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Deng X, Garcia-Knight MA, Khalid MM, Servellita V, Wang C, Morris MK, Sotomayor-González A, Glasner DR, Reyes KR, Gliwa AS, Reddy NP, Sanchez San Martin C, Federman S, Cheng J, Balcerek J, Taylor J, Streithorst JA, Miller S, Sreekumar B, Chen PY, Schulze-Gahmen U, Taha TY, Hayashi JM, Simoneau CR, Kumar GR, McMahon S, Lidsky PV, Xiao Y, Hemarajata P, Green NM, Espinosa A, Kath C, Haw M, Bell J, Hacker JK, Hanson C, Wadford DA, Anaya C, Ferguson D, Frankino PA, Shivram H, Lareau LF, Wyman SK, Ott M, Andino R, Chiu CY. Transmission, infectivity, and neutralization of a spike L452R SARS-CoV-2 variant. Cell 2021; 184:3426-3437.e8. [PMID: 33991487 PMCID: PMC8057738 DOI: 10.1016/j.cell.2021.04.025] [Citation(s) in RCA: 313] [Impact Index Per Article: 104.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/02/2021] [Accepted: 04/15/2021] [Indexed: 01/07/2023]
Abstract
We identified an emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant by viral whole-genome sequencing of 2,172 nasal/nasopharyngeal swab samples from 44 counties in California, a state in the western United States. Named B.1.427/B.1.429 to denote its two lineages, the variant emerged in May 2020 and increased from 0% to >50% of sequenced cases from September 2020 to January 2021, showing 18.6%-24% increased transmissibility relative to wild-type circulating strains. The variant carries three mutations in the spike protein, including an L452R substitution. We found 2-fold increased B.1.427/B.1.429 viral shedding in vivo and increased L452R pseudovirus infection of cell cultures and lung organoids, albeit decreased relative to pseudoviruses carrying the N501Y mutation common to variants B.1.1.7, B.1.351, and P.1. Antibody neutralization assays revealed 4.0- to 6.7-fold and 2.0-fold decreases in neutralizing titers from convalescent patients and vaccine recipients, respectively. The increased prevalence of a more transmissible variant in California exhibiting decreased antibody neutralization warrants further investigation.
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Affiliation(s)
- Xianding Deng
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Miguel A Garcia-Knight
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Mir M Khalid
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Venice Servellita
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Candace Wang
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | | | - Alicia Sotomayor-González
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Dustin R Glasner
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Kevin R Reyes
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Amelia S Gliwa
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Nikitha P Reddy
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Claudia Sanchez San Martin
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA
| | - Scot Federman
- Laboratory for Genomics Research, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jing Cheng
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Joanna Balcerek
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jordan Taylor
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jessica A Streithorst
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Steve Miller
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Bharath Sreekumar
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Pei-Yi Chen
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Ursula Schulze-Gahmen
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Taha Y Taha
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Jennifer M Hayashi
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Camille R Simoneau
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - G Renuka Kumar
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Sarah McMahon
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA
| | - Peter V Lidsky
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Yinghong Xiao
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Peera Hemarajata
- Los Angeles County Public Health Laboratories, Downey, CA 90242, USA
| | - Nicole M Green
- Los Angeles County Public Health Laboratories, Downey, CA 90242, USA
| | - Alex Espinosa
- California Department of Public Health, Richmond, CA 94804, USA
| | - Chantha Kath
- California Department of Public Health, Richmond, CA 94804, USA
| | - Monica Haw
- California Department of Public Health, Richmond, CA 94804, USA
| | - John Bell
- California Department of Public Health, Richmond, CA 94804, USA
| | - Jill K Hacker
- California Department of Public Health, Richmond, CA 94804, USA
| | - Carl Hanson
- California Department of Public Health, Richmond, CA 94804, USA
| | - Debra A Wadford
- California Department of Public Health, Richmond, CA 94804, USA
| | - Carlos Anaya
- Monterey County Department of Public Health, Monterey, CA 93906, USA
| | - Donna Ferguson
- Monterey County Department of Public Health, Monterey, CA 93906, USA
| | - Phillip A Frankino
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Haridha Shivram
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Liana F Lareau
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Stacia K Wyman
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Melanie Ott
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Gladstone Institute of Virology, San Francisco, CA 94158, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
| | - Raul Andino
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA.
