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Horne RS, Harrewijn I, Hunt CE. Physiology during sleep in preterm infants: Implications for increased risk for the sudden infant death syndrome. Sleep Med Rev 2024; 78:101990. [PMID: 39116607 DOI: 10.1016/j.smrv.2024.101990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 07/14/2024] [Accepted: 07/26/2024] [Indexed: 08/10/2024]
Abstract
Approximately 15 million babies are born preterm (<37 weeks of completed gestation) worldwide annually. Although neonatal and perinatal medicine have contributed to the increased survival rate of preterm newborn infants, premature infants are at increased risk of mortality in the first years of life. Infants born preterm are at four times the risk of Sudden Infant Death Syndrome (SIDS) compared to infants born at term. SIDS is believed to be multifactorial in origin. The Triple Risk hypothesis has been proposed to explain this. The model suggests that when a vulnerable infant, such as one born preterm, is at a critical but unstable developmental period in homeostatic control, death may occur if exposed to an exogenous stressor, such as being placed prone for sleep. The highest risk period is at ages 2-4 months, with 90 % of deaths occurring before 6 months. The final pathway to SIDS is widely believed to involve some combination of immature cardiorespiratory control and a failure of arousal from sleep. This review will focus on the physiological factors which increase the risk for SIDS in preterm infants and how these factors may be identified and potentially lead to effective preventative strategies.
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Affiliation(s)
| | | | - Carl E Hunt
- Uniformed Services University, Bethesda, MD, USA
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2
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Poets CF, Quante M. Rethinking the Pathophysiology of Cardiorespiratory Events in Infants Born Preterm. J Pediatr 2023; 262:113651. [PMID: 37527701 DOI: 10.1016/j.jpeds.2023.113651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 07/26/2023] [Indexed: 08/03/2023]
Affiliation(s)
- Christian F Poets
- Department of Neonatology, Tübingen University Hospital, Tübingen, Germany.
| | - Mirja Quante
- Department of Neonatology, Tübingen University Hospital, Tübingen, Germany
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3
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Manferdelli G, Narang BJ, Bourdillon N, Debevec T, Millet GP. Physiological Responses to Exercise in Hypoxia in Preterm Adults: Convective and Diffusive Limitations in the O 2 Transport. Med Sci Sports Exerc 2023; 55:482-496. [PMID: 36459101 DOI: 10.1249/mss.0000000000003077] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
PURPOSE Premature birth induces long-term sequelae on the cardiopulmonary system, leading to reduced exercise capacity. However, the mechanisms of this functional impairment during incremental exercise remain unclear. Also, a blunted hypoxic ventilatory response was found in preterm adults, suggesting an increased risk for adverse effects of hypoxia in this population. This study aimed to investigate the oxygen cascade during incremental exercise to exhaustion in both normoxia and hypobaric hypoxia in prematurely born adults with normal lung function and their term born counterparts. METHODS Noninvasive measures of gas exchange, cardiac hemodynamics, and both muscle and cerebral oxygenation were continuously performed using metabolic cart, transthoracic impedance, and near-infrared spectroscopy, respectively, during an incremental exercise test to exhaustion performed at sea level and after 3 d of high-altitude exposure in healthy preterm ( n = 17; gestational age, 29 ± 1 wk; normal lung function) and term born ( n = 17) adults. RESULTS At peak, power output, oxygen uptake, stroke volume indexed for body surface area, and cardiac output were lower in preterm compared with term born in normoxia ( P = 0.042, P = 0.027, P = 0.030, and P = 0.018, respectively) but not in hypoxia, whereas pulmonary ventilation, peripheral oxygen saturation, and muscle and cerebral oxygenation were similar between groups. These later parameters were modified by hypoxia ( P < 0.001). Hypoxia increased muscle oxygen extraction at submaximal and maximal intensity in term born ( P < 0.05) but not in preterm participants. Hypoxia decreased cerebral oxygen saturation in term born but not in preterm adults at rest and during exercise ( P < 0.05). Convective oxygen delivery was decreased by hypoxia in term born ( P < 0.001) but not preterm adults, whereas diffusive oxygen transport decreased similarly in both groups ( P < 0.001 and P < 0.001, respectively). CONCLUSIONS These results suggest that exercise capacity in preterm is primarily reduced by impaired convective, rather than diffusive, oxygen transport. Moreover, healthy preterm adults may experience blunted hypoxia-induced impairments during maximal exercise compared with their term counterparts.
