Monitoring perioperative changes in distribution of pulmonary ventilation by functional electrical impedance tomography

Background: Electrical impedance tomography (EIT) is a noninvasive technique providing cross-sectional images of the thorax. We have tested an extended evaluation procedure, the functional EIT (f-EIT), to identify the local shifts of ventilation known to occur during the transition between spontaneous, controlled and assisted ventilation modes.
Methods: Ten patients scheduled for elective laparotomy were studied in the surgical ward, operating theatre and ICU during spontaneous and different modes of mechanical ventilation. Sixteen ECG electrodes were placed on the circumference of the thorax and connected with an EIT device (APT System Mark I, IBEES, Sheffield, UK). Measurements lasting 180 s were performed and f-EIT images of regional ventilation computed. The geometrical centre of ventilation was determined to quantify the regional distribution of lung ventilation during individual modes of ventilation.
Results: F-EIT confirmed the differences in the distribution of ventilation associated with various modes of artificial ventilation. Accentuated ventilation of the dependent lung regions was observed during spontaneous breathing, whereas a shift of the centre of ventilation to the nondependent regions was found during controlled ventilation. In the course of assisted ventilation a continuous displacement of the centre of ventilation back towards the dependent lung regions, consistent with an increased proportion of spontaneous breathing, was detected. Unassisted spontaneous breathing after weaning from mechanical ventilation resulted in a similar ventilation distribution as during tidal breathing prior to surgery.
Conclusion: F-EIT determined the redistribution of lung ventilation during different modes of mechanical ventilation. We expect that f-EIT will become a useful noninvasive bedside monitoring technique for imaging regional ventilation in pulmonary diseased patients during mechanical ventilation.     

Right hemisphere superiority for initial stages of letter processing

When single letters, which could be perfectly recognized when presented alone, were embedded in an overlapping masking stimulus, observers recognized more letters from the left than from the right visual field. This left visual field-right hemisphere advantage persisted over short time intervals between the letter and the mask, regardless of which stimulus occurred first. Such results suggest that the right cerebral hemisphere is more efficient than the left at extracting relevant visual features of letters when the letters are perceptually degraded, even though letters are highly associated with language and, therefore, readily processed along verbal-analytic dimensions.     

Acute cardiac side effects of iodecol, a new nonionic dimer roentgen contrast medium, in intracoronary injection

The effects of intracoronary injections of Iodecol, a nonionic-dimeric contrast medium (iodine content 350 mg/ml, osmolality 0.34 osmol/kg, viscosity 13.8 mPa X s) on haemodynamics, coronary blood flow, ECG, and cationic content as well as osmolality of coronary sinus blood have been evaluated and compared to those of Iopamidol and Amidotrizoate. Experiments were carried out in 9 closed-chest dogs using heart catheterisation techniques. After Iodecol and Iopamidol only positive inotropism was seen while Amidotrizoate initially had cardiodepressive effects. Iodecol caused less increase of peak velocity of pressure rise and systolic blood pressure than Iopamidol. All contrast media led to an increase in coronary blood flow of the same extent. ECG changes were most marked following Amidotrizoate and only slight after Iodecol. Decrease of cationic content and increase of osmolality in coronary sinus blood were seen after each compound. Changes were only small after Iodecol and always greater after Amidotrizoate. Moreover, an overproportional decrease of coronary sinus calcium content was seen after Amidotrizoate due to calcium binding. Thus, based on these animal experiments, a further slight reduction of acute cardiac side effects during coronary arteriography could be expected from the use of nonionic dimeric compounds, compared to ionic and currently used nonionic contrast media.     

Interhemispheric interaction in bilateral redundancy gain: effects of stimulus format

Previous visual laterality experiments have shown that identification is better when 2 copies of the same stimulus are presented--1 to each hemisphere--than when only a single copy is presented to 1 hemisphere. New experiments were conducted to vary whether the 2 stimuli on a bilaterally redundant trial were physically identical or identical in format in addition to leading to identical responses. Substantial bihemispheric gain was obtained even when the 2 stimuli were perceptually distinctive (e.g., letter trigrams differing in case and font or the same numeric quantity represented by digits and dots). Thus, much of the bihemispheric advantage involves relatively abstract aspects of information processing. However, when the formats were sufficiently distinctive, there were small effects on bihemispheric performance, suggesting some role for less abstract processes that are sensitive to physical characteristics.     

Innervation of supporting cells in the apical turns of the guinea pig cochlea is from type II afferent fibers

The outer supporting cells in the apical turns of the guinea pig cochlea receive a dense innervation. Our previous study (Fechner et al. [1998] J. Comp. Neurol. 400:299-300) suggested that this innervation of the Deiters' and Hensen's supporting cells was not derived from efferent fibers of the olivocochlear bundle, but its origin has not been further specified. To test the hypothesis that the innervation was afferent in origin, we traced apical afferent fibers that were retrogradely labeled by extracellular injections of horseradish peroxidase. Labeled afferent fibers were of two types: type I fibers contacted inner hair cells, whereas type II fibers crossed the tunnel and contacted outer hair cells. Significantly, most of the type II fibers also formed branches to the outer supporting cells. Although a few olivocochlear efferent fibers formed such branches, counts indicated that the overwhelming majority of the branches were produced by type II afferent fibers. These branches were not produced by basal type II fibers. Apical type II fibers also differed from basal fibers by having shorter lengths, spiraling both apically and basally, and contacting all three rows of outer hair cells. These innervation differences suggest differences in the ways that information from outer hair cells is processed in the apex versus the base of the cochlea.     

诺氟沙星的吸附行为及其测定

诺氟沙星在0.05mol·L^-1NH₄Cl (pH 5.8)溶液中,出现一灵敏的示波极谱还原峰。峰电位为-1.44 V (vs SCE)。峰高与诺氟沙星的浓度在1.0×10^-7～4.0×10^-6mol·L^-1范围内成正比,检出限为5.0×10^-8mol·L^-1,并用于样品的测定。用线性扫描与循环伏安法等手段研究体系的吸附性质。实验表明,该电极过程为具有吸附性的不可逆过程。     

Effect of proton pump inhibitors on the detection of Helicobacter pylori in gastric biopsies.

BACKGROUND: Proton pump inhibitors are known to decrease the activity of Helicobacter pylori organisms within the stomach and to shift their distribution proximally. This effect may reduce the sensitivity of histological examination and rapid urease testing for H. pylori on biopsies taken from recommended sites. It is of particular relevance if a proton pump inhibitor has been prescribed before the patient has undergone diagnostic endoscopy. METHODS: We studied patients referred to our open-access upper gastrointestinal endoscopy service who had either been on no medication (controls) or were already taking proton pump inhibitors. Biopsies taken from the gastric antrum and corpus were used for rapid urease testing and for histological examination. Sera, taken from patients who had no evidence of H. pylori in biopsies, were tested for IgG H. pylori antibodies as an alternative indicator of infection. RESULTS: H. pylori organisms were detected by histological examination in 27 of 40 controls (68%) and in 13 of 25 patients taking proton pump inhibitors (52%). Among patients with positive histology (organisms detected in either antral or corpus biopsies, or both), only the sensitivity of the antral urease test read at 1 h was significantly lower in patients taking proton pump inhibitors than in controls, with no significant difference in sensitivities of the antral urease test at 24 h, of the corpus urease test at 1 or 24 h, or of histology from the antrum or corpus. Of patients with negative histology, none of 13 controls compared with six of 12 patients taking proton pump inhibitors (50%) had positive serology (P = 0.005). Five (83%) of the six histology-negative, seropositive patients taking proton pump inhibitors had histological changes consistent with H. pylori gastritis even though no organisms were detected. CONCLUSIONS: Treatment with a proton pump inhibitor before endoscopy reduces the sensitivity of antral and corpus biopsies for H. pylori detection, both by urease testing and histological examination. If proton pump inhibitors already prescribed cannot be discontinued for an adequate period before endoscopy, patients should have biopsies taken from the corpus as well as from the antrum, and serum should be tested for H. pylori.