The backscattered intensity from low-intensity laser illumination of the skin in the area of vascular plexus is investigated in vivo. The exposure of blood to low power laser light in the absorption range of haemoglobin leads to increasing intensity of the backscattered light. Theoretical evaluation using an existing optical model of erythrocyte aggregation has suggests that the fragmentation of erythrocyte aggregates is the most probable mechanism leading to the enhanced backscattering.
Preliminary results are reported from a research project analysing
congestive heart failure in terms a stochastic coupled-oscillator
model of the cardiovascular system. Measurements of blood flow by
laser Doppler flowmetry (LDF) have been processed by use of the
wavelet transform to separate its oscillatory components, which
number at least five. Particular attention was concentrated on the
frequency content near 0.01 Hz, which is known to be associated
with endothelial function. The LDF was carried out in conjunction
with iontophoretically administered acetylcholine (ACh) and sodium
nitroprusside (SNP) in order to evaluate endothelial reactivity.
Measurements were made on 17 congestive heart failure (CHF)
patients (a) on first diagnosis, and (b) again several weeks later
after their treatment with a β-blocker had been stabilised.
The results of these two sets of measurements are being compared
with each other, and with data from an age and sex-matched group
of healthy controls. It is confirmed that endothelial reactivity
is reduced in CHF patients, as compared to healthy controls, and
it is found that one effect of the Beta-blocker is to ameliorate the loss of endothelial function in CHF. The implications of these results are discussed.
The human cardiovascular system is a complex system with the pumping activity of the heart as the main generator of oscillations. Besides the heartbeat there are several other oscillatory components which determine its dynamics. Their nonlinear nature and a weak coupling between them both require special treatment while studying this system. A particular characteristic of the oscillatory components is their frequency fluctuations in time. Consequently, their interactions also fluctuate in time.
Therefore the wavelet transform is applied to trace the oscillatory components in time, and specific quantitative measures are introduced to quantify the contribution of each of the oscillatory components involved on the time scale of up to three minutes. Oscillatory components are then analysed from signals obtained by simultaneous measurements of blood flow in the microcirculation, ECG, respiration and blood pressure. Based on quantitative evaluation of the oscillatory components related to (I) the heart beat (0.6-2Hz), (II) respiration (0.145-0.6Hz), (III) intrinsic myogenic activity (0.052-0.145Hz), (IV) sympathetic activity (0.021-0.052Hz), (V, VI) endothelial related activity (0.0095-0.021Hz, 0.005 - 0.0095 Hz), 30-minutes recording taken on 109 healthy subjects, 75 patients with diabetes, and 82 patients after acute myocardial infarction (AMI) were analysed.
Classification of the effect of ageing, diabetes and AMI from blood flow signals simultaneously recorded in the skin of four extremities, the heart rate and heart rate variability from R-R intervals will be presented and discussed.
The intensity of light backscattered when low-power laser radiation is incident on the skin is investigated under in vivo conditions. The exposure of blood to low-power laser light in the absorption range of haemoglobin leads an increased intensity of the backscattered light. The theoretical calculation using the existing optical model of erythrocyte aggregation has suggest that the fragmentation of erythrocyte aggregates is it most probable mechanism leading to the enhanced backscattering.