Safety devices for neonatal intensive care

Three relatively simple devices for improving safety in neonatal intensive care are described. When umbilical artery catheters are used, an inexpensive pressure switch is utilized to detect abnormally low pressures associated with catheter withdrawal or excessive fluid leakage from the catheter system. A capacitive, intravenous-line air bubble detector, consisting of a section of the intravenous line as the dielectric of a capacitor, is used to alert the clinical staff when air bubbles pass between the capacitor plates. An electronic temperature controller maintains the temperature of neonatal breathing gases to avoid temperature variations which occur with presently used techniques. These are relatively simple and inexpensive devices which can be fabricated by most hospital clinical engineering services.     

A comparative study of the exchangein vivo of major constituents of bone mineral

Groups of young and old rats were injected with a variety of labelled substanzes (urea, Cl^–, K⁺, Na⁺, HCO ₃ ^– , PO ₄ ^3– , Ca⁺⁺). Data for Mg⁺⁺ were taken from the literature. One and a half hours later, compact shafts of long bones were removed and cleaned scrupulously, and analyses were performed for both cold and isotopic concentrations of substances. This time point was chosen to insure equilibration of the aqueous phase of bone while minimizing contributions from surface exchange, recrystallization, solid diffusion, growth or resorption.With fixed variables of time, species, bone specimen, and methodology, uambiguous comparisons of the exchange in bone could be made between the many substances studied. The exchange data could be divided into three categories: a) complete exchange (urea Cl^–, and K⁺); b) partial exchange, decreasing variably with age (Na⁺, CO₂, and Mg⁺⁺); and c) minimal exchange (Ca⁺⁺ and PO ₄ ^3– ). Clearly the traditional classification of available and unavailable skeleton is ambiguous and determined by the conditions and the ion or substance chosen for study. Clearly also, a new overall concept of bone exchangein vivo is badly needed.Calculations of the apparent concentration of the various electrolytes in bone water reveal that the aqueous phase of bone has a composition markedly different from plasma water. In particular, the concentration of potassium in bone water was found to be remarkably high.This work was supported in part by the United States Public Health Service grants no. 1 T1 DE 175 and R-501-Am 08271 and in part by the United States Atomic Energy Commission, contract no. W-7401-Eng-49 and has been assigned Report No. UR-49-898.     

Histamine release from platelets for assay of byssinogenic substances in cotton mill dust and related materials.

Previous reports suggest that byssinosis, an asthma-like condition among textile workers, may be mediated in part by histamine liberated following inhalation of dust. A simple, sensitive, and reliable procedure using pig platelets which contain the unusually high concentration of 0.8-1.6 microgram histamine/10(9) cells has been devised for the assay of histamine-releasing factors in cotton mill dust and related materials, and has yielded results generally in accordance with earlier assays using chopped lung tissue. As little as 50--100 microgram of total extractable substances from cotton mill dust can be measured. The activity of the extract is associated with the non-dialysable high molecular weight portion. However, conditions of acid hydrolysis do not destroy the activity. Extracts of leaves from different varieties of plant are highly potent, which suggests that the factors responsible for byssinosis are widely distributed plant components, present in textile fibre plants and converted to a respirable form by handling processes. Ellagic acid and sodium metasilicate release histamine from pig platelets, and represent new classes of compounds with possible roles in the aetiology of byssinosis.     

Evaluation of fetal monitoring by telemetry.

A radiotelemetry system for the direct monitoring of fetal heart rate and intrauterine pressure during labor has been evaluated at 5 different institutions. A conventional fetal scalp electrode and a special intrauterine pressure sensor are connected to a radio transmitter placed on the patient's thigh. The receiver can be located up to 50 feet away from the transmitter and is either a self-contained monitor or a unit that converts a conventional fetal monitor to a telemetric one. The telemetry recordings are of similar quality to those obtained from conventional monitors. Telemetry allows for greater patient comfort and mobility as well as greater convenience to the clinical staff. Continuous data can be obtained from patients while they are ambulatory or sitting in a chair as well as while they are in bed.     

Videodensitometric quantitation of stenosis: in vitro and in vivo validation

Percentage of stenosis of a vascular lumen was quantitated using a digital subtraction angiography system with videodensitometric analysis. To validate the algorithm and methods, we used precisely drilled Lucite rods of three inner diameters and various reduced diameters to give known luminal reduction. Both in vitro and in vivo results of stenosis measurements resulted in an excellent correlation between actual and measured values (correlation coefficient greater than 0.9 for all trials). Consistent underestimation of stenosis of about 5% was attributed to the various image degradations inherent with the imaging procedure and equipment. Errors were greatest with midrange stenoses and less at the extremes of the lesion values. An insufficient signal-to-noise ratio was caused by low photon flux and/or low contrast material concentration and overlying vasculature filled with contrast material. Overall, the videodensitometric technique is accurate, easy to implement, objective, and relatively free of errors associated with the geometric/edge detection method.     

Blood/bone disequilibrium: IV. Reciprocal effects of calcium and phosphate concentrations on ion fluxes

Summary Quantitative measurements were made of the ion fluxes of calcium and phosphate into and from calvaria (mouse or rat) when clamped in specially designed micro-Ussing chambers. The effects of varying concentrations of calcium were examined on the influx and efflux of calcium and of its counterion, phosphate. A comparable series of experiments was performed with varying phosphate concentrations. Both ions, as their concentrations increased, depressed their own influx, increased their own efflux, and significantly increased the equilibrium concentration, E/K, supported by the calvaria. Similarly, both ions, as their concentrations increased, affected the influx or efflux of their counterion only slightly but did depress the counterion's equilibrium level, E/K, significantly. In spite of these changes it was shown that calvaria effectively buffered the medium at physiological concentrations of calcium and phosphate. The buffering capacity, however, was small, and the balance, E/K, was modified by small uptake or loss of either ion. The small size of the interacting mineral pool was confirmed by direct measurement of the rapidly exchanging fractions of both calcium or phosphate. They were only ∼1% of the total ions present. The significance of these findings is discussed.     

TDT with covariates and genomic screens with mod scores: Their behavior on simulated data

We describe an extension to the TDT (transmission/disequilibrium test) which allows for more than two marker alleles and for covariates measured on the parent or offspring. We also describe a systematic genomic search where the mod score (maximized lod score) is computed for each marker under constraints on the population prevalence or penetrances of a single locus. © 1995 Wiley-Liss, Inc.