| | - Charles Y Chiu
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA; UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA 94158, USA; Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
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Deng X, Garcia-Knight MA, Khalid MM, Servellita V, Wang C, Morris MK, Sotomayor-González A, Glasner DR, Reyes KR, Gliwa AS, Reddy NP, Martin CSS, Federman S, Cheng J, Balcerek J, Taylor J, Streithorst JA, Miller S, Kumar GR, Sreekumar B, Chen PY, Schulze-Gahmen U, Taha TY, Hayashi J, Simoneau CR, McMahon S, Lidsky PV, Xiao Y, Hemarajata P, Green NM, Espinosa A, Kath C, Haw M, Bell J, Hacker JK, Hanson C, Wadford DA, Anaya C, Ferguson D, Lareau LF, Frankino PA, Shivram H, Wyman SK, Ott M, Andino R, Chiu CY. Transmission, infectivity, and antibody neutralization of an emerging SARS-CoV-2 variant in California carrying a L452R spike protein mutation. medRxiv 2021:2021.03.07.21252647. [PMID: 33758899 PMCID: PMC7987058 DOI: 10.1101/2021.03.07.21252647] [Citation(s) in RCA: 106] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We identified a novel SARS-CoV-2 variant by viral whole-genome sequencing of 2,172 nasal/nasopharyngeal swab samples from 44 counties in California. Named B.1.427/B.1.429 to denote its 2 lineages, the variant emerged around May 2020 and increased from 0% to >50% of sequenced cases from September 1, 2020 to January 29, 2021, exhibiting an 18.6-24% increase in transmissibility relative to wild-type circulating strains. The variant carries 3 mutations in the spike protein, including an L452R substitution. Our analyses revealed 2-fold increased B.1.427/B.1.429 viral shedding in vivo and increased L452R pseudovirus infection of cell cultures and lung organoids, albeit decreased relative to pseudoviruses carrying the N501Y mutation found in the B.1.1.7, B.1.351, and P.1 variants. Antibody neutralization assays showed 4.0 to 6.7-fold and 2.0-fold decreases in neutralizing titers from convalescent patients and vaccine recipients, respectively. The increased prevalence of a more transmissible variant in California associated with decreased antibody neutralization warrants further investigation.
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Affiliation(s)
- Xianding Deng
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Miguel A Garcia-Knight
- Department of Microbiology and Immunology, University of California San Francisco, California, USA
| | - Mir M Khalid
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Venice Servellita
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Candace Wang
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Mary Kate Morris
- California Department of Public Health, Richmond, California, USA
| | - Alicia Sotomayor-González
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Dustin R Glasner
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Kevin R Reyes
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Amelia S Gliwa
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Nikitha P Reddy
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Claudia Sanchez San Martin
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
| | - Scot Federman
- Laboratory for Genomics Research, University of California San Francisco, California, USA
| | - Jing Cheng
- Department of Medicine, University of California San Francisco, California, USA
| | - Joanna Balcerek
- Department of Laboratory Medicine, University of California San Francisco, California, USA
| | - Jordan Taylor
- Department of Laboratory Medicine, University of California San Francisco, California, USA
| | - Jessica A Streithorst
- Department of Laboratory Medicine, University of California San Francisco, California, USA
| | - Steve Miller
- Department of Laboratory Medicine, University of California San Francisco, California, USA
| | - G Renuka Kumar
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Bharath Sreekumar
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Pei-Yi Chen
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Ursula Schulze-Gahmen
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Taha Y Taha
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Jennifer Hayashi
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Camille R Simoneau
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Sarah McMahon
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
| | - Peter V Lidsky
- Department of Microbiology and Immunology, University of California San Francisco, California, USA
| | - Yinghong Xiao
- Department of Microbiology and Immunology, University of California San Francisco, California, USA
| | - Peera Hemarajata
- Los Angeles County Department of Public Health, Los Angeles, California, USA
| | - Nicole M Green
- Los Angeles County Department of Public Health, Los Angeles, California, USA
| | - Alex Espinosa
- California Department of Public Health, Richmond, California, USA
| | - Chantha Kath
- California Department of Public Health, Richmond, California, USA
| | - Monica Haw
- California Department of Public Health, Richmond, California, USA
| | - John Bell
- California Department of Public Health, Richmond, California, USA
| | - Jill K Hacker
- California Department of Public Health, Richmond, California, USA
| | - Carl Hanson
- California Department of Public Health, Richmond, California, USA
| | - Debra A Wadford
- California Department of Public Health, Richmond, California, USA
| | - Carlos Anaya
- Monterey County Department of Public Health, Monterey, California, USA
| | - Donna Ferguson
- Monterey County Department of Public Health, Monterey, California, USA
| | - Liana F Lareau
- Department of Bioengineering, University of California Berkeley, Berkeley, California, USA
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
| | - Phillip A Frankino
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
| | - Haridha Shivram
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
| | - Stacia K Wyman
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
| | - Melanie Ott
- Department of Medicine, University of California San Francisco, California, USA
- Gladstone Institute of Virology, San Francisco, California, USA
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
| | - Raul Andino
- Department of Microbiology and Immunology, University of California San Francisco, California, USA
| | - Charles Y Chiu
- Department of Laboratory Medicine, University of California San Francisco, California, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, California, USA
- Department of Medicine, University of California San Francisco, California, USA
- Innovative Genomics Institute, University of California Berkeley, Berkeley, California, USA
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Reddy NP, Rothschild BM, Verrall E, Joshi A. Noninvasive measurement of acceleration at the knee joint in patients with rheumatoid arthritis and spondyloarthropathy of the knee. Ann Biomed Eng 2001; 29:1106-11. [PMID: 11853263 DOI: 10.1114/1.1424916] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Spondyloarthropathy represents a group of joint diseases with a tendency to reactive new bone formation. Spondyloarthropathy includes Reiter's syndrome, ankylosing spondylitis, and the arthropathy of inflammatory diseases (ulcerative colitis and Crohn's disease). Usually, an extensive investigation is required to distinguish spondyloarthropathy of the knee joint from rheumatoid arthritis. Recently, Reddy et al. (Ann. Biomed. Eng. 23:78-84, 1995) have developed the accelerometry technique to characterize various types of arthritis. The question remains if noninvasive acceleration measurements can be used to distinguish between spondyloarthropathy and rheumatoid arthritis. An ultraminiature accelerometer was placed on the patella, and the subject was asked to rhythmically rotate the knee from 90 flexion to full extension. Results have shown that the mean power of acceleration signal in the range of 100-500 Hz is significantly different (p<0.05) for spondyloarthropathy patients when compared to rheumatoid arthritis patients. The noninvasive accelerometry technique represents a potential tool for characterization of spondyloarthropathy patients.
