Significant reduction in minute ventilation and peak inspiratory pressures with arteriovenous CO2 removal during severe respiratory failure.

Objectives: To quantify CO2 removal using an extracorporeal low-resistance membrane gas exchanger placed in an arteriovenous shunt and evaluate its effects on the reduction of ventilatory volumes and airway pressures during severe respiratory failure induced by smoke inhalation injury.

Design: Prospective study.

Setting: Research laboratory.

Epidemic Venezuelan equine encephalitis in La Guajira, Colombia, 1995.

In 1995, the first Venezuelan equine encephalitis (VEE) outbreak in Colombia in 22 years caused an estimated 75,000 human cases, 3000 with neurologic complications and 300 fatal, in La Guajira State. Of the state's estimated 50,000 equines, 8% may have died. An epizootic IC virus, probably introduced from Venezuela, was rapidly amplified among unvaccinated equines.

A comparison of the repetitive click and conditioning-testing P50 paradigms.

The auditory P50 ERP component has previously been studied either in the repetitive click or the conditioning-testing (C-T) paradigm. For 20 subjects, we compared 4 repetitive click and 4 C-T protocols in a single experimental session with identical recording techniques and with interclick intervals comparable to the C-T intervals. In the C-T protocols, a long interval between click pairs ensured full recovery of P50 to the C click.

Environmental tobacco smoke and lung cancer mortality in the American Cancer Society's Cancer Prevention Study. II.

Environmental tobacco smoke (ETS) has been classified as a human lung carcinogen by the United States Environmental Protection Agency (EPA), based both on the chemical similarity of sidestream and mainstream smoke and on slightly higher lung cancer risk in never-smokers whose spouses smoke compared with those married to nonsmokers. We evaluated the relation between ETS and lung cancer prospectively in the US, among 114,286 female and 19,549 male never-smokers, married to smokers, compared with about 77,000 female and 77,000 male never-smokers whose spouses did not smoke. Multivariate analyses, based on 247 lung cancer deaths, controlled for age, race, diet, and occupation.

Determination of low blood flow limits for arteriovenous carbon dioxide removal.

Arteriovenous carbon dioxide removal (AVCO2R) has been shown to achieve total carbon dioxide (CO2) exchange. To determine optimal blood and gas flow parameters that can provide maximal gas exchange and evaluate the utility of AVCO2R at reduced blood flow, the authors used a low resistance membrane gas exchanger within an arteriovenous shunt in mechanically ventilated sheep. Adult female sheep (n = 5) were anesthetized and underwent placement of the gas exchange device in a simple arteriovenous shunt created between the carotid artery and common jugular vein.

Correction of blood pH attenuates changes in hemodynamics and organ blood flow during permissive hypercapnia.

Objectives: To determine whether changes in cardiac output, regional blood flow, and intracranial pressure during permissive hypercapnia are blood pH-dependent and can be attenuated by correction of intravascular acidemia.

Design: Prospective, controlled study.

Setting: Research laboratory.

Stragegies to reduce surface area requirements for carbon dioxide removal for an intravenacaval gas exchange device.

Experimental and clinical use of the intravascular oxygenator (IVOX), an intravenacaval gas exchange device, in acute respiratory failure yielded a CO2 transfer of 40-70 ml/min (approximately 30% of adult CO2 production) at normocapnia. Although significant, this rate of CO2 removal is not clinically useful. To maximize CO2 transfer, given the same gas exchange properties and structure design of the IVOX, the authors analyzed the effects of permissive hypercapnia (stepwise increase in arterial blood pCO2 up to 100 mmHg) and active blood mixing (with an intraaortic balloon pump) on different sizes of IVOX (sizes 7, 8, and 9 mm, surface area 0.

Comparison of the infusion requirements and recovery profiles of vecuronium and cisatracurium 51W89 in intensive care unit patients.

