Ivan Romero - Academia.edu (original) (raw)

Papers by Ivan Romero

IEEE Transactions on Biomedical Engineering, 2008

Ventricular tachyarrhythmias are potentially lethal cardiac pathologies and the commonest cause o... more Ventricular tachyarrhythmias are potentially lethal cardiac pathologies and the commonest cause of sudden cardiac death. Efforts to predict the onset of such events are based on feature extraction from the surface ECG. T-wave alternans (TWAs) are considered a marker of abnormal ventricular function that may be associated with ventricular tachycardia (VT) and ventricular fibrillation. A novel TWA detection algorithm utilizing the continuous wavelet transform is described in this paper. Simulated ECGs containing artificial TWA were used to test the algorithm that achieved a sensitivity of 91.40% and a specificity of 94.00%. The algorithm was subsequently used to analyze the ECGs of eight patients prior to the onset of VT. Of these, the algorithm indicated that five patients exhibited TWA prior to the onset of the tachyarrhythmic events, while the remaining three patients did not exhibit identifiable TWA. Healthy individuals were also studied in which one short TWA episode was detected by the algorithm. However, closer visual inspection of the data revealed this to be a likely false positive result.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1999

Zinc is a necessary component in the action and structural stability of many enzymes. Some of the... more Zinc is a necessary component in the action and structural stability of many enzymes. Some of them are well characterized, but in others, Zn stoichiometry and its association is not known. PIXE has been proven to be a suitable technique for analyzing metallic proteins embedded in electrophoresis gels. In this study, PIXE has been used to investigate the Zn content of enzymes that are known to carry Zn atoms. These include the carbonic anhydrase, an enzyme well characterized by other methods and the cytoplasmic pyrophosphatase of Rhodospirillum rubrum that is known to require Zn to be stable but not how many metal ions are involved or how they are bound to the enzyme. Native proteins have been puri®ed by polyacrylamide gel electrophoresis and direct identi®cation and quanti®cation of Zn in the gel bands was performed with an external proton beam of 3.7 MeV energy. Ó 0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 1 0 1 2 -X

With new advances in ambulatory monitoring new challenges appear due to degradation in signal qua... more With new advances in ambulatory monitoring new challenges appear due to degradation in signal quality and limitations in hardware requirements. Existing signal analysis methods should be re-evaluated in order to adapt to the restrictive requirements of these new applications. With this motivation, we chose a robust beat detection algorithm and optimized it further to be running in an embedded platform within a cardiac monitoring sensor node. The algorithm was designed in floating point in Matlab and evaluated in order to study its performance under a wide range of conditions. The initial PC version of the algorithm obtained a good performance under a wide variety of conditions (Se = 99.65% and + P = 99.79% on the MIT/BIH arrhythmia database and Se = 99.88%, + P = 99.93% on our own database with ambulatory data). In this study, the algorithm is adapted and further optimized to work in real time on an embedded digital processor, while keeping this performance without degradation. The run-time memory usage of the application was of 150 KB with an execution time of 1.5 million cycles and an average power consumption of 494 ¿W for an ECG of 3 seconds length and sampling frequency of 198 Hz. The algorithm implementation in a general purpose processor will put significant limits on the performance in terms of power consumption. We propose possible specifications for an application-optimized processor for more efficient ECG analysis.

This paper discusses ultra-low-power wireless sensor nodes intended for wearable biopotential mon... more This paper discusses ultra-low-power wireless sensor nodes intended for wearable biopotential monitoring. Specific attention is given to mixed-signal design approaches and their impact on the overall system power dissipation. Examples of trade-offs in power dissipation between analog front-ends and digital signal processing are also given. It is shown how signal filtering can further reduce the internal power consumption of a node. Such power saving approaches are indispensable as real-life tests of custom wireless ECG patches reveal the need for artifact detection and correction. The power consumption of such additional features has to come from power savings elsewhere in the system as the overall power budget cannot increase.

Clinical Immunology and Immunopathology, 1998

meric structure, sequence homology, and calcium-de-C-reactive protein (CRP) is an acute phase ser... more meric structure, sequence homology, and calcium-de-C-reactive protein (CRP) is an acute phase serum pendent ligand binding (reviewed in (1, 2)). CRP is protein that binds to phosphocholine (PC) and to coman acute phase protein with functional activities that ponents of damaged tissue. CRP resembles antibody suggest a role in host defense. Complexes between in that it binds to ligands and activates the classical CRP and polyvalent ligands activate complement by complement pathway. To compare the processing of the classical pathway resulting in C4b and C3b bind-CRP complexes to that of IgG complexes, we have preing. CRP binds both to the high affinity receptor for pared complexes containing the same ligand, PC-con-IgG (FcgRI, CD64) (3, 4) and to additional receptors jugated BSA, and IgG antibody to either BSA or CRP. on monocytes, neutrophils (PMN), and myeloid cell We previously demonstrated similar complement-melines (5, 6) and can promote phagocytosis (7, 8). Each diated binding of these complexes to erythrocyte comof the five identical subunits of CRP contains a calplement receptors. CRP and IgG also bind to receptors cium-dependent binding site for phosphocholine (PC) on neutrophils (PMN), providing another possible through which CRP binds to the C-polysaccharide pathway for clearance of ligands. PMN binding of IgG (PnC) of Streptococcus pneumoniae and to the phoscomplexes can lead to activation with damaging inpholipids, sphingomyelin and phosphatidylcholine. flammatory consequences. In the present report we have used CRP and IgG complexes containing PC-BSA Prior injection of CRP protects mice against lethal to compare binding to PMN and activation of PMN infection with S. pneumoniae (9) and complement acadherence to endothelial cells. The results indicate tivation contributes to this protection (10).

