Multimodal non-invasive monitoring to apply an open lung approach strategy in morbidly obese patients during bariatric surgery.

To evaluate the use of non-invasive variables for monitoring an open-lung approach (OLA) strategy in bariatric surgery. Twelve morbidly obese patients undergoing bariatric surgery received a baseline protective ventilation with 8 cmH2O of positive-end expiratory pressure (PEEP). Then, the OLA strategy was applied consisting in lung recruitment followed by a decremental PEEP trial, from 20 to 8 cmH2O, in steps of 2 cmH2O to find the lung's closing pressure. Baseline ventilation was then resumed setting open lung PEEP (OL-PEEP) at 2 cmH2O above this pressure. The multimodal non-invasive variables used for monitoring OLA consisted in pulse oximetry (SpO2), respiratory compliance (Crs), end-expiratory lung volume measured by a capnodynamic method (EELVCO2), and esophageal manometry. OL-PEEP was detected at 15.9 ± 1.7 cmH2O corresponding to a positive end-expiratory transpulmonary pressure (PL,ee) of 0.9 ± 1.1 cmH2O. ROC analysis showed that SpO2 was more accurate (AUC 0.92, IC95% 0.87-0.97) than Crs (AUC 0.76, IC95% 0.87-0.97) and EELVCO2 (AUC 0.73, IC95% 0.64-0.82) to detect the lung's closing pressure according to the change of PL,ee from positive to negative values. Compared to baseline ventilation with 8 cmH2O of PEEP, OLA increased EELVCO2 (1309 ± 517 vs. 2177 ± 679 mL) and decreased driving pressure (18.3 ± 2.2 vs. 10.1 ± 1.7 cmH2O), estimated shunt (17.7 ± 3.4 vs. 4.2 ± 1.4%), lung strain (0.39 ± 0.07 vs. 0.22 ± 0.06) and lung elastance (28.4 ± 5.8 vs. 15.3 ± 4.3 cmH2O/L), respectively; all p < 0.0001. The OLA strategy can be monitored using noninvasive variables during bariatric surgery. This strategy decreased lung strain, elastance and driving pressure compared with standard protective ventilatory settings.Clinical trial number NTC03694665.

Photoplethysmographic characterization of vascular tone mediated changes in arterial pressure: an observational study.

To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normotension (SAP 90-140 mmHg), hypertension (SAP > 140 mmHg) and hypotension (SAP < 90 mmHg) were analyzed in 15 cardiac surgery patients. SAP and two surrogates of the vascular tone, systemic vascular resistance (SVR) and vascular compliance (Cvasc = stroke volume/pulse pressure) were compared with PPGc. Changes in PPG amplitude (foot-to-peak distance) and dicrotic notch position were used to define 6 classes taking class III as a normal vascular tone with a notch placed between 20 and 50% of the PPG amplitude. Class I-to-II represented vasoconstriction with notch placed > 50% in a small PPG, while class IV-to-VI described vasodilation with a notch placed < 20% in a tall PPG wave. 190 datasets were analyzed including 61 episodes of hypertension [SAP = 159 (151-170) mmHg (median 1st-3rd quartiles)], 84 of normotension, SAP = 124 (113-131) mmHg and 45 of hypotension SAP = 85(80-87) mmHg. SAP were well correlated with SVR (r = 0.78, p < 0.0001) and Cvasc (r = 0.84, p < 0.0001). The PPG-based classification correlated well with SAP (r = - 0.90, p < 0.0001), SVR (r = - 0.72, p < 0.0001) and Cvasc (r = 0.82, p < 0.0001). The PPGc misclassified 7 out of the 190 episodes, presenting good accuracy (98.4% and 97.8%), sensitivity (100% and 94.9%) and specificity (97.9% and 99.2%) for detecting episodes of hypotension and hypertension, respectively. Changes in arterial pressure and vascular tone were closely related to the proposed classification based on PPG waveform.Clinical Trial Registration NTC02854852.

The Sensitivity and Specificity of Pulmonary Carbon Dioxide Elimination for Noninvasive Assessment of Fluid Responsiveness.

