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Yao Z, Zhao C, Zhang Y, Fan X, Zhao D, Gao L. Gastroesophageal reflux disease increases the risk of essential hypertension: results from the Nationwide Readmission Database and Mendelian randomization analysis. Postgrad Med J 2024; 100:242-251. [PMID: 38223944 DOI: 10.1093/postmj/qgad123] [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: 09/12/2023] [Revised: 11/03/2023] [Accepted: 11/17/2023] [Indexed: 01/16/2024]
Abstract
BACKGROUND The link between gastroesophageal reflux disease (GERD) and essential hypertension (EH) and its causal nature remains controversial. Our study examined the connection between GERD and the risk of hypertension and assessed further whether this correlation has a causal relationship. METHODS First, we utilized the National Readmission Database including 14 422 183 participants to conduct an observational study. Dividing the population into GERD and non-GERD groups, we investigated the correlation between GERD and EH using multivariate logistic regression. Next, bidirectional two-sample Mendelian randomization was adopted. The summary statistics for GERD were obtained from a published genome-wide association study including 78 707 cases and 288 734 controls. We collected summary statistics for hypertension containing 70 651 cases and 223 663 controls from the FinnGen consortium. We assessed causality primarily by the inverse-variance weighted method with validation by four other Mendelian randomization approaches as well as an array of sensitivity analyses. RESULTS In the unadjusted model, GERD patients had a higher risk of EH than the non-GERD group, regardless of gender (odds ratio, 1.43; 95% confidence interval: 1.42-1.43; P < .001). Further adjusting for critical confounders did not change this association. For Mendelian randomization, we found that genetically predicted GERD was causally linked to an enhanced risk of EH in inverse-variance weighted technique (odds ratio, 1.52; 95% confidence interval: 1.39-1.67; P = 3.51 × 10-18); conversely, EH did not raise the risk of GERD causally. CONCLUSIONS GERD is a causal risk factor for EH. Further research is required to probe the mechanism underlying this causal connection.
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Affiliation(s)
- Zhenyu Yao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
- Shandong Clinical Research Center of Diabetes and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Institute of Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- "Chuangxin China" Innovation Base of Stem Cell and Gene Therapy for Endocrine Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Laboratory of Prevention and Control for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Research Center of Stem Cell and Gene Therapy for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
| | - Chunhui Zhao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
- Shandong Clinical Research Center of Diabetes and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Institute of Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- "Chuangxin China" Innovation Base of Stem Cell and Gene Therapy for Endocrine Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Laboratory of Prevention and Control for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Research Center of Stem Cell and Gene Therapy for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
| | - Yue Zhang
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
- Shandong Clinical Research Center of Diabetes and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Institute of Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- "Chuangxin China" Innovation Base of Stem Cell and Gene Therapy for Endocrine Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Laboratory of Prevention and Control for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Research Center of Stem Cell and Gene Therapy for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
| | - Xiude Fan
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
- Shandong Clinical Research Center of Diabetes and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Institute of Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- "Chuangxin China" Innovation Base of Stem Cell and Gene Therapy for Endocrine Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Laboratory of Prevention and Control for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Research Center of Stem Cell and Gene Therapy for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
| | - Dong Zhao
- Center for Endocrine Metabolism and Immune Diseases, Beijing Luhe Hospital, Capital Medical University, Beijing 101149, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing 101149, China
| | - Ling Gao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
- Shandong Clinical Research Center of Diabetes and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Institute of Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- "Chuangxin China" Innovation Base of Stem Cell and Gene Therapy for Endocrine Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Laboratory of Prevention and Control for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Shandong Engineering Research Center of Stem Cell and Gene Therapy for Endocrine and Metabolic Diseases, Jinan, Shandong 250021, China
- Central Laboratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China
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Buchholz KJ, Neumueller SE, Burgraff NJ, Hodges MR, Pan L, Forster HV. Chronic moderate hypercapnia suppresses ventilatory responses to acute CO<sub>2</sub> challenges. J Appl Physiol (1985) 2022; 133:1106-1118. [PMID: 36135953 PMCID: PMC9621709 DOI: 10.1152/japplphysiol.00407.2022] [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: 07/11/2022] [Revised: 09/10/2022] [Accepted: 09/11/2022] [Indexed: 11/22/2022] Open
Abstract
