The Impact of Recirculation on Extracorporeal Gas Exchange and Patient Oxygenation during Veno-Venous Extracorporeal Membrane Oxygenation-Results of an Observational Clinical Trial.

Background: Recirculation during veno-venous extracorporeal membrane oxygenation reduces extracorporeal oxygen exchange and patient oxygenation. To minimize recirculation and maximize oxygen delivery (DO2) the interaction of cannulation, ECMO flow and cardiac output requires careful consideration. We investigated this interaction in an observational trial. Methods: In 19 patients with acute respiratory distress syndrome and ECMO, we measured recirculation with the ultrasound dilution technique and calculated extracorporeal oxygen transfer (VO2), extracorporeal oxygen delivery (DO2) and patient oxygenation. To assess the impact of cardiac output (CO), we included CO measurement through pulse contour analysis. Results: In all patients, there was a median recirculation rate of approximately 14−16%, with a maximum rate of 58%. Recirculation rates >35% occurred in 13−14% of all cases. In contrast to decreasing extracorporeal gas exchange with increasing ECMO flow and recirculation, patient oxygenation increased with greater ECMO flows. High CO diminished recirculation by between 5−20%. Conclusions: Extracorporeal gas exchange masks the importance of DO2 and its effects on patients. We assume that increasing DO2 is more important than reduced VO2. A negative correlation of recirculation to CO adds to the complexity of this phenomenon. Patient oxygenation may be optimized with the direct measurement of recirculation.

Characterization of Flow Efficiency, Pulsatility, and Respiratory Variability in Different Types of Fontan Circuits Using Quantitative Parameters.

PURPOSE: Details on the hemodynamic differences among Fontan operations remain unclear according to respiratory and cardiac cycles. This study was undertaken to investigate hemodynamic characteristics in different types of Fontan circulation by quantification of blood flow with the combined influence of cardiac and respiratory cycles. MATERIALS AND METHODS: Thirty-five patients [10 atriopulmonary connections (APC), 13 lateral tunnels (LT), and 12 extracardiac conduits (ECC)] were evaluated, and parameters were measured in the superior vena cava, inferior vena cava (IVC), hepatic vein (HV), baffles, conduits, and left and right pulmonary artery. Pulsatility index (PIx), respiratory variability index (RVI), net antegrade flow integral (NAFI), and inspiratory/expiratory blood flow (IQ/EQ) were measured by intravascular Doppler echocardiography. RESULTS: The PIx between APC and total cavopulmonary connection (TCPC; LT and ECC) showed significant differences at all interrogation points regardless of respiratory cycles. The PIxs of HVs and IVCs in APC significantly increased, compared with that in LT and ECC, and the RVI between APC and TCPC showed significant differences at all interrogation points (p<0.05). The NAFI and IQ/EQ between APC and TCPC showed significant differences at some interrogation points (p<0.05). CONCLUSION: Patients with different types of Fontan circulation show different hemodynamic characteristics in various areas of the Fontan tract, which may lead to different risks causing long-term complications. We believe the novel parameters developed in this study may be used to determine flow characteristics and may serve as a clinical basis of management in patients after Fontan operations.

Characterization of Flow Efficiency, Pulsatility, and Respiratory Variability in Different Types of Fontan Circuits Using Quantitative Parameters

PURPOSE: Details on the hemodynamic differences among Fontan operations remain unclear according to respiratory and cardiac cycles. This study was undertaken to investigate hemodynamic characteristics in different types of Fontan circulation by quantification of blood flow with the combined influence of cardiac and respiratory cycles. MATERIALS AND METHODS: Thirty-five patients [10 atriopulmonary connections (APC), 13 lateral tunnels (LT), and 12 extracardiac conduits (ECC)] were evaluated, and parameters were measured in the superior vena cava, inferior vena cava (IVC), hepatic vein (HV), baffles, conduits, and left and right pulmonary artery. Pulsatility index (PIx), respiratory variability index (RVI), net antegrade flow integral (NAFI), and inspiratory/expiratory blood flow (IQ/EQ) were measured by intravascular Doppler echocardiography. RESULTS: The PIx between APC and total cavopulmonary connection (TCPC; LT and ECC) showed significant differences at all interrogation points regardless of respiratory cycles. The PIxs of HVs and IVCs in APC significantly increased, compared with that in LT and ECC, and the RVI between APC and TCPC showed significant differences at all interrogation points (p < 0.05). The NAFI and IQ/EQ between APC and TCPC showed significant differences at some interrogation points (p < 0.05). CONCLUSION: Patients with different types of Fontan circulation show different hemodynamic characteristics in various areas of the Fontan tract, which may lead to different risks causing long-term complications. We believe the novel parameters developed in this study may be used to determine flow characteristics and may serve as a clinical basis of management in patients after Fontan operations.