BACKGROUND: We sought to determine whether the response of pulmonary elimination of CO2 (VCO2) to a sudden increase in positive end-expiratory pressure (PEEP) could predict fluid responsiveness and serve as a noninvasive surrogate for cardiac index (CI). METHODS: Fifty-two patients undergoing cardiovascular surgery were included in this study. By using a constant-flow ventilation mode, we performed a PEEP challenge of 1-minute increase in PEEP from 5 to 10 cm H2O. At PEEP of 5 cm H2O, patients were preloaded with 500 mL IV saline solution after which a second PEEP challenge was performed. Patients in whom fluid administration increased CI by ≥15% from the individual baseline value were defined as volume responders. Beat-by-beat CI was derived from arterial pulse contour analysis, and breath-by-breath VCO2 data were collected during the protocol. The sensitivity and specificity of VCO2 for detecting the fluid responders according to CI was performed by the receiver operating characteristic curves. RESULTS: Twenty-one of 52 patients were identified as fluid responders (40%). The PEEP maneuver before fluid administration decreased CI from 2.65 ± 0.34 to 2.21 ± 0.32 L/min/m (P = 0.0011) and VCO2 from 150 ± 23 to 123 ± 23 mL/min (P = 0.0036) in responders, whereas the changes in CI and VCO2 were not significant in nonresponders. The PEEP challenge after fluid administration induced no significant changes in CI and VCO2, in neither responders nor nonresponders. PEEP-induced decreases in CI and VCO2 before fluid administration were well correlated (r = 0.75, P < 0.0001) but not thereafter. The area under the receiver operating characteristic curves for a PEEP-induced decrease in ΔCI and ΔVCO2 was 0.99, with a 95% confidence interval from 0.96 to 0.99 for ΔCI and from 0.97 to 0.99 for ΔVCO2. During the PEEP challenge, a decrease in VCO2 by 11% predicted fluid responsiveness with a sensitivity of 0.90 (95% confidence interval, 0.87-0.93) and a specificity of 0.95 (95% confidence interval, 0.92-0.98). CONCLUSIONS: PEEP-induced changes in VCO2 predicted fluid responsiveness with accuracy in patients undergoing cardiac surgery.

Noninvasive monitoring of lung recruitment maneuvers in morbidly obese patients: the role of pulse oximetry and volumetric capnography.

BACKGROUND: We conducted this study to determine whether pulse oximetry and volumetric capnography (VCap) can determine the opening and closing pressures of lungs of anesthetized morbidly obese patients. METHODS: Twenty morbidly obese patients undergoing laparoscopic bariatric surgery with capnoperitoneum were studied. A lung recruitment maneuver was performed in pressure control ventilation as follows: (1) During an ascending limb, the lungs' opening pressure was detected. After increasing positive end-expiratory pressure (PEEP) from 8 to 16 cm H2O, fraction of inspired oxygen (FIO2) was decreased until pulse oximetric arterial saturation (SpO2) was <92%. Thereafter, end-inspiratory pressure was increased in steps of 2 cm H2O, from 36 to a maximum of 50 cm H2O. The opening pressure was attained when SpO2 exceeded 97%. (2) During a subsequent decreasing limb, the lungs' closing pressure was identified. PEEP was decreased from 22 to 10 cm H2O in steps of 2 cm H2O. The closing pressure was determined as the PEEP value at which respiratory compliance decreased from its maximum value. We continuously recorded lung mechanics, SpO2, and VCap. RESULTS: The lungs' opening pressures were detected at 44 (4) cm H2O (median and interquartile range) and the closing pressure at 14 (2) cm H2O. Therefore, the level of PEEP that kept the lungs without collapse was found to be 16 (3) cm H2O. Using respiratory compliance as a reference, receiver operating characteristic analysis showed that SpO2 (area under the curve [AUC] 0.80 [SE 0.07], sensitivity 0.65, and specificity 0.94), the elimination of CO2 per breath (AUC 0.91 [SE 0.05], sensitivity 0.85, and specificity 0.98), and Bohr's dead space (AUC 0.83 [SE 0.06], sensitivity 0.70, and specificity 0.95] were relatively accurate for detecting lung collapse during the decreasing limb of a recruitment maneuver. CONCLUSIONS: Lung recruitment in morbidly obese patients could be effectively monitored by combining noninvasive pulse oximetry and VCap. SpO2, the elimination of CO2, and Bohr's dead space detected the individual's opening and closing pressures.

Reference values for volumetric capnography-derived non-invasive parameters in healthy individuals.

