3-D Dynamic Walking Trajectory Generation for a Bipedal Exoskeleton with Underactuated Legs: A Proof of Concept.

This paper presents a framework to address three dimensional (3-D) dynamic walking for a bipedal exoskeleton with underactuated legs. To achieve this goal, the framework is constructed via a trajectory generator and an optimized inverse kinematics algorithm that can cope with underactuation. In order to feasibly attain task velocities with underactuated legs, the inverse kinematics algorithm makes use of a task prioritization method via the exploitation of null space. In doing so, the tasks with lower priority, e.g., swing foot orientation, are attained as much as possible without disrupting the higher priority tasks, such as CoM trajectory. Meanwhile, the trajectory generator utilizes the ZMP concept analytically and ensures the acceleration continuity throughout the whole walking period, regardless of the contact and phase changes. The proposed method is verified via a lumped human-bipedal exoskeleton model that is developed and simulated in MSC.ADAMS simulation environment. As a result, we obtained feasible and dynamically balanced 3-D walking motion, in which no oblique foot landing or exaggerated torso orientation variations were observed, despite the underactuated nature of the robot legs.

Use of tunnelled catheters in haematological malignancy patients with neutropenia.

This prospective study analysed 83 patients (age 45 +/- 17 years) with haematological neoplasms, implanted with 93 tunnelled catheters, who were neutropenic or developed neutropenia during treatment. Catheters were implanted in the right (n = 82) or left (n = 11) jugular vein by the same surgical team using the same technique. They remained in place for 124 +/- 88 days: 29% were removed due to infection; 18% due to treatment termination and 2% due to mechanical problems. Seventeen patients died with catheters in place. At 30, 60, 90, 120 and 200 days mean catheter duration rates were 82%, 75%, 65%, 60% and 35%, respectively, and freedom from catheter removal due to infection was 92%, 88%, 80%, 77% and 67%, respectively. Patient diagnosis and history of previous catheter infection did not increase catheter infection risk, but patients undergoing stem cell transplantation had an increased infection risk. Tunnelled catheters can be used in high-risk patients with neutropenia. Systemic infections can be managed in most patients without catheter removal.

Vasorelaxant effect of iloprost on isolated human internal mammary artery.

In this study, vasodilator effect of iloprost on KCl-induced contraction in human internal mammary artery (IMA) was studied and compared with other vasodilators papaverin and diltiazem. Ring segments of IMA were studied in organ baths for measurement of isometric tension. After the tissues has reached their baseline tension, precontraction was induced by 100 mm KCl and cumulative concentration-relaxation was measured by the application of iloprost (10(-9)-10(-6) m), papaverine (10(-5)-10(-4) m), diltiazem (10(-9)-10(-4) m) or ethanol; a solvent for iloprost; alone. The maximal relaxation of IMA segments to iloprost was 13.5 +/- 2.2%. Iloprost caused significantly limited relaxation when compared with papaverin (106.0 +/- 2.9%) and diltiazem (93.6 +/- 2.5%) (P < 0.001). Papaverin produced the greatest maximal relaxation to KCl-induced contraction of IMA. The potency of iloprost (-log EC(50) = 6.59 +/- 0.19) was significantly higher than those of papaverine (-log EC(50) = 4.21 +/- 0.11) and diltiazem (-log EC(50) = 5.63 +/- 0.06) (P < 0.001). In addition, -log EC(50) of diltiazem was significantly greater than papaverin (P < 0.001). Iloprost appears to be more potent than those of papaverine and diltiazem but it was inefficient in maximal inhibition on KCl-induced contraction. Iloprost may have little benefit in KCl-related vasoconstriction on human IMA segments.

Fresh homografts obtained through a national organ-sharing programme for repair of congenital heart disease.