Chronic hypercapnia (CH) is a hallmark of chronic lung disease, and CH increases the risk for acute-on-chronic exacerbations leading to greater hypoxemia/hypercapnia and poor health outcomes. However, the role of hypercapnia per se (duration and severity) in determining an individual's ability to tolerate further hypercapnic exacerbations is unknown. Our primary objective herein was to test the hypothesis that mild-to-moderate CH (arterial [Formula: see text] ∼50-70 mmHg) increases susceptibility to pathophysiological responses to severe acute CO<sub>2</sub> challenges. Three groups (GR) of adult female goats were studied during 14 days of exposure to room air (<i>GR 1</i>; control) or 6% inspired CO<sub>2</sub> (<i>GR 2</i>; mild CH), or 7 days of 6% inspired CO<sub>2</sub> followed by 7 days of 8% inspired CO<sub>2</sub> (<i>GR 3</i>; moderate CH). Consistent with previous reports, there were no changes in physiological parameters in <i>GR 1</i> (RA control), but mild CH (<i>GR 2</i>) increased steady-state ventilation and transiently suppressed CO<sub>2</sub>/[H<sup>+</sup>] chemosensitivity. Further increasing InCO<sub>2</sub> from 6% to 8% (<i>GR 3</i>) transiently increased ventilation and arterial [H<sup>+</sup>]. Similar to mild CH, moderate CH increased ventilation to levels greater than predicted. However, in contrast to mild CH, acute ventilatory chemosensitivity was suppressed throughout the duration of moderate CH, and the arterial - mixed expired CO<sub>2</sub> gradient became negative. These data suggest that moderate CH limits physiological responses to acute severe exacerbations and provide evidence of recruitment of extrapulmonary systems (i.e., gastric CO<sub>2</sub> elimination) during times of moderate-severe hypercapnia.<b>NEW & NOTEWORTHY</b> Moderate levels of chronic hypercapnia (CH; ∼70 mmHg) in healthy adult female goats elicited similar steady-state physiological adaptations compared with mild CH (∼55 mmHg). However, unlike mild CH, moderate CH chronically suppressed acute CO<sub>2</sub>/[H<sup>+</sup>] chemosensitivity and reversed the arterial to mixed expired CO<sub>2</sub> gradient. These findings suggest that moderate CH suppresses vital mechanisms of ventilatory control and recruits additional physiological systems (i.e., gastric CO<sub>2</sub> release) to help buffer excess CO<sub>2</sub>.
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Affiliation(s)
- Kirstyn J Buchholz
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | | | - Nicholas J Burgraff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Matthew R Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Lawrence Pan
- Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin
| | - Hubert V Forster
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
- Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
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Dean JB, Stavitzski NM. The O2-sensitive brain stem, hyperoxic hyperventilation, and CNS oxygen toxicity. Front Physiol 2022; 13:921470. [PMID: 35957982 PMCID: PMC9360621 DOI: 10.3389/fphys.2022.921470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
Central nervous system oxygen toxicity (CNS-OT) is a complex disorder that presents, initially, as a sequence of cardio-respiratory abnormalities and nonconvulsive signs and symptoms (S/Sx) of brain stem origin that culminate in generalized seizures, loss of consciousness, and postictal cardiogenic pulmonary edema. The risk of CNS-OT and its antecedent “early toxic indications” are what limits the use of hyperbaric oxygen (HBO2) in hyperbaric and undersea medicine. The purpose of this review is to illustrate, based on animal research, how the temporal pattern of abnormal brain stem responses that precedes an “oxtox hit” provides researchers a window into the early neurological events underlying seizure genesis. Specifically, we focus on the phenomenon of hyperoxic hyperventilation, and the medullary neurons presumed to contribute in large part to this paradoxical respiratory response; neurons in the caudal Solitary complex (cSC) of the dorsomedial medulla, including putative CO2 chemoreceptor neurons. The electrophysiological and redox properties of O2-/CO2-sensitive cSC neurons identified in rat brain slice experiments are summarized. Additionally, evidence is summarized that supports the working hypothesis that seizure genesis originates in subcortical areas and involves cardio-respiratory centers and cranial nerve nuclei in the hind brain (brainstem and cerebellum) based on, respectively, the complex temporal pattern of abnormal cardio-respiratory responses and various nonconvulsive S/Sx that precede seizures during exposure to HBO2.
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Marullo AL, Bird JD, Ciorogariu-Ivan AM, Boulet LM, Strzalkowski NDJ, Day TA. Acute hyperglycemia does not affect central respiratory chemoreflex responsiveness to CO 2 in healthy humans. Respir Physiol Neurobiol 2021; 296:103803. [PMID: 34653661 DOI: 10.1016/j.resp.2021.103803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 10/05/2021] [Accepted: 10/10/2021] [Indexed: 11/17/2022]
Abstract
The central respiratory chemoreceptor complex (CCRC) is comprised of brainstem neurons and surrounding interoceptors, which collectively increase ventilation in response to elevated brainstem tissue CO2/[H+] (i.e., central chemoreflex; CCR). The extent that the CCRC detects/responds to other metabolically related chemostimuli is unknown. We aimed to test the effects of acute oral glucose ingestion on CCR reactivity in heathy human participants (n = 38). We instrumented participants with a pneumotachometer (minute ventilation) and a gas sample line connected to a dual gas analyzer (pressure of end-tidal CO2). Following a baseline (BL) period and capillary blood [glucose] (BG) sample, fasted (F) participants underwent a modified hyperoxic rebreathing test to assess CCR reactivity. Participants then consumed a 75 g standard glucose beverage (glucose loaded; GL). Following 30-min, they underwent a second BL, BG sample and hyperoxic rebreathing test. BG and metabolic rate were higher in GL, confirming the metabolic stimulus. However, the ventilatory recruitment threshold and the CCR responses were unchanged between F and GL states.