The aim of this study was to determine typical values for non-invasive volumetric capnography (VCap) parameters for healthy volunteers and anesthetized individuals. VCap was obtained by a capnograph connected to the airway opening. We prospectively studied 33 healthy volunteers 32 ± 6 years of age weighing 70 ± 13 kg at a height of 171 ± 11 cm in the supine position. Data from these volunteers were compared with a cohort of similar healthy anesthetized patients ventilated with the following settings: tidal volume (VT) of 6-8 mL/kg, respiratory rate 10-15 bpm, PEEP of 5-6 cmH2O and FiO2 of 0.5. Volunteers showed better clearance of CO2 compared to anesthetized patients as indicated by (median and interquartile range): (1) an increased elimination of CO2 per mL of VT of 0.028 (0.005) in volunteers versus 0.023 (0.003) in anesthetized patients, p < 0.05; (2) a lower normalized slope of phase III of 0.26 (0.17) in volunteers versus 0.39 (0.38) in anesthetized patients, p < 0.05; and (3) a lower Bohr dead space ratio of 0.23 (0.05) in volunteers versus 0.28 (0.05) in anesthetized patients, p < 0.05. This study presents reference values for non-invasive volumetric capnography-derived parameters in healthy individuals. Mechanical ventilation and anesthesia altered these values significantly.

The Diastolic Oscillation Amplitude Used as an Arterial Aging Indicator.

Introduction: The compliance of the distal arteries depends on their vasoconstrictor tone and distensibility and is sensitive to endothelial function and aging. C2, a component of the Windkessel model, is a measure of distal arterial compliance, and establishes the magnitude of the pressure rise during early diastole. It is calculated from the diastolic portion of the radial pulse wave using sophisticated analyses. C2 is used as a cardiovascular risk indicator since it decreases with aging, high blood pressure, and diabetes. Here, we propose an alternative method to assess the distal arteries distensibility by measuring the amplitude of the oscillation that occurs at the beginning of diastole. Methods: Peripheral pulse wave was evaluated noninvasively by applanation tonometry in 511 individuals (264 women) aged between 13 and 70 years. Diastolic amplitude (DA) was measured as the peak-to-peak amplitude of the diastolic oscillation. Radial augmentation index (RAIx) and pulse wave velocity (PWV) were also calculated. Results: DA decreased approximately 2% per decade of life between 16 and 70 years from 19% to 7%, and was higher in men than in women (p<0.0001). Linear regression analysis identified RAIx as the strongest predictor of AD (p<0.0001), followed by age and height. Sex modified the age-related decrease in DA (p< 0.001). By applying the method to measure DA from previously published data, we found a strong linear correlation with C2. Conclusion: DA decreased linearly with age in a reciprocal manner to the increase in radial augmentation index, was greater in men than women, and was independent of blood pressure and heart rate, as previously reported for C2. We propose that measuring DA could provide an alternative index to evaluate distal arterial compliance and aging.

[Velocity estimation of aortic propagation based on radial pulse wave analysis]. / Estimación de la velocidad de propagación aórtica basada en el análisis de la onda de pulso radial.

We analyzed the possibility of using the radial pulse wave morphology, obtained by a movement transducer, to evaluate the aortic pulse wave velocity. The radial pulse wave signals were obtained by using a transducer, located on the pulse palpation area, in 167 healthy normotensive male volunteers, ages 20 to 70. The reflected wave was identified in every case. Also, a speed coefficient was defined as the ratio between the individual's height and the time between the maximum systolic wave and the arrival time of the reflected wave. We found that the specified coefficient in normotensive individuals increased linearly with age, in a similar way to the increase in aortic propagation velocity measured by other methods. The procedure was repeated on another set of 125 individuals with hypertension, without other risk factors, aged between the 3rd and 7th decade. This time we found similar values to normotensive individuals only on the 3th decade, and a pronounced increase on the velocity coefficient at advanced ages was observed. These findings support the feasibility of using this type of signals to indirectly evaluate the propagation velocity together with the increase index, a parameter commonly used in pulse wave analysis.

Lung recruitment and positive end-expiratory pressure have different effects on CO2 elimination in healthy and sick lungs.