Homografts have been used in congenital cardiac surgery for over 30 years. We utilized the resources of a national organ-sharing programme to obtain fresh homografts and report their use in correcting cardiac pathologies in 20 children between March 2001 and May 2003. In 16 patients, a valved conduit was used to form a connection between the pulmonary ventricle and the pulmonary artery. In three patients, a non-valved aortic conduit was used to form an extra-cardiac Fontan circulation and in one patient, non-valved pulmonary and aortic conduits were used to repair an infected aortic aneurysm. Three patients died following surgery. Survivors were followed up using echocardiography between 2 and 24 months post-surgery. Results demonstrate that, with the help of a national organ-sharing programme, the use of fresh homograft conduits is feasible in a paediatric patient population with reasonable waiting times.

Effect of left ventricular volume on results of coronary artery bypass grafting.

After coronary artery bypass grafting, our patients with ischemic cardiomyopathy and significant left ventricular (LV) dilation demonstrated an improvement in angina symptoms, acceptable operative and medium-term survival, a trend toward improvement in LV ejection fraction, and a significant reduction in LV chamber size. Our results suggest that patients with ischemic cardiomyopathy and LV dilation should not be excluded from surgical revascularization based on ventricular size alone.

Increased nitric oxide in exhaled air in patients with rheumatic heart disease.

BACKGROUND: Endogenous production of nitric oxide and its presence in exhaled air was observed in humans. Prior studies have yielded contrasting information about the production of nitric oxide in patients with heart failure. AIMS: The aim of this study was to measure nitric oxide in the exhaled air of patients with chronic rheumatic heart disease with and without pulmonary hypertension. METHODS: Seventy-four patients (6 patients had isolated mitral stenosis; 13 patients had combined mitral stenosis and mitral regurgitation; 1 patient had isolated mitral regurgitation; 54 patients had combined mitral and aortic valve disease) and 27 healthy subjects were entered in the study. The nitric oxide concentration in exhaled air was determined with a chemiluminescence analyser. Echocardiography was performed in all patients to assess the severity of the valve disease and for the measurement of pulmonary artery pressure. RESULTS: The level of exhaled nitric oxide was significantly greater in patients with rheumatic heart disease than in controls. The value of nitric oxide concentration in exhaled air was significantly increased in patients with pulmonary hypertension, as compared with patients who had normal pulmonary artery systolic pressure. CONCLUSION: We found increased nitric oxide in the exhaled air in patients with rheumatic heart disease, especially in those with pulmonary hypertension, compared with healthy patients.

Effects of nitric oxide donor and inhibitor on prostaglandin E2-like activity, malondialdehyde and reduced glutathione levels after skeletal muscle ischemia-reperfusion.

Oxygen free radicals are implicated in the pathophysiology of ischemia-reperfusion (I/R) injury in skeletal muscle. Nitric oxide (NO) and prostaglandin E2 (PGE2) are important regulators of the microcirculation in skeletal muscle. The effects of L-arginine, substrate for NO, and N(G)-nitro L-arginine methyl ester (L-NAME) on PGE2 synthesis, lipid peroxidation and reduced glutathione (GSH) levels was investigated in the rat gastrocnemius muscle after 3 h of reperfusion following 2 h of ischemia. Lipid peroxidation and GSH levels showed a non-significant changes in the I/R groups compared to the control group. According to these results, it can be assumed that skeletal muscle can resist 2 h of ischemia followed by 3 h of reperfusion-induced oxidative stress. PGE2-like activity in the gastrocnemius muscle increased in the L-NAME treated and I/R groups. L-arginine administration reversed the increase in PGE2-like activity of reperfused skeletal muscle. These findings support the conclusion that endothelium-derived PGE2 synthesis increases during reperfusion and suggest that PGE2 may have a protective role in the maintenance of endothelial function.

Dissection of the ascending aorta due to metastatic carcinoma.

