Noninvasive determination of cardiac output using single breath CO2 analysis

OBJECTIVE: To examine the utility of single breath CO2 analysis as a noninvasive measure of cardiac output. SETTING: An animal laboratory in a university-affiliated medical center. DESIGN: A prospective, animal cohort study comparing 21 parameters derived from single breath CO2 analysis with cardiac output determined by an ultrasonic flow probe. SUBJECTS: Six healthy adult sheep. METHODS: The single breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor, and computer software with capability for both on- and off-line data analysis. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of cardiac output. Cardiac output was manipulated by successive injections of a hydraulic constrictor placed around the inferior vena cava. MEASUREMENTS AND MAIN RESULTS: Thirty-four measurements of cardiac output were available for comparison with derived variables from the CO2 expirogram. Stepwise linear regression identified two variables that were most predictive of cardiac output: a) the angle between the slope lines for phase II and III of the CO2 expirogram divided by the volume of CO2 per breath (angle/mL CO2); and b) the slope of phase II. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 = .94, p < .0001). The bias and precision of the calculated cardiac output were .00 and .23, respectively. The mean percent difference for the cardiac output estimate derived from the single breath CO2 analysis station was 0.36%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about the cardiovascular system. Specifically, two variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in cardiac output in healthy adult sheep with an adjusted coefficient of determination of .94. Prospective application of this technology in the setting of lung injury and rapidly changing physiology will be essential in determining the clinical usefulness of the technique.     

IL-10 inhibits alloreactive cytotoxic T lymphocyte generation in vivo

In this report, we present evidence that the CTL response directed against MHC Class I allo-determinants can be inhibited as a result of IL-10 expression in vivo. The presence of localized IL-10 secretion at the site of allogeneic tumor cell challenge resulted in marked inhibition of the CTL response and allowed growth of the tumor in the allogeneic host. Using purified CD4+ T cells from mice immunized in the presence or absence of IL-10, we have shown that the loss of alloreactivity as a consequence of IL-10 expression results from the inhibition of CD4+ T cell function. The expression of either IL-2 or IFN-gamma with IL-10 locally at the time of allogeneic cell challenge completely restored CTL alloreactivity, suggesting that the action of IL-10 could be bypassed by providing helper T lymphocyte-derived cytokines of the Th1 type at the site of immunization. Inhibition of alloreactivity by IL-10 was observed using either purified macrophages or dendritic cells as APC in an in vitro assay. Thus, the expression of IL-10 following antigenic challenge (such as that observed in Th2-like immune responses) may profoundly limit the ability for generating functional CTL in vivo.     

Hyperthermia following MDMA administration in rats: effects of ambient temperature, water consumption, and chronic dosing

In two experiments it was found that the hyperthermia which follows MDMA ("Ecstasy") results from an interaction of direct pharmacological effect of the drug and the prevailing environmental conditions in which it is administered. In Experiment 1, rats given fixed doses of either 2.5, 5.0 or 7.5 mg/kg MDMA or saline were injected on different days at ambient temperatures (Ta's) of 11, 24, and 30 degrees C. At each Ta drinking water was freely available following dosing on one session and temporarily unavailable on a second. The hyperthermic and hyperkinetic responses were monitored using remote biotelemetry. Experiment 2 used a between-subject design in which each group of rats received a standard 7.5 mg/kg dose of MDMA administered at only one of the three levels of Ta(24 degrees C) and at only one level of the water-availability factor. Dosing in some groups was continued for a further 13 days to test for tolerance or sensitization effects. Ambient temperature significantly affected the magnitude of the hyperthermia but not the hyperkinesis. Water deprivation during the drugged period significantly augmented the hyperthermia, but only in the high Ta (30 degrees C.) condition. Chronic dosing produced sensitization of both hyperthermic and hyperkinetic responses. The findings indicate that ambient temperature, water consumption and frequency of drug use affect the hyperthermia which follows MDMA administration.     

Further studies on the influence of genotype and dietary protein on the performance of broilers

An experiment was conducted to quantify genetic differences in response to dietary protein level of male vs female broilers. Broilers (1 d old) from a "high-yield" strain cross (Ross x Ross 208) and a "fast-growing" strain cross (Peterson x Arbor Acres) were placed on fresh pine shavings in floor pens. From Day 0 to 18, all birds were fed a 23% CP starter diet. During Days 18 to 53 male birds were fed either a 16, 18, 20, 22, 24, or 26% CP diet (3,200 kcal ME/kg) and female birds were fed the 16, 20, or 24% CP diet. Significant differences (P < 0.05) were noted in the performance of the different strains. Ross x Ross 208 male birds had a higher body weight (3.37 vs 3.16 kg), higher feed intake (7.08 vs 6.78 kg), higher breast yield (31.76 vs 29.25%), higher carcass yield (73.90 vs 71.85%), and a lower adjusted feed conversion ratio (FCR; 2.10 vs 2.16 g:g) than Peterson x Arbor Acres males at 53 d of age. As compared to Peterson x Arbor Acres females, Ross x Ross 208 female broilers also had a higher body weight (2.68 vs 2.55 kg), higher breast meat yield (33.61 vs 30.80%), higher carcass yield (75.31 vs 73.91%), and lower adjusted FCR (1.97 vs 2.04 g:g). Qualitative differences in the response of these strains were confirmed and better qualitative data is presented that can be used to predict the important output parameters from the import inputs in broiler production.     