The selection and administration of neuromuscular blocking (NMB) drugs in intensive care unit (ICU) patients remain controversial. We compared the dose-response and recovery pharmacodynamics of a new intermediate-acting NMB drug, cisatracurium besylate, to the intermediate-acting NMB drug, vecuronium (VEC), in a prospective, randomized, double-blind, multicenter study in critically ill adults. After informed consent, 58 mechanically ventilated ICU patients from five medical centers were randomized to receive either cisatracurium or VEC.

Transmission of HIV in dialysis centre.

In August, 1993, 13 dialysis patients at one dialysis centre in Colombia, South America, were found to be HIV positive, and this prompted an epidemiological investigation. We carried out a cohort study of all dialysis centre patients during January, 1992 to December, 1993 (epidemic period) to determine risk factors for HIV seroconversion. Haemodialysis and medical records were reviewed, dialysis centre staff and surviving patients were interviewed, and dialysis practices were observed.

Frequency domain estimation of covariate effects in multichannel brain evoked potential data.

An evoked potential is the recorded brain electrical response to a stimulus such as an auditory click. In most evoked potential experiments, the response is studied as a function of covariates such as stimulus characteristics and drug states. We propose a frequency domain model of multichannel evoked potential data that includes parameters representing the effects of covariates on the amplitude and latency (time from stimulus presentation) of the response.

A multichannel, model-free method for estimation of event-related potential amplitudes and its comparison with dipole source localization.

We present a multichannel, model-free method for estimation of event-related potential (ERP) amplitude ratios and amplitudes using singular value decomposition (SVD), and compare with the Dipole Components Model (DCM). When the ERPs are generated by a single or multiple dipoles with equal amplitude ratios, the SVD method is superior to DCM in terms of reliable estimation of amplitude and is comparable with DCM for reliable and unbiased estimation of amplitude ratios. We show that dipole model misspecification leads to unbiased amplitude ratios and biased amplitudes when the ERP data sets are (1) generated and fit with a single dipole, or (2) generated by N dipoles with equal amplitude ratios and fit with M < or = N dipoles, because the effect of model misspecification 'cancels' for a ratio.

Intravascular membrane oxygenation and carbon dioxide removal with IVOX: can improved design and permissive hypercapnia achieve adequate respiratory support during severe respiratory failure?

The intravenacaval oxygenator and carbon dioxide removal device (IVOX) conceived by Mortensen at CardioPulmonics is a diffusion-limited device capable of removing 30% of CO2 production of an adult at normocapnia with minimal reduction in ventilator requirements. Through mathematical modeling, an ex vivo venovenous bypass circuit to model the vena cava and animal models of severe smoke inhalation injury, the practice of permissive hypercapnia has been established to enhance CO2 removal by IVOX. By allowing the blood PCO2 to rise gradually, the CO2 excretion by IVOX can be linearly increased in a 1:1 relationship.

Permissive hypercapnia in acute respiratory failure.

Objective: To evaluate the potential efficacy of pressure limitation with permissive hypercapnia in the treatment of acute respiratory failure/adult respiratory distress syndrome on the basis of current theories of ventilator-induced lung injury, potential complications of systemic hypercarbia, and available human outcome studies.

Data Sources: Articles were identified through MEDLINE, reference citations of published data, and consultation with authorities in their respective fields.

Study Selection: Animal model experimentation and human clinical trials were selected on the basis of whether they addressed the questions of pressure limitation with or without hypercapnia, the pathophysiologic effects of hypercapnia, or the concept of ventilator-induced parenchymal lung injury.

Improved gas exchange performance of the intravascular oxygenator by active blood mixing.

The intravascular oxygenator and carbon dioxide removal device (IVOX; CardioPulmonics, Salt Lake City, UT) has been shown to perform 30% of the gas exchange in animals and patients with acute respiratory failure. Among the factors that limit gas exchange is the mass transfer resistance in the blood phase. To determine if a reduction in mass transfer resistance by mixing venous blood can enhance the O2 transfer and CO2 removal by IVOX, a right atrium-pulmonary artery venovenous bypass circuit was used in sheep to model the adult vena cava.