The association of aortic dissection with a malignancy is a rare finding and previous reports are usually those of primary aortic sarcomas. In this report we present a case with typical ascending aorta dissection associated with metastatic carcinoma originating from the lungs. The metastatic infiltration of the vasovasorum of the aorta by carcinoma cells may have caused aortic dissection by decreasing medial strength and integrity. This is a mechanism of aortic dissection that we have not encountered in previous reports.

Pathogenesis of systemic air embolism during bronchoscopic Nd:YAG laser operations.

BACKGROUND: The occurrence of systemic air embolism during bronchoscopic neodymium:yttrium-aluminum garnet laser operations has been suspected. Here we describe its mechanism. METHODS: Two patients with embolic cardiac and neurologic complications after bronchoscopic neodymium: yttrium-aluminum garnet laser tumor ablation are described. A subsequent third patient was monitored for intracardiac and aortic air by transesophageal echocardiography. A review of the literature and safety recommendations are discussed. RESULTS: The appearance of systemic air emboli was related to the use of the laser fiber air coolant at high flow and resolved by decreasing the air flow. The presence of intracardiac and aortic air was associated with hypotension and inferior ischemic electrocardiographic changes. CONCLUSIONS: Systemic air embolism during bronchoscopic laser operations is a potentially catastrophic complication and is related to the use of gas-cooled laser fibers and contact probes. We recommend using the noncontact mode whenever possible and maintaining the coaxial coolant air flow at the minimum level or using a fluid coolant if contact is necessary.

Retrograde cerebral perfusion with hypothermic circulatory arrest in a child.

This report describes a 4-year-old boy who presented with infective endocarditis involving the ascending aorta and the arch vessels, with supravalvular aortic stenosis as the underlying pathology. Operation was indicated because of the embolic potential of the vegetations inside the aorta. Retrograde cerebral perfusion was utilized in conjunction with hypothermic circulatory arrest, to flush particulate materials from the arch vessels during operation.

Low dose systemic thrombolytic therapy for treatment of deep venous thrombosis.

BACKGROUND: Thrombolytic therapy is still not used widely for treatment of deep vein thrombosis despite its known efficacy. This reluctance to use it stems from worries about its hemorrhagic complications. METHODS: In a 4-year period 97 patients with deep vein thrombosis diagnosed by duplex study were enrolled into the study. Fifty patients received streptokinase as a bolus of 250,000 units followed by 100,000 units/hr with a maximum of 4,000,000 units and 47 patients received anticoagulation with heparin. RESULTS: Minor hemorrhagic complications occurred in 2 patients (4%) in the thrombolytic therapy group. An improvement in the control duplex study was observed in 56% of the patients in the thrombolytic therapy group compared to 5% in the heparin group (p=0.000). The patients treated within 4 days of onset of symptoms had significantly higher success rates compared to those treated later (p=0.000). Higher success rates were obtained for those with either femoral vein or more distal venous thrombosis compared to those with iliac vein and vena cava thrombosis (p=0.007). These results show that systemic low dose streptokinase achieves significantly higher recanalization rates compared to heparin alone. CONCLUSIONS: Hemorrhagic complications at these dose levels are within acceptable ranges. Low dose streptokinase regimen could be beneficial in patients who present within 4 days of femoral or more distal venous thrombosis.

Ligation of patent ductus arterious by the method of video-assisted thoracoscopic surgery and our other VATS experiences.

In April and May 1996, two cases of PDA ligation were performed firstly in Turkey by the method of video assisted thoracoscopic surgery (VATS) in Dokuz Eylül Medical Faculty, Thoracic and Cardiovascular Surgery Department. There was not any complication in these patients in the postoperative period and they were discharged on the second day in symptom-free condition by the detection of closed ductus in their echocardiographic examination. Between February 1993 and October 1996, a total of 46 patients have undergone interventional application by VATS. While in six of these patients the procedure could not be manipulated because of massive pleural fibrosis, there was no mortality or morbidity among the patients, and they were discharged on average on the second day. The ratio of complications, such as bleeding, air leak, arrhythmia and empyema are so low in these operations, and hospital stay, with return to work time are shorter than with the open technique.

