Blood Flow Sensor Research Articles

A combined tc-PO2 and skin blood flow sensor.

A new approach to the determination of energy delivered to the skin during transcutaneous oxygen tension (tc-PO2) measurements was tested. The test was carried out using a tc-PO2 electrode constructed with an active thermal shield in order to provide more sensitive and specific heat transport measurements, and consequently to create the possibility of determining skin blood flow rates. The oxygen measurement properties did not differ from the conventional tc-PO2 electrode. In vivo measurements were performed on 11 adult volunteers. Skin blood flow was determined by a blood flow cessation technique to be 0.124 +/- 0.053 ml . cm-2 . min-1 at the start of the experiments, rising to 0.164 +/- 0.61 ml . cm-2 . min-1. Tc-PO2 changed from 56.2 +/- 9.8 mmHg (7.5 +/- 1.3 kPa) to 68.3 +/- 9.0 mmHg(9.1 +/- 1.2 kPa). It is concluded that a thermally shielded electrode makes it possible to determine the convectional component of the heat loss from the electrode to the skin and consequently to compute a relative measure of skin blood flow rate. The observed change in computed skin blood flow rate was correlated to the observed change in tc-PO2 (P less than 0.1).

Response to pulsatile flow of a miniaturised electromagnetic blood flow sensor studied by means of a laser-Doppler method.

Electromagnetic (e.m.) flowmeter systems are commonly used in physiological experiments. Little information, however, is available about their accuracy in a time-dependent flow field. In miniaturised sensors especially the magnetic flux density cannot be made uniform, which may result in a non-ideal response to axisymmetric flows. The measured flow rate may therefore differ from the actual flow rate owing to the varying shape of the velocity profile. To study this effect unsteady flow experiments were performed to relate the e.m. flowmeter reading to the flow rate deduced from laser-Doppler anemometry. The experiments were performed in a straight circular tube with an internal diameter of 4 mm. The fluid (saline) flow was fully developed, laminar and pulsatile with flow reversal occurring near the wall in certain phases of the cycle. The frequency of the pulsations varied from 0·2 to 2 Hz. The fluid velocity was measured with a single component laser-Doppler system. The velocity profiles obtained were integrated to obtain the instantaneous flow rates and compared with those measured electromagnetically (Transflow 601). The results show no significant differences in the mean volume flow rates (averaged during one cycle). For momentary flow rates the differences are hardly significant. Small but briefly significant differences were found in the instantaneous flow rates, the largest deviation (7·8%) being found at flow reversal. Variation of the pulsation frequency (by a factor 10) or the mean flow rate (by a factor 4) has no significant effect on these differences.

The effect of norepinephrine, isoprenaline and acetylcholine on the testicular and epididymal circulation in the pig.

Blood flow to the testis and epididymis of 7 anaesthetized male pigs was measured using electromagnetic blood flow sensors. An average blood flow to the testis of 12 ml/min/100 g and in the epididymal arteries of 19 ml/min/100 g was measured. The effect of intravenously administered norepinephrine, isoprenaline and acetylcholine on alpha and beta 2 adrenergic and cholinergic receptor sites, respectively, was investigated. As neither norepinephrine nor isoprenaline, nor acetylcholine changed vascular conductance of the testis, we could not demonstrate adrenergic and cholinergic receptor activity. The possibility of autonomic regulation by the nonvascular smooth muscles of the spermatic cord and the inner layer of the tunica albuginea has been discussed.

Semiconductor thermoelectric information transducers for medical purposes

The authors have developed and now recommend for medical practice the following sensors: gas flow rate sensor, blood-flow volume rate sensor, temperature sensor and relative humidity meter. All these sensors are based on semiconductor thermoelectric materials.