Obtenció de matrius poroses d'àcid polilàctic (PDLLA) mitjançant fluids comprimits per a ús en regeneració tissular

En aquest treball es pretén obtenir material porós de PDLLA, amb ús potencial com a bastida en enginyeria tissular, mitjançant l’ús de freó R-134a com a fluid escumant. Per aquest motiu, s’ha realitzat un estudi on es valoren diferents variables com la temperatura de procés, la pressió de treball i l’ús de N2 en la despressurització que poden modificar la microestructura final de la bastida.

Implicacions pronòstiques de la saturació tissular d’oxigen en pacients amb xoc sèptic.

Estudi prospectiu observacional per analitzar el valor pronòstic de la saturació tissular d’oxigen (StO2) en 35 pacients amb xoc sèptic i pressió arterial mitjana normalitzada d’una unitat de cures intensives. Mitjançant espectroscòpia de llum infraroja, i realitzant una maniobra d’oclusió vascular, es van obtenir la StO2 i les pendents de desoxigenació (DeOx) i de reoxigenació (ReOx). No hi van haver diferències en els paràmetres hemodinàmics, StO2, DeOx i ReOx entre supervivents i no-supervivents. En la nostra mostra, una pitjor DeOx i ReOx es van associar amb major estada a UCI i hospitalària, però no amb mortalitat.

Medida de la Velocidad de Onda de Pulso mediante Ecografía Doppler: Concordancia con el Método Complior

La rigidez arterial es un parámetro establecido dentro de la valoración del riesgo cardio-vascular. Actualmente disponemos de múltiples métodos para determinar la velocidad de onda de pulso (VOP) y entre ellos los más utilizados son los métodos mecánicos, como el Complior o el Sphigmocor, que precisan de dispositivos específicos y una inversión importante en aprendizaje y tiempo de exploración. La utilización del doppler guiado por ecografía 2D es una buena alternativa a estos métodos. Realizamos un estudio comparativo para evaluar la fiabilidad del eco-doppler en la medida de la VOP carótida-femoral respecto al método Complior. Se estudió la VOP carótida-femoral utilizando los dos sistemas en 40 pacientes, mostrando ambos métodos muy buena concordancia (R=0’91). En el análisis de reproducibilidad de la VOP por doppler no se hallaron diferencias intra e interobservador. En base a los resultados, el estudio demuestra que la ecografía doppler puede ser usada para medir la VOP aórtica de manera fiable y reproducible, similar otros métodos más establecidos.

Controlled contrast transcranial Doppler and arterial blood gas analysis to quantify shunt through patent foramen ovale.

BACKGROUND AND PURPOSE: A right-to-left shunt can be identified by contrast transcranial Doppler ultrasonography (c-TCD) at rest and/or after a Valsalva maneuver (VM) or by arterial blood gas (ABG) measurement. We assessed the influence of controlled strain pressures and durations during VM on the right-to-left passage of microbubbles, on which depends the shunt classification by c-TCD, and correlated it with the right-to-left shunt evaluation by ABG measurements in stroke patients with patent foramen ovale (PFO). METHODS: We evaluated 40 stroke patients with transesophageal echocardiography-documented PFO. The microbubbles were recorded with TCD at rest and after 4 different VM conditions with controlled duration and target strain pressures (duration in seconds and pressure in cm H2O, respectively): V5-20, V10-20, V5-40, and V10-40. The ABG analysis was performed after pure oxygen breathing in 34 patients, and the shunt was calculated as percentage of cardiac output. RESULTS: Among all VM conditions, V5-40 and V10-40 yielded the greatest median number of microbubbles (84 and 95, respectively; P<0.01). A significantly larger number of microbubbles were detected in V5-40 than in V5-20 (P<0.001) and in V10-40 than in V10-20 (P<0.01). ABG was not sensitive enough to detect a shunt in 31 patients. CONCLUSIONS: The increase of VM expiratory pressure magnifies the number of microbubbles irrespective of the strain duration. Because the right-to-left shunt classification in PFO is based on the number of microbubbles, a controlled VM pressure is advised for a reproducible shunt assessment. The ABG measurement is not sensitive enough for shunt assessment in stroke patients with PFO.

Assessment of melanocytic skin lesions with a high-definition laser Doppler imaging system.

