on the pod coils. Plants of the two taxa were equally vigorous and both were widespread, occurring sympatrically in many Mediterranean countries. The 2n = 16 and 2n = 14 taxa do not cross and should be recognized as separate species. A reexamination showed that Willdenow's original material of M. murex was most likely to be of the 2n = 16 species. We suggest that the name of the 2n = 14 species is Medicago sphaerocarpos Bertol. Key words: Medicago murex, Medicago lesinsii, Medicago heterocarpa, taxonomy, distribution, speciation.

Effect of Kabatiella caulivora isolates and host growth stage on symptom expression and resistance in Trifolium subterraneum

Occasional severe clover scorch disease outbreaks from Kabatiella caulivora have occurred in the 2 partially resistant Trifolium subterraneum cultivars, Karridale and Meteora. All K. caulivora isolates screened, including isolates taken from severely damaged field swards of Karridale and Meteora, were highly pathogenic, but there was variation in the pathogenicity of some isolates and there was a significant cultivar x isolate interaction in 1 of 2 studies. Plant age affected development of disease. Cultivars Karridale, Mt Barker and Woogenellup were least susceptible when inoculated 10 weeks from sowing, and there was a strong plant age x cultivar interaction. However, there was no suggestion that severe disease in Karridale was due to increased susceptibility at a particular plant growth stage. In resistance screening studies, the resistance rankings of subterranean clover varieties sometimes changed markedly depending upon the test isolate, and in 1 of 2 studies, there was a significant cultivar x isolate interaction. While there was significant overall correlation between glasshouse and field data, this only accounted for 49.9 and 20.5%, respectively, of the variation. Glasshouse screening was not suitable for replacing field screening but it was useful for confirming the field resistance of some highly resistant genotypes.

Intraoperative ultrasonographically guided biopsy in testicular sarcoidosis: a case report

We present a case of sarcoidosis with involvement of a solitary testis that was discovered incidentally on an ultrasonogram of the scrotum. This appears to be case 8 of sarcoidosis with genitourinary involvement limited to the testis. We believe it is the second report of intraoperative ultrasonography used to locate and perform a biopsy of impalpable testicular lesions. We consider this technique to be useful in instances of solitary gonads or in cases of bilateral lesions.

Ventilation-perfusion distribution after aortic valve replacement

In eight patients, the ventilation-perfusion (Va/Q) relationships after uncomplicated aortic valve replacement were studied by the multiple inert gas technique. Postoperatively, all patients had a right-to-left intrapulmonary shunt (Qsp/Qt) (range 2.4% to 14.4%) and abnormal distribution of Va/Q patterns to varying degrees. No single mechanism was identified that defined gas exchange in all patients. In three patients, moving from the supine to the right lateral decubitus position resulted in improved oxygenation which occurred because of better matching of Va/Q, not because of a decrease in Qsp/Qt.

Timing of tracheostomy in the critically ill patient

The decision for timing of tracheostomy remains controversial. The relative complication rates in two retrospective series, in which 79 and 150 critically ill patients were examined, respectively, showed increased incidence of late complications with tracheostomy and led Petty's group to conclude "The value of tracheotomy when an artificial airway is required for periods as long as 3 weeks is not supported by data obtained in this study."

Effect of positional change on ventilation-perfusion distribution in unilateral pleural effusion

The effect of pleural effusion on lung function and gas exchange has not been adequately defined. We used the multiple "inert" gas technique to study gas exchange and ventilation-perfusion relationships in both the left and the right lateral decubitus positions in a patient with a moderate unilateral (left) pleural effusion. With position change, only a small change in oxygenation (3 mm Hg) and no change in carbon dioxide tension occurred. The ventilation-perfusion relationships were also nearly identical for both body positions. We conclude that a pleural effusion of moderate size has little effect on overall gas exchange and ventilation-perfusion relationships and that complex mechanisms of the respiratory system compensate for the effusion.

