Decentralized Passivity-Based Control With a Generalized Energy Storage Function for Robust Biped Locomotion.

This paper details a decentralized passivity-based control (PBC) to improve the robustness of biped locomotion in the presence of gait-generating external torques and parametric errors in the biped model. Previous work demonstrated a passive output for biped systems based on a generalized energy that, when directly used for feedback control, increases the basin of attraction and convergence rate of the biped to a stable limit cycle. This paper extends the concept with a theoretical framework to address both uncertainty in the biped model and a lack of sensing hardware, by allowing the designer to neglect arbitrary states and parameters in the system. This framework also allows the control to be implemented on wearable devices, such as a lower limb exoskeleton or powered prosthesis, without needing a model of the user's dynamics. Simulations on a six-link biped model demonstrate that the proposed control scheme increases the convergence rate of the biped to a walking gait and improves the robustness to perturbations and to changes in ground slope.

Is there a national variation in cardiothoracic trainees' satisfaction? Evaluation of the United Kingdom General Medical Council national training surveys.

BACKGROUND: The national training surveys was first started in 2006, with an aim to determine the quality of the national training standard. All trainees working in a General Medical Council approved training post are required to complete the survey. We aimed to evaluate cardiothoracic trainees' satisfaction and determine whether there is variation in the United Kingdom. METHOD: The national training survey report in cardiothoracic surgery from 2012 to 2019 was obtained from the General Medical Council website. The cardiothoracic centers were divided based on their geographic locations. Comparisons in all 18 indicators in the national training surveys report were made between the four counties (national) and four local education training boards (LETBs) in England (Regional). Centers with less than 4 years of data were excluded from this study. RESULTS: Thirty-three cardiothoracic centers are included in this study The top three areas that trainees are most satisfied are clinical supervision (out of hours) (91.65), clinical supervision (90.65), and educational supervision (88.27). On the other hand, trainees are less satisfying with the handover (62.63), rota design (61.91), and workload (45.07). It is worth noting that workload is the only area of less than 60%. In addition, there is no national variation in all 18 indicators CONCLUSION: Our data suggested that there is no difference in overall trainee satisfaction in the United Kingdom. However, there are differences in various indicators between England and the three other nations. Individual hospital should reflect on trainees' evaluation on the national training surveys report and improve on specific areas if deemed unsatisfactory.

Passivity-Based Control with a Generalized Energy Storage Function for Robust Walking of Biped Robots.

This paper offers a novel generalization of a passivity-based, energy tracking controller for robust bipedal walking. Past work has shown that a biped limit cycle with a known, constant mechanical energy can be made robust to uneven terrains and disturbances by actively driving energy to that reference. However, the assumption of a known, constant mechanical energy has limited application of this passivity-based method to simple toy models (often passive walkers). The method presented in this paper allows the passivity-based controller to be used in combination with an arbitrary inner-loop control that creates a limit cycle with a constant generalized system energy. We also show that the proposed control method accommodates arbitrary degrees of underactuation. Simulations on a 7-link biped model demonstrate that the proposed control scheme enlarges the basin of attraction, increases the convergence rate to the limit cycle, and improves robustness to ground slopes.

Effects of preoperative statin treatment on the incidence of postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting.

BACKGROUND: Postoperative atrial fibrillation is still a common complication in patients undergoing coronary artery bypass grafting. The aim of this study was to evaluate the effect of preoperative statin therapy on new onset of postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting. METHODS: Of 8,946 patients undergoing isolated coronary artery bypass grafting at the Bristol Heart Institute from April 1996 to September 2006, 6,321 (70.6%) received preoperative statins. Of these, 2,152 patients (statin group) were matched to a control group (no statin) by propensity score analysis. RESULTS: Preoperative characteristics, number of distal anastomoses, and the use of off -pump procedures were similar in both groups. Hospital mortality was 1.3% (56 patients) with no difference between the two groups. Postoperative atrial fibrillation was significantly higher in the statin compared with the no statin group (411, 19.5%, versus 336; 15.8% respectively; p = 0.002). In a multivariate regression analysis, age (odds ratio [OR], 1.04; 95% confidence interval [CI], 1.02 to 1.05), pulmonary disease (OR, 1.42; 95% CI, 1.12-1.82), history of paroxysmal atrial fibrillation (OR, 3; 95% CI, 2.13 to 4.19), preoperative angiotensin-converting enzyme inhibitor therapy (OR, 1.26; 95% CI, 1.07 to 1.49), ejection fraction less than 0.30 (OR, 1.71; 95% CI, 1.22 to 2.38), emergency operations (OR, 4.5; 95% CI, 2 to 10.12), and preoperative statin treatment (OR, 1.31; 95% CI, 1.11 to 1.55) were all independent predictors of postoperative atrial fibrillation. CONCLUSIONS: Preoperative statin is associated with a significantly higher incidence of postoperative atrial fibrillation compared with no statin treatment in patients undergoing isolated coronary artery bypass grafting.

Intracoronary shunts reduce transient intraoperative myocardial dysfunction during off-pump coronary operations.

