Use of long catheters for multipatient anesthetic monitoring at high respiratory frequencies

Anesthetic gases from several patients can be monitored simultaneously with a centrally located mass spectrometer. Such monitoring requires catheters from patient to spectrometer that are several meters long. Scamman (J Clin Monit 1988;4:227–229) found that when the respiratory frequency is high, as with infants, the CO₂ signal from the patient is unacceptably distorted during passage down the catheter. This is due to Taylor dispersion of the input signal. An outline of the theory of Taylor dispersion is given. The equations describe the interaction between the velocity distribution (which, in laminar flow, is parabolic) and the radial diffusion of CO₂. This interaction keeps a tracer signal together in a pulse, as it moves down the tube with themean velocity, spreading somewhat as it proceeds. How much does an initially sharp signal become blurred? The spread of such a signal when it reaches the detector, measured in time, can be expressed in various ways. Measurement is complicated, however, by the fact that the gas pressure may fall by as much as a factor of 10 along the line. The resultant expansion and acceleration of the gas cannot be ignored. A full treatment of this complication is given elsewhere, but the following simple equation is described: {ie237-1} Typically, the spread time is up to a quarter of a second for catheters of 50 m, such as used by Scamman. This is comparable with the period of CO₂ rise and fall for infants and explains the serious distortion in wave form that Scamman found. Some distortion can be eliminated by reducing R to 0.1 or less, but the extent of this improvement is small. Ideally, for fast-breathing patients, the catheter length should be reduced to 20 m or less, if possible.     

Nutritional Status Outcomes for Children: Ethnic, Cultural, and Environmental Contexts

The objective of this literature review was to explore the relationship between nutritional status outcomes among ethnically diverse children and cultural and environmental contexts. Articles from the literature on anthropometric/body composition measures, diet, and physiologic outcomes among ethnically diverse children were identified through on-line literature searches and references from articles reviewed. These studies were critically reviewed and selected if they reported findings resulting from use of accepted methodologies. Explanations consistent with evaluation of results from the studies and reports were developed by synthesis of the findings. Children from underserved, ethnically diverse population groups were at increased risk for obesity, increased serum lipid levels, and dietary consumption patterns that do not meet the Dietary Guidelines for Americans. More than 80% of all US children consume more than the recommended amount of total fat and saturated fat. These factors, which were noted during childhood, may track into adolescence, placing these children at increased risk for the early onset of chronic diseases such as non-insulin-dependent diabetes mellitus, cardiovascular disease, hypertension, and some forms of cancer. Although federally funded food assistance programs are changing rapidly, currently they provide foods that, when eaten as recommended, exceed the Dietary Guidelines for these children. Future interventions to improve the health and nutritional status of our nation's children, especially those from underserved, ethnically diverse groups, should be culturally appropriate and implemented at the levels of individuals, families, and communities. J Am Diet Assoc. 1996; 96:891-900,903.     

A prospective study of tobacco use and multiple myeloma: evidence against an association

The relationship between the use of cigarettes and other tobacco products and the risk of multiple myeloma was examined in a cohort of nearly 250,000 American veterans followed prospectively for 26 years. Compared with men who had never used tobacco, the risk of death from myeloma was not increased among current (relative risk [RR]=0.9, 95 percent confidence interval [CI]=0.8–1.2) or former (RR=1.0, CI=0.8–1.3) cigarette smokers, nor among users of chewing tobacco or snuff (RR=1.0, CI=0.4–2.3). Risk was only slightly and nonsignificantly increased among pipe or cigar smokers (RR=1.2, CI=0.9–1.5). There was no indication of increasing risk with amount of tobacco used or earlier age at first use. With over 90 percent power to detect a 30 percent increased risk of this tumor occuring among current cigarette smokers, this study provides the strongest evidence to date against an association of cigarette smoking with multiple myeloma.Epidemiology and Biometry Program, Division of Cancer Etiology, National Cancer Institute. Westat, Inc. Rockville, MD. National Cancer Institute, 6130 Executive Blvd, Room 418, Rockville, MD 20892, USA.