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Affiliation(s)
- Anthony L Marullo
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Jordan D Bird
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Anna-Maria Ciorogariu-Ivan
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Lindsey M Boulet
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Colombia Okanagan, Kelowna, BC, Canada
| | - Nicholas D J Strzalkowski
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada.
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5
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Buchholz KJ, Burgraff NJ, Neumueller SE, Hodges MR, Pan LG, Forster HV. Physiological and neurochemical adaptations following abrupt termination of chronic hypercapnia in goats. J Appl Physiol (1985) 2021; 130:1259-1273. [PMID: 33539265 PMCID: PMC8262788 DOI: 10.1152/japplphysiol.00909.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic hypercapnia (CH) is a hallmark of respiratory diseases such as chronic obstructive pulmonary disease. In such patients, mechanical ventilation is often used to restore normal blood-gas homeostasis. However, little is known regarding physiological changes and neuroplasticity within physiological control networks after termination of CH. Utilizing our goat model of increased inspired CO2-induced CH, we determined whether termination of CH elicits time-dependent physiological and neurochemical changes within brain stem sites of physiological control. Thirty days of CH increased [Formula: see text] (+15 mmHg) and steady-state ventilation (SS V̇i; 283% of control). Within 24 h after terminating CH, SS V̇i, blood gases, arterial [H+], and most physiological measurements returned to control. However, the acute ventilatory chemoreflex (ΔV̇i/Δ[H+]) was greater than control, and measured SS V̇i exceeded ventilation predicted by arterial [H+] and ΔV̇i/Δ[H+]. Potentially contributing to these differences were increased excitatory neuromodulators serotonin and norepinephrine in the nucleus tractus solitarius, which contrasts with minimal changes observed at 24 h and 30 days of hypercapnia. Similarly, there were minimal changes found in markers of neuroinflammation and glutamate receptor-dependent neuroplasticity upon termination of CH, which were previously increased following 24 h of hypercapnia. Thus, following termination of CH: 1) ventilatory, renal, and other physiological functions rapidly return to control; 2) neuroplasticity within the ventilatory control network may contribute to the difference between measured vs. predicted ventilation and the elevation in the acute ventilatory [H+] chemoreflex; and 3) neuroplasticity is fundamentally distinct from acclimatization to CH.NEW & NOTEWORTHY In healthy adult goats, steady-state ventilation and most physiological measures return to control within 24 h after termination of chronic hypercapnia (CH). However, the acute [H+] chemoreflex is increased, and measured ventilation exceeds predicted ventilation. At 24 h of recovery, excitatory neuromodulators are above control, but other measured markers of neuroplasticity are unchanged from control. Our data suggest that CH elicits persistent physiological and neurochemical changes for up to 24 h after termination of CH.
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Affiliation(s)
- Kirstyn J. Buchholz
- 1Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Nicholas J. Burgraff
- 5Center for Integrated Brain Research, Seattle Children’s Research Institute, Seattle, Washington
| | | | - Matthew Robert Hodges
- 1Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin,3Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Lawrence G. Pan
- 2Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin
| | - Hubert V. Forster
- 1Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin,3Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin,4Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
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6
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Larcombe AN, Papini MG, Chivers EK, Berry LJ, Lucas RM, Wyrwoll CS. Mouse Lung Structure and Function after Long-Term Exposure to an Atmospheric Carbon Dioxide Level Predicted by Climate Change Modeling. ENVIRONMENTAL HEALTH PERSPECTIVES 2021; 129:17001. [PMID: 33439053 PMCID: PMC7805407 DOI: 10.1289/ehp7305] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 11/30/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Climate change models predict that atmospheric carbon dioxide [CO2] levels will be between 700 and 900 ppm within the next 80 y. Despite this, the direct physiological effects of exposure to slightly elevated atmospheric CO2 (as compared with ∼410 ppm experienced today), especially when exposures extend from preconception to adulthood, have not been thoroughly studied. OBJECTIVES In this study we aimed to assess the respiratory structure and function effects of long-term exposure to 890 ppm CO2 from preconception to adulthood using a mouse model. METHODS We exposed mice to CO2 (∼890 ppm) from prepregnancy, through the in utero and early life periods, until 3 months of age, at which point we assessed respiratory function using the forced oscillation technique, and lung structure. RESULTS CO2 exposure resulted in a range of respiratory impairments, particularly in female mice, including higher tissue elastance, longer chord length, and lower lung compliance. Importantly, we also assessed the lung function of the dams that gave birth to our experimental subjects. Even though these mice had been exposed to the same level of increased CO2 for a similar amount of time (∼8wk), we measured no impairments in lung function. This suggests that the early life period, when lungs are undergoing rapid growth and development, is particularly sensitive to CO2. DISCUSSION To the best of our knowledge, this study, for the first time, shows that long-term exposure to environmentally relevant levels of CO2 can impact respiratory function in the mouse. https://doi.org/10.1289/EHP7305.