BACKGROUND: We studied the effects that the lung recruitment maneuver (RM) and positive end-expiratory pressure (PEEP) have on the elimination of CO(2) per breath (Vtco(2,br)). METHODS: In 7 healthy and 7 lung-lavaged pigs at constant ventilation, PEEP was increased from 0 to 18 cm H(2)O and then decreased to 0 in steps of 6 cm H(2)O every 10 minutes. Cycling RMs with plateau pressure/PEEP of 40/20 (healthy) and 50/25 (lavaged) cm H(2)O were applied for 2 minutes between 18-PEEP steps. Volumetric capnography, respiratory mechanics, blood gas, and hemodynamic data were recorded. RESULTS: In healthy lungs before the RM, Vtco(2,br) was inversely proportional to PEEP decreasing from 4.0 (3.6-4.4) mL (median and interquartile range) at 0-PEEP to 3.1 (2.8-3.4) mL at 18-PEEP (P < 0.05). After the RM, Vtco(2,br) increased from 3.3 (3-3.6) mL at 18-PEEP to 4.0 (3.5-4.5) mL at 0-PEEP (P < 0.05). In lavaged lungs before the RM, Vtco(2,br) increased initially from 2.0 (1.7-2.3) mL at 0-PEEP to 2.6 (2.2-3) mL at 12-PEEP (P < 0.05) but then decreased to 2.4 (2-2.8) mL when PEEP was increased further to 18 cm H(2)O (P < 0.05). After the RM, the highest Vtco(2,br) of 2.9 (2.1-3.7) mL was observed at 12-PEEP and then decreased to 2.5 (1.9-3.1) mL at 0-PEEP (P < 0.05). Vtco(2,br) was directly related to changes in lung perfusion, the area of gas exchange, and alveolar ventilation but inversely related to changes in dead space. CONCLUSIONS: CO(2) elimination by the lungs was dependent on PEEP and recruitment and showed major differences between healthy and lavaged lungs.

Model fitting of volumetric capnograms improves calculations of airway dead space and slope of phase III.

BACKGROUND: This study assessed the performance of a Functional Approximation based on a Levenberg-Marquardt Algorithm (FA-LMA) to calculate airway dead space (VD(aw)) and the slope of phase III (S(III)) from capnograms. METHODS: We performed mathematical simulations to test the effect of noises on the calculation of VD(aw) and S(III). Data from ten mechanically ventilated patients at 0, 5 and 10 cmH(2)O of PEEP were also studied. FA-LMA was compared with the traditional Fowler's method (FM). RESULTS: Simulations showed that: (1) The FM determined VD(aw) with accuracy only if the capnogram approximated a symmetrical curve (S(III) = 0). When capnograms became asymmetrical (S(III) > 0), the FM underestimated VD(aw) (-3.1% to -0.9%). (2) When adding noises on 800 capnograms, VD(aw) was underestimated whenever the FM was used thereby creating a bias between -5.54 and -1.28 ml at standard deviations (SD) of 0.1-1.8 ml (P < 0.0001). FA-LMA calculations of VD(aw) were close to the simulated values with the bias ranging from -0.21 to 0.16 ml at SD from 0.1 to 0.4 ml. The FM overestimated S(III) and showed more bias (0.0041-0.0078 mmHg/ml, P < 0.0001) than the FA-LMA (0.0002-0.0030 mmHg/ml). When calculating VD(aw) from patients, variability was less with the FA-LMA leading to mean variation coefficients of 0.0102, 0.0111 and 0.0123 compared to the FM (0.0243, 0.0247 and 0.0262, P < 0.001) for 0, 5 and 10 cmH(2)O of PEEP, respectively. The FA-LMA also showed less variability in S(III) with mean variation coefficients of 0.0739, 0.0662 and 0.0730 compared to the FM (0.1379, 0.1208 and 0.1246, P < 0.001) for 0, 5 and 10 cmH(2)O of PEEP, respectively. CONCLUSIONS: The Functional Approximation based on a Levenberg-Marquardt Algorithm showed less bias and dispersion compared to the traditional Fowler's method when calculating VD(aw) and S(III).

Monitoring dead space during recruitment and PEEP titration in an experimental model.

