China
Africa
Explore chapters and articles related to this topic
Biomedical Sensors and Data Acquisition
Published in Rajarshi Gupta, Dwaipayan Biswas, Health Monitoring Systems, 2019
ECG is the time-averaged representation of tiny electrical potentials that are developed on cardiac muscles and propagate over specialized conducting fibers over the heart surface. These tiny electric potentials originate on the sinoatrial node (SA) of the right atrium and propagate to the atrioventricular (AV) node first, and then spread over the left and right ventricles over the Purkinje fibers. As a result, the atrial and ventricular cells sequentially depolarize and repolarize, generating the pumping action of the heart. One complete cardiac cycle comprises of following events: (a) collection of impure blood from inferior and superior vena cava in the right atrium, with simultaneous collection of oxygen-rich blood at left atrium to fill the atria; (b) atrial contraction to force fill blood into the ventricles from atria; (c) ventricular contraction to send the impure blood from right ventricles to lungs for purification, with simultaneous pumping of blood to body parts through aorta [5]. This generates the P-QRS-T waveform of the ECG, given by Einthoven, the inventor. A typical ECG waveform and associated electrophysiological events are shown in Figure 2.6.
Medical Decision Making
Published in Pat Croskerry, Karen S. Cosby, Mark L. Graber, Hardeep Singh, Diagnosis, 2017
Aging but experienced mentors sometimes have to convince the cynical student that old-fashioned methods of physical examination still have merit and are worth the investment of time and effort. Exhortations about the importance of the physical examination may be heard resounding from the hallways and corridors of academic medical centers, such as: You can’t see what you don’t look for. You will never diagnose papilledema without a funduscopic exam.You aren’t inclined to look for what you don’t expect to see. If your clinical experience is limited you may never learn to recognize some of the occult manifestations of disease. Necrotizing fasciitis may be detected by palpating distant from the initial skin findings; the surprise soft crunch of soft tissue air may be felt before the erythema spreads. The presence of dilated vessels in the upper torso may provide the first clue of a superior vena cava syndrome, the finding of an underlying lung cancer. One of the thrilling parts of learning medicine is the unexpected clue, the recognition of its relevance to the matter at hand, and the delight in using and sharing the finding to “crack the case.” I still recall the delight of an intern who detected the low rumbling diastolic murmur of mitral stenosis that helped establish the diagnosis of endocarditis, a finding and diagnosis missed by all the other members of the more senior examining team. The finding likely saved the patient’s life.Success depends on the expertise and interest you bring to the exam. As described by Stanley and Campos, “sometimes even a minor detail—an inadvertent gesture; a change in voice or speech; the mood of a patient; a factor such as foreign travel … can lead the observer in a different direction for diagnosing” [19]. Those who minimize the value of the exam will likely never benefit from its value. Physical exam skills come from personal experience with patients and cannot be gained from sitting in the library reading a textbook. They are the gift patients give us to unlock their mystery.The absence of a finding is not necessarily proof of lack of disease. Many have witnessed firsthand the typical symptoms of zoster only to have the rash appear after the onset of pain, remote from the first exam. That fact can be acknowledged without undermining the argument to look for a rash and the willingness to revisit the exam on another day.The presence of a pathognomonic finding may be very specific for disease, and the presence of one cardinal finding may save unnecessary tests. A constellation of findings often provides very strong, if not conclusive, evidence of disease.
Numerical study on the injury mechanism of blunt aortic rupture of the occupant in frontal and side-impact
Published in International Journal of Crashworthiness, 2023
Fang Tong, FengChong Lan, JiQing Chen, DongRi Li, Xiong Li
The occupant FE model used in the current study was the 50 percentile Chinese male model established previously based on computerized tomography data [26–31]. The model consists of the head, neck, torso, and limbs as shown in Figure 1. The assembled human model and each part of it were all validated by PMHS tests from published literature [32–35], including frontal thorax impact, lateral thorax impact, head impact, bone bending tests, etc. In the thoracic cavity, the heart is connected with the lungs by the pulmonary artery. The descending aorta was constrained with the spine to simulate the action of the intercostal arteries. The low region of the heart and the distal end of the descending aorta were also constrained to represent the contact with the diaphragm. The whole model contained 1 734 889 elements and 1 006 365 nodes, respectively. In the human model, the property of the skeleton was defined as elastoplastic, and the ultimate strain was set to simulate the rib fracture. Organs like the heart and lungs were represented by viscoelastic materials. Vessels like pulmonary artery, pulmonary vein, and superior vena cava were set as linear elastic to improve the computational efficiency. For more detailed material properties of the human FE model, see the previous studies [26–31].
Amplatzer patent foramen ovale occluder: safety and efficacy
Published in Expert Review of Medical Devices, 2019
Raouf Madhkour, Andreas Wahl, Fabien Praz, Bernhard Meier
The choice of the device size should be made according to the thickness of the septum secundum (SS, cranial part of interatrial septum) as well as the presence and extent of an atrial septal aneurysm (ASA). The length of the PFO tunnel is of little importance. The SS is best seen by transesophageal echocardiography (TEE) using a short axis view cutting the aortic root. The long axis bicaval view (a misnomer as it shows the superior vena cava to the right and the coronary sinus to the left but not the inferior vena cava) can also be used. The 25 mm Amplatzer PFO Occluder fits PFOs without thick SS or ASA. In the presence of one or both of these features (about 10–20%), a larger device (preferably the 35 mm Amplatzer PFO Occluder, or a 30 mm Amplatzer Cribriform Occluder with twin 30 mm disks, initially designed for cribriform atrial septal defects) is recommended [14]. The presence of a long tunnel, a small exit hole, or an ASA remote from the PFO may obviate the need for a larger occluder.
1D simulation of blood flow characteristics in the circle of Willis using THINkS
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
George P. Huang, Hongtao Yu, Zifeng Yang, Ryan Schwieterman, Bryan Ludwig
In the flow simulation for the heart modeling, a lumped model of the circulation between the heart and the lungs was taken into account (Müller and Toro 2014; Huang and Muller 2015). A 4-chamber 0D model for the heart is used to simulate the blood flow from the superior vena cava and inferior vena cava, through the pulmonary system, and then to the ascending aorta. In addition to the 4 valves inside the heart, there are also 15 venous valves used in the venous system. The 1D model is intentionally constructed in such a way that each blood vessel is adjustable, replaceable and removable according to various blood vessel typologies. Therefore, in order to satisfy the patient’s vascular typologies, the computational code can be customized very easily. The individual physiological anomalies for the subject discussed in this study can also be found in the previous work (Müller and Toro 2014; Huang and Muller 2015). All 0D, 1D equations and modeling parameters were discussed and presented in detail in our previous work (Huang and Muller 2015). The equations used to describe the vessel junctions were formulated by Riemann variables, conservations of mass, and Bernoulli equation (Müller and Toro 2014). The 0D and 1D equations were solved using optimal third-order TVD Runge-Kutta method and shock-capturing TVD scheme.