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Diekman CO, Thomas PJ, Wilson CG. COVID-19 and silent hypoxemia in a minimal closed-loop model of the respiratory rhythm generator. BIOLOGICAL CYBERNETICS 2024:10.1007/s00422-024-00989-w. [PMID: 38884785 DOI: 10.1007/s00422-024-00989-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 03/28/2024] [Indexed: 06/18/2024]
Abstract
Silent hypoxemia, or "happy hypoxia," is a puzzling phenomenon in which patients who have contracted COVID-19 exhibit very low oxygen saturation ( SaO 2 < 80%) but do not experience discomfort in breathing. The mechanism by which this blunted response to hypoxia occurs is unknown. We have previously shown that a computational model of the respiratory neural network (Diekman et al. in J Neurophysiol 118(4):2194-2215, 2017) can be used to test hypotheses focused on changes in chemosensory inputs to the central pattern generator (CPG). We hypothesize that altered chemosensory function at the level of the carotid bodies and/or the nucleus tractus solitarii are responsible for the blunted response to hypoxia. Here, we use our model to explore this hypothesis by altering the properties of the gain function representing oxygen sensing inputs to the CPG. We then vary other parameters in the model and show that oxygen carrying capacity is the most salient factor for producing silent hypoxemia. We call for clinicians to measure hematocrit as a clinical index of altered physiology in response to COVID-19 infection.
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Affiliation(s)
- Casey O Diekman
- Department of Mathematical Sciences, New Jersey Institute of Technology, University Heights, Newark, NJ, 07102, USA.
| | - Peter J Thomas
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA
| | - Christopher G Wilson
- Department of Pediatrics and Basic Sciences, Lawrence D. Longo, MD Center for Perinatal Biology, Loma Linda University, 11223 Campus St, Loma Linda, CA, 92350, USA
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2
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Li S, Zhang Z, Wang L, Yan X, Jiang Y, Yu L. Diagnostic significance of peripheral blood indices for eosinophilic chronic rhinosinusitis in Chinese adults. Eur Arch Otorhinolaryngol 2024; 281:1337-1345. [PMID: 37938374 DOI: 10.1007/s00405-023-08324-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 10/27/2023] [Indexed: 11/09/2023]
Abstract
OBJECTIVE Eosinophilic chronic rhinosinusitis (eCRS) is a refractory subtype of CRS. This study aimed to compare the differences in clinical features and peripheral blood indices between eCRS and non-eCRS Chinese patients and identify the predictive factors for eCRS. METHODS In this study, a total of 1352 patients with CRS were enrolled and divided into eCRS and non-eCRS groups based on the degree of eosinophilic infiltration in histopathology, and their demographic and clinical characteristics, as well as peripheral blood indices, were compared. Logistic regression analysis was used to identify the factors associated with eCRS, and the optimal cut-off values of predictors were determined using subject working curves. RESULTS As compared to those in the non-eCRS group patients, the proportion of males, age, proportion of smokers, peripheral blood eosinophil count, and erythrocyte count were significantly higher, while the peripheral blood neutrophil count, platelet count, neutrophil/lymphocyte count ratio (NLR), platelet/lymphocyte count ratio (PLR), and neutrophil × platelet/lymphocyte count ratio (SII index) were significantly lower in the eCRS group patients. Logistic regression analysis showed that age, peripheral blood neutrophil count, eosinophil count, and platelet count were independent predictors of eCRS, and eosinophil count > 2.05 × 108/L could be used as a diagnostic marker for eCRS with a sensitivity and specificity of 87.1% and 78.3%, respectively. CONCLUSIONS There were significant differences in the clinical features of eCRS and non-eCRS patients. Peripheral blood eosinophil count could early and more accurately predict eCRS.