OBJECTIVE: To test the usefulness of dead space for determining open-lung PEEP, the lowest PEEP that prevents lung collapse after a lung recruitment maneuver. DESIGN: Prospective animal study. SETTING: Department of Clinical Physiology, University of Uppsala, Sweden. SUBJECTS: Eight lung-lavaged pigs. INTERVENTIONS: Animals were ventilated using constant flow mode with VT of 6ml/kg, respiratory rate of 30bpm, inspiratory-to-expiratory ratio of 1:2, and FiO(2) of 1. Baseline measurements were performed at 6cmH(2)O of PEEP. PEEP was increased in steps of 6cmH(2)O from 6 to 24cmH(2)O. Recruitment maneuver was achieved within 2min at pressure levels of 60/30cmH(2)O for Peak/PEEP. PEEP was decreased from 24 to 6cmH(2)O in steps of 2cmH(2)O and then to 0cmH(2)O. Each PEEP step was maintained for 10min. MEASUREMENTS AND RESULTS: Alveolar dead space (VD(alv)), the ratio of alveolar dead space to alveolar tidal volume (VD(alv)/VT(alv)), and the arterial to end-tidal PCO(2) difference (Pa-ET: CO(2)) showed a good correlation with PaO(2), normally aerated areas, and non-aerated CT areas in all animals (minimum-maximum r(2)=0.83-0.99; p<0.01). Lung collapse (non-aerated tissue>5%) started at 12[Symbol: see text]cmH(2)O PEEP; hence, open-lung PEEP was established at 14cmH(2)O. The receiver operating characteristics curve demonstrated a high specificity and sensitivity of VD(alv) (0.89 and 0.90), VD(alv)/VT(alv) (0.82 and 1.00), and Pa-ET: CO(2) (0.93 and 0.95) for detecting lung collapse. CONCLUSIONS: Monitoring of dead space was useful for detecting lung collapse and for establishing open-lung PEEP after a recruitment maneuver.

[Evaluation of hypertensive patients by radial arterial diameter variation recording]. / Evaluacion de hipertensos en base a registros de variacion de diametro arterial radial.

A blood less analysis technique of the diameter variation signal at radial artery was used to evaluate the arterial disease and the cardiovascular risk in hypertensive patients. A movement transducer was used to record the wrist pulse. A radial augmentation index was proposed to quantify the magnitude of the pressure wave reflections in the aortic region. The experiment was carried out with a group of 47 hypertensive men and compared with a similar study performed on 81 normotensive healthy men. The last ones presented smaller values of this index, but as age progresses, values of both groups come closer among them. This was confirmed by morphological comparison of both groups. Similar behavior was found in signals coming from healthy normotensive and hypertensive old men with similar age. Furthermore, some of the hypertensive youth presented similar morphological characteristics to normotensive of the same age. That indicates they still conserved the elastic behavior characteristic of its age group. These results, using available technology of smaller cost, were well-matched to those achieved by pressure signals at radial artery obtained by means of applanation tonometry.

[Alterations in arterial compliance of dyslipidemic patients]. / Alteraciones en la distensibilidad arterial de pacientes dislipidémicos.

INTRODUCTION: We studied the alteration on the distensibility of the arterial walls caused by dyslipidemia LDLc dependent, along the decades of life, by means of a study of the radial artery pulse wave. METHODS: We made an analysis of the radial artery pulse wave records acquired by means a movement displacement sensor, placed on radial palpation area. We recruited 100 dyslipidemic men without other cardiovascular risk factors, between the 3rd and the 6th decade. We identified the reflected wave in the records and we computed the augmentation index in order to quantify its amplitude and position. This index is useful to assess the endothelial dysfunction. Besides, we defined a velocity coefficient as the ratio between the size of the individuals and the delay time between the peak of the systolic wave and the arrival of the reflected wave. Results were compared against those obtained in a group of 161 healthy volunteers. RESULTS: We found that dyslipidemic patients presented augmentation index values similar to controls until the fourth decade, increasing thereafter with significant differences only in the 6th decade. No significant differences were found in the velocity index in any of the ages studied. CONCLUSIONS: We conclude that alterations produced by dyslipidemia take decades to manifest, and they begin affecting the mechanism of vasodilation of distal arteries with highest proportion of smooth muscle, without altering the proximal conduit arteries with more elastin content.

Estudio de detección del riesgo en diabetes en Atención Primaria según cuestionario FINDRISC en el Municipio de Gral. Pueyrredón (Estudio DR. DIAP) / Diabetes risk detection study in Primary Care according to FINDRISC questionnaire in the Municipality of Gral. Pueyrredón (DR. DIAP STUDY)

