T Ti im me e c co on ns st ta an nt t/ /v vo ol lu um me e r re el la at ti io on ns sh hi ip p o of f p pa as ss si iv ve e e ex xp pi ir ra at ti io on n i in n m me ec ch ha an ni ic ca al ll ly y v ve en nt ti il la at te ed d A AR RD DS S p pa at ti ie en nt ts s The mean values of τE for each volume slice did not differ significantly throughout expiration, averaging 690±218 ms (mean±SD of five slices and 12 patients). We show that the flow-dependent resistance of the endotracheal tube (RETT) is mainly responsible for the observed time constant homogeneity.We conclude that in ARDS patients during uninterrupted mechanical ventilation the time constants of passive expiration are markedly modified by the flow-dependent resistance of the endotracheal tube (RETT), and also by the external resistance of tubing and ventilator (REX). RETT and REX render τE about three times larger than the time constant of the patient's respiratory system alone.
The elemental composition of 10 methanogenic species was determined by inductively coupled plasma emission spectrometry and by a C-H-N-analyzer. The 10 species were representative of all three orders of the methanogens and were cultivated under defined conditions. Special emphasis was given toMethanosarcina barkeri, represented by 5 strains and cultivated on various substrates. The following elements with the lowest and highest values in parentheses were determined: C (37-44%, w/w), H (5.5-6.5%), N (9.5-12,8%); Na (0.3-4.0%), K (0.13-5.0%), S (0.56-1.2%), P (0.5-2.8%), Ca (order I: 85-550 ppm; order II: 1000-4500 ppm), Mg (0.09-0.53%), Fe (0.07-0.28%), Ni (65-180 ppm), Co (10-120 ppm). Mo (10-70 ppm), Zn (50-630 ppm), Cu (<10-160 ppm), Mn (<5-25 ppm). The biggest variations were found with respect to N and K, which both seem to have important physiological functions. Although it is unknown whether zinc and copper are essential trace elements for methanogens, all investigated species contained remarkably high zinc contents, whereas copper seemed to be present only in some species.
In a three-year prospective investigation, a total of 6,952 patients were investigated prospectively in nine intensive care wards and their rate of nosocomial infections was analysed. The frequency of the nosocomial infections varied between 3% and 27%. The most frequent nosocomial infections were urinary tract infections, sepsis, infections of the skin and of the subcutaneous tissue, pneumonia and wound infections. The most frequent causes of sepsis were ventilation pneumonia, venous catheters, wound infections and urinary tract infections. The pathogen spectrum was analysed. By specific control of infection with employment of an infection control nurse, the frequency of nosocomial infections on intensive care wards was lowered from 17.2% to 14.3% within one year in one of the hospitals.
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