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Affiliation(s)
| | | | - Nicolas Bourdillon
- Institute of Sport Sciences, University of Lausanne, Lausanne, SWITZERLAND
| | | | - Grégoire P Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, SWITZERLAND
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4
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Zannin E, Stoecklin B, Choi JY, Simpson SJ, Veneroni C, Dellaca RL, Pillow JJ. Ventilatory response and stability of oxygen saturation during a hypoxic challenge in very preterm infants. Pediatr Pulmonol 2023; 58:1454-1462. [PMID: 36748837 DOI: 10.1002/ppul.26343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 01/17/2023] [Accepted: 02/05/2023] [Indexed: 02/08/2023]
Abstract
BACKGROUND Preterm infants have immature control of breathing and impaired pulmonary gas exchange. We hypothesized that infants with bronchopulmonary dysplasia (BPD) have a blunted ventilatory response and peripheral oxygen saturation (SpO2 ) instability during a hypoxic challenge. METHODS We evaluated the response to hypoxia in 57 very preterm infants (38 no BPD, 10 mild BPD, 9 moderate-to-severe BPD) at 36 weeks' postmenstrual age. The fraction of inspired oxygen (FI O2 ) was reduced stepwise at 5-min intervals to achieve peripheral SpO2 between 86% and 95%. The lowest permissible FI O2 and SpO2 were 0.14% and 86%. We recorded SpO2 , FI O2 , and the respiratory signal (respiratory inductive plethysmography). We calculated respiratory rate (RR), tidal volume (VT ), minute ventilation (VE ), and respiratory drive (ratio between VT and inspiratory time, VT /TI ). SpO2 variability was expressed as the interquartile range (IQR). RESULTS FI O2 was reduced from a median (Q1, Q3) of 0.21 (0.21, 0.21) to 0.17 (0.17, 0.18). We observed a marked individual variability in the ventilatory response to the hypoxic challenge, regardless of BPD severity. At the lowest permissible FI O2 , 37 (65%) infants reduced their VE , and 20 (35%) increased minute ventilation; 20 infants (35%) developed periodic breathing associated with increased SpO2 IQR and lower SpO2 minima, and 16 (28%) exhibited an oscillatory pattern in VE and SpO2 without end-expiratory pauses, regardless of BPD severity. CONCLUSION In very preterm infants, a mild hypoxic challenge reduced ventilation, increased SpO2 variability and periodic breathing regardless of BPD severity.
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Affiliation(s)
- Emanuela Zannin
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.,Neonatal Intensive Care Unit, Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy
| | - Benjamin Stoecklin
- School of Human Sciences, University of Western Australia, Perth, Australia.,Department of Neonatology, Children's Lung Health, University Children's Hospital Basel (UKBB), Basel, Switzerland
| | - Jane Y Choi
- School of Human Sciences, University of Western Australia, Perth, Australia.,Children's Lung Health, Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia
| | - Shannon J Simpson
- Children's Lung Health, Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia.,School of Physiotherapy and Exercise Science, Curtin School of Allied Health, Curtin University, Perth, Australia
| | - Chiara Veneroni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Raffaele L Dellaca
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Jane J Pillow
- School of Human Sciences, University of Western Australia, Perth, Australia.,Children's Lung Health, Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia
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5
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Ji M, Ikegami T, Debru E, Easton PA. Parasternal Intercostal Function during Sustained Hypoxia. J Appl Physiol (1985) 2022; 132:622-631. [PMID: 35112930 DOI: 10.1152/japplphysiol.00771.2020] [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
Ventilatory response to sustained isocapnic hypoxia in adult humans and other mammals is characterized by a biphasic pattern, with attenuation of neuromotor output to the diaphragm. However, there is no a priori reason that hypoxic mediated attenuation of respiratory drive would be a common event among other respiratory muscles. At present, little is known about the function of the chest wall muscles during sustained hypoxia. As an obligatory inspiratory muscle with potential to act as a surrogate for neural drive to the relatively inaccessible costal diaphragm, parasternal intercostal has gained interest clinically: its function during a sustained hypoxic insult, as may occur in respiratory failure, warrants investigation. Therefore, in eleven chronically instrumented awake canines, we recorded simultaneously muscle length, shortening and electromyogram (EMG) activity of the parasternal chest wall inspiratory muscle, along with breathing pattern, during moderate levels of sustained isocapnic hypoxia lasting 20-25 minutes (mean 80 ± 2% oximeter oxygen saturation). Phasic inspiratory shortening and EMG activity of the parasternal intercostal was observed throughout room air and hypoxic ventilation in all animals. Temporal changes in parasternal intercostal shortening tracked the biphasic changes in ventilation during sustained hypoxia. Mean shortening and EMG activity of parasternal intercostal muscle increased significantly with initial hypoxia (P < 0.01), then markedly declined with constant hypoxia (P < 0.05). We conclude that attenuation of central neural respiratory drive extends to the primary chest wall inspiratory muscle, the parasternal intercostals, during sustained hypoxia, thus directly contributing to biphasic changes in ventilation.