Objetivos: conocer la magnitud del riesgo de padecer diabetes mellitus 2 (DM2) en la población del Municipio de Gral. Pueyrredón que concurre a los Centros Asistenciales de Atención Primaria. Materiales y métodos: estudio observacional para determinar el riesgo de padecer DM2 mediante una entrevista donde se indagaron sobre las ocho preguntas del cuestionario FINDRISC. Resultados: la muestra del estudio estuvo constituida por 2.784 pacientes, el 54% conformada por mujeres. La edad fue agrupada en menos de 45 años el 47,5% (1.323), de 45 a 54 años el 20,9% (582), de 55 a 64 años el 18,3% (510) y más de 64 años el 13,2% (368). El 20% de la población presentó una puntuación de la escala de riesgo del cuestionario FINDRISC igual o mayor a 15, alto riesgo a muy alto riesgo de padecer diabetes en los próximos 10 años. El 43,38% presentó un IMC>30 y el 25,97% declaró recibir medicación para la hipertensión arterial. El 55,37% refería actividad física baja, el 50,79% no ingería verduras y frutas en forma diaria y el 17,98% declaró cifras de glucemias elevadas. Las variables que con mayor frecuencia se asociaron a una escala de riesgo >15 fueron: sedentarismo (80,9%), cintura >102/88 (65,7/77,2%), antecedente de hiperglucemia (64,0%), alimentación no saludable (61,9%) e IMC>30 (61,8%). El riesgo >15 según IMC fue: IMC 30 el 45,4%. Conclusiones: el 20% de la población encuestada está en alto riesgo de padecer diabetes. Una de cada dos o tres personas sin diabetes que asisten a un centro de Atención Primaria tiene un FINDRISC >15. Esta escala de riesgo es una herramienta simple, económica, de rápida confección, no invasiva y segura para detectar individuos con alto riesgo de padecer diabetes tipo 2. También puede usarse para identificar DM2 no detectada y factores de riesgo de enfermedad cardiovascular

Estimación de la velocidad de propagación aórtica basada en el análisis de la onda de pulso radial / Velocity estimation of aortic propagation based on radial pulse wave analysis

Se exploró la posibilidad de utilizar la morfología del registro de onda de pulso radial obtenida mediante un transductor de movimiento para evaluar la velocidad de propagación aórtica. Se efectuó el registro de onda de pulso en arteria radial mediante un transductor apoyado sobre la zona de palpación del pulso, sobre un conjunto de 167 voluntarios varones sanos normotensos de edades comprendidas entre la 2ª y la 7ª década. Se identificó en los registros la onda reflejada y se definió un coeficiente de velocidad como el cociente entre la talla del individuo y el tiempo transcurrido entre el máximo de la onda sistólica y el instante de llegada de dicha onda. Se halló que en los normotensos el coeficiente mencionado aumentó en forma lineal con la edad, en una proporción similar al aumento de velocidad de propagación aórtica medido con otros métodos. Se repitió el procedimiento en otro conjunto de 125 varones hipertensos sin otros factores de riesgo, de edades entre la 3ª y la 7ª década, hallándose valores similares a los normotensos solamente en la 3ª década, a partir de la cual se registró un incremento significativo de dicho índice. Tales hallazgos sustentan la factibilidad de utilizar tal tipo de registros para evaluar indirectamente la velocidad de propagación junto con el índice de aumentación, un parámetro habitualmente utilizado en el análisis de onda de pulso.

We analyzed the possibility of using the radial pulse wave morphology, obtained by a movement transducer, to evaluate the aortic pulse wave velocity. The radial pulse wave signals were obtained by using a transducer, located on the pulse palpation area, in 167 healthy normotensive male volunteers, ages 20 to 70. The reflected wave was identified in every case. Also, a speed coefficient was defined as the ratio between the individual's height and the time between the maximum systolic wave and the arrival time of the reflected wave. We found that the specified coefficient in normotensive individuals increased linearly with age, in a similar way to the increase in aortic propagation velocity measured by other methods. The procedure was repeated on another set of 125 individuals with hypertension, without other risk factors, aged between the 3rd and 7th decade. This time we found similar values to normotensive individuals only on the 3th decade, and a pronounced increase on the velocity coefficient at advanced ages was observed. These findings support the feasibility of using this type of signals to indirectly evaluate the propagation velocity together with the increase index, a parameter commonly used in pulse wave analysis.

