Shape analysis of the microcirculatory flow wave.

The cardiovascular system and its alterations are a crucial aspect of physiology and medicine. Non-invasive assessment of the functional properties of circulation is of considerable interest to clinicians and physiologists. In this work we investigate the possibility of detecting alterations of the flow waveform in microcirculation, using non-invasive measurements based on a laser Doppler flowmeter. As a test case, we focus on the effect of ageing. Skin is warmed up to a fixed temperature (44 °C) during measurement, to increase blood flow. The shape of the perfusion waveform during each heart beat after the flow was stabilized was used to estimate dynamic parameters of the microcirculatory system. Both the wave rise time, defined as the delay between the diastolic minimum and the following systolic maximum, and the oscillation fraction, defined as the normalized difference between the maximum and minimum flow, present significant variation with age.

Analysis of the microcirculatory pulse wave: age-related alterations.

Morphological analysis of the pulse wave of central blood pressure signal is commonly used for the study of cardiac and vascular properties, but very few attempts were performed for analyzing the peripheral pulse wave of blood flow. In this work, we analyzed this waveform using classical methods, based on the application of FFT, followed by principal components analysis, for assessing the properties of the blood flow. As a sample problem, we evaluated the capability of the proposed method of assessing the alterations correlated with the aging of the vascular system. Results show a good discrimination between the different age groups, confirming the validity of the approach.

Effect of local blood flow in thermal regulation in diabetic patient.

The presence of dysautonomia in diabetic neuropathy is correlated with impairment of vasomotor activity that drives blood microcirculation. Microcirculation, in turn, plays an important role in thermoregulation. In this work, we investigate the changes between two different physiological conditions of diabetic patients, induced by FREMS application, in the control of skin temperature, using a minimally invasive experiment. Skin is warmed up to a fixed temperature (44 °C) for a few minutes, then the heat source is turned off, letting the skin recover its physiological temperature. Both temperature and local blood flow, the latter measured with laser Doppler, are monitored during the experiment. A simple model of the cooling phase is used to evaluate the time constants involved in the process. Results indicate that significant differences exist in the model parameters between the two conditions.

Periodic Limbic Movement Disorder during Sleep as Diabetes-Related Syndrome? A Polysomnographic Study.

Introduction. Periodic limb movements during sleep (PLMs) is common in the elderly. When quality-of-life drops due to sleep disturbances, we speak about periodic limb movement disorder during sleep (PLMD). Another similar disorder, restless legs syndrome (RLS), is considered to be related to diabetes; RLS and PLMDs are genetically related. Our aim was to detect PLMDs in a population of diabetic patients and identify them as possible hallmarks of these autonomic disorders. Material and Methods. We selected 41 type-2 diabetics with no sleep comorbidity, and compared them with 38 healthy matched volunteers. All participants underwent the Epworth Sleepiness Scale (ESS) and polysomnography (PSG). A periodic limb movement (PLM) index >5, that is, the higher number of PLMs/sleep hour for the entire night, was considered as abnormal. Results. Diabetics showed lower sleep efficiency than controls on the ESS, lower proportions of REM and non-REM sleep, and higher arousal and PLM indexes, as assessed through PSG. PLMDs were diagnosed in 13 of 41 diabetic patients (31%); the latter showed lower sleep efficiency, lower non-REM slow-wave sleep, and increased arousal and PLM indexes. Conclusion. The relationship between PLMs-related sleep fragmentation and endocrine carbohydrate metabolism regulation might be casual or genetically determined. This deserves further investigations.

Recovery of 0.1Hz microvascular skin blood flow in dysautonomic diabetic (type 2) neuropathy by using Frequency Rhythmic Electrical Modulation System (FREMS).

Synchronized oscillation of smooth muscle cells tension in arterioles is the main control system of microvascular skin blood flow. An important autogenic vasomotion activity is recognized in 0.1Hz oscillations through power spectrum analysis of laser Doppler flowmetry. Severe dysautonomia in diabetic neuropathy is correlated with loss of 0.1Hz vasomotor activity, hence with impaired blood microcirculation. FREMS is a novel transcutaneous electrotherapy characterized by sequences of electrical stimuli of high voltage and low pulse duration which vary both in frequency and duration. We have evaluated the changes in laser Doppler flow in the volar part of the forearm before, during and after FREMS. Normal controls (n=10, 6 females, age range 21-39 years) demonstrated significant 0.1Hz vasomotion power spectra at baseline conditions associated with large oscillations of adrenergic cutaneous sweat activity sampled from the hand; people with diabetes type 2 and severe dysautonomia (n=10, 5 females, age range 63-75 years) displayed a significant decrease of 0.1Hz vasomotion power spectra. During FREMS application we observed an increase (p<0.05) of 0.1Hz vasomotion power spectra only in the diabetic group, despite persistence of adrenergic cutaneous sweat activity suppression in this group. However, after the application of the stimuli, the relative energy values around the 0.1Hz peak remained significantly higher than preapplication values in the diabetic group (p<0.05). From these findings, we suggest that FREMS is able to synchronize smooth cell activity, inducing and increasing 0.1Hz vasomotion, independently from the autonomic nervous system.

