A dynamic model of oxygen transport through the outer skin layers and a polarographic sensor was developed for the analysis of transcutaneous oxygen tension (tcPO2). It provides a basis for quantifying the factors that determine the relationship between tcPO2 and arterial oxygen tension (PaO2). Model simulations show the importance of stratum papillare metabolic oxygen consumption; the oxygen permeability of the skin relative to that of the sensor membrane and electrolyte; and temperature and the oxyhemoglobin dissociation curve. These simulations were consistent with experimental data obtained by using microcathode transcutaneous oxygen sensors, which were placed on the skin of 10 healthy adults. Furthermore, the model indicates that accurate evaluation of arterial oxygen tension by using transcutaneous measurements requires continuous estimation of skin perfusion. On the basis of tcPO2 measurements made during arterial occlusion, simulations indicate that quantitative evaluation of the metabolic oxygen consumption of the viable skin tissues is possible only when the oxygen permeabilities of the skin and sensor are known.

Adult↗

PubMedDate not supplied

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.

Cardiac Catheterization↗

PubMedDate not supplied

Fabrication of miniature PO2 and pH sensors using microelectronic techniques.

Miniature PO2 and pH sensors can be used in combination with enzymatic catalysts such as glucose oxidase and glucose dehydrogenase as the basis for the development of a small glucose sensor. The applications of microelectronic techniques such as photolithography techniques and thick- and thin-film metallization are novel approaches in fabricating highly uniform and reproducible sensors that are relatively simple to calibrate and operate.

Blood Glucose↗

PubMedDate not supplied

Thermal contact-sensing electronic thermometer.

The design and evaluation of a neonatal skin surface temperature-monitoring instrument that indicates when the temperature sensor becomes loose is presented. The skin surface temperature is sensed using a standard clinical thermistor probe. Thermal contact with the skin is evaluated every 4.5 min by determining the heat dissipation properties of the probe. A 6.1-mA, 14-s pulse is applied to the thermistor and the rate of temperature rise of the sensor is determined. Differences in this rate were found when the probe was in contact with skin and when it was in air, and an electronic circuit has been designed to recognize this difference. Evaluation on ten infants in incubators demonstrated that the instrument could accurately detect probe separation from the skin in all cases. When the instrument was evaluated on ten infants in bassinets at room temperature and ten adults, alarm conditions were seen in nine of ten cases when one side of the probe was separated from the skin by a 1.0-mm gap.

Adult↗