Which techniques to improve the early detection and prevention of pressure ulcers?

Pressure ulcers are a serious health problem for people with mobility disorders, like elders in acute care, long-term care, and home care settings. It also concerns paraplegics, tetraplegics or persons with burned injuries. Pressure ulcers result in significant morbidity and mortality. Consequences are a high human suffering, with high cost in terms of treatment. Several risk factors have been identified for the development of pressure ulcers: they are classified into extrinsic and intrinsic factors. Extrinsic factors include interface pressure, shear forces, friction. Intrinsic factors are the nutritional state of the patient, its age, diseases. There is little information about the mechanism of the formation of pressure sores but it is agreed that it is a complex process. The difficulty of the prevention lies in the evaluation of these factors. It is an essential stage to optimize the preventative measures. Actually, no quantifiable parameters exist to predict the formation of a pressure ulcer. This article is aimed to propose new techniques developed for the early detection of pressure ulcers. First, extrinsic parameters as the interface pressure and its consequences on the mobility are investigated. A new actimeter is presented to monitor the movements of the patient. The second part is dedicated to the presentation of a new imaging technique which can help the physician to control tissue elasticity of the patient. The technique is called elastography, it is a 3D strain estimation of soft biological tissues. Finally, the last way of investigation is the combination of extrinsic and intrinsic factors evaluation for a most relevant earlier diagnosis. Before the description of these techniques, it is essential to understand the phenomenology associated to the development of pressure sores. Only in this way, new techniques can be developed.

Reversible meiotic abnormalities in azoospermic men with bilateral varicocele after microsurgical correction.

Because of a possible relationship between microenvironmental disturbances and meiotic abnormalities and of a straight relationship between lower-quality semen in patient carrying a varicocele and first meiotic non-disjunction, bilateral bipolar testicular biopsies are realized according the thermic differential gradient described in varicocele. Systematic meiotic studies of multiple testicular biopsies from 65 azoospermic men with bilateral varicocele were done in a multi-centric study on microsurgical correction of bilateral varicocele with microthermic intra-operative evaluation using minimally invasive thermal microsensors (Betatherm 10K3MCD2). In the present study abnormal temperature raising, histomorphometric abnormalities (spermatocyte arrest) and meiotic abnormalities (class IIC) are strongly correlated. In the ten patients submitted to another testicular biopsy procedure six months after surgery for TESE, normal thermal differential is registered and no meiotic abnormalities recurrences are found.

Autonomic nervous system activity associated with postural disturbances in patients with perilymphatic fistula: sympathetic or vagal origin?

The study focused on patients suffering from perilymphatic fistula (PLF), whether they had undergone surgery or not. Vestibular disturbances can be harmless but are associated with varying symptoms, demonstrating disorders within the autonomic nervous system (ANS). The aim was to test whether the orthosympathetic is involved as the vagal part is often suspected of eliciting a feeling of sickness. Non-invasive and uninterrupted recording of ANS activity represents an objectivation technique to evidence such disturbances. Electrodermal activity, thermovascular variables, instantaneous cardiac rate and blood pressure were recorded. Discomfort was triggered experimentally by applying various stimulations successively to the intact ear then to the PLF (or operated) side. Twelve subjects took part in the experiment. Two types of ANS activity were distinguished: (1) phasic responses during stimulation and (2) tonic evolution thereafter. Results show strong activation in orthosympathetic variables when the PLF side was stimulated. No further significant difference between the two sides was to be observed following surgery. After stimulation, a sudden increase in skin resistance was observed, associated with slight bradycardia. No vagal signs having been evidenced, actual nausea may result from brief inhibition of sympathetic activation resulting, in turn from primary over-activation of this system.

The relationship between normal lung sounds, age, and gender.

Auscultation is one of the most important noninvasive and feasible methods for the detection of lung diseases. Systematic changes in breathing sounds with increasing age are of diagnostic importance. To investigate these changes, we recorded lung sounds taken from four locations in the posterior thorax of 162 subjects, together with airflow. The data were analyzed according to age, sex, and smoking habit. In order to describe the power spectrum of the lung sounds, we calculated mean and median frequency, frequency with the highest power, and a ratio (Q) of relative power of the two frequency bands of 330 to 600 Hz and 60 to 330 Hz. Linear regression analysis was used as a measurement of age-dependence of these variables. Significant differences in Q were found in men versus women (p < 0.05), but not in smokers versus nonsmokers. Within the groups, a small but significant correlation existed between Q and age (r(2) /= +/- 5%) have no clinical significance and need not to be considered in the automatic detection of lung diseases by analyzing lung sounds.

Thermal diffusion probe and instrument system for tissue blood flow measurements: validation in phantoms and in vivo organs.