Autonomic function testing: Compliance and consequences.

BACKGROUND: The deep breathing test (DB) and Valsalva maneuver (VM) are used to detect autonomic dysfunction. The VM induces sympathetically mediated changes in blood pressure (phase II late, phase IV, and recovery time) and both tests induce vagally mediated heart rate changes. There is limited information on effects of key variables, compliance with testing and the effects of non-compliance This study has twin goals of evaluating compliance with standard instructions and the effects of changes in key variables. We also evaluated the effect of position on the VM. MATERIAL AND METHODS: Forty healthy males performed DB at air exchange volumes of 50, 80, and 100% of vital lung capacity (VLC). The VM was performed at 40 and 30mmHg expiratory pressure for 15 and 10s in sitting and supine position, respectively. RESULTS: Participants performed DB at lower volumes than intended and were not able to maintain 100% VLC for the duration of the test. The DB heart rate response decreased 6.3beats/min per liter below VLC. During the VM, subjects blew at lower pressures than instructed. The VM responses were significantly larger with longer expiration durations, higher expiratory pressures and when performed sitting. Performing the VM at 40mmHg for 10s in supine position increased the odds ratio of experiencing flat-top responses. CONCLUSION: The ability of subjects to strictly comply with methodological guidelines significantly improves results. Recording of both test parameters and ensuing results is suggested.

Hemocompatibility-Related Outcomes in the MOMENTUM 3 Trial at 6 Months: A Randomized Controlled Study of a Fully Magnetically Levitated Pump in Advanced Heart Failure.

BACKGROUND: The HeartMate 3 (HM3) Left Ventricular Assist System (LVAS) (Abbott) is a centrifugal, fully magnetically levitated, continuous-flow blood pump engineered to enhance hemocompatibility and reduce shear stress on blood components. The MOMENTUM 3 trial (Multicenter Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate 3) compares the HM3 LVAS with the HeartMate II (HMII) LVAS (Abbott) in advanced heart failure refractory to medical management, irrespective of therapeutic intention (bridge to transplant versus destination therapy). This investigation reported its primary outcome in the short-term cohort (n=294; 6-month follow-up), demonstrating superiority of the HM3 for the trial primary end point (survival free of a disabling stroke or reoperation to replace the pump for malfunction), driven by a reduced need for reoperations. The aim of this analysis was to evaluate the aggregate of hemocompatibility-related clinical adverse events (HRAEs) between the 2 LVAS. METHODS: We conducted a secondary end point evaluation of HRAE (survival free of any nonsurgical bleeding, thromboembolic event, pump thrombosis, or neurological event) in the short-term cohort (as-treated cohort n=289) at 6 months. The net burden of HRAE was also assessed by using a previously described hemocompatibility score, which uses 4 escalating tiers of hierarchal severity to derive a total score for events encountered during the entire follow-up experience for each patient. RESULTS: In 289 patients in the as-treated group (151 the HM3 and 138 the HMII), survival free of any HRAE was achieved in 69% of the HM3 group and in 55% of the HMII group (hazard ratio, 0.62; confidence interval, 0.42-0.91; P=0.012). Using the hemocompatibility score, the HM3 group demonstrated less pump thrombosis requiring reoperation (0 versus 36 points, P<0.001) or medically managed pump thrombosis (0 versus 5 points, P=0.02), and fewer nondisabling strokes (6 versus 24 points, P=0.026) than the control HMII LVAS. The net hemocompatibility score in the HM3 in comparison with the HMII patients was 101 (0.67±1.50 points/patient) versus 137 (0.99±1.79 points/patient) (odds ratio, 0.64; confidence interval, 0.39-1.03; P=0.065). CONCLUSIONS: In this secondary analysis of the MOMENTUM 3 trial, the HM3 LVAS demonstrated greater freedom from HRAEs in comparison with the HMII LVAS at 6 months. CLINICAL TRIAL REGISTRATION: URL: http://clinicaltrials.gov. Unique identifier: NCT02224755.