Oxygen uptake during weaning from mechanical ventilation

Total body oxygen uptake (VO2) increases during the transition from machine-assisted ventilation to spontaneous breathing. Since the volume of oxygen consumed by the respiratory muscles must contribute to the increase in VO2 (delta VO2), we explored whether delta VO2 and/or measurements of respiratory power output (Wresp) provide clinically useful information in the evaluation of disease state and weaning decisions in patients with respiratory failure. We determined the metabolic, ventilatory, and hemodynamic responses of ten patients during weaning from controlled mechanical ventilation, and compared delta VO2 and Wresp of patients without overt heart-lung disease (group 1) to that of patients with significant cardiopulmonary dysfunction and ventilator-dependent respiratory failure (group 2). We reasoned that for delta VO2 to be clinically useful, individual values must either clearly differ between groups, must be higher in patients with heart-lung disease, and/or correlate with weaning outcome and independent measurements of respiratory work. The VO2 increased in nine of ten patients. The differences between the groups in the values of delta VO2 (27 ml/min and 49 ml/min) and respiratory power (9.38 J/min and 11.99 J/min) were not significant. delta VO2 and Wresp were not correlated (r = 0.2), and neither predicted weaning outcome. We conclude that the sensitivity and specificity of delta VO2 and Wresp appear insufficient for evaluation of disease state and weaning decisions in individual patients.

Human milk-derived lactoferrin inhibits mitogen and alloantigen induced human lymphocyte proliferation

Purified lactoferrin (LF), isolated from human milk, was tested for its effect on human T-lymphocyte proliferative responses to phytohemagglutinin (PHA) and to alloantigens in mixed lymphocyte culture. LF inhibited proliferation in both assays in a dose-dependent manner. The suppressive effect was not due to LF mediated cytotoxicity since washing cells that had been pre-incubated with LF restored their proliferative activity. LF was most effective in suppressing the PHA response when added within 24 h of culture initiation. Iron saturated LF failed to inhibit PHA-induced proliferation, suggesting that the mechanisms of suppression involve the chelating property of LF. The suppressive effect of LF on T-lymphocyte proliferative response in vitro supports the notion that LF has significant immunoregulatory potential in vivo.

Body position and ventilation-perfusion relationships in unilateral pulmonary disease

The effect of positional change (right vs left lateral decubitus) on the distribution of ventilation and perfusion ratios was determined in four patients with respiratory failure and chest roentgenographic findings of unilateral pulmonary disease. In these patients with a unilateral interstitial pattern, improvement in oxygenation which occurred when the "good" side was dependent (down) was associated with changes in the patterns of ventilation-perfusion distribution; two patients showed a predominant decrease in right-to-left intrapulmonary shunt, and two showed an improvement in ventilation-perfusion equality. Therefore, when unilateral interstitial pulmonary disease was present, positional change resulted in changes in right-to-left intrapulmonary shunt or low ventilation-perfusion ratios or both. Variability between patients can be explained by the nonhomogeneity of pulmonary disease in patients with respiratory failure.

Oxygenation during ventilation by high-frequency oscillation in dogs with acute lung injury

The effect of ventilation by high-frequency oscillation (HFO) on gas exchange in the abnormal lung is not well defined. In this study the efficiency of oxygenation by HFO (stroke volume 2.5 to 3.5 ml/kg, frequency 15 to 30 Hz) and by conventional mechanical ventilation (CMV) (tidal volume 15 to 20 ml/kg, frequency 8 to 15 breath/min) was compared in dogs with acute lung injury. Sixteen normal animals were studied under general anesthesia (halothane) on day 0 (control) and then injected intraperitoneally with 10 mg/kg of paraquat in divided doses over 3 consecutive days. Eight dogs were restudied on day 4 (moderate lung injury) and the other eight dogs on day 8 (more severe lung injury). With acute lung injury there was a progressive decrease in total lung capacity, decrease in lung compliance, and hypoxemia. In the moderate lung injury group, at equal alveolar ventilation, HFO resulted in a significant improvement in oxygenation (PaO2 95 to 104 torr) with a corresponding increase in mean lung volume when compared with CMV. In the severe lung injury animals, there were no significant differences in oxygenation or in mean lung volume between HFO and CMV.

Clinical outcome of respiratory failure in patients requiring prolonged (greater than 24 hours) mechanical ventilation

Patients requiring prolonged (greater than 24 hours) mechanical ventilation have various conditions that result in respiratory failure. All patients requiring prolonged mechanical ventilation were subdivided into the following six groups: uncomplicated acute lung injury; respiratory failure complicated by multisystem failure; previous lung disease; trauma; other medical causes; and routine postoperative ventilation. During a one-year period, 327 patients required prolonged mechanical ventilation; acute lung injury and chronic obstructive pulmonary disease were the predominant conditions. Sepsis was both the major predisposing factor for and complication of acute lung injury. Mortality for patients with acute lung injury was 40 percent in the uncomplicated group and 81 percent in patients with acute lung injury complicated by multisystem failure. Acute respiratory failure in association with acute renal failure had a mortality of 89 percent. Number of organ systems involved also correlated with mortality. In patients with chronic obstructive pulmonary disease and pneumonitis or retained secretions, mortality was lower (30 percent), but a significant percentage of these patients (43 percent) became ventilator-dependent. Ventilator dependence did not significantly increase mortality during the course of respiratory failure.