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Affiliation(s)
- Michael Ji
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Tetsunori Ikegami
- Department of Emergency Medicine, Kurashiki Central Hospital, Miwa Kurashiki, Okayama, Japan
| | - Estifanos Debru
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Paul A Easton
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Bishop M, Weinhold M, Turk AZ, Adeck A, SheikhBahaei S. An open-source tool for automated analysis of breathing behaviors in common marmosets and rodents. eLife 2022; 11:e71647. [PMID: 35049499 PMCID: PMC8856653 DOI: 10.7554/elife.71647] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
The respiratory system maintains homeostatic levels of oxygen (O2) and carbon dioxide (CO2) in the body through rapid and efficient regulation of breathing frequency and depth (tidal volume). The commonly used methods of analyzing breathing data in behaving experimental animals are usually subjective, laborious, and time-consuming. To overcome these hurdles, we optimized an analysis toolkit for the unsupervised study of respiratory activities in animal subjects. Using this tool, we analyzed breathing behaviors of the common marmoset (Callithrix jacchus), a New World non-human primate model. Using whole-body plethysmography in room air as well as acute hypoxic (10% O2) and hypercapnic (6% CO2) conditions, we describe breathing behaviors in awake, freely behaving marmosets. Our data indicate that marmosets' exposure to acute hypoxia decreased metabolic rate and increased sigh rate. However, the hypoxic condition did not augment ventilation. Hypercapnia, on the other hand, increased both the frequency and depth (i.e., tidal volume) of breathing.
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Affiliation(s)
- Mitchell Bishop
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, United States
| | - Maximilian Weinhold
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, United States
| | - Ariana Z Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, United States
| | - Afuh Adeck
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, United States
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, United States
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7
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Freislich Z, Stoecklin B, Hemy N, Pillow JJ, Hall GL, Wilson AC, Simpson SJ. The ventilatory response to hypoxia is blunted in some preterm infants during the second year of life. Front Pediatr 2022; 10:974643. [PMID: 36389388 PMCID: PMC9661422 DOI: 10.3389/fped.2022.974643] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 10/05/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Preterm birth and subsequent neonatal ventilatory treatment disrupts development of the hypoxic ventilatory response (HVR). An attenuated HVR has been identified in preterm neonates, however it is unknown whether the attenuation persists into the second year of life. We investigated the HVR at 12-15 months corrected postnatal age and assessed predictors of a blunted HVR in those born very preterm (<32 weeks gestation). METHODS HVR was measured in infants born very preterm. Hypoxia was induced with a three-step reduction in their fraction of inspired oxygen (FIO2) from 0.21 to 0.14. Respiratory frequency (f), tidal volume (V T), minute ventilation (V E), inspiratory time (t I), expiratory time (t E), V T/t I, tI/t TOT, V T/t TOT, area under the low-volume loop and peak tidal expiratory flow (PTEF) were measured at the first and third minute of each FIO2. The change in respiratory variables over time was assessed using a repeated measures ANOVA with Greenhouse-Geisser correction. A blunted HVR was defined as a <10% rise in V E, from normoxia. The relationship between neonatal factors and the magnitude of HVR was assessed using Spearman correlation. RESULTS Thirty nine infants born very preterm demonstrated a mean (SD) HVR of 11.4 (10.1)% (increase in V E) in response to decreasing FIO2 from 0.21 to 0.14. However, 17 infants (44%) failed to increase V E by ≥10% (range -14% to 9%) and were considered to have a blunted response to hypoxia. Males had a smaller HVR than females [ΔV E (-9.1%; -15.4, -2.8; p = 0.007)]. CONCLUSION Infants surviving very preterm birth have an attenuated ventilatory response to hypoxia that persists into the second year of life, especially in males.