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Affiliation(s)
- Shunke Li
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China
| | - Zengxiao Zhang
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China
| | - Lin Wang
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China
| | - Xudong Yan
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China
| | - Yan Jiang
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China.
| | - Longgang Yu
- Department of Otorhinolaryngology Head and Neck Surgery, The Affiliated Hospital of Qingdao University, No. 59, Haier Road, Laoshan District, Qingdao, 266003, China.
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3
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Song J, Sundar KM, Horvathova M, Gangaraju R, Indrak K, Christensen RD, Genzor S, Lundby C, Divoky V, Ganz T, Prchal JT. Increased blood reactive oxygen species and hepcidin in obstructive sleep apnea precludes expected erythrocytosis. Am J Hematol 2023; 98:1265-1276. [PMID: 37350302 DOI: 10.1002/ajh.26992] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 05/18/2023] [Indexed: 06/24/2023]
Abstract
Obstructive sleep apnea (OSA) causes intermittent hypoxia during sleep. Hypoxia predictably initiates an increase in the blood hemoglobin concentration (Hb); yet in our analysis of 527 patients with OSA, >98% did not have an elevated Hb. To understand why patients with OSA do not develop secondary erythrocytosis due to intermittent hypoxia, we first hypothesized that erythrocytosis occurs in these patients, but is masked by a concomitant increase in plasma volume. However, we excluded that explanation by finding that the red cell mass was normal (measured by radionuclide labeling of erythrocytes and carbon monoxide inhalation). We next studied 45 patients with OSA before and after applying continuous positive airway pressure (CPAP). We found accelerated erythropoiesis in these patients (increased erythropoietin and reticulocytosis), but it was offset by neocytolysis (lysis of erythrocytes newly generated in hypoxia upon return to normoxia). Parameters of neocytolysis included increased reactive oxygen species from expanded reticulocytes' mitochondria. The antioxidant catalase was also downregulated in these cells from hypoxia-stimulated microRNA-21. In addition, inflammation-induced hepcidin limited iron availability for erythropoiesis. After CPAP, some of these intermediaries diminished but Hb did not change. We conclude that in OSA, the absence of significant increase in red cell mass is integral to the pathogenesis, and results from hemolysis via neocytolysis combined with inflammation-mediated suppression of erythropoiesis.
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Affiliation(s)
- Jihyun Song
- Division of Hematology, University of Utah, Salt Lake City, Utah, USA
| | - Krishna M Sundar
- Division of Pulmonary and Critical Care Medicine, University of Utah, Salt Lake City, Utah, USA
| | - Monika Horvathova
- Department of Biology, Palacky University Olomouc, Olomouc, Czech Republic
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, Olomouc, Czech Republic
| | - Radhika Gangaraju
- Division of Hematology, University of Utah, Salt Lake City, Utah, USA
- Institute for Cancer Outcomes and Survivorship, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Karel Indrak
- Department of Hemato-Oncology, Palacky University and University Hospital Olomouc (PUUHO), Olomouc, Czech Republic
| | | | - Samuel Genzor
- Department of Pulmonary Diseases and Tuberculosis, Faculty of Medicine and Dentistry, PUUHO, Olomouc, Czech Republic
| | - Carsten Lundby
- Centre for Physical Activity Research, Copenhagen, Denmark
| | - Vladimir Divoky
- Department of Biology, Palacky University Olomouc, Olomouc, Czech Republic
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, Olomouc, Czech Republic
| | - Tomas Ganz
- Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Josef T Prchal
- Division of Hematology, University of Utah, Salt Lake City, Utah, USA
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Diekman CO, Thomas PJ, Wilson CG. COVID-19 and silent hypoxemia in a minimal closed-loop model of the respiratory rhythm generator. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.19.536507. [PMID: 37131753 PMCID: PMC10153159 DOI: 10.1101/2023.04.19.536507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Silent hypoxemia, or 'happy hypoxia', is a puzzling phenomenon in which patients who have contracted COVID-19 exhibit very low oxygen saturation (SaO2 < 80%) but do not experience discomfort in breathing. The mechanism by which this blunted response to hypoxia occurs is unknown. We have previously shown that a computational model (Diekman et al., 2017, J. Neurophysiol) of the respiratory neural network can be used to test hypotheses focused on changes in chemosensory inputs to the central pattern generator (CPG). We hypothesize that altered chemosensory function at the level of the carotid bodies and/or the nucleus tractus solitarii are responsible for the blunted response to hypoxia. Here, we use our model to explore this hypothesis by altering the properties of the gain function representing oxygen sensing inputs to the CPG. We then vary other parameters in the model and show that oxygen carrying capacity is the most salient factor for producing silent hypoxemia. We call for clinicians to measure hematocrit as a clinical index of altered physiology in response to COVID-19 infection.