BACKGROUND: This study investigated the hemodynamic changes in patients undergoing multiple vessel beating heart coronary revascularization in the presence or absence of an intracoronary shunt. METHODS: Forty patients were randomized to off-pump with a shunt (n = 20) or with the proximal coronary artery occluded by a soft snare (n = 20). Hemodynamic measurements were recorded at base line, during construction, and after completion of each distal anastomosis. RESULTS: Grafting of the left anterior descending coronary artery anastomosis was associated with a significant decrease in stroke volume, cardiac index, and mean arterial pressure, and an increase in pulmonary capillary wedge pressure and systemic vascular resistance in the snare but not in the shunt group. During grafting of the posterior descending coronary artery there was a marked decrease in stroke volume and cardiac index, and an increase in central venous pressure in both groups, and an increase in heart rate, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, and systemic vascular resistance only in the snare group. The most extensive changes were observed during the circumflex coronary artery anastomosis with a reduction in stroke volume, cardiac index, and mean arterial pressure, and an increase in central venous pressure, pulmonary capillary wedge pressure, pulmonary arterial pressure, and systemic vascular resistance in both groups. In all settings, these changes were transient and recovered after the heart was returned to its anatomical position in the shunt group, whereas stroke volume and cardiac index remained reduced, and systemic vascular resistance was elevated in all settings in the snare group. CONCLUSIONS: Stabilization of the left anterior descending coronary artery to perform the anastomosis resulted in temporary hemodynamic changes, which are prevented by the use of an intracoronary shunt. The hemodynamic deterioration during the construction of the posterior descending coronary artery and circumflex coronary artery anastomoses is transient in the shunt group, whereas the snaring technique is associated with an impairment of early functional recovery.

Magnesium-supplemented warm blood cardioplegia in patients undergoing coronary artery revascularization.

BACKGROUND: Although there is growing evidence to suggest that the administration of magnesium (Mg2+) to patients undergoing coronary artery bypass grafting (CABG) and to patients after myocardial infarction is beneficial, the addition of Mg2+ to cardioplegic solutions remains controversial. The aim of this study was to compare the effects of intermittent warm blood cardioplegia with and without Mg2+ supplementation on the early postoperative clinical outcomes in patients undergoing both elective or urgent CABG. METHODS: Four hundred patients undergoing CABG were prospectively randomized to receive either blood cardioplegia without Mg2+ (BC, n = 200) or supplemented with Mg2+ (BC-Mg2+, n = 200). Serial plasma Mg2+ concentrations were recorded at base line and postoperatively from days 1 to 4. RESULTS: Patient characteristics were similar and no significant differences were found in early mortality and morbidity in the two groups. Analysis of 178 patients undergoing urgent CABG for unstable symptoms (BC = 95, BC-Mg2+ = 83) demonstrated a significantly lower requirement for internal defibrillation and temporary epicardial pacing in the BC-Mg2+ group. Furthermore, there was a nearly twofold lower incidence of new postoperative atrial fibrillation in the BC-Mg2+ group compared with the BC group (19% versus 34%, p = 0.03). Postoperative plasma Mg2+ levels were consistently lower in those patients who developed new postoperative atrial fibrillation compared with those who did not (p = 0.05). CONCLUSIONS: The addition of Mg2+ to warm blood cardioplegia resulted in a lower incidence of intraoperative and postoperative arrhythmias in patients undergoing urgent CABG for unstable angina.

Effect of off-pump coronary surgery with right ventricular assist device on organ function and inflammatory response: a randomized controlled trial.

BACKGROUND: Right ventricular assist devices (RVADs) have been proposed to improve exposure of the coronary arteries in off-pump surgery. In this study we investigated the impact of the A-Med RVAD on inflammatory response and organ function in patients undergoing coronary artery bypass grafting. METHODS: Sixty patients were prospectively randomized to conventional surgery with cardiopulmonary bypass (CPB) and cardioplegic arrest, beating heart surgery (off-pump), or beating heart surgery with the RVAD. Serial blood samples were collected postoperatively, for analysis of inflammatory markers, troponin I, protein S100, and free hemoglobin. Renal tubular function was assessed by measuring urine N-acetyl-glucosaminidase activity. RESULTS: No hospital deaths or major postoperative complications occurred in the study population. Interleukin-6, interleukin-8, C3a, and troponin I levels after surgery were significantly higher in the CPB group compared with the off-pump and RVAD groups. Free hemoglobin levels immediately after the operation, peak and total S100 levels, and N-acetyl-glucosaminidase activity were also significantly higher in the CPB group. CONCLUSIONS: Off-pump coronary revascularization, with or without RVAD, reduces inflammatory response, myocardial, neurologic, and renal injury, and decreases hemolysis when compared with conventional surgery with CPB and cardioplegic arrest.

Accessory spleniculi in the right hemithorax.

Accessory spleniculi are present in the thoracic cavity without a history of trauma due to anomalies in the development of spleen. We report the case of a 62-year-old woman with hereditary spherocytosis and previous splenectomy with an incidental mass on a chest radiograph and an indeterminate diagnosis on needle biopsy. The probable sequence of embryological events that may explain the anatomic presence of splenic tissue in the thorax is discussed.