Cervical aortic arch. A case report.

Cervical aortic arch is a rare type of aortic arch anomaly that is presumed to result from persistence of the third aortic arch and regression of the normal fourth arch. Most of the patients with this anomaly are asymptomatic, but symptoms of dysphagia and respiratory distress due to the compression by the vascular ring have been reported. Other findings such as a supraclavicular pulsatile mass, blood pressure discrepancies between the upper limbs, and loss of femoral or opposite-upper-limb pulses with compression of the cervical mass may also be present. In this article a twenty-two-year-old woman with symptomatic cervical aortic arch is presented. The patient had a left cervical pulsatile mass and elevated blood pressure on her right upper limb and was treated surgically with reanastomosis of the aorta.

A multicentre study of abdominal aorta diameters in a Turkish population.

The aim of this study was to determine the normal values for aortic diameters and the prevalence of aortic dilatation in a mixed Turkish population. Between March 1998 and May 2000, patients who were undergoing abdominal ultrasonography examination for pathologies not involving the aorta, in three different cities, were enrolled into the study prospectively. The anterior posterior aortic diameters were measured at the subdiaphragmatic and aortic bifurcation levels using ultrasonography. A total of 596 patients were included (302 females, 294 males). The mean age was 48 +/- 16 years (range, 6-88 years). The mean aortic diameter in the whole group was 19.0 +/- 3.9 mm (10-45 mm) at the subdiaphragmatic level and 15.7 +/- 3.6 mm (9-65 mm) at the aortic bifurcation level. The mean subdiaphragmatic aortic diameter was 18 +/- 3 mm in females and 19 +/- 4 mm in males. The mean aortic diameters at the bifurcation level was 15 +/- 3 mm in females and 16 +/- 4 mm in males. An aortic bifurcation diameter > 30 mm was encountered in 0.67% of the population. This ratio increased to 1.8% in patients over 55 years of age, regardless of sex. A subdiaphragmatic aorta diameter above 30 mm was observed in 1.2% of the population. In patients over the age of 55 years, this ratio increased to 2.7% (3.6% in males and 1.9% in females). In this national study, the subdiaphragmatic aortic diameters were similar to mean values reported in the world literature. The mean aortic bifurcation diameters were generally lower when compared with the literature, which may be due to difficulties in standardization of the measurements. Aneurysmal dilatation rates in this study also conform to those reported in studies conducted in other countries. Considering the significant number of patients with aneurysmal dilatation of the aorta in the elderly population, we believe it would be prudent to evaluate the aorta in all patients undergoing abdominal ultrasonographic examination.

Comparison of remifentanil and fentanyl in anaesthesia for elective cardioversion.

This prospective, randomized, double-blind study was designed to compare the recovery characteristics of remifentanil and fentanyl in combination with propofol for direct current cardioversion. Patients undergoing elective cardioversion received either intravenous fentanyl 1 microg/kg (n=33) or remifentanil 0.25 microg/kg (n=30) and propofol was titrated to a Ramsay sedation score of 5 by slow intravenous injection. Heart rate, systolic, diastolic and mean blood pressures decreased significantly following sedation in both groups but did not show a significant difference between the groups. Time to answer a question (306 +/- 83 vs 383 +/- 131s, mean +/- SD, P=0.014) and time to sit up (412 +/- 90 vs 511 +/- 126s, P=0.002) were significantly shorter in the remifentanil group compared to the fentanyl group. Side-effects and patient discomfort were similar for both groups. Remifentanil can be used as a suitable supplement to propofol for direct current cardioversion and may provide a faster recovery profile than fentanyl.

Pseudoaneurysm of the right ventricular outflow tract complicating balloon dilatation for tetralogy of fallot.