A minimally invasive probe and instrument system for real-time measurements of temperature, thermal conductivity and tissue blood flow has been designed for research and clinical use. The essence of the probe is a thermistor, located at the tip of catheters or glass and steel needles, and operating in transient self-heated mode at constant temperature increment. Thermal conductivity and tissue blood flow are determined by use of a coupled tissue-probe thermal model. The effects of temporal baseline temperature shifts are minimized by a novel, automatic, analog compensation circuit. Very short heating periods (3 s) and cooling periods (12 s) provided near-continuous measurements (4/min). Calibration experiments performed in media of known thermal conductivity exhibit a linear response with respect to thermal conductivity. In vitro experiments performed in isolated perfused dog liver preparations are presented to evaluate this instrument system. In vivo experiments performed in cat brain, dog liver, and human tumor demonstrate the ability of this instrument system to perform physiologically valid measurements (comparison inter-subjects and intra-subjects). The minimally invasive probes (0.8 mm OD) are capable of long term measurements (several months), with minimal tissue reactions (0.3 mm around the probe).

Comparison of different techniques of hypothermic pig heart preservation.

The aim of this study was to compare several methods of hypothermic heart preservation. Isolated pig hearts were preserved for 24 hours in cold cardioplegic solution (St. Thomas' Hospital modified solution) by continuous perfusion (group I), microperfusion (group II), or simple storage (group III). The findings were then compared with those from hearts harvested and immediately reperfused (the control group). Group III hearts showed lower adenosine triphosphate preservation (0.47 +/- 0.18 mumol/g) than did group I and II hearts and the control hearts (1.86 +/- 0.40, 1.98 +/- 0.27, and 1.84 +/- 0.55 mumol/kg, respectively). Electronic microscopy studies also revealed that the myocardial cells in the group III hearts appeared to be damaged. After the hearts had undergone preservation, myocardial function was studied for 60 minutes under nonworking conditions using an ex vivo functional testing system. For group III, the mean left ventricular developed pressure and ventricular compliance (16 +/- 22 and 63 +/- 48 mm Hg, respectively) differed significantly from those for group I (83 +/- 26 and 0 +/- 0 mm Hg, respectively), group II (83 +/- 33 and 14 +/- 18 mm Hg, respectively), and the control group (115 +/- 13 and 0 +/- 0 mm Hg, respectively). We concluded from our findings that perfusion methods are superior to cold storage but inadequate to maintain heart viability for the long term during hypothermia. These techniques must be improved before they can be adopted for clinical use.

Quantitative reduction of MTT by hearts biopsies in vitro is an index of viability.

The aim of this study is to evaluate the use of tetrazolium reductase (TR) activity as an indicator of myocardial viability in an isolated arrested pig heart biopsy model. Methyl Tetrazolium (MTT) is cleaved by an enzyme in the presence of coenzymes NAD, NADP. Cleavage yields a highly colored formazan product which is DMSO soluble. Efficient bioreduction of MTT has been investigated with heart biopsies. The relationship between MTT reduction and (1) oxygen consumption (r = 0.96, P < 0.001), (2) the sum of the adenine nucleotide levels (r = 0.87, P < 0.001) and (3) localization of coloration, has been established. The use of MTT in colorimetric assays offers high sensitivity. MTT reduction is a valid method. It is rapid and reproducible, and can be used as an indicator of myocardial viability. The MTT test has been used to rapidly compare the effect of different cardioplegic solutions (St Thomas and improved St Thomas) on hypothermic cardiac preservation. Significant differences have been established between the two solutions (P < 0.01).

Comparison of continuous microperfusion and cold storage for pig heart preservation.

The aim of this study was to compare two methods of hypothermic heart preservation. Isolated hearts of pigs were preserved in cold cardioplegic solution (St. Thomas Hospital solution) either by simple storage or continuous microperfusion (with a new perfusion device) for 6 hours (group I, n = 12), 12 hours (group II, n = 12) and 24 hours (group III, n = 12). After storage, the myocardial function was studied for 60 minutes under nonworking conditions with an ex vivo functional testing system. Hearts preserved 24 hours by cold storage (group III) showed ventricular compliance and mean spontaneous left ventricular developed pressure significantly lower than hearts preserved by microperfusion (respectively, 63 +/- 47 versus 14 +/- 18 mm Hg and 16.8 +/- 22.0 versus 83 +/- 33 mm Hg). After 12 hours (group II) of preservation, mean left ventricular developed pressure was higher in microperfused hearts compared to immersed hearts (respectively, 133.3 +/- 39.0 versus 83.1 +/- 27.0 mm Hg, p < 0.05), whereas after 6 hours of preservation, no functional difference was observed between the microperfused and the immersed hearts. Hearts were also studied using myocardial biopsy specimens taken at the end of the preservation. The biopsy specimens were analyzed for high-energy phosphates. After 6 hours of preservation, the microperfusion group showed higher levels of adenosine triphosphate and total adenine nucleotides (adenosine triphosphate + adenosine diphosphate + adenosine monophosphate) (respectively, 4.60 +/- 0.5 mumol/gm and 5.98 +/- 0.5 mumol/gm fresh tissue) versus the cold storage group (respectively, 3.10 +/- 0.4 mumol/gm and 3.75 +/- 0.4 mumol/gm).(ABSTRACT TRUNCATED AT 250 WORDS)