Early assessment of diaphragmatic dysfunction in children in the ITU: chest radiology and phrenic nerve stimulation

Diaphragmatic dysfunction is a common postoperative complication of cardiac surgery in children, with important effects on respiratory morbidity. Its early diagnosis, followed by prompt surgical intervention, has been shown to reduce morbidity. However, the commonest method of diagnosis, based on hemi-diaphragmatic elevation on the chest radiograph, may be less accurate than direct techniques for assessing phrenic nerve function. We have compared electrophysiological and radiological diagnoses of diaphragmatic abnormality in 100 children (aged 3 days to 17.5 yrs) undergoing cardiac surgery, looking at respiratory morbidity as assessed by the duration of ventilation, the time spent on the cardiac intensive care unit (CICU), and the requirement for reintubation. Despite showing good reproducibility, radiological diagnosis was neither sensitive nor specific in identifying patients with electrophysiological phrenic nerve damage. Analysis of the measures of outcome supported the electrophysiological technique. Patients with electrophysiological evidence of damage had a longer duration of ventilation, spent longer on the CICU, and had a greater incidence of reintubation than either radiologically abnormal or "normal" patients. Chest X-rays are not a good method for diagnosing phrenic nerve damage in the early postoperative period in children. If early diagnosis is needed, then direct assessment of phrenic nerve function, such as the measurement of phrenic latency, may be a better technique.     

多关节测量臂的小生境混沌优化校准

多关节测量臂是一种便携式的坐标测量设备,它由一系列的旋转关节组成。为了提高多关节测量臂的测量精度和可重复性水平,必须对其运动学参数进行校准。首先,利用小生境的混沌优化算法提出了一种新的运动学校准方法以及一种混合目标的运动学校准函数,它考虑了诸如单点测量实验、容积性测量实验等多种性能测量实验的实验结果,然后,采用Levenberg Marquardt(L-M)算法和小生境混沌优化算法应用于运动学参数校准。小生境混沌优化算法显示出了优于L-M算法的性能。实验结果表明:使用NCOA算法校准后,测量误差的标准差始终优于LMA算法,并且校准前后多关节测量臂的测量精度提高了40倍。采用L-M算法和小生境混沌优化算法应用于运动学参数校准。小生境混沌优化算法显示出了优于L-M算法的性能。     

Effect of recombinant erythropoietin on hospital admissions, readmissions, length of stay, and costs of dialysis patients

To examine the effects of recombinant human erythropoietin (rHuEPO) on hospital utilization, hospital costs, and Medicare reimbursements for hospital care, a longitudinal, matched cohort study was conducted using Medicare claims data of 23,806 Medicare-eligible, dialysis patients who received rHuEPO, did not have a transplant, and were alive for 18 mo or longer and 22,720 controls matched on age, sex, race, cause of ESRD, and dialysis modality. The relative odds (rHuEPO versus control) of admission for all causes and for specific causes over 9 mo, adjusted for admission in the prior 9 mo and the per patient change in total admissions, inpatient days, hospital costs, and Medicare hospital payments between the prior 9-mo period and the subsequent 9-mo period was examined. The adjusted relative odds (95% confidence interval) of admission (rHuEPO versus control) was: higher and statistically significant for all causes, 1.08 (1.03 to 1.14); seizure, 1.52 (1.28 to 1.75); vascular access revision, 1.11 (1.06 to 1.17), and heart failure, 1.17 (1.09 to 1.26); higher but not statistically significant for angina, 1.09 (0.99 to 1.20) and stroke, 1.08 (0.86 to 1.31); and lower but not statistically significant for myocardial infarction, 0.91 (0.72 to 1.10); peripheral vascular disease, 0.81 (0.60 to 1.02); anemia, 0.86 (0.56 to 1.17); and depression, 0.89 (0.37 to 1.40). The mean change per 1,000 patients in admissions was less by 38 (P = 0.03) because of fewer readmissions, and in days was 1,309 less (P < 0.001), for patients treated with rHuEPO versus controls. The mean change per patient in hospital costs was $371 less and was statistically significant (P = 0.03) and in Medicare hospital payments was $132 less but was not statistically significant (P = 0.43) for patients treated with rHuEPO versus controls. rHuEPO was associated with an increase in the probability of hospital admission (particularly admissions potentially related to adverse effects) but a decrease in readmissions, overall admissions, hospital days, and cost to hospitals in this cohort of patients surviving for 18 mo. Although not realized short term, Medicare savings from potential rHuEPO-related reductions in hospital care may be long term through future adjustments in diagnosis-related group-based hospital payment.     

Moult speed predicts pairing success in male harlequin ducks

The bright plumage of male ducks in sexually dichromatic species is thought to have evolved through intense sexual selection. This study examined the relationship between the timing and speed of moult into this bright plumage and subsequent mating success of male harlequin ducks, Histrionicus histrionicus. Males that moulted relatively slowly had a lower chance of establishing a pair bond than others. The timing of moult was unrelated to whether a male obtained a mate. Moult speed and timing were not correlated within individual males, but were significantly repeatable in individual males over 2 years. Moult speed probably reflects the condition of males, whereas timing of moult is more likely to be related to the distance to an individual's breeding area, which determines the timing of arrival to the moulting grounds. In waterfowl species that have been studied, males usually form dominance hierarchies before pairing and females tend to choose dominant males. We suggest that male harlequin ducks that moult slowly are poor-quality individuals, which are relegated to subordinate status and are unlikely to attract a mate the following autumn. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.