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Affiliation(s)
- Zoe Freislich
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia
| | - Benjamin Stoecklin
- Department of Neonatology, University Children's Hospital Basel UKBB, Basel, Switzerland.,School of Human Sciences, The University of Western Australia, Perth, Australia
| | - Naomi Hemy
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia
| | - J Jane Pillow
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia.,School of Human Sciences, The University of Western Australia, Perth, Australia
| | - Graham L Hall
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia.,Curtin School of Allied Health, Curtin University, Perth, Australia
| | - Andrew C Wilson
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia.,Curtin School of Allied Health, Curtin University, Perth, Australia.,Department of Respiratory and Sleep Medicine, Perth Children's Hospital, Perth, Australia
| | - Shannon J Simpson
- Wal-yan Respiratory Centre, Telethon Kids Institute, Perth, Australia.,Curtin School of Allied Health, Curtin University, Perth, Australia
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8
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de Sousa Abreu RP, Bondarenko E, Feldman JL. Phase- and state-dependent modulation of breathing pattern by preBötzinger complex somatostatin expressing neurons. J Physiol 2022; 600:143-165. [PMID: 34783033 PMCID: PMC9261878 DOI: 10.1113/jp282002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 11/12/2021] [Indexed: 01/03/2023] Open
Abstract
As neuronal subtypes are increasingly categorized, delineating their functional role is paramount. The preBötzinger complex (preBötC) subpopulation expressing the neuropeptide somatostatin (SST) is classified as mostly excitatory, inspiratory-modulated and not rhythmogenic. We further characterized their phenotypic identity: 87% were glutamatergic and the balance were glycinergic and/or GABAergic. We then used optogenetics to investigate their modulatory role in both anaesthetized and freely moving mice. In anaesthetized mice, short photostimulation (100 ms) of preBötC SST+ neurons modulated breathing-related variables in a combinatory phase- and state-dependent manner; changes in inspiratory duration, inspiratory peak amplitude (Amp), and phase were different at higher (≥2.5 Hz) vs. lower (<2.5 Hz) breathing frequency (f). Moreover, we observed a biphasic effect of photostimulation during expiration that is probabilistic, that is photostimulation given at the same phase in consecutive cycles can evoke opposite responses (lengthening vs. shortening of the phase). These unexpected probabilistic state- and phase-dependent responses to photostimulation exposed properties of the preBötC that were not predicted and cannot be readily accounted for in current models of preBötC pattern generation. In freely moving mice, prolonged photostimulation decreased f in normoxia, hypoxia or hypercapnia, and increased Amp and produced a phase advance, which was similar to the results in anaesthetized mice when f ≥ 2.5 Hz. We conclude that preBötC SST+ neurons are a key mediator of the extraordinary and essential lability of breathing pattern. KEY POINTS: PreBötzinger complex (preBötC) SST+ neurons, which modulate respiratory pattern but are not rhythmogenic, were transfected with channelrhodopsin to investigate phase- and state-dependent modulation of breathing pattern in anaesthetized and freely behaving mice in normoxia, hypoxia and hypercapnia. In anaesthetized mice, photostimulation during inspiration increased inspiratory duration and amplitude regardless of baseline f, yet the effects were more robust at higher f. In anaesthetized mice with low f (<2.5 Hz), photostimulation during expiration evoked either phase advance or phase delay, whereas in anaesthetized mice with high f (≥2.5 Hz) and in freely behaving mice in normoxia, hypoxia or hypercapnia, photostimulation always evoked phase advance. Phase- and state-dependency is a function of overall breathing network excitability. The f-dependent probabilistic modulation of breathing pattern by preBötC SST+ neurons was unexpected, requiring reconsideration of current models of preBötC function, which neither predict nor can readily account for such responses.
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Affiliation(s)
- Raquel P. de Sousa Abreu
- Department of Neurobiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, 90095
| | - Evgeny Bondarenko
- Department of Neurobiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, 90095
| | - Jack L. Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, 90095
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9
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Abstract
The development of the control of breathing begins in utero and continues postnatally. Fetal breathing movements are needed for establishing connectivity between the lungs and central mechanisms controlling breathing. Maturation of the control of breathing, including the increase of hypoxia chemosensitivity, continues postnatally. Insufficient oxygenation, or hypoxia, is a major stressