Automatic jet ventilation in children anaesthetized by the T-piece circuit

Investigation was carried out in ten children aged between one month and six years, who were anaesthetized by the T-piece circuit. The volume of the reservoir tubing of the T-piece was 250 ml. Ventilation was controlled automatically by oxygen jets which were delivered via an injector attached to the reservoir tubing. The oxygen jets were regulated by an electronically-controlled solenoid valve. The children were ventilated by a tidal volume about 12 ml±kg^?1 at a rate of 12-20 per min depending on their age, while the FGF varied between 3 and 6 l min^?1 depending on their body weight. The resulting FIO₂ ranged between 0.32 and 0.34 which was expected from the oxygen:nitrous oxide mixture (1:2), denoting no mixing of the oxygen jets with the anaesthetic mixture. The PA_co2 was ventilation-dependent, and ranged between 4±6-5±3 kPa (35-41 mmHg). The results suggest that automatic jet ventilation facilitates controlled ventilation in children anaesthetized by the T-piece circuit, while maintaining the original simplicity of the T-piece.;     

Crystal and molecular structure of two geometrically restricted chemotactic tripeptides,analogues of formyl-methionine-leucine-phenylalanine*

The crystal structures of HCO-Met-Leu-Phe-OC(CH₃)₃, (CH₂₅H₃₉N₃O⁵S), fMLP-OtBu, and HCO-Metψ[CSNH]-Leu-Phe-OCH₃, (C₃₃H₃₃N₃O₄S₂), fM^SLP-OMe, have been determined by single crystal X-ray diffraction, and their conformational properties investigated by molecular mechanics energy calculations. Crystals of fMLP-OtBu are monoclinic, space group P2₁, a = 12.027(4), b = 9.492(3), c = 12.660(4) Å, β= 101.99(3)°, Z = 2; those of fM^SLP-OMe are orthorhombic, space group P2₁2₁2₁, a = 7.130(1), b = 12.097(2), c = 31.060(5) Å, Z = 4. The first compounds fMLP-OtBu is the t-butyl ester of the tripeptide fMLP that represents one of the most potent compounds in inducing the lysozyme release from human neutrophils that reflects the chemotactic activity. From the crystal structure, it is shown that the orientation of the phenylalanine side chain is largely affected by the presence of the bulky group. fM^SLP-OMe was shown to be inactive after thionation of the methionine residue in the original tripeptide. Nevertheless, the crystal structure does not reveal any influence of the presence of the thionated peptidic bond on the backbone conformation. The X-ray results have been used to generate parameters for empirical energy calculations. Subsequently, a strategy based on random generation of conformations followed by energy-minimization was applied to investigate the conformational space of thiopeptides, in comparison with normal peptides. From molecular free energy calculations, it is shown that the main influence of the introduction of a thioamide bond on the molecular structure is to prevent the existence of C⁷_eqconformations involving the thiomethionine residue. Consequently, a larger number of conformers are found to form intramolecular hydrogen bonds involving the formyl group, reducing its availability to interact with the receptor. For the first time, the theoretical prediction of the existence of C⁷_eq conformations for fMLP is made. The resulting conformers are compared to previously active structures of these chemotactic agents.     

TESTS OF GEOGRAPHICAL CORRELATION WITH ADJUSTMENT FOR EXPLANATORY VARIABLES: AN APPLICATION TO DYSPNOEA IN THE ELDERLY

We propose a test of correlation of the residuals in generalized linear models which is a generalization of the spatial autocorrelation test based on Moran's I. It allows adjustment for sizes of geographical areas and for explanatory variables. A formula is given to compute the weights according to the alternative hypothesis. We compare inference using the distribution in the model and using the permutation distribution. A simulation study showed that the model-based test may be very conservative and this leads to a loss of power compared to the permutation test or to the model-based test with correction for estimated parameters. As this latter is intractable for very large samples when the model includes explanatory variables, we recommend the use of the permutation test. The permutation test is used to study geographical correlation of dyspnoea in the elderly. © 1997 by John Wiley & Sons, Ltd.