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Affiliation(s)
- Alexander N. Larcombe
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
- Occupation, Environment and Safety, School of Population Health, Curtin University, Perth, Australia
| | - Melissa G. Papini
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
- School of Human Sciences, University of Western Australia, Nedlands, Western Australia, Australia
| | - Emily K. Chivers
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
| | - Luke J. Berry
- Respiratory Environmental Health, Wal-yan Respiratory Research Centre, Telethon Kids Institute, Perth, Australia
| | - Robyn M. Lucas
- National Centre for Epidemiology and Population Health, Research School of Population Health, College of Health and Medicine, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Caitlin S. Wyrwoll
- School of Human Sciences, University of Western Australia, Nedlands, Western Australia, Australia
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7
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Ciarlone GE, Hinojo CM, Stavitzski NM, Dean JB. CNS function and dysfunction during exposure to hyperbaric oxygen in operational and clinical settings. Redox Biol 2019; 27:101159. [PMID: 30902504 PMCID: PMC6859559 DOI: 10.1016/j.redox.2019.101159] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 02/20/2019] [Accepted: 03/01/2019] [Indexed: 12/26/2022] Open
Abstract
Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is the acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms, many of which appear to be of brainstem origin involving cranial nerve nuclei and autonomic and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate as generalized tonic-clonic seizures. The initial safe latent period makes the use of HBO2 practical in hyperbaric and undersea medicine; however, the latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure are highly conservative. This review examines the disorder of CNS-OT and summarizes current ideas on its underlying pathophysiology, including specific areas of the CNS and fundamental neural and redox signaling mechanisms that are thought to be involved in seizure genesis and propagation. In addition, conditions that accelerate the onset of seizures are discussed, as are current mitigation strategies under investigation for neuroprotection against redox stress while breathing HBO2 that extend the latent period, thus enabling safer and longer exposures for diving and medical therapies.
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Affiliation(s)
- Geoffrey E Ciarlone
- Undersea Medicine Department, Naval Medical Research Center, 503 Robert Grant Ave., Silver Spring, MD, USA
| | - Christopher M Hinojo
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Nicole M Stavitzski
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
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Changes in the SID Actual and SID Effective Values in the Course of Respiratory Acidosis in Horses With Symptomatic Severe Equine Asthma-An Experimental Study. J Equine Vet Sci 2019; 78:107-111. [PMID: 31203972 DOI: 10.1016/j.jevs.2019.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 04/20/2019] [Accepted: 05/01/2019] [Indexed: 11/20/2022]
Abstract
Equine asthma syndrome is an allergic, inflammatory airway disease that usually affects older horses. Respiratory acidosis is an acid-base imbalance caused by alveolar hypoventilation. The acid-base balance may be assessed using the Henderson-Hasselbalch equation as well as the Stewart model. The authors hypothesized that systemic respiratory acidosis changes the ionic concentrations affecting water dissociation. The study group included 16 Warmblood, mixed breed horses of both sexes with a history of severe equine asthma, and 10 healthy horses were used as controls. Arterial and venous blood were collected from all the horses. The pH, pO2, and pCO2 and HCO3- were assessed in the arterial blood. Na, K, Cl, albumin, and Pinorganic (Pi) were assessed in the venous blood. The obtained results were used to calculate the anion gap (AG), modified AG, actual strong ion difference (SIDa), weak non-volatile acids, and effective strong ion difference (SIDe) values for all the horses. A systemic, compensatory respiratory acidosis was diagnosed in the study group. The concentration of Na in the blood serum in the study group was significantly higher, whereas the concentration of Cl was significantly lower than the values in the control group. The SIDa and SIDe values calculated in the horses from the study group were significantly higher than those in the control group. Significantly higher SIDa and SIDe values confirm the presence of ionic changes that affect water dissociation in the course of respiratory acidosis in horses. The SIDa and SIDe values may be useful in the diagnosis and treatment of respiratory acidosis in horses, which warrant further investigation.