Alteraciones en la distensibilidad arterial de pacientes dislipidémicos / Alterations in arterial compliance of dyslipidemic patients

Introducción: Se estudió la alteración en la distensibilidad de las paredes arteriales producidas por la dislipidemia dependiente de c-LDL a lo largo de las distintas décadas de la vida, utilizando el análisis de onda de pulso radial. Métodos: Se efectuó el registro de onda de pulso en la arteria radial mediante un transductor de movimiento apoyado sobre la zona de palpación, sobre un conjunto de 100 varones dislipidémicos sin otros factores de riesgo, de edades comprendidas entre la 3.a y la 6.a décadas de la vida. Se calculó en cada caso el índice de aumentación. También se identificó en los registros la onda reflejada y se definió un coeficiente de velocidad como el cociente entre la talla del individuo y el tiempo transcurrido entre el máximo de la onda sistólica y el instante de llegada de dicha onda. Los resultados se compararon con los de un conjunto de 161 voluntarios sanos. Resultados: Se halló que los dislipidémicos presentaron valores del índice de aumentación similares a los controles hasta la 4.a década, aumentando a partir de entonces, con diferencias significativas a partir de la 6.a década. No se hallaron diferencias significativas en el índice de velocidad en ninguna de las edades estudiadas. Conclusiones: Se concluye que las alteraciones producidas por la dislipidemia requieren décadas para manifestarse, y comienzan afectando al mecanismo de vasodilatación de las arterias distales con mayor proporción de músculo liso, sin alterar las arterias de conducción proximales con mayor contenido de elastina

Introduction: We studied the alteration on the distensibility of the arterial walls caused by dyslipidemia LDLc dependent, along the decades of life, by means of a study of the radial artery pulse wave. Methods: We made an analysis of the radial artery pulse wave records acquired by means a movement displacement sensor, placed on radial palpation area. We recruited 100 dyslipidemic men without other cardiovascular risk factors, between the 3rd and the 6th decade. We identified the reflected wave in the records and we computed the augmentation index in order to quantify its amplitude and position. This index is useful to assess the endothelial dysfunction. Besides, we defined a velocity coefficient as the ratio between the size of the individuals and the delay time between the peak of the systolic wave and the arrival of the reflected wave. Results were compared against those obtained in a group of 161 healthy volunteers. Results: We found that dyslipidemic patients presented augmentation index values similar to controls until the fourth decade, increasing thereafter with significant differences only in the 6th decade. No significant differences were found in the velocity index in any of the ages studied. Conclusions: We conclude that alterations produced by dyslipidemia take decades to manifest, and they begin affecting the mechanism of vasodilation of distal arteries with highest proportion of smooth muscle, without altering the proximal conduit arteries with more elastin content

Índice para la evaluación de las reflexiones mediante análisis de la onda de pulso radial / Index of Pressure Wave Reflection Assessed from Radial Pulse Wave Analysis

En el presente trabajo se analiza la posibilidad de utilizar un parámetro obtenido del registro de la onda de pulso radial, el ancho de la onda sistólica, que es más sencillo de medir aún que el índice de aumentación radial y que complementaría a este último en la evaluación de la amplitud de la reflexión sistólica, directamente relacionada con el grado de disfunción endotelial y el fenómeno de aumentación aórtica. Se efectuó un estudio poblacional sobre 120 varones normotensos sanos con edades entre 17 y 65 años. Se obtuvo en ellos el registro de la onda de pulso radial en base al registro del movimiento de las paredes de la arteria mediante un sensor capacitivo aplicado sobre la zona de palpación del pulso. Cada registro se procesó y normalizó en amplitud y se calculó el índice de aumentación radial y el ancho de la onda sistólica al 50% de su altura máxima. Se halló que individuos con el mismo índice de aumentación poseían distintos valores de ancho de onda sistólica, lo cual evidencia distintos valores de amplitud de la onda reflejada. Ambos parámetros aumentaron con la edad y su correlación r resultó de 0,9. Se propone la utilización del ancho de la onda sistólica como un índice de envejecimiento alternativo, que permitiría evaluar el sistema arterial cuando la medición del índice de aumentación resultara dificultosa o la comparación entre individuos fuera ambigua.

Systolic wave width, a parameter obtained from the record of radial pulse wave, is easier to measure than the augmentation index. The aim of this study was to analyze the possibility of using systolic wave width as a complementary tool for the assessment of systolic wave reflection which is directly related to the degree of endothelial dysfunction and to aortic augmentation. We performed a population study on 120 healthy men between 17 and 65 years old with normal blood pressure. Records of the radial wave pulse were obtained, based on the movement of the arterial walls, by a capacitive sensor in contact with the surface of the wrist over the radial artery. Each record was processed and its amplitude was normalized; the augmentation index and systolic wave width at half its maximum height were calculated. We found that systolic wave width was different among subjects with the same augmentation index, showing different values of the amplitude of the reflected wave. Both parameters increased with age (r correlation value 0.9). The systolic wave width is an alternative index of ageing. It might assess the arterial system when it is difficult to measure augmentation index or when comparisons between individuals result ambiguous.