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Affiliation(s)
- Casey O Diekman
- Department of Mathematical Sciences, New Jersey Institute of Technology, University Heights, Newark NJ 07102
| | - Peter J Thomas
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland OH 44106
| | - Christopher G Wilson
- Department of Pediatrics & Basic Sciences, Loma Linda University, Lawrence D. Longo, MD Center for Perinatal Biology, 11223 Campus St, Loma Linda CA 92350
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Caballero-Eraso C, Colinas O, Sobrino V, González-Montelongo R, Cabeza JM, Gao L, Pardal R, López-Barneo J, Ortega-Sáenz P. Rearrangement of cell types in the rat carotid body neurogenic niche induced by chronic intermittent hypoxia. J Physiol 2023; 601:1017-1036. [PMID: 36647759 DOI: 10.1113/jp283897] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 01/12/2023] [Indexed: 01/18/2023] Open
Abstract
The carotid body (CB) is a prototypical acute oxygen (O2 )-sensing organ that mediates reflex hyperventilation and increased cardiac output in response to hypoxaemia. CB overactivation, secondary to the repeated stimulation produced by the recurrent episodes of intermittent hypoxia, is believed to contribute to the pathogenesis of sympathetic hyperactivity present in sleep apnoea patients. Although CB functional plasticity induced by chronic intermittent hypoxia (CIH) has been demonstrated, the underlying mechanisms are not fully elucidated. Here, we show that CIH induces a small increase in CB volume and rearrangement of cell types in the CB, characterized by a mobilization of immature quiescent neuroblasts, which enter a process of differentiation into mature, O2 -sensing and neuron-like, chemoreceptor glomus cells. Prospective isolation of individual cell classes has allowed us to show that maturation of CB neuroblasts is paralleled by an upregulation in the expression of specific glomus cell genes involved in acute O2 -sensing. CIH enhances mitochondrial responsiveness to hypoxia in maturing neuroblasts as well as in glomus cells. These data provide novel perspectives on the pathogenesis of CB-mediated sympathetic overflow that may lead to the development of new pharmacological strategies of potential applicability in sleep apnoea patients. KEY POINTS: Obstructive sleep apnoea is a frequent condition in the human population that predisposes to severe cardiovascular and metabolic alterations. Activation of the carotid body, the main arterial oxygen-sensing chemoreceptor, by repeated episodes of hypoxaemia induces exacerbation of the carotid body-mediated chemoreflex and contributes to sympathetic overflow characteristic of sleep apnoea patients. In rats, chronic intermittent hypoxaemia induces fast neurogenesis in the carotid body with rapid activation of neuroblasts, which enter a process of proliferation and maturation into O2 -sensing chemoreceptor glomus cells. Maturing carotid body neuroblasts and glomus cells exposed to chronic intermittent hypoxia upregulate genes involved in acute O2 sensing and enhance mitochondrial responsiveness to hypoxia. These findings provide novel perspectives on the pathogenesis of carotid body-mediated sympathetic hyperactivation. Pharmacological modulation of carotid body fast neurogenesis could help to ameliorate the deleterious effects of chronic intermittent hypoxaemia in sleep apnoea patients.