BACKGROUND: Early detection is a major goal in the management of malignant melanoma. Besides clinical assessment many noninvasive technologies such as dermoscopy, digital dermoscopy and in vivo laser scanner microscopy are used as additional methods. Herein we tested a system to assess lesional perfusion as a tool for early melanoma detection.¦METHODS: Laser Doppler flow (FluxExplorer) and mole analyser (MA) score (FotoFinder) were applied to histologically verified melanocytic nevi (33) and malignant melanomas (12).¦RESULTS: Mean perfusion and MA scores were significantly increased in melanoma compared to nevi. However, applying an empirically determined threshold of 16% perfusion increase only 42% of the melanomas fulfilled the criterion of malignancy, whereas with the mole analyzer score 82% of the melanomas fulfilled the criterion of malignancy.¦CONCLUSION: Laser Doppler imaging is a highly sensitive technology to assess skin and skin tumor perfusion in vivo. Although mean perfusion is higher in melanomas compared to nevi the high numbers of false negative results hamper the use of this technology for early melanoma detection.

Doppler ultrasound in the measurement of pulse wave velocity: agreement with the Complior method

Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84-0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for themeasurement of aortic PWV

Interplay of spectral efficiency, power and doppler spectrum for reference-signal-assisted wireless communication

Expressions relating spectral efficiency, power, and Doppler spectrum, are derived for Rayleigh-faded wireless channels with Gaussian signal transmission. No side information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated in accordance with the functioning of most wireless systems. The analysis relies on a well-established lower bound, generally tight and asymptotically exact at low SNR. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in the derived expressions, imbuing them with practical significance. Closed-form relationships are obtained for the popular Clarke-Jakes spectrum and informative expansions, valid for arbitrary spectra, are found for the low- and high-power regimes. While the paper focuses on scalar channels, the extension to multiantenna settings is also discussed.

Estimation of the viscoelastic properties of vessel walls using a computational model and Doppler ultrasound

Human arteries affected by atherosclerosis are characterized by altered wall viscoelastic properties. The possibility of noninvasively assessing arterial viscoelasticity in vivo would significantly contribute to the early diagnosis and prevention of this disease. This paper presents a noniterative technique to estimate the viscoelastic parameters of a vascular wall Zener model. The approach requires the simultaneous measurement of flow variations and wall displacements, which can be provided by suitable ultrasound Doppler instruments. Viscoelastic parameters are estimated by fitting the theoretical constitutive equations to the experimental measurements using an ARMA parameter approach. The accuracy and sensitivity of the proposed method are tested using reference data generated by numerical simulations of arterial pulsation in which the physiological conditions and the viscoelastic parameters of the model can be suitably varied. The estimated values quantitatively agree with the reference values, showing that the only parameter affected by changing the physiological conditions is viscosity, whose relative error was about 27% even when a poor signal-to-noise ratio is simulated. Finally, the feasibility of the method is illustrated through three measurements made at different flow regimes on a cylindrical vessel phantom, yielding a parameter mean estimation error of 25%.

Intrauterine growth restriction and absent or reverse end-diastolic blood flow in umbilical artery (Doppler class II or III): A retrospective study of short- and long-term fetal morbidity and mortality.

OBJECTIVE: Absent or reverse end-diastolic flow (Doppler II/III) in umbilical artery is correlated with poor perinatal outcome, particularly in intrauterine growth restricted (IUGR) fetuses. The optimal timing of delivery is still controversial. We studied the short- and long-term morbidity and mortality among these children associated with our defined management. STUDY DESIGN: Sixty-nine IUGR fetuses with umbilical Doppler II/III were divided into three groups; Group 1, severe early IUGR, no therapeutic intervention (n = 7); Group 2, fetuses with pathological biophysical profile, immediate delivery (n = 35); Group 3, fetuses for which expectant management had been decided (n = 27). RESULTS: In Group 1, stillbirth was observed after a mean delay of 6.3 days. Group 2 delivered at an average of 31.6 weeks and two died in the neonatal period (6%). In Group 3 after a mean delay of 8 days, average gestational age at delivery was 31.7 weeks; two intra uterine and four perinatal deaths were observed (22%). Long-term follow-up revealed no sequelae in 25/31 (81%) and 15/18 (83%), and major handicap occurred in 1 (3%) and 2 patients (11%), respectively, for Groups 2 and 3. CONCLUSION: Fetal mortality was observed in 22% of this high risk group. After a mean period of follow-up of 5 years, 82% of infants showed no sequelae. According to our management, IUGR associated with umbilical Doppler II or III does not show any benefit from an expectant management in term of long-term morbidity.