Evaluación de hipertensos en base a registros de variación de diámetro arterial radial / Evaluation of hypertensive patients by radial arterial diameter variation recording

Se utilizó la técnica de análisis del registro incruento de las variaciones de diámetro de arteria radial para evaluar el deterioro arterial y el riesgo cardiovascular en pacientes hipertensos. El transductor utilizado consistió en un sensor de movimiento apoyado sobre la zona de palpación del pulso radial. Se efectuó la determinación del índice de aumentación radial, un parámetro que cuantifica la magnitud de las reflexiones de la onda de presión en la región aórtica, sobre un conjunto de 47 hipertensos, y se lo comparó con otro estudio similar efectuado sobre 81 normotensos sanos. Estos últimos presentaron menores valores de dicho índice, pero al avanzar la edad los valores de ambos grupos tendieron a coincidir. Esto fue confirmado al comparar morfológicamente los registros de ambos grupos, hallándose que los registros de ancianos normotensos sanos e hipertensos de edades similares resultaron visiblemente parecidos. Se halló también que determinados hipertensos jóvenes presentaron ciertas características morfológicas similares a las de normotensos de la misma edad, indicando que aún conservaban las características elásticas propias de su grupo etario. Los resultados fueron similares a los logrados sobre registros de presión arterial radial obtenidos mediante tonometría de aplanación, utilizándose una tecnología disponible en nuestro medio y de menor costo

A blood less analysis technique of the diameter variation signal at radial artery was used to evaluate the arterial disease and the cardiovascular risk in hypertensive patients. A movement transducer was used to record the wrist pulse. A radial augmentation index was proposed to quantify the magnitude of the pressure wave reflections in the aortic region. The experiment was carried out with a group of 47 hypertensive men and compared with a similar study performed on 81 normotensive healthy men. The last ones presented smaller values of this index, but as age progresses, values of both groups come closer among them. This was confirmed by morphological comparison of both groups. Similar behavior was found in signals coming from healthy normotensive and hypertensive old men with similar age. Furthermore, some of the hypertensive youth presented similar morphological characteristics to normotensive of the same age. That indicates they still conserved the elastic behavior characteristic of its age group. These results, using available technology of smaller cost, were well-matched to those achieved by pressure signals at radial artery obtained by means of applanation tonometry

Relación entre el envejecimiento y la morfología de los registros de variación de diámetro arterial: clasificación con redes neuronales artificiales / Relation between aging and the morphology of radial artery diameter variation registers: classification using artificial neural networks

El objetivo de este trabajo fue el estudio de la modificación de las ondas de variación de diámetro de la arteria radial (VDA) con el envejecimiento. Su registro se obtuvo con un sistema de adquisición que utiliza un transductor capacitivo apoyado sobre la piel a nivel de la arteria radial. Para evaluar la relación entre la pérdida de distensibilidad con el envejecimiento y las modificaciones de la VDA, el experimento se llevó a cabo en un grupo de 64 varones normotensos: 20 jóvenes, 24 adultos y 20 ancianos. Se extrajeron parámetros descriptivos morfológicos y se evaluó su poder para clasificar los registros de VDA según la edad con una red neuronal artificial de Kohonen. El proceso de análisis reveló la existencia de tres ondas constitutivas: dos ondas sistólicas, primera y segunda, y una diastólica. El envejecimiento produjo cambios importantes en la morfología de la señal, como el ensanchamiento de la primera onda sistólica, la disminución de amplitud de la onda diastólica y el ascenso de la segunda onda sistólica acercándose y solapándose con el vértice de la primera onda sistólica. La red neuronal artificial clasificó los 64 registros correctamente, localizándolos en el grupo de edades correspondiente. Considerando el carácter normotenso de los integrantes de la muestra se reveló la existencia de un modelo de envejecimiento arterial en pacientes sanos. Este sistema podría poner en evidencia precozmente la existencia de patologías arteriales que involucren incremento de la rigidez arterial con pérdida de distensibilidad (esclerosis, hipertensión).