Comparação dos Efeitos Hemodinâmicos e Respiratórios no Uso dos Sistemas de Aspiração Traqueal Aberto e Fechado / Comparison of Hemodynamic and Respiratory Effects in the Use of Open and Closed Tracheal Suctioning Systems

Objetivo do estudo foi comparar o sistema fechado de aspiração (SFA) com o sistema aberto de aspiração (SAA) e, para cada sistema, comparar variáveis hemodinâmicas e respiratórias para cada um dos momentos. Incluídos pacientes adultos, em ventilação mecânica em pós-operatório eletivo. Variáveis registradas pré-coleta, 15 e 30 minutos após a adaptação do SFA, imediatamente, após a oxigenação pós-aspiração com SFA, nos minutos 6, 16, 31 e 61 após aspiração com o SFA. O mesmo processo foi repetido para o SAA. Foram incluídos quarenta pacientes. Quando comparado o momento imediato a pós-oxigenação com o momento 6 minutos após a aspiração foi encontrado aumento da frequência cardíaca (FC) (p = 0,04), diminuição (p= 0,034) com o momento 31 minutos e diminuição (p= 0,032) com o momento 61 minutos. Observou-se que a FC teve diminuição significativa, em todos os momentos analisados após a aspiração, comparando com o momento imediato pós-oxigenação, no SAA. Também foi evidenciado aumento (p=0,03) no valor de volume corrente (VT), quando comparado o momento 31 minutos do SFA com o SAA. Conclusão: Apesar de apresentar alterações significativas, em algumas variáveis, quando comparados os sistemas, as modificações se mantiveram dentro da normalidade e retornaram ao valor basal em uma hora após a aspiração. (AU)

The goal was to compare the closed suction system - CSS to the open suction system - OSS and, for each system, compare hemodynamic and respiratory parameters in different moments. The group was comprised of mechanically ventilated adult patients in pos operatory period. Variables were recorded before CSS adaptation, 15 and 30 minutes after CSS adaptation , immediately after post-oxygenation aspiration with CSS, 6, 16, 31 and 61 minutes after aspiration with CSS. The same process was repeated for the OSS. Forty patients were included. When compared the post-oxygenation increased heart rate was found (p=0,04) to the 6 minutes after CSS, decreased heart rate after 31 minutes (p=0.034) and 61 minutes (p=0,032) after CSS. It was observed that the HR was significantly reduced at all times examined after aspiration, compared to the time immediately post-oxygenation for the OSS. It was also demonstrated an increase (p = 0.03) in the amount of tidal volume (TV), when CSS was compared to the OSS 31 minutes after suction. Despite showing significant changes in some variables, it remained within the normal range and returned to baseline one hour after suction. (AU)

Increasing positive end-expiratory pressure (re-)improves intraoperative respiratory mechanics and lung ventilation after prone positioning.