Frequency rhythmic electrical modulation system (FREMS) on H-reflex amplitudes in healthy subjects.

AIM: Changes in the amplitude of Hoffmann reflex (H-reflex) may reflect variations in the characteristics of the largely monosynaptic circuitry that is explored and are a possible target for diagnostic and physical therapeutic intervention. However, previous attempts to induce predictable changes in the H-reflex amplitude by transcutaneous electrical nervous stimulation (TENS) have generally failed. Previous workers applied fixed frequency in the low- (2-5 Hz) or in the high- (100 Hz) field, but they did not attempt to vary frequency and/or impulse duration in time. METHODS: We evaluated the effect of a new type of painless electric stimulation, i.e. frequency rhythmic electrical modulation system (FREMS). FREMS is characterized by the use of transcutaneous electric pulses with sequentially modulated frequency (f: 1-39 Hz) and width (w: 10-40 micro s) at constant, perceptive threshold voltage (approximately 150 V). FREMS was applied at the abductor hallucis muscle (AHM), as conditioning stimulus of the H-reflex which was recorded ipsilaterally at the soleus muscle, according to the classic method, in 10 normal volunteers (age range 21-40 years). RESULTS: H-reflex amplitude was substantially decreased (-50%) during FREMS and H-reflex amplitude variations were influenced by w/f variation in time during FREMS subphase C in a predictable way (r(2)=0.43; P<0.001). Our results suggest an effective ability of FREMS to modulate H reflex amplitude. CONCLUSIONS: The ability to achieve large and predictable changes of the H-reflex amplitude simply by modulating both frequency and duration of a conditioning painless electrical stimulation offers new possibilities for the treatment of diseases characterized by motoneuron excitability abnormalities.

Induction of vascular endothelial growth factor release by transcutaneous frequency modulated neural stimulation in diabetic polyneuropathy.

BACKGROUND: Pharmacological treatment for diabetic polyneuropathy (DP) has shown limited benefit; frequency-modulated electrical stimulation (FREMS) has shown positive results in pain control and nerve conduction velocity in DP. OBJECTIVE: To investigate the effects of FREMS vs transcutaneous electrical nerve stimulation (TENS) on the release of vascular endothelial growth factor (VEGF) in Type 2 diabetic and in non-diabetic subjects. METHODS: 10 non-diabetic [mean age 37+/-5 yr; females (F)/males (M): 6/4] and 10 Type 2 diabetic subjects (mean age 52+/-6 yr; F/M: 5/5) with DP underwent TENS (for 10 min) followed by 30 min interval without electrical stimulation, and then FREMS (for 10 min) over the forearm volar surface. Blood samples for VEGF measurements were obtained from the contra-lateral arm every 2 min during TENS/FREMS application and every 10 min during the intervals. RESULTS: We observed a significant rise in plasma VEGF during FREMS in both non-diabetic and diabetic subjects (maximal response 89.4+/-80.3 pg/ml and 48.5+/-18.3 pg/ml, respectively; p<0.01 vs basal) with a lower, but still significant response in diabetics. No changes in VEGF were observed during TENS application. CONCLUSION: VEGF release during FREMS may help explain the positive effects on nerve conduction velocity in DP, possibly mediated by favorable effects on vasa nervorum microangiopathy.

Hypokaliemic rhabdomyolysis associated with liquorice ingestion: report of an atypical case.

We here present an unusual case of hypokaliemic rhabdomyolysis, characterised by a sthenic deficit exclusively involving the distal muscles of the upper limbs and secondary to chronic glycyrrhizic acid intoxication, and by the absence of even ictal arterial hypertension. We discuss the etiopathogenetic bases and the risks related to the development of this secondary hypokaliemic syndrome, also in relation to other concomitant risk factors such as prolonged physical exercise and exposure to low temperatures.