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Burgraff NJ, Neumueller SE, Buchholz K, Langer TM, Hodges MR, Pan L, Forster HV. Ventilatory and integrated physiological responses to chronic hypercapnia in goats. J Physiol 2018; 596:5343-5363. [PMID: 30211447 DOI: 10.1113/jp276666] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/07/2018] [Indexed: 02/06/2023] Open
Abstract
KEY POINTS Chronic hypercapnia per se has distinct effects on the mechanisms regulating steady-state ventilation and the CO2 /H+ chemoreflex. Chronic hypercapnia leads to sustained hyperpnoea that exceeds predicted ventilation based upon the CO2 /H+ chemoreflex. There is an integrative ventilatory, cardiovascular and metabolic physiological response to chronic hypercapnia. Chronic hypercapnia leads to deterioration of cognitive function. ABSTRACT Respiratory diseases such as chronic obstructive pulmonary disease (COPD) often lead to chronic hypercapnia which may exacerbate progression of the disease, increase risk of mortality and contribute to comorbidities such as cognitive dysfunction. Determining the contribution of hypercapnia per se to adaptations in ventilation and cognitive dysfunction within this patient population is complicated by the presence of multiple comorbidities. Herein, we sought to determine the role of chronic hypercapnia per se on the temporal pattern of ventilation and the ventilatory CO2 /H+ chemoreflex by exposing healthy goats to either room air or an elevated inspired CO2 (InCO2 ) of 6% for 30 days. A second objective was to determine whether chronic hypercapnia per se contributes to cognitive dysfunction. During 30 days of exposure to 6% InCO2 , steady-state (SS) ventilation ( V ̇ I ) initially increased to 335% of control, and then within 1-5 days decreased and stabilized at ∼230% of control. There was an initial respiratory acidosis that was partially mitigated over time due to increased arterial [HCO3 - ]. There was a transient decrease in the ventilatory CO2 /H+ chemoreflex, followed by return to pre-exposure levels. The SS V ̇ I during chronic hypercapnia was greater than predicted from the acute CO2 /H+ chemoreflex, suggesting separate mechanisms regulating SS V ̇ I and the chemoreflex. Finally, as assessed by a shape discrimination test, we found a sustained decrease in cognitive function during chronic hypercapnia. We conclude that chronic hypercapnia per se results in: (1) a disconnect between SS V ̇ I and the CO2 /H+ chemoreflex, and (2) deterioration of cognitive function.
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Affiliation(s)
| | | | - Kirstyn Buchholz
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Thomas M Langer
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Matthew R Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Lawrence Pan
- Department of Physical Therapy, Marquette University, Milwaukee, WI, USA
| | - Hubert V Forster
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Zablocki Veterans Affairs Medical Center, Milwaukee, WI, 53226, USA
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10
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Abstract
GOALS We assessed the relationship between gastroesophageal reflux disease (GERD) and hypertension and whether antiacid therapy could be used to control blood pressure (BP) on hypertension in patients with GERD. BACKGROUND Gastroesophageal reflux disease (GERD) may provoke cardiovascular disease. Many factors are involved in the development of essential hypertension, but whether GERD has a role needs further study. STUDY Patients with essential hypertension (n=86) were studied by 24-hour continuous BP monitoring and esophageal impedance and pH monitoring. Patients fulfilling the GERD criteria received 14-day therapy with omeprazole (20 mg twice a day), and the effect on BP was studied. RESULTS Of the 86 essential hypertension patients, 38 (44.2%) had GERD. Among these 38 patients, 494 episodes of pathologic reflux (PR), and 684 episodes of high BP were recorded. PR was significantly more common at nighttime especially when supine. Of the 684 episodes of hypertension, 102 (14.9%) were synchronous with PR. GERD patients had significantly higher nocturnal BP than non-GERD patients. Antiacid therapy brought about significant reduction in all esophageal monitoring parameters as well as in BP parameters in GERD patients. CONCLUSIONS This study demonstrated that there is significant correlation between hypertension and GERD. Antiacid therapy can restore normal esophageal pH and help maintain normal BP.
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Sackett JR, Schlader ZJ, O'Leary MC, Chapman CL, Johnson BD. Central chemosensitivity is augmented during 2 h of thermoneutral head-out water immersion in healthy men and women. Exp Physiol 2018. [DOI: 10.1113/ep086870] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- James R. Sackett
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY 14214 USA
| | - Zachary J. Schlader
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY 14214 USA
| | - Morgan C. O'Leary
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY 14214 USA
| | - Christopher L. Chapman
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY 14214 USA
| | - Blair D. Johnson
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY 14214 USA
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12
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Baldy C, Chamberland S, Fournier S, Kinkead R. Sex-Specific Consequences of Neonatal Stress on Cardio-Respiratory Inhibition Following Laryngeal Stimulation in Rat Pups. eNeuro 2017; 4:ENEURO.0393-17.2017. [PMID: 29308430 PMCID: PMC5753062 DOI: 10.1523/eneuro.0393-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 12/15/2017] [Accepted: 12/18/2017] [Indexed: 11/21/2022] Open
Abstract
The presence of liquid near the larynx of immature mammals triggers prolonged apneas with significant O2 desaturations and bradycardias. When excessive, this reflex (the laryngeal chemoreflex; LCR) can be fatal. Our understanding of the origins of abnormal LCR are limited; however, perinatal stress and male sex are risk factors for cardio-respiratory failure in infants. Because exposure to stress during early life has deleterious and sex-specific consequences on brain development it is plausible that respiratory reflexes are vulnerable to neuroendocrine dysfunction. To address this issue, we tested the hypothesis that neonatal maternal separation (NMS) is sufficient to exacerbate LCR-induced cardio-respiratory inhibition in anesthetized rat pups. Stressed pups were separated from their mother 3 h/d from postnatal days 3 to 12. At P14-P15, pups were instrumented to monitor breathing, O2 saturation (Spo2), and heart rate. The LCR was activated by water injections near the larynx (10 µl). LCR-induced apneas were longer in stressed pups than controls; O2 desaturations and bradycardias were more profound, especially in males. NMS increased the frequency and amplitude of spontaneous EPSCs (sEPSCs) in the dorsal motor nucleus of the vagus (DMNV) of males but not females. The positive relationship between corticosterone and testosterone observed in stressed pups (males only) suggests that disruption of neuroendocrine function by stress is key to sex-based differences in abnormal LCR. Because testosterone application onto medullary slices augments EPSC amplitude only in males, we propose that testosterone-mediated enhancement of synaptic connectivity within the DMNV contributes to the male bias in cardio-respiratory inhibition following LCR activation in stressed pups.