BACKGROUND: Turning a patient prone, changes the respiratory mechanics and potentially the level of positive end-expiratory pressure (PEEP) that is necessary to prevent alveolar collapse. In this prospective clinical study we examined the impact of PEEP on the intratidal respiratory mechanics and regional lung aeration in the prone position. We hypothesized that a higher PEEP is required to maintain compliance and regional ventilation in the prone position. METHODS: After ethical approval, 45 patients with healthy lungs undergoing lumbar spine surgery were examined in the supine position at PEEP 6 cm H2O and in the prone position at PEEP (6, 9 and 12 cm H2O). Dynamic compliance (CRS) and intratidal compliance-volume curves were determined and regional ventilation was measured using electrical impedance tomography. The compliance-volume curves were classified to indicate intratidal derecruitment, overdistension, or neither. RESULTS: CRS did not differ between postures and PEEP levels (P>0.28). At a PEEP of 6 cm H2O a compliance-volume profile indicating neither derecruitment nor overdistension was observed in 38 supine, but only in 20 prone positioned patients (P<0.001). The latter increased to 33 and 37 (both P<0.001) when increasing PEEP to 9 and 12 cm H2O, respectively. Increasing PEEP from 6 to 9 cm H2O in the prone position increased peripheral ventilation significantly. CONCLUSIONS: Respiratory system mechanics change substantially between supine and prone posture, which is not demonstrated in routine measurements. The intratidal compliance analysis suggests that in most patients a PEEP above commonly used settings is necessary to avoid alveolar collapse in the prone position. CLINICAL TRIAL REGISTRATION: DRKS 00005692.

Estatus ponderal y aptitud cardiorrespiratoria en escolares de la región central del Perú / Weight status and cardiorespiratory fitness in school students in the central region of Peru

Objetivos. Determinar la frecuencia del sobrepeso y obesidad, en función a los niveles de aptitud cardiorrespiratoria (AptCR) en escolares de cuatro distritos de la región central del Perú, y analizar la asociación entre estas variables. Materiales y métodos. El peso, altura y la AptCR fueron evaluados en 7841 escolares que residen en cuatro distritos ubicados en la costa, sierra y selva de la región central del Perú. El sobrepeso y la obesidad fueron clasificados según los criterios propuestos por Cole. La AptCR fue evaluada mediante la prueba de correr/caminar de doce minutos de la batería de la American Alliance for Health, Recreation and Dance. Se utilizó el ANOVA y la regresión logística para examinar las diferencias de las medias y asociaciones entre estas variables. Resultados. Escolares de ambos sexos presentan frecuencias semejantes de sobrepeso y obesidad (20,9% en mujeres y 20,1% en varones). Residentes en la costa (Barranco) manifiestan elevadas frecuencias de sobrepeso y obesidad (37,8%). La edad, el sexo, área geográfica y la AptCR fueron predictores significativos para el sobrepeso y la obesidad. Escolares que viven en Barranco tienen cinco veces más probabilidades de ser obesos (OR=4,67; IC95%: 3,55-6,14); los que residen en la sierra (Junín) tienen una menor probabilidad de ser obesos (OR=0,03; IC95%: 0,01-0,20); y quienes muestran una baja AptCR tienen una mayor probabilidad de ser obesos (OR=11 ,82; IC95%: 7,25-19,27), en comparación con aquellos con alta AptCR. Conclusiones. Los escolares que residen en Barranco presentan frecuencias de sobrepeso y obesidad elevados. Una baja AptCR está asociada al desarrollo del sobrepeso y la obesidad.

Objectives. To determine the frequency of overweight and obesity in relation to cardiorespiratory fitness (CRF) levels in school students in 4 districts of the central region of Peru, and to analyze the relations among these variables. Materials and methods. Weight, height and CRF were evaluated in 7841 school students who reside in four districts located on the coast, in the highlands and in the jungle of the central region of the country. Overweight and obesity were classified according to the criteria proposed by Cole. CRF was evaluated by a 12-minute run/walk test taken from the American Alliance for Health, Physical Education, Recreation and Dance’s test battery. ANOVA and logistic regression were used to examine the differences of the averages and the associations among these variables. Results. Both male and female school students have similar frequency of overweight and obesity (20.9% in women and 20.1% in men). Residents of the coast (Barranco) presen thigh frequency of overweight and obesity (37.8%). Age, sex, geographical area and CRF were significant predictors of overweight and obesity. School students who live in Barranco are five times more likely to be obese (OR=4.67; CI95%: 3.55-6.14), while those who reside in the highlands (Junin) are less likely to be obese (OR=0.03; CI95%: 0.01-0.20). Furthermore, in contrast with students with high CRF, those with low CRF are more likely to be obese (OR=11.82; CI95%: 7.25-19.27). Conclusions. There was a high frequency of overweight and obesity among school students who reside in Barranco. Low CRF is associated with overweight and obesity.