Early detection of microcirculatory perfusion changes with a high resolution, real time laser Doppler imaging camera--frostbite case study.

A 41-year-old male presented with severe frostbite that was monitored clinically and with a new laser Doppler imaging (LDI) camera that records arbitrary microcirculatory perfusion units (1-256 arbitrary perfusion units (APU's)). LDI monitoring detected perfusion differences in hand and foot not seen visually. On day 4-5 after injury, LDI showed that while fingers did not experience any significant perfusion change (average of 31±25 APUs on day 5), the patient's left big toe did (from 17±29 APUs day 4 to 103±55 APUs day 5). These changes in regional perfusion were not detectable by visual examination. On day 53 postinjury, all fingers with reduced perfusion by LDI were amputated, while the toe could be salvaged. This case clearly demonstrates that insufficient microcirculatory perfusion can be identified using LDI in ways which visual examination alone does not permit, allowing prognosis of clinical outcomes. Such information may also be used to develop improved treatment approaches.

Transcranial Doppler after traumatic brain injury: is there a role?

PURPOSE OF REVIEW: To present the practical aspects of transcranial Doppler (TCD) and provide evidence supporting its use for the management of traumatic brain injury (TBI) patients. RECENT FINDINGS: TCD measures systolic, mean, and diastolic cerebral blood flow (CBF) velocities and calculates the pulsatility index from basal intracranial arteries. These variables reflect the brain circulation, provided there is control of potential confounding factors. TCD can be useful in patients with severe TBI to detect low CBF, for example, during intracranial hypertension, and to assess cerebral autoregulation. In the emergency room, TCD might complement brain computed tomography (CT) scan and clinical examination to screen patients at risk for further neurological deterioration after mild-to-moderate TBI. SUMMARY: The diagnostic value of TCD should be incorporated into other findings from multimodal brain monitoring and CT scan to optimize the bedside management of patients with TBI and help guide the choice of appropriate therapies.

Prediction of clinical response after renal angioplasty: respective value of renal Doppler sonography and scintigraphy.

OBJECTIVE: The goal of our study was to compare Doppler sonography and renal scintigraphy as tools for predicting the therapeutic response in patients after undergoing renal angioplasty. SUBJECTS AND METHODS. Seventy-four hypertensive patients underwent clinical examination, Doppler sonography, and renal scintigraphy before and after receiving captopril in preparation for renal revascularization. The patients were evaluated for the status of hypertension 3 months after the procedure. The predictive values of the findings of clinical examination, Doppler sonography, renal scintigraphy, and angiography were assessed. RESULTS: For prediction of a favorable therapeutic outcome, abnormal results from renal scintigraphy before and after captopril administration had a sensitivity of 58% and specificity of 57%. Findings of Doppler sonography had a sensitivity of 68% and specificity of 50% before captopril administration and a sensitivity of 81% and specificity of 32% after captopril administration. Significant predictors of a cure or reduction of hypertension after revascularization were low unilateral (p = 0.014) and bilateral resistive (p = 0.016) indexes on Doppler sonography before (p = 0.009) and after (p = 0.028) captopril administration. On multivariate analysis, the best predictors were a unilateral resistive index of less than 0.65 (odds ratio [OR] = 3.7) after captopril administration and a kidney longer than 93 mm (OR = 7.8). The two best combined criteria to predict the favorable therapeutic outcome were a bilateral resistive index of less than 0.75 before captopril administration combined with a unilateral resistive index of less than 0.70 after captopril administration (sensitivity, 76%; specificity, 58%) or a bilateral resistive index of less than 0.75 before captopril administration and a kidney measuring longer than 90 mm (sensitivity, 81%; specificity, 50%). CONCLUSION: Measurements of kidney length and unilateral and bilateral resistive indexes before and after captopril administration were useful in predicting the outcome after renal angioplasty. Renal scintigraphy had no significant predictive value.