Equivalent dipole parameter estimation using simulated annealing.

Equivalent-electrical dipole source modeling of evoked potential signals requires complicated non-linear multivariate optimization. Newton and non-linear simplex optimization methods often converge to a local minimum, and their results are affected by the procedure's starting parameter estimates. This paper describes simulated annealing, a more robust and resistant global optimization method.

Confounding by time since hire in internal comparisons of cumulative exposure in occupational cohort studies.

We use a simple, empirical model to describe the healthy worker effect mortality pattern. Under this simple model, internal comparisons of risk with increasing cumulative exposure will tend to be biased away from the null because of the healthy worker effect. We illustrate the potential magnitude of the bias in a simple situation and show that controlling for time since hire, by means of standard epidemiologic methods, eliminates the bias.

The reliability of P50 suppression as measured by the conditioning/testing ratio is vastly improved by dipole modeling.

Suppression of auditory P50 evoked potential amplitude to the second of a pair of clicks is potentially important in psychiatric research because it has been shown to be abnormal in both schizophrenics and their relatives. However, its clinical utility using the standard single-channel electroencephalographic (EEG) peak picking methodology is under question because of low test-retest reliability. Dipole Components Modeling of the P50 component was attempted as a method for increasing the reliability of the P50 suppression measure.

Waterborne cholera in Riohacha, Colombia, 1992.

Between 1 January and 31 July 1992 a cholera epidemic caused 548 reported cases (an incidence of about 8 cases per 1,000 inhabitants) in Riohacha, Colombia. Following an initial review of hospital and laboratory data, a cross-sectional household survey and case-control study were conducted to investigate this epidemic. The cross-sectional survey found an increased risk of cholera between November 1991 and September 1992 among subjects who usually drank unchlorinated piped water from the municipal water system (prevalence odds ratio, POR = 5.

Protective effect of antibiotics on mortality risk from acute respiratory infections in Mexican children.

A case-control study of mortality from acute respiratory infections (ARI) among children under five years of age was conducted in Naucalpan, an urban-suburban area of Mexico City, and in rural localities of Tlaxcala, Mexico. The study found that ARI deaths tended to occur in the poorest neighborhoods; 78% of the deceased study subjects were infants under six months old; and 68% of the deaths occurred at home. Comparison of the data for cases (fatalities) and control children who had severe ARI but recovered showed that failure to receive antibiotics was associated with death (odds ratio 28.

[Changes in the conditions for child survival in Mexico and strategies for the future].

Conditions of infant and child survival in Mexico have improved considerably over the last 60 years. Infant mortality rates were reduced from more than 250 deaths per 1,000 infants born alive in 1929-1931, to a rate of less than 50 in the period 1982-1987, a figure which still places Mexico among the countries with a high infant mortality rate. Though improvements in the living conditions of the population have undoubtedly played a part in the reduction of infant and child mortality, the early introduction of sanitation campaigns and, more recently of immunization, antibiotics and other modern health techniques have probably been more important.

[Postneonatal mortality caused by diarrhea: a case-control study].

A matched case-control study was undertaken in Naucalpan de Juárez, Estado de México. The goal of this study was to identify the risk factors for diarrheal disease in children between seven days and one year of age. We identified 63 case and 188 controls.

Reiter's syndrome, immunodepression and strongyloidiasis. Report of a fatal case.

We present the case of a 52-year-old white male who showed arthritis, conjunctivitis and non-gonococcal urethritis. Besides those manifestations, the patient also showed mucocutaneous lesions that were both clinically and histologically indistinguishable from those of pustular psoriasis. Due to the severity of the disease it was necessary to treat this patient with corticosteroids and immunosuppressors.