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Affiliation(s)
- N P Reddy
- Biomedical Engineering Department, University of Akron, OH 44325-0302, USA.
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Das A, Reddy NP, Narayanan J. Hybrid fuzzy logic committee neural networks for recognition of swallow acceleration signals. Comput Methods Programs Biomed 2001; 64:87-99. [PMID: 11137191 DOI: 10.1016/s0169-2607(00)00099-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Biological signals are complex and often require intelligent systems for recognition of characteristic signals. In order to improve the reliability of the recognition or automated diagnostic systems, hybrid fuzzy logic committee neural networks were developed and the system was used for recognition of swallow acceleration signals from artifacts. Two sets of fuzzy logic-committee networks (FCN) each consisting of seven member networks were developed, trained and evaluated. The FCN-I was used to recognize dysphagic swallow from artifacts, and the second committee FCN-II was used to recognize normal swallow from artifacts. Several networks were trained and the best seven were recruited into each committee. Acceleration signals from the throat were bandpass filtered, and several parameters were extracted and fed to the fuzzy logic block of either FCN-I or FCN-II. The fuzzified membership values were fed to the committee of neural networks which provided the signal classification. A majority opinion of the member networks was used to arrive at the final decision. Evaluation results revealed that FCN correctly identified 16 out of 16 artifacts and 31 out of 33 dysphagic swallows. In two cases, the decision was ambiguous due to the lack of a majority opinion. FCN-II correctly identified 24 out of 24 normal swallows, and 28 out of 29 artifacts. In one case, the decision was ambiguous due to the lack of a majority opinion. The present hybrid intelligent system consisting of fuzzy logic and committee networks provides a reliable tool for recognition and classification of acceleration signals due to swallowing.
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Affiliation(s)
- A Das
- Department of Biomedical Engineering, Human Interface Laboratory, University of Akron, 4435-0302, Akron, OH, USA
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Reddy NP, Katakam A, Gupta V, Unnikrishnan R, Narayanan J, Canilang EP. Measurements of acceleration during videofluorographic evaluation of dysphagic patients. Med Eng Phys 2000; 22:405-12. [PMID: 11086251 DOI: 10.1016/s1350-4533(00)00047-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Accelerometry represents a noninvasive technique for the assessment of the swallowing mechanism. However, the underlying physiological events that give rise to the acceleration signal are poorly understood. In the present study, the acceleration signal was measured simultaneously during videofluorography examination. Preliminary results revealed that the signal occurred during laryngeal elevation and the magnitude of acceleration correlated well with the laryngeal displacement. Acceleration measurements present a potentially useful noninvasive tool.
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Affiliation(s)
- N P Reddy
- Biomedical Engineering, University of Akron, Akron, OH 44325-0302, USA.
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Reddy NP, Simcox DL, Gupta V, Motta GE, Coppenger J, Das A, Buch O. Biofeedback therapy using accelerometry for treating dysphagic patients with poor laryngeal elevation: case studies. J Rehabil Res Dev 2000; 37:361-72. [PMID: 10917268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Dysphagia, a swallowing disorder, is a problem encountered frequently in the rehabilitation of stroke and head injury patients. In normal individuals, safe passage of a food bolus into the esophagus is ensured by laryngeal elevation and closure of the airway. Inadequate laryngeal elevation can lead to aspiration, choking, and even death. The course of recovery in the current clinical practice is rather tedious. Recently, investigators have developed and evaluated the accelerometry technique for noninvasive assessment of laryngeal elevation. The purpose of the present paper is to present case reports of patients with poor laryngeal elevation treated with computerized biofeedback therapy using dynamic acceleration measurements. Acceleration was measured from the dysphagic patient during swallowing, and was dynamically displayed on the computer screen along with an acceleration signal from a typical, normal subject. The patient was asked to elicit a swallow response such that his/her acceleration display matched the display of the normal subject. Each patient had nine therapy sessions, lasting about half an hour each. All five patients improved significantly in acceleration magnitude and in swallowing function as confirmed by the videofluorography evaluation.
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Affiliation(s)
- N P Reddy
- Department of Biomedical Engineering, University of Akron, OH 44325-0302, USA.
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Abstract
Nonlinear analysis techniques are necessary to understand the complexity of the EMG. The purpose of the present study was to determine the fractal dimension of surface EMG obtained from the biceps brachii of normal subjects during isokinetic flexion-extension of the arm. The measurements were obtained with different loading conditions on the arm and for various rates of flexion-extension. Fractal dimensions of the surface EMG signals were calculated for each of these conditions. ANOVA results showed statistically significant differences between the fractal dimensions calculated for different loading conditions and rates of flexion-extensin (P < or = 0.005). Linear regression analysis showed a correlation coefficient of 0.99 between the fractal dimension and the load, and a correlation coefficient of 0.98 between the fractal dimension and the rate of flexion-extension. The results of the study show that the fractal dimension can be used along with other parameters to characterize the EMG signal.
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Affiliation(s)
- V Gupta
- Department of Biomedical Engineering, University of Akron, OH 44325-0302, USA
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Abstract
Within the sphere of dysphagia management, there is a growing need for the development of noninvasive methods of quantification of swallowing disorders. The purpose of the present investigation was to determine if surface electromyogram (EMG) at the throat could be measured during swallowing. Surface EMG was measured from 35 normal human subjects during dry and wet swallowing. The EMG signals recorded were highpass filtered using digital fourth order highpass Butterworth filter to eliminate baseline variations. Spectral analysis was performed on the filtered signals. The mean power values of the surface EMG signals were then calculated. Paired t-test between the mean power values of surface EMG during dry and wet swallowing showed a statistically significant difference (p < 0.005). The results of the study confirmed the hypothesis that surface EMG at the throat during swallowing could be measured. Mean power of surface EMG measurement provides a reliable noninvasive measure of swallowing.
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Affiliation(s)
- V Gupta
- Department of Biomedical Engineering, University of Akron, Ohio 44325-0302, USA
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Gupta V, Reddy NP. Surface electromyogram for the control of anthropomorphic teleoperator fingers. Stud Health Technol Inform 1995; 29:482-7. [PMID: 10163777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Growing importance of telesurgery has led to the need for the development of synergistic control of anthropomorphic teleoperators. Synergistic systems can be developed using direct biological control. The purpose of this study was to develop techniques for direct biocontrol of anthropomorphic teleoperators using surface electromyogram (EMG). A computer model of a two finger teleoperator was developed and controlled using surface EMG from the flexor digitorum superficialis during flexion-extension of the index finger. The results of the study revealed a linear relationship between the RMS EMG and the flexion-extension of the finger model. Therefore, surface EMG can be used as a direct biocontrol for teleoperators and in VR applications.
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Affiliation(s)
- V Gupta
- Department of Biomedical Engineering, University of Akron, OH 44325-0302, USA
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Suryanarayanan S, Reddy NP, Gupta V. An intelligent system with EMG-based joint angle estimation for telemanipulation. Stud Health Technol Inform 1995; 29:546-52. [PMID: 10163782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Bio-control of telemanipulators is being researched as an alternate control strategy. This study investigates the use of surface EMG from the biceps to predict joint angle during flexion of the arm that can be used to control an anthropomorphic telemanipulator. An intelligent system based on neural networks and fuzzy logic has been developed to use the processed surface EMG signal and predict the joint angle. The system has been tested on various angles of flexion-extension of the arm and at several speeds of flexion-extension. Preliminary results show the RMS error between the predicted angle and the actual angle to be less than 3% during training and less than 15% during testing. The technique of direct bio-control using EMG has the potential as an interface for telemanipulation applications.
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Affiliation(s)
- S Suryanarayanan
- Department of Biomedical Engineering, University of Akron, OH 44325-0302, USA
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Chu TM, Reddy NP. Stress distribution in the ankle-foot orthosis used to correct pathological gait. J Rehabil Res Dev 1995; 32:349-60. [PMID: 8770799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Abnormal motion of the ankle-foot complex presents a major problem in the rehabilitation of stroke patients. These patients often develop drop foot, a problem involving excessive and uncontrolled plantar flexion. An ankle-foot orthosis (AFO) is prescribed to constrain and inhibit this abnormal motion. The purpose of this investigation was to simulate the drop foot problem to determine the stress distribution in the orthosis. A quasi-static 3-D finite element analysis of the AFO complex was conducted using ADINA. Results confirmed the hypotheses that the maximum peak stress occurs in the neck, heel, and side-arc region of the AFO. However, the neck region of the AFO experienced the largest amount of stress. High stress concentration in the neck region observed in the present analysis is consistent with the common clinical observation that AFOs break down in the neck region.
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Affiliation(s)
- T M Chu
- Department of Mechanical Engineering, New Jersey Institute of Technology, Newark 07102, USA.
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12
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Abstract
An asymmetric 3-dimensional finite element model (FEM) of the ankle-foot orthosis (AFO) together with the ankle-foot complex was developed using the computer aided design (CAD) program PATRAN. Static analysis of normal and pathological motions of the ankle-foot complex such as the "drop-foot" problem were conducted using the FEM program ADINA. A total of 313 three dimensional solid elements and 10 truss elements were used. Heel strike and toe-off condition were simulated. Results revealed that the peak compressive stress (1.6 MPa) in the AFO model occurred in the heel regions of the AFO and the maximum tensile stress (0.8 MPa) occurred in the neck region of the AFO during toe-off. Parametric analyses revealed that the model was sensitive to the elastic moduli of the AFO and of the soft tissue, but was relatively insensitive to the ligament stiffness. The results confirmed the hypothesis that peak stresses in the orthosis occur in the heal and neck regions of the orthosis.