Pulmonary dysfunction during paraquat-induced lung injury: a model of acute alveolar injury

Acute lung injury produced by paraquat causes progressive pulmonary insufficiency. To define the pattern of this injury, the sequence of changes in respiratory mechanics and pulmonary gas exchange was studied in eight mongrel dogs which received repetitive doses of paraquat intraperitoneally. Four other dogs served as controls. All dogs were studied while supine during halothane anesthesia. After baseline measurements, saline (control) or paraquat was administered and the studies repeated at 2, 4, 7, and 9 days. Control dogs showed no significant changes. Dogs receiving paraquat had reduced lung volume, decreased lung compliance with a shift of the static deflation pressure-volume curve downward and to the right, and hypoxemia which could not be entirely accounted for by an increased right-to-left intrapulmonary shunt. This study demonstrated that repeated doses of paraquat given intraperitoneally produced a pattern of acute lung injury in the dog which permitted the study of respiratory mechanics and gas exchange during progressive stages of lung injury.

Use of an acoustic helium analyzer and microprocessor for rapid measurement of absolute lung volume during mechanical ventilation

A technique developed to measure functional residual capacity during mechanical ventilation uses an acoustic helium analyzer and microprocessor to perform open-circuit helium washout. The acoustic helium analyzer has acceptable linearity up to a helium concentration of 50% and is stable. The microprocessor combines output from the acoustic analyzer and a ventilator with an expiratory flow signal, to compute lung volume rapidly during mechanical ventilation. In a sample of ten patients with various lung problems, open-circuit helium washout gave results similar to those of a closed-circuit helium-dilution technique during assist control or intermittent mandatory ventilation modes, with or without positive end-expiratory pressure. This open-circuit system has an advantage over other techniques because it is small and portable and can measure lung volume quickly without complicated maneuvers.

High-frequency ventilation. A new concept in mechanical ventilation

High-frequency ventilation has been shown to provide adequate pulmonary gas exchange in patients who require mechanical ventilation. The advantage of this method of ventilation is that it may allow effective gas transport without high airway pressure or depression of hemodynamic function and thus avoid barotrauma or decreased cardiac output. Currently, three major systems have evolved. (1) High-frequency positive-pressure ventilation uses frequencies of 60 to 120/min, and gas is delivered through a pneumatic valve system. It has been successfully used during surgical procedures, laryngoscopy, and bronchoscopy. (2) High-frequency jet ventilation uses compressed gas delivered through a small-bore cannula at frequencies of up to 400/min. This technique has been used during laryngoscopy and seems to be promising for ventilation of patients with disruption of the airway. (3) High-frequency oscillation uses a wide range of frequencies, up to 40 HZ, and small quasi-sinusoidal volume excursions. It has been reported to provide adequate pulmonary gas exchange in human volunteers and patients in respiratory failure requiring mechanical ventilation. The mechanism of gas transport during high-frequency, low-tidal-volume ventilation is not well understood, but theoretic models suggest that enhanced diffusion, interregional mixing, and intra-airway velocity profiles may be important factors.

Comparison of intraesophageal balloon pressure measurements with a nasogastric-esophageal balloon system in volunteers

Recently, an esophageal balloon incorporated into a nasogastric tube was designed that allowed measurement of intraesophageal pressure. To define the performance of this nasogastric-esophageal balloon (NG-EB) system, comparative measurements were made with a standard esophageal balloon while subjects were in the sitting, supine, and left lateral decubitus and right lateral decubitus positions. Values for dynamic pulmonary compliance, pulmonary resistance, and cough pressure were not statistically different between the two systems. Mean static deflation pressure-volume (P-V) curves using the NG-EB were shifted to the left of the esophageal balloon P-V curve in all body positions, but static lung compliance (CL) was not statistically different. For both balloon systems, CL showed no significant difference between sitting and right lateral decubitus positions. Results from this study indicate that the NG-EB system acceptably reflects esophageal balloon pressure measurements and should be useful in estimating lung and chest wall mechanics in acutely ill patients requiring mechanical ventilation.