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Affiliation(s)
- Cécile Baldy
- Department of Pediatrics, Centre de Recherche de l’Institut de Cardiologie et Pneumologie de Québec, Université Laval, Québec, G1V 4G5, Canada
| | - Simon Chamberland
- Department of Psychiatry and Neuroscience, Québec Mental Health Institute, Université Laval, Québec, G1J 2G3, Canada
| | - Stéphanie Fournier
- Department of Pediatrics, Centre de Recherche de l’Institut de Cardiologie et Pneumologie de Québec, Université Laval, Québec, G1V 4G5, Canada
| | - Richard Kinkead
- Department of Pediatrics, Centre de Recherche de l’Institut de Cardiologie et Pneumologie de Québec, Université Laval, Québec, G1V 4G5, Canada
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13
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Abstract
Conventional wisdom holds that the avian respiratory system is unique because air flows in the same direction through most of the gas-exchange tubules during both phases of ventilation. However, recent studies showing that unidirectional airflow also exists in crocodilians and lizards raise questions about the true phylogenetic distribution of unidirectional airflow, the selective drivers of the trait, the date of origin, and the functional consequences of this phenomenon. These discoveries suggest unidirectional flow was present in the common diapsid ancestor and are inconsistent with the traditional paradigm that unidirectional flow is an adaptation for supporting high rates of gas exchange. Instead, these discoveries suggest it may serve functions such as decreasing the work of breathing, decreasing evaporative respiratory water loss, reducing rates of heat loss, and facilitating crypsis. The divergence in the design of the respiratory system between unidirectionally ventilated lungs and tidally ventilated lungs, such as those found in mammals, is very old, with a minimum date for the divergence in the Permian Period. From this foundation, the avian and mammalian lineages evolved very different respiratory systems. I suggest the difference in design is due to the same selective pressure, expanded aerobic capacity, acting under different environmental conditions. High levels of atmospheric oxygen of the Permian Period relaxed selection for a thin blood-gas barrier and may have resulted in the homogeneous, broncho-alveolar design, whereas the reduced oxygen of the Mesozoic selected for a heterogeneous lung with an extremely thin blood-gas barrier. These differences in lung design may explain the puzzling pattern of ecomorphological diversification of Mesozoic mammals: all were small animals that did not occupy niches requiring a great aerobic capacity. The broncho-alveolar lung and the hypoxia of the Mesozoic may have restricted these mammals from exploiting niches of large body size, where cursorial locomotion can be advantageous, as well as other niches requiring great aerobic capacities, such as those using flapping flight. Furthermore, hypoxia may have exerted positive selection for a parasagittal posture, the diaphragm, and reduced erythrocyte size, innovations that enabled increased rates of ventilation and more rapid rates of diffusion in the lung.
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14
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Ostrowski TD, Hasser EM, Heesch CM, Kline DD. H₂O₂ induces delayed hyperexcitability in nucleus tractus solitarii neurons. Neuroscience 2014; 262:53-69. [PMID: 24397952 DOI: 10.1016/j.neuroscience.2013.12.055] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 12/23/2013] [Accepted: 12/24/2013] [Indexed: 12/19/2022]
Abstract
Hydrogen peroxide (H₂O₂) is a stable reactive oxygen species and potent neuromodulator of cellular and synaptic activity. Centrally, endogenous H₂O₂ is elevated during bouts of hypoxia-reoxygenation, a variety of disease states, and aging. The nucleus tractus solitarii (nTS) is the central termination site of visceral afferents for homeostatic reflexes and contributes to reflex alterations during these conditions. We determined the extent to which H₂O₂ modulates synaptic and membrane properties in nTS neurons in rat brainstem slices. Stimulation of the tractus solitarii (which contains the sensory afferent fibers) evoked synaptic currents that were not altered by 10-500 μM H₂O₂. However, 500 μM H₂O₂ modulated several intrinsic membrane properties of nTS neurons, including a decrease in input resistance (R(i)), hyperpolarization of resting membrane potential (RMP) and action potential (AP) threshold (THR), and an initial reduction in AP discharge to depolarizing current. H₂O₂ increased conductance of barium-sensitive potassium currents, and block of these currents ablated H₂O₂-induced changes in RMP, Ri and AP discharge. Following washout of H₂O₂ AP discharge was enhanced due to depolarization of RMP and a partially maintained hyperpolarization of THR. Hyperexcitability persisted with repeated H₂O₂ exposure. H₂O₂ effects on RMP and THR were ablated by intracellular administration of the antioxidant catalase, which was immunohistochemically identified in neurons throughout the nTS. Thus, H₂O₂ initially reduces excitability of nTS neurons that is followed by sustained hyperexcitability, which may play a profound role in cardiorespiratory reflexes.
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Affiliation(s)
- T D Ostrowski
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - E M Hasser
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - C M Heesch
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - D D Kline
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA.
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15
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Cruz-Martinez R, Castañon M, Moreno-Alvarez O, Acosta-Rojas R, Martinez JM, Gratacos E. Usefulness of lung-to-head ratio and intrapulmonary arterial Doppler in predicting neonatal morbidity in fetuses with congenital diaphragmatic hernia treated with fetoscopic tracheal occlusion. ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2013; 41:59-65. [PMID: 22689226 DOI: 10.1002/uog.11212] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/18/2012] [Indexed: 06/01/2023]
Abstract
OBJECTIVE To explore the potential value of intrapulmonary artery Doppler velocimetry in predicting neonatal morbidity in fetuses with left-sided congenital diaphragmatic hernia (CDH) treated with fetoscopic tracheal occlusion (FETO). METHODS Observed/expected lung-to-head ratio (O/E-LHR), and intrapulmonary Doppler pulsatility index and peak early-diastolic reversed flow were evaluated within 24 h before FETO in a consecutive cohort of 51 fetuses with left-sided CDH at between 24 and 33 weeks' gestation. Lung Doppler parameters were converted into Z-scores and defined as abnormal if the pulsatility index had a Z-score of > 1.0 or the peak early-diastolic reversed flow had a Z-score of > 3.5. The association of O/E-LHR and Doppler velocimetry with neonatal outcome was assessed using multiple linear or logistic regression analysis adjusted for gestational age at birth. RESULTS Among the 26 fetuses that survived, 18 (69.2%) had normal and eight (30.8%) had abnormal Doppler values. O/E-LHR was not associated with neonatal morbidity in surviving fetuses. Compared with the group with normal Doppler parameters, cases with abnormal intrapulmonary Doppler were associated with a significant increase in the duration of mechanical ventilation (average increase of 21.2 (95% CI, 9.99-32.5) days; P < 0.01), conventional ventilation (15.2 (95% CI, 7.43-23.0) days; P < 0.01), high-frequency ventilation (6.34 (95% CI, 0.69-11.99) days; P < 0.05), nitric oxide therapy (5.73 (95% CI, 0.60-10.9) days; P < 0.05), oxygen support (36.5 (95% CI, 16.3-56.7) days; P < 0.01), parenteral nutrition (19.1 (95% CI, 7.53-30.7) days; P < 0.01) and stay in neonatal intensive care unit (42.7 (95% CI, 22.9-62.6) days; P < 0.001), and with significantly higher rates of high-frequency ventilation (87.5 vs. 44.4%;P < 0.05), oxygen requirement at 28 days of age (75.0 vs. 11.1%; P < 0.01), gastroesophageal reflux (62.5 vs. 22.2%; P < 0.05) and tube feeding at discharge (37.5 vs. 5.56%; P < 0.05). CONCLUSION As previously reported, O/E-LHR did not predict neonatal morbidity. In contrast, intrapulmonary artery Doppler evaluation was predictive of neonatal morbidity in CDH fetuses treated with FETO.