Balloon dilatation is one of the treatment options in symptomatic infants with tetralogy of Fallot and hypoplastic pulmonary annulus and pulmonary artery. A balloon dilatation was performed on a 28-day-old infant with tetralogy of Fallot with an appropriate balloon. The patient developed two pseudoaneurysms on the right ventricular outflow tract after the procedure which were diagnosed when the patient was admitted for total correction at 20 months of age. This case demonstrates an unusual but potentially life-threatening long-term complication of this procedure.

Valve replacement due to tricuspid valve anomalies in corrected transposition.

Left atrioventricular (A-V) valve anomalies are very frequent in corrected transposition, but left A-V valve replacement has seldom been reported. These anomalies are an important cause of morbidity and mortality in these patients, and due to anatomical presentation valve replacement may be difficult. We present 4 cases of left A-V valve replacement with emphasis given to Ebstein's anomaly of the left A-V valve.

An unusual case of cor triatriatum.

Cor triatriatum (CT) is a rare congenital cardiac anomaly. A case is presented of subdivided left atrium, corrected surgically, which can be considered a type of CT not previously reported.

Long-term oral ciprofloxacin in the treatment of prosthetic valve endocarditis due to Pseudomonas aeruginosa.

Prosthetic valve endocarditis caused by Pseudomonas aeruginosa is refractory to medical treatment alone and early valve replacement is necessary. We describe a 40-year-old patient in whom endocarditis developed in the early postoperative period, and reoperation was not considered feasible. Ciprofloxacin was administered orally in order to suppress bacteremia for 36 months. Long-term oral ciprofloxacin may provide an opportunity in the treatment of prosthetic valve endocarditis caused by Ps. aeruginosa in patients who are unfavorable candidates for reoperation.

Surgical patent foramen ovale closure for prevention of paradoxical embolism-related cerebrovascular ischemic events.

BACKGROUND: The role of surgical closure of patent foramen ovale (PFO) for cerebral infarction (CI) or transient ischemic attack (TIA) resulting from paradoxical embolism is unclear, and its effect on recurrence is unknown. Our objective was to determine the outcome of surgical closure of PFO in patients with a prior ischemic neurological event, define the rate of CI or TIA recurrence after PFO closure, and identify risk factors for these recurrences. METHODS AND RESULTS: We retrospectively analyzed 91 patients (58 men, 33 women) with >/=1 previous cerebrovascular ischemic events who underwent surgical PFO closure between April 1982 and March 1998. The presence of a PFO with a right-to-left shunt was confirmed with transesophageal echocardiography. Mean age was 44.2+/-12.2 years. The index event was a CI in 59 and a TIA in 32; a Valsalva-like episode preceded the event in 15 patients. Deep venous thrombosis was documented in 9 patients, and a hypercoagulable state was identified in 10. Surgical closure was performed with extracorporeal circulation by either direct suture (n=82) or patch closure (n=9). Limited incisions were used in 18.7% of patients. There was no operative mortality. Morbidity included transient atrial fibrillation (n=11), pericardial drainage for effusion (n=4), exploration for bleeding (n=3), and superficial wound infection (n=1). Follow-up totaled 176.3 patient-years, and mean follow-up was 2.0 years. No one had a CI, and 8 had a TIA during follow-up, with 1 caused by temporal arteritis. Transesophageal echocardiography demonstrated all closures to be intact in these patients. The overall freedom from TIA recurrence during follow-up was 92.5+/-3.2% at 1 year and 83.4+/-6.0% at 4 years. Having multiple neurological events before PFO closure was the only significant risk factor for TIA or CI recurrence after closure by univariate analysis (P=0.05); the small number of post-PFO closure cerebral ischemic events precluded multivariate analysis. CONCLUSIONS: Surgical closure of PFO can be performed with minimal morbidity and mortality. PFO closure may decrease the risk of recurrent stroke or TIA and may avoid lifelong anticoagulation in the young adult if there is no other indication. Recurrent cerebrovascular ischemic events after surgery should prompt further evaluation to identify causes other than paradoxical embolism.