[A comparison of intermittent compression with single and multi-chamber systems in treatment of secondary arm lymphedema following mastectomy]. / Ein Vergleich der intermittierenden Kompression von Ein- und Mehrkammersystemen zur Behandlung von sekundären Armlymphödemen nach Ablatio mammae.

In a comparative study 38 patients with secondary unilateral lymphatic oedema after mastectomy were investigated with regard to the efficacy of intermittent compression treatment using uni- or multichamber systems (Jobst and Lymph-a-mat respectively). Although both machines significantly reduce oedema, there is no difference between their reduction capacities.

Measurements of effective thermal conductivity during hyperthermia: a comparison of experimental and clinical results.

Temperature and effective thermal conductivity (including the convective effects due to tissue blood flow) profiles have been mapped both within a perfused phantom model containing a differentially perfused pseudo-tumour and in patients undergoing microwave (915 MHz) hyperthermia. These measurements demonstrate the influence of differential thermal characteristics of tumour vs. normal tissue on the temperature distributions obtained during hyperthermia. Effective thermal conductivity was measured using a self-heated thermistor probe, and temperature profiles were measured by means of conventional thermocouples and fibre-optic temperature probes. Measurements of effective thermal conductivity obtained in patients prior to microwave hyperthermia, and temperature profiles obtained once steady-state treatment conditions had been attained, show a strong relation between the effective thermal conductivity profile and the ability to obtain therapeutic temperatures without excessive heating of intervening tissues. These observations were confirmed in phantom experiments, demonstrating that this perfused phantom is a more realistic physical model than the conventional unperfused gels usually employed as physical models for hyperthermia experiments. These results demonstrate that tissue thermal clearance is an important determinant of treatment temperature fields, independent of and in addition to the SAR distribution of the particular applicator. Effective thermal conductivity measurements of the different tissues constituting the volume to be heated could be an important index in the planning and optimization of treatment strategies.

Relationship between pulse amplitude and thermal exchange in the finger: the effect of smoking.

In 24 healthy volunteers finger pulse amplitude and heart rate (HR) were monitored by pulse plethysmography and thermal exchange from the finger and were compared before and after the smoking of a single cigarette. Thermal exchange was measured using a direct calorimeter consisting of a recording bath and a reference bath, both of which were filled with water at 18 degree C. The subject immersed the two distal phalanx of a finger into the recording bath. The water thermal gradient between both baths after 4 min of finger immersion and the maximal value of heat loss from the finger to the water were recorded. Decreases in the water thermal gradient (from 6.06 to 5.33 degrees C, P less than 0.05) in maximal value of heat loss (from 22.5 to 18.75 w.m-2, P less than 0.01) and in plethysmographic wave amplitude (from 25.8 to 14.6 mm, P less than 0.01) and increased HR (from 72 to 83 beats min-1) were observed in smokers. These changes were not statistically significant in non-smokers. Water thermal gradient and maximal value of heat loss correlated with plethysmographic wave amplitude before and after smoking but not with HR in the 24 subjects studied. The present study shows a good relationship between vascular phenomena and thermal exchange in the fingers. The variations of finger pulse amplitude provide an adequate and sensitive adjustment of thermal exchange since the effects of smoking a single cigarette can be detected by both PWA and calorimetric measurements in the finger.

Heat loss and anticipatory finger vasoconstriction induced by a smoking of a single cigarette.

The effects of smoking of a single cigarette on finger vasomotion were investigated in 15 healthy subjects classified according to their smoking habit into one of 3 groups: heavy, light, and non-smokers. Finger pulse amplitude was recorded using a plethysmographic mercury gauge before, during and after cigarette smoking and finger heat loss evaluated using direct calorimetry before and after smoking. Heavy smokers showed a decrease of finger pulse amplitude at the sight of the cigarette and before the first puff. Finger pulse amplitude in light smokers decreased during cigarette smoking. In heavy smokers and light smokers finger heat loss decreased after smoking. In non-smokers, there was no change either in finger heat loss or in finger pulse amplitude. Anticipatory finger vasoconstriction in response to the sight of a cigarette may represent a pavlovian conditioning occurring in heavy smokers only.