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Affiliation(s)
- T M Chu
- Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark 07102, USA
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13
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Abstract
Identification and classification of the dysphagic patient at risk of aspiration is important from a clinical point of view. Recently, we have developed techniques to quantify various biomechanical parameters that characterize the dysphagic patient, and have developed an expert system to classify patients based on these measurements. The purpose of the present investigation was to develop a fuzzy logic diagnosis system for classification of the patient with pharyngeal dysphagia into four categories of risk for aspiration. Non-invasive acceleration and swallow pressure measurements were obtained and five parameters were extracted from these measurements. A set of membership functions were defined for each parameter. The measured parameter values were fuzzified and fed to a rule base which provided a set of output membership values corresponding to each of the categories. The set of output values were defuzzified to obtain a continuous measure of classification. The fuzzy system was evaluated using the data obtained from 22 subjects. There was a complete agreement between the fuzzy system classification and the clinician's classification in 18 of the 22 patients. The fuzzy system overestimated the risk by half a category in two patients and underestimated by half a category in two patients. The fuzzy logic diagnosis system, together with the biomechanical measures, provides a tool for continued patient assessment on a daily basis to identify the patient who needs further videofluorography examination.
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Affiliation(s)
- S Suryanarayanan
- Department of Biomedical Engineering, University of Akron, OH 44325-0302, USA
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14
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Abstract
Proper understanding of the mechanisms of fluid absorption and flow through the terminal lymphatics is essential for the control of several pathological conditions such as edema, bedsores and cancer. A mathematical model of the terminal lymphatics was developed using the principles of mechanics. Computer simulation results substantiate the hypothesis that fluid absorption and flow through the terminal lymphatics occur due to suction mechanisms of the adjacent contractile lymphatic segments and due to periodic fluctuations in the interstitial fluid pressure. In addition, the results suggested that increasing the length of a terminal lymphatic vessel beyond a certain limit does not cause further increase in fluid flow into the terminal lymphatic.
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Affiliation(s)
- N P Reddy
- Department of Biomedical Engineering, University of Akron, Ohio 44325-0302, USA
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15
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Reddy NP, Rothschild BM, Mandal M, Gupta V, Suryanarayanan S. Noninvasive acceleration measurements to characterize knee arthritis and chondromalacia. Ann Biomed Eng 1995; 23:78-84. [PMID: 7762885 DOI: 10.1007/bf02368303] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Devising techniques and instrumentation for early detection of knee arthritis and chondromalacia presents a challenge in the domain of biomedical engineering. The purpose of the present investigation was to characterize normal knees and knees affected by osteoarthritis, rheumatoid arthritis, and chondromalacia using a set of noninvasive acceleration measurements. Ultraminiature accelerometers were placed on the skin over the patella in four groups of subjects, and acceleration measurements were obtained during leg rotation. Acceleration measurements were significantly different in the four groups of subjects in the time and frequency domains. Power spectral analysis revealed that the average power was significantly different for these groups over a 100-500 Hz range. Noninvasive acceleration measurements can characterize the normal, arthritis, and chondromalacia knees. However, a study on a larger group of subjects is indicated.
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Affiliation(s)
- N P Reddy
- Biomedical Engineering Department, University of Akron, OH 44325-0302, USA
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16
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Reddy NP, Thomas R, Canilang EP, Casterline J. Toward classification of dysphagic patients using biomechanical measurements. J Rehabil Res Dev 1994; 31:335-344. [PMID: 7869281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Identification of a patient at risk of aspiration is a major problem in the rehabilitation of the dysphagic patient. The present methods of diagnosis are based on clinical evaluation or videofluorography or fiberoptic endoscopic examination of swallowing (FEES). Recently, we developed biomechanical techniques for noninvasive quantitative assessment of the dysphagic patient. The purpose of the present investigation was to assess the clinical validity of the technique. In a double-blind study, both biomechanical test results and videofluorography (including bedside evaluation) results were used to independently classify the patients into four categories of risk for aspiration. Of the 36 patients studied, there was complete agreement between the biomechanical and clinical classifications in 21 patients. In 11 patients, the biomechanical technique overestimated the risk by one category, and underestimated the risk by one category in four patients. The biomechanical technique presents a useful tool for continued patient assessment; however, further studies are needed.