IEEE Transactions on Biomedical Engineering, 2008

Ventricular tachyarrhythmias are potentially lethal cardiac pathologies and the commonest cause o... more Ventricular tachyarrhythmias are potentially lethal cardiac pathologies and the commonest cause of sudden cardiac death. Efforts to predict the onset of such events are based on feature extraction from the surface ECG. T-wave alternans (TWAs) are considered a marker of abnormal ventricular function that may be associated with ventricular tachycardia (VT) and ventricular fibrillation. A novel TWA detection algorithm utilizing the continuous wavelet transform is described in this paper. Simulated ECGs containing artificial TWA were used to test the algorithm that achieved a sensitivity of 91.40% and a specificity of 94.00%. The algorithm was subsequently used to analyze the ECGs of eight patients prior to the onset of VT. Of these, the algorithm indicated that five patients exhibited TWA prior to the onset of the tachyarrhythmic events, while the remaining three patients did not exhibit identifiable TWA. Healthy individuals were also studied in which one short TWA episode was detected by the algorithm. However, closer visual inspection of the data revealed this to be a likely false positive result.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1999

Zinc is a necessary component in the action and structural stability of many enzymes. Some of the... more Zinc is a necessary component in the action and structural stability of many enzymes. Some of them are well characterized, but in others, Zn stoichiometry and its association is not known. PIXE has been proven to be a suitable technique for analyzing metallic proteins embedded in electrophoresis gels. In this study, PIXE has been used to investigate the Zn content of enzymes that are known to carry Zn atoms. These include the carbonic anhydrase, an enzyme well characterized by other methods and the cytoplasmic pyrophosphatase of Rhodospirillum rubrum that is known to require Zn to be stable but not how many metal ions are involved or how they are bound to the enzyme. Native proteins have been puri®ed by polyacrylamide gel electrophoresis and direct identi®cation and quanti®cation of Zn in the gel bands was performed with an external proton beam of 3.7 MeV energy. Ó 0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 1 0 1 2 -X

With new advances in ambulatory monitoring new challenges appear due to degradation in signal qua... more With new advances in ambulatory monitoring new challenges appear due to degradation in signal quality and limitations in hardware requirements. Existing signal analysis methods should be re-evaluated in order to adapt to the restrictive requirements of these new applications. With this motivation, we chose a robust beat detection algorithm and optimized it further to be running in an embedded platform within a cardiac monitoring sensor node. The algorithm was designed in floating point in Matlab and evaluated in order to study its performance under a wide range of conditions. The initial PC version of the algorithm obtained a good performance under a wide variety of conditions (Se = 99.65% and + P = 99.79% on the MIT/BIH arrhythmia database and Se = 99.88%, + P = 99.93% on our own database with ambulatory data). In this study, the algorithm is adapted and further optimized to work in real time on an embedded digital processor, while keeping this performance without degradation. The run-time memory usage of the application was of 150 KB with an execution time of 1.5 million cycles and an average power consumption of 494 ¿W for an ECG of 3 seconds length and sampling frequency of 198 Hz. The algorithm implementation in a general purpose processor will put significant limits on the performance in terms of power consumption. We propose possible specifications for an application-optimized processor for more efficient ECG analysis.

This paper discusses ultra-low-power wireless sensor nodes intended for wearable biopotential mon... more This paper discusses ultra-low-power wireless sensor nodes intended for wearable biopotential monitoring. Specific attention is given to mixed-signal design approaches and their impact on the overall system power dissipation. Examples of trade-offs in power dissipation between analog front-ends and digital signal processing are also given. It is shown how signal filtering can further reduce the internal power consumption of a node. Such power saving approaches are indispensable as real-life tests of custom wireless ECG patches reveal the need for artifact detection and correction. The power consumption of such additional features has to come from power savings elsewhere in the system as the overall power budget cannot increase.

Clinical Immunology and Immunopathology, 1998

meric structure, sequence homology, and calcium-de-C-reactive protein (CRP) is an acute phase ser... more meric structure, sequence homology, and calcium-de-C-reactive protein (CRP) is an acute phase serum pendent ligand binding (reviewed in (1, 2)). CRP is protein that binds to phosphocholine (PC) and to coman acute phase protein with functional activities that ponents of damaged tissue. CRP resembles antibody suggest a role in host defense. Complexes between in that it binds to ligands and activates the classical CRP and polyvalent ligands activate complement by complement pathway. To compare the processing of the classical pathway resulting in C4b and C3b bind-CRP complexes to that of IgG complexes, we have preing. CRP binds both to the high affinity receptor for pared complexes containing the same ligand, PC-con-IgG (FcgRI, CD64) (3, 4) and to additional receptors jugated BSA, and IgG antibody to either BSA or CRP. on monocytes, neutrophils (PMN), and myeloid cell We previously demonstrated similar complement-melines (5, 6) and can promote phagocytosis (7, 8). Each diated binding of these complexes to erythrocyte comof the five identical subunits of CRP contains a calplement receptors. CRP and IgG also bind to receptors cium-dependent binding site for phosphocholine (PC) on neutrophils (PMN), providing another possible through which CRP binds to the C-polysaccharide pathway for clearance of ligands. PMN binding of IgG (PnC) of Streptococcus pneumoniae and to the phoscomplexes can lead to activation with damaging inpholipids, sphingomyelin and phosphatidylcholine. flammatory consequences. In the present report we have used CRP and IgG complexes containing PC-BSA Prior injection of CRP protects mice against lethal to compare binding to PMN and activation of PMN infection with S. pneumoniae (9) and complement acadherence to endothelial cells. The results indicate tivation contributes to this protection (10).