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Affiliation(s)
- R Cruz-Martinez
- Department of Maternal-Fetal Medicine, Institute Clínic of Gynecology, Obstetrics and Neonatology, Hospital Clinic-IDIBAPS, University of Barcelona and Centre for Biomedical Research on Rare Diseases, Barcelona, Spain
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16
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Austgen JR, Dantzler HA, Barger BK, Kline DD. 5-hydroxytryptamine 2C receptors tonically augment synaptic currents in the nucleus tractus solitarii. J Neurophysiol 2012; 108:2292-305. [PMID: 22855775 DOI: 10.1152/jn.00049.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The nucleus tractus solitarii (nTS) is the primary termination and integration point for visceral afferents in the brain stem. Afferent glutamate release and its efficacy on postsynaptic activity within this nucleus are modulated by additional neuromodulators and transmitters, including serotonin (5-HT) acting through its receptors. The 5-HT(2) receptors in the medulla modulate the cardiorespiratory system and autonomic reflexes, but the distribution of the 5-HT(2C) receptor and the role of these receptors during synaptic transmission in the nTS remain largely unknown. In the present study, we examined the distribution of 5-HT(2C) receptors in the nTS and their role in modulating excitatory postsynaptic currents (EPSCs) in monosynaptic nTS neurons in the horizontal brain stem slice. Real-time RT-PCR and immunohistochemistry identified 5-HT(2C) receptor message and protein in the nTS and suggested postsynaptic localization. In nTS neurons innervated by general visceral afferents, 5-HT(2C) receptor activation increased solitary tract (TS)-EPSC amplitude and input resistance and depolarized membrane potential. Conversely, 5-HT(2C) receptor blockade reduced TS-EPSC and miniature EPSC amplitude, as well as input resistance, and hyperpolarized membrane potential. Synaptic parameters in nTS neurons that receive sensory input from carotid body chemoafferents were also attenuated by 5-HT(2C) receptor blockade. Taken together, these data suggest that 5-HT(2C) receptors in the nTS are located postsynaptically and augment excitatory neurotransmission.
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Affiliation(s)
- James R Austgen
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
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17
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Lindsey BG, Rybak IA, Smith JC. Computational models and emergent properties of respiratory neural networks. Compr Physiol 2012; 2:1619-70. [PMID: 23687564 PMCID: PMC3656479 DOI: 10.1002/cphy.c110016] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Computational models of the neural control system for breathing in mammals provide a theoretical and computational framework bringing together experimental data obtained from different animal preparations under various experimental conditions. Many of these models were developed in parallel and iteratively with experimental studies and provided predictions guiding new experiments. This data-driven modeling approach has advanced our understanding of respiratory network architecture and neural mechanisms underlying generation of the respiratory rhythm and pattern, including their functional reorganization under different physiological conditions. Models reviewed here vary in neurobiological details and computational complexity and span multiple spatiotemporal scales of respiratory control mechanisms. Recent models describe interacting populations of respiratory neurons spatially distributed within the Bötzinger and pre-Bötzinger complexes and rostral ventrolateral medulla that contain core circuits of the respiratory central pattern generator (CPG). Network interactions within these circuits along with intrinsic rhythmogenic properties of neurons form a hierarchy of multiple rhythm generation mechanisms. The functional expression of these mechanisms is controlled by input drives from other brainstem components,including the retrotrapezoid nucleus and pons, which regulate the dynamic behavior of the core circuitry. The emerging view is that the brainstem respiratory network has rhythmogenic capabilities at multiple levels of circuit organization. This allows flexible, state-dependent expression of different neural pattern-generation mechanisms under various physiological conditions,enabling a wide repertoire of respiratory behaviors. Some models consider control of the respiratory CPG by pulmonary feedback and network reconfiguration during defensive behaviors such as cough. Future directions in modeling of the respiratory CPG are considered.
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Affiliation(s)
- Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology and Neuroscience Program, University of South Florida College of Medicine, Tampa, Florida, USA.
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18
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Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
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Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
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19
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Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
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Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
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20
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Forster HV. Increased gastric acid secretion contributes to elimination of CO2 during hypercapnia. Respir Physiol Neurobiol 2011; 176:12-3. [DOI: 10.1016/j.resp.2010.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 12/18/2010] [Indexed: 12/01/2022]
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21
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Jin W, Jiang J, Wang X, Zhu X, Wang G, Song Y, Bai C. Continuous intra-arterial blood pH monitoring in rabbits with acid-base disorders. Respir Physiol Neurobiol 2011; 177:183-8. [PMID: 21402180 DOI: 10.1016/j.resp.2011.03.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/08/2011] [Accepted: 03/08/2011] [Indexed: 11/28/2022]
Abstract
The acid-base balance of arterial blood is important for the clinical management of seriously ill patients, especially patients with acute lung injury or acute respiratory distress syndrome. We developed a novel fluorosensor for continuous blood pH monitoring and evaluated its performance both in vitro and in vivo in rabbits with acid-base disorders. The pH sensor is made of N-allyl-4-piperazinyl-1, 8-napthalimide and 2-hydroxyethyl methacrylate, which were bonded at the distal end of the optical fiber. The fluorescence intensity increased as the pH decreased with good reproducibility, selectivity and linearity in the pH range of 6-8. The pH measurement precision was 0.03 ± 0.03 pH units with a bias of -0.02 ± 0.04 (n = 105) and -0.00 ± 0.05 pH units (n=189) in rabbits with metabolic and respiratory acid-base orders, respectively. The optical pH sensor can accurately measure pH fluctuations with a fast response and is a promising candidate for continuous in-line measurements of blood pH in critical care patients.
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Affiliation(s)
- Weizhong Jin
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai 200032, China
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