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Affiliation(s)
- N P Reddy
- Department of Biomedical Engineering, University of Akron, OH 44325-0302
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17
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Sukthankar SM, Reddy NP, Canilang EP, Stephenson L, Thomas R. Design and development of portable biofeedback systems for use in oral dysphagia rehabilitation. Med Eng Phys 1994; 16:430-5. [PMID: 7952683 DOI: 10.1016/1350-4533(90)90011-v] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The management of dysphagia presents a major problem in the comprehensive rehabilitation of stroke and head injury patients. Dysphagia is a disorder of the swallowing process. Oral dysphagia refers to abnormalities in the oral phase of the swallowing mechanism. The oral phase of the swallowing mechanism is important for the proper triggering of the swallowing reflex. Current techniques in oral dysphagia rehabilitation include oro-motor exercises using tongue depressors and mouth-care swabs. There is thus a need for a better therapeutic method for oral dysphagia. The purpose of this paper is to report the development of audio-visual biofeedback devices for treating oral dysphagia. Portable biofeedback devices rendering feedback of biomechanical parameters characterizing the oral phase were developed and evaluated in preliminary clinical trials. A patient progress index (PPI) was developed and used to quantify the overall patient progress. The devices demonstrated good patient acceptability.
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Affiliation(s)
- S M Sukthankar
- Department of Biomedical Engineering, University of Akron, OH 44325-0302
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18
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Abstract
A spatially lumped mathematical model was developed and used for a computer simulation of the neonate-incubator system for parametric analysis of the factors that influence neonatal thermo-regulation. The simulation examined the effects of the following parameters: (1) size of the infant; (2) respiratory rate; (3) metabolic rate; (4) heart rate; (5) thermal properties of the mattress; (6) specific heat capacity of the incubator wall; (7) air flow rate; (8) heater control mechanisms.
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Affiliation(s)
- B N Simon
- Department of Biomedical Engineering, University of Akron, OH 44325
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19
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Abstract
Mechanical stresses developed in the tissue during sitting or reclining could cause bedsores in paralyzed individuals. Cushions are usually prescribed to redistribute the stresses. Two two-dimensional physical models of the buttock were developed and used to study whether the stress distribution is different with round- and flat-base bone core geometries and to find out whether the relative cushion responses are dependent on loading direction and bone core geometries. In these models, PVC gel simulated the soft tissue and a wooden core simulated the bony prominence. One model had a round-base core and the other had a flat-base bone core. A grid etched on the model allowed strain measurements, and stress calculations. The sharp-base bone core model generated large regions of high shear stress during vertical and inclined loading. However, the round-base core produced maximum compressive stress during vertical loading. The relative cushion responses were dependent on bone core geometry and loading direction.
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Affiliation(s)
- R S Candadai
- Biomedical Engineering Department University of Akron, OH 44325
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20
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Abstract
A lumped parameter mathematical model to describe the propulsion of blood in the splanchnic circulation was developed by integrating the principles of mechanics and physiology. A set of governing equations by derived by specifically considering the contractility of the portal vein, hepatic vein, liver sinusoids, and of the draining lymphatics. These equations were then simulated on a computer. The present simulation results substantiate previous experimental observations that hepatic venous pressure leads to portal hypertension and increased liver interstitial fluid volume.
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Affiliation(s)
- T M Chu
- Department of Biomedical Engineering, University of Akron, Ohio 44325
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21
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Reddy NP, Canilang EP, Casterline J, Rane MB, Joshi AM, Thomas R, Candadai R. Noninvasive acceleration measurements to characterize the pharyngeal phase of swallowing. J Biomed Eng 1991; 13:379-83. [PMID: 1795505 DOI: 10.1016/0141-5425(91)90018-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Swallowing disorder (dysphagia) presents a major problem in the rehabilitation of stroke and head injured patients. In the present investigation, a new technique is developed for noninvasive assessment of the pharyngeal phase of the swallowing mechanism. Acceleration was measured with two ultra-miniature accelerometers placed on the skin over the throat. Simultaneously, the swallow suction pressure was monitored. Swallowing in normal individuals gave rise to a characteristic acceleration pattern which was quite reproducible, and was in phase with the swallow pressure. In dysphagic patients, the acceleration response was either absent or significantly delayed. The accelerometry technique provides a tool for continuing patient assessment and demonstrating the clinical improvements.
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Affiliation(s)
- N P Reddy
- Biomedical Engineering Department, University of Akron, OH 44325
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22
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Abstract
Dysphagia is a disorder of the swallowing mechanism and presents a major problem in the rehabilitation of stroke patients and head injured patients. The authors have identified several biomechanical parameters that characterize the oral musculature and have developed techniques to quantify these parameters in normal and dysphagic patients. These parameters include lip closure pressure, lip interface shear force, tongue thrust, and swallow pressure. Significant differences were found in each of these parameters measured in normal and dysphagic patients. The quantitative measurements may aid the physician in choosing the appropriate therapy during the course of recovery.
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Affiliation(s)
- N P Reddy
- Department of Biomedical Engineering, University of Akron, OH 44325
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23
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Reddy NP, Askew MJ, Baniewicz FM, Melby A, Fuller KA, Steurer PA, Herr JE, Sheffer DE. A technique for quantitative assessment of three-dimensional motion with applications to human joints. Proc Inst Mech Eng H 1989; 203:207-13. [PMID: 2701958 DOI: 10.1243/pime_proc_1989_203_041_01] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A technique is developed for quantitative measurement of general three-dimensional motion, and this technique is applied to the kinematics of anatomical joints. The spatial locations of three orthogonal points representing coordinate frames on each member of the joint are measured during motion of the joint by photo encoders of a three-dimensional mechanical pointer. Kinematic calculations are used to derive, from the experimentally collected data, the six orthogonal components of the motion of one member relative to the other. The accuracy of this technique is presented. Applications to the knee and ankle are discussed.