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Affiliation(s)
- Candela Caballero-Eraso
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Unidad Médico Quirúrgica de Enfermedades Respiratorias, Hospital Universitario Virgen del Rocío/IBIS, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Respiratorias (CIBERES), Madrid, Spain
| | - Olaia Colinas
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Verónica Sobrino
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain
| | - Rafaela González-Montelongo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain
| | - José María Cabeza
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain
| | - Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Ricardo Pardal
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
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Martelli V, Carelli E, Tomlinson GA, Orchanian-Cheff A, Kuo KHM, Lyons OD, Ryan CM. Prevalence of elevated hemoglobin and hematocrit levels in patients with obstructive sleep apnea and the impact of treatment with continuous positive airway pressure: a meta-analysis. HEMATOLOGY (AMSTERDAM, NETHERLANDS) 2022; 27:889-901. [PMID: 35962574 DOI: 10.1080/16078454.2022.2109346] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES Obstructive sleep apnea (OSA) is reported to be a cause of secondary polycythemia. The present study (i) reviewed the literature reporting the prevalence of secondary polycythemia in patients with OSA and (ii) determined the effect of continuous positive airway pressure (CPAP) therapy on hemoglobin and hematocrit levels in patients with OSA. METHODS We searched MEDLINE, Embase and Cochrane for studies of adult patients with OSA that reported hemoglobin and/or hematocrit levels. We performed summary estimates of (i) polycythemia prevalence and a subgroup analysis according to OSA severity, and (ii) change in hemoglobin and hematocrit levels following treatment with CPAP. RESULTS Synthesis of seven studies including 3,654 patients revealed an overall polycythemia prevalence of 2% (95% CI 1-4%); 2% (95% CI 1-3%) in mild-to moderate and 6 % (95% CI 3-12%) in severe OSA. In the pooled analysis of ten single-arm trials including 434 patients, CPAP treatment reduced hemoglobin by 3.76 g/L (95% CI -4.73 to -2.80 g/L). Similarly, pooled analysis of ten single-arm trials including 356 patients without baseline polycythemia showed that CPAP treatment reduced hematocrit by 1.1% (95% CI -1.4 to -0.9%). CONCLUSION Our pooled analysis supports an increased prevalence of secondary polycythemia in OSA. This estimated prevalence is likely underestimated due to the change in the polycythemia diagnostic criteria in 2016. Future randomized controlled trials are needed to evaluate the effect of CPAP in patients with baseline polycythemia. HIGHLIGHTS Pooled analysis shows OSA is associated with an increased prevalence of secondary polycythemiaPrevalence of polycythemia is greater in severe OSACPAP treatment for OSA reduces both the hemoglobin and hematocrit.
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Affiliation(s)
| | - Eric Carelli
- Department of Medicine, University of Toronto, Toronto, Canada
| | - George A Tomlinson
- Toronto General Hospital Research Institute, Toronto, Canada.,Institute for Health Policy, Management, and Evaluation, University of Toronto, Toronto, Canada
| | - Ani Orchanian-Cheff
- Library and Information Services, University Health Network, Toronto, Canada
| | - Kevin H M Kuo
- Department of Medicine, University of Toronto, Toronto, Canada.,Division of Medical Oncology & Hematology, University Health Network, Toronto, Canada
| | - Owen D Lyons
- Department of Medicine, University of Toronto, Toronto, Canada.,Division of Respirology, Women's College Hospital, Toronto, Canada.,Sleep Research Laboratory, Toronto Rehabilitation Institute, Toronto, Canada.,Division of Respirology, University Health Network, Toronto, Canada
| | - Clodagh M Ryan
- Toronto General Hospital Research Institute, Toronto, Canada.,Sleep Research Laboratory, Toronto Rehabilitation Institute, Toronto, Canada.,Division of Respirology, University Health Network, Toronto, Canada
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