Biomedical subjects

O G Martinsen

Publications and source records attributed to O G Martinsen.

8 recordsLinked to original sources

PubMed2004

The Microfiltrometer (MicroFM): a new filtration device for the assessment of less deformable erythrocyte subpopulations.

The hardware of a new filtration device, the Microfiltrometer (MicroFM), is described. The different components of the device; impedance meter, power supply, measuring cell and its 5-micron Oligopore filter are described and it is shown how they are interrelated and interfaced to a computer for data acquisition. The properties of the filter and the general functioning principle of the device are also elucidated. For each run, the MicroFM generates elementary signals from individual passages of many hundreds of red blood cells (RBCs) through micropores of a given 5-micron Oligopore filter. Analysis of each elementary signal provides two complementary parameters, the transit time tau of the explored RBC and the change in electrical impedance deltaZ caused by the temporary flow of the considered RBC through a particular micropore of the filter. These two parameters can be utilized for reliable assessment of erythrocyte deformability on a cellular level.

Cell Size↗

PubMed2004

Basic principles for evaluation of less deformable erythrocyte subpopulations with the Microfiltrometer.

The Microfiltrometer consists of a filtration system for diluted erythrocyte suspensions, through a filter containing 30 cylindrical micropores, 5 microm in diameter, under the influence of a driving pressure. A feeding sinusoidal alternating current of 40 kHz, 300 microA is delivered to the filter. The change in impedance is collected for each temporary flow of erythrocytes through a given micropore. Two main parameters are measured for individually explored erythrocytes: the entry time tau in the micropore and the maximal variation of impedance deltaZ occurring for the transitory flow. The slope deltaZ/tau defines the velocity of pore blockage. A "Microfiltrometer Deformability Index" (MDI) is established by using this slope. When MDI > or = 1, the erythrocyte is considered to be deformable and, conversely, when MDI < 1, the erythrocyte is considered to be undeformable. Using this procedure, less than 2% undeformable erythrocytes in healthy blood samples are identified, with a specificity of 99% and a sensitivity of 97.5%.

Cell Shape↗

PubMed2001

Line patterns in the mosaic electrical properties of human skin--a cross-correlation study.

A vehicle with 16 electrodes for the two-dimensional electrical admittance mapping of human skin is presented. Measurements on 20 test subjects have been carried out and analyzed for the possible detection of line patterns in the electrical properties of the skin, claimed to coincide with the so-called acupuncture meridian lines of ancient Chinese medicine. No such lines were found.

Acupuncture Therapy↗

PubMed2001

Facts and myths about electrical measurement of stratum corneum hydration state.

Some of the views presented in the chapter on 'Examination of stratum corneum hydration state by electrical methods' in Skin Bioengineering - Techniques and Applications in Dermatology and Cosmetology (Karger, 1998) are in strong disagreement with the results from basic research that has been conducted on skin impedance measurement over the last decades. This research has e.g. non-ambiguously shown that the frequency response of the stratum corneum does not obey the Cole equation and that measurement depth is strongly dependent on measurement frequency. One consequence of these findings is that multifrequency electrical measurements on stratum corneum are impossible to achieve in vivo with any electrode system known today. Hence, electrical measurements of stratum corneum hydration must be conducted at one single, low frequency.

Body Water↗

PubMed2000

The development of a software program for analyzing spontaneous and externally elicited skin conductance changes in infants and adults.

OBJECTIVES: Changes in palmar and plantar skin conductance (SC) are due to outgoing bursts in the postganglionic efferent sympathetic cholinergic fibres, which responds to changes in central arousal state. The purpose of this study was designed to develop a software program for analyzing spontaneous and external elicited SC changes for infants and adults. METHODS: The program was designed to calculate the number and mean amplitude of the waves as well as the mean basal level in a given period. Different pre-set values for the minimum amplitude, maximum slope and minimum width of the spontaneous waves were used in the analysis program, and the results were compared with manually counted waves. The program was also used to perform coherent averaging of repeated elicited SC changes. For the mean elicited skin conductance responses, the latency time, response amplitude and recovery time were calculated. The habituation pattern could be calculated semi-automatically by analyzing each response. RESULTS: For SC waves, the minimum amplitude and the maximum slope should be, respectively, 0.02 microsiemens (microS) and 2 microS/s for infants and adults, and the width of the waves should be at least 1 s for adults, and unlimited for infants. The coherent average method was found to be a satisfactory method for revealing whether a subject responded to stimuli, and is recommended, especially for infants. CONCLUSIONS: Spontaneous and stimulated skin conductance are easily analyzed by this software program.

Adult↗

PubMed1997

Dielectric properties of some keratinised tissues. Part 1: Stratum corneum and nail in situ.

Blister-skin and warts have been studied as possible sources of 'pure' stratum corneum without sweat ducts. The purpose of the study was to assess whether the DC electrical conductance measured on human skin is totally dominated by the sweat ducts, or is also significantly contributed to by the stratum corneum itself. By means of galvanic skin response (GSR) measurements, these tissues were found to be unrealiable as sources of 'pure' stratum corneum. This is because they displayed significant GSR waves, and hence should have some form of active pores. However, measurements on blister-skin and nail in situ revealed a substantial frequency independent electrical conductance at frequencies typically below 10 Hz.

Blister↗

PubMed1997

Dielectric properties of some keratinised tissues. Part 2: Human hair.

Some electrical properties of human hair have been investigated to determine whether a significant DC electrical conductance is present in keratinised tissues. The DC conductance was found to be substantial and highly dependent on the moisture level in the hair fibres. At high moisture levels, the conductance was found to be almost frequency independent below 1 kHz. Absorption and desorption profiles were also monitored, revealing different stages of sorption mechanisms in the fibres. Although absorption was found to be a slow process with 'time constants' in the range of hours, desorption was much faster, in the range of a few minutes.

Absorption↗

PubMed1995

Electrical methods for skin moisture assessment.

Skin sites on 8 test subjects were treated with moisturizers, and different electrical measuring methods were compared regarding their quality in the assessment of the induced changes in the stratum corneum hydration level. Low frequency susceptance measurements were found preferable to high frequency admittance measurements, and the advantages of monopolar measurements with the three-electrode system are described.

Adult↗