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24
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Reddy NP. Biomedical engineering education and technology transfer. IEEE Eng Med Biol Mag 1989; 8:8-9. [PMID: 18238297 DOI: 10.1109/51.32397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The author examines the role of a biomedical engineering educator in the technology transfer in health care delivery. He identifies the problem as lack of proper communication between the physician and the engineer and suggests ways to remedy it. He discusses the role that the biomedical engineering educator can play in enhancing the acceptability of technological. He concludes that technology transfer will proceed as the normal course of events only when the biomedical engineer establishes him/herself as a part of the health care delivery team.
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Affiliation(s)
- N P Reddy
- Dept. of Biomed. Eng., Akron Univ., OH
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25
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Abstract
Cellular dynamics play an important role in bone remodelling. The mesenchymal cells, osteoclasts, osteoblasts and osteocytes are the four types of bone cells, which mediate bone remodelling involving bone formation and resorption throughout the human life-span. A stochastic compartmental model of bone cells is formulated in the present analysis assuming these four types of cells to be in four distinct compartments. The cumulant generating function is first derived using the transition parameters for intercompartmental diffusion. Equations for the mean, variance and covariance for the number density of these cells are then derived from the partial differential equation for the cumulant generating function. The simulation results are consistent with previous experimental observations.
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Affiliation(s)
- N P Reddy
- Biomedical Engineering Department, University of Akron, OH 44325
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26
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Reddy NP, Kesavan SK. Perspectives in non-traditional biofluid mechanics. Eng Med 1987; 16:43-5. [PMID: 3556715 DOI: 10.1243/emed_jour_1987_016_010_02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Although biofluid mechanics has been studied extensively, most of the studies have concentrated on cardiovascular biofluid mechanics. Very little attention has been paid to the other important problems in biomedicine. Several non-traditional areas which offer interesting and challenging problems remain unexplored, and fluid mechanics can have fruitful interaction with these disciplines. This paper brings into focus some of the important areas of biomedicine which offer fertile grounds for biofluid mechanics studies.
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27
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Kesavan SK, Reddy NP, Yazdani-Ardakani S. Experimental measurement of impact pressures delivered by oral water irrigation devices. IEEE Trans Biomed Eng 1986; 33:898-900. [PMID: 3759125 DOI: 10.1109/tbme.1986.325788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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28
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Reddy NP, Kesavan SK. A simple coding method for computer storage and handling of drug information. Int J Biomed Comput 1986; 18:131-4. [PMID: 3699917 DOI: 10.1016/0020-7101(86)90054-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An ever-growing body of knowledge in pharmacology has created a need for devising improved methods for handling drug information. We have developed an eleven digit comprehensive cardiovascular number to represent vital information on the effects of a drug on the cardiovascular system. Each digit of the number signifies an important cardiovascular phenomenon, and can vary from 0 to 9. This coding method provides a simple technique for computer handling of vital information on the effects of pharmacoactive agents in a semi-quantitative manner. Using this procedure, similar numbers for neuromuscular and immune systems can be easily developed.
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29
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Abstract
Oral water irrigation devices (WIDs) are widely used for oral physiotherapy in homes and dental clinics throughout the world. A major area of concern in the use of WIDs has been the possibility of injury to the sulcular epithelium and underlying tissue. There are several documented clinical cases of tissue injury with the use of WIDs. The existing WIDs exert excessive pressures on the sulcular epithelium. Although it is known that the high jet impact pressures exerted by the WIDs cause the tissue damage, the underlying damage mechanisms are poorly understood. The damage to the sulcular epithelium and underlying tissue is mediated through several physiological and micromechanical processes and includes, among others, the following damage mechanisms: pressure-induced, diffusion-mediated, deposition of bacteria and toxins into the underlying tissue, damage to the collagen network integrity in the tissue, damage to the blood and lymphatic microcirculation, especially damage to the anchoring filaments attached to the terminal lymphatic wall, and direct mechanical damage due to abnormal shear forces induced by the jet. All these damage processes could lead to tissue necrosis.
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30
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Abstract
Water irrigation devices (WIDs) are widely used in homes and dental offices across the country for oral hygiene. There have been several reported cases of tissue damage with the use of these devices. In the present investigation, two commercially available oral water irrigation devices were evaluated using bioengineering principles. The flow rates delivered by these devices were measured at different control settings. The exit jet velocities and the jet impact thrust were subsequently calculated. Both of the tested commercial oral water irrigation devices were found to exert abnormally high thrust which could cause serious damage to the sulcular epithelium and the underlying tissues. These pressures are far in excess of the pressure intensity necessary to perform the cleaning action. Moreover, the existing designs using reciprocating pumps are unsafe and are potentially dangerous, particularly with small diameter tips. Low operating pressures and the use of centrifugal pumps are recommended.
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31
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Reddy NP, Palmieri V, Cochran GV. Evaluation of transducer performance for buttock-cushion interface pressure measurements. J Rehabil Res Dev 1984; 21:43-50. [PMID: 6527289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
To assess the performance of transducers used clinically to measure pressure at the skin-cushion interface of seated patients, transducers were placed between slabs of gel and/or foam materials compressed between platens. The recorded pressures consistently exceeded the nominal pressures calculated using the surface area of the slabs. This overestimation, observed in both miniature diaphragm transducers and air cell transducers, appeared to result from preferential loading of the transducer due to insufficient structural compliance in the environs. On the other hand, air cell transducers placed at a skin-foam interface beneath the thighs of human subjects gave readings which agreed closely with subcutaneous tissue pressure measurements obtained from a wick catheter inserted at the same location. These results suggest that, although pressure measurements are prone to error due to load sharing, results obtained clinically from subjects on soft cushions are reasonably accurate because of the high compliance of human soft tissue and the foam. Under low loads these distribute the pressure equitably and avoid concentrations of load on the transducer.
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33
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Abstract
Mechanical stress states that develop in the buttock during sitting may exceed tissue tolerance and lead to decubitus ulcer formation in susceptible patients, such as those with spinal cord injury. The danger of this complication can be reduced by using suitable cushions to minimize stress magnitudes and gradients within soft tissues. In this investigation, a two-dimensional physical model of the buttock-cushion system was developed to aid in cushion design. The model consists of PVC gel simulating flesh, cast around a wooden core simulating the ischium bone. A grid etched on the gel permits measurement of strains via photographs of the undeformed and deformed model buttock supported by various cushion materials. The displacement field is analyzed, using a finite strain theory and a strain energy function, to obtain the "tissue stresses'. In this manner, the performances of five clinically used cushion materials were compared with respect to the high stress regimes developed in the model buttock.
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34
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Abstract
Interstitial fluid pressure (IFP) distribution generated as a result of externally applied pressure (EAP) may play an important role in the etiology of decubitus ulcers. In the forelimbs of 10 thiopental sodium-anesthetized Yorkshire pigs, weighing 16-20 kg, we placed wick catheters 2-5 mm below the skin. After equilibration, we applied a pediatric cuff and added EAP. With zero EAP, the IFP was -3.9 +/- 1.4 (SD) mmHg. In each case of EAP, IFP as measured with the wick catheter increased and reached a plateau within 10-15 min. In normal tissues, IFP reached approximately 65-75% of EAP. When we created an edematous condition by preinfusing with excess saline, IFP was found to reach 100% of EAP. The total normal stress in the tissue, generated as a result of external cuff pressure, can be considered as a sum of interstitial fluid pressure and extranormal stress. Integrity of the fibrous network and pore fraction may be important in transmitting pressure to the fluid.
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36
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Reddy NP, Krouskop TA. Modelling the cell-mediated immunity in homograft refection. Int J Biomed Comput 1978; 9:327-40. [PMID: 750500 DOI: 10.1016/0020-7101(78)90041-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Lymphocytes which become sensitised at the periphery travel to the regional lymph nodes where they initiate an immunological response by increasing the production of immuno-competent lymphocytes. These lymphocytes migrate into the tissues via the blood stream and bring about the destruction of target cells. These notions, in the present analysis, are translated into a simple mathematical model. The model specifically considers the lymphocyte memory and increased secondary response.
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Abstract
Understanding of the etiology of decubitus ulcer formation is fragmentary and the existing literature contains much experimental data that are inconsistent with the idea that pressure sore formation is due extensively to depriving a tissue region of blood. In fact, there is substantial data that illustrate that tissue can remain viable for very extended lengths of time, up to 13 hours, when subjected to externally applied pressures that collapse the blood microvasculature in a region. Based on these observations and on studies done in this laboratory on lymph propulsion and pressure sore prevention, an hypothesis has been formulated that is consistent with the published data and with clinical observations. The hypothesis states that a major contributing factor to pressure sores is the tissue necrosis that is caused by the accumulation of anaerobic metabolic waste products due to occlusion of the lymph vessels.
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40
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Reddy NP, Krouskop TA, Newell PH. Development of lymph hypertension during lymphatic occlusion. Lymphology 1975; 8:105-9. [PMID: 1202296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effects of obstruction of lymph flow on the intralymphatic pressure are studied through a mathematical model using a digital computer and intralymphatic pressure was observed to increase.
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42
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43
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Abstract
The principles of mechanics and the current notions of lymphatic physiology are integrated into a simple mathematical model of a lymphatic vessel which establishes a theoretical base for lymph propulsion in the lymphatic system. The model specifically considers the active and passive contractilities of the lymphatics. The model is simulated on a digital computer. The pressure and flow patterns derived from the model are consistent with the currently available experimental data.
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Reddy NP. Brief communications. Local hematocrit as a factor in autoregulation of renal blood flow. Microvasc Res 1973; 6:235-7. [PMID: 4748023 DOI: 10.1016/0026-2862(73)90023-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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