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Biomedical subjects

M A Afromowitz

Publications and source records attributed to M A Afromowitz.

9 recordsLinked to original sources
PubMed1998

Feasibility study of the spectroscopic measurement of oxyhemoglobin using whole blood without pre-treatment.

A feasibility study was carried out to evaluate a chemometrics-enhanced measurement of oxyhemoglobin concentration in whole blood without pre-treatment by lysing cellular components in the sample. Conventional in vitro multi-wavelength CO oximeters pre-process blood by sonication or detergent dilution to lyse blood cells to reduce light scattering. Two limitations result: (1) residual cell membrane fragments can seed surface biofouling and (2) dilution errors can occur. A full wavelength method using multivariate analysis in chemometrics was applied to correct the light scattering effect in the measurement of oxyhemoglobin concentration. Whole blood specimens were adjusted to different oxyhemoglobin concentrations with gas mixtures (N2, CO2 and O2). An Ocean Optics miniaturized spectrophotometer with a 100 microns pathlength optical cell was used for transmission measurements from 500 to 700 nm. Original spectra were smoothed and a second derivative transformation was performed to eliminate the baseline shift and slope changes from light scattering. Indirect calibration was applied to the second derivative spectra. Two-factor cross-validation by principle components regression on two sets of data showed r2 = 0.985 and 0.946 between predicted oxyhemoglobin concentration and those measured by an AVL 912 CO oximeter with RSD = 3.85 and 6.83%, respectively. Error analysis gave s = 2.36 x 10(-5) (RSD = 0.23%) on derivative absorbance for the spectrophotometer measurement alone. Specimen settling and specimen sampling gave imprecision on derivative absorbance of s = 6.17 x 10(-4) (RSD = 4.4%) and s = 4.52 x 10(-4) (RSD = 1.4%), respectively.

Feasibility Studies↗
PubMed1991

Development of medical pressure and temperature sensors employing optical spectrum modulation.

Fiber optic Fabry-Perot sensors have been developed whose optical reflectance varies with optical cavity depth (pressure) or with change in a material's refractive index (temperature). These sensors employ a unique combination of features: they are interrogated by an LED; they are designed to operate within a single reflectance cycle; and their returned light is analyzed by a dichroic ratio technique. The sensors use a step index glass fiber and are relatively insensitive to absolute light levels and fiber bending. They have an expanded linear operating range and can be built for low cost disposable applications. Sensor performance meets or exceeds established medical requirements.

Blood Pressure Determination↗
PubMed1984

Burn depth estimation--man or machine.

A Burn Depth Indicator, utilizing reflectance ratios of red, green, and infrared light, has been devised and clinically tested for 18 months at our Burn Center. Using the endpoint of wound healing in less than or more than 3 weeks, clinical assessment by two experienced surgeons of intermediate depth wounds was compared to readings from the BDI . In about one third of cases the surgeons were unwilling to commit themselves to a prediction. In the cases where the surgeons were willing to make a prediction, they were incorrect about 25% of the time. The BDI was significantly more accurate than the clinical assessment in those predicted not to heal by the surgeons and maintained an accuracy of 79% in the wounds where the surgeons would not make a prediction. The BDI is portable, noninvasive, and provides an immediate reading. It may have utility as a triage tool for emergency rooms or combat situations, and has utility at present in our Burn Center as a more accurate tool than our clinical judgment in predicting which wounds should be excised and grafted during the first few days after injury.

Burns↗
PubMed1977

Fabrication of pH-sensitive implantable electrode by thick film hybrid technology.

We report preliminary results of our experiments directed at fabricating pH-sensitive electrodes suitable for in vivo use by means of thick film screening techniques. Our results show that glass membranes of suitable thickness and possessing nearly theoretical sensitivity to pH can be fabricated by this process. A hybrid electrode structure permits the incorporation of a source follower FET amplifier directly adjacent to the pH membrane, significantly reducing response time and noise pick-up. Extension of the basic electrode structure to accommodate membranes sensitive to other ions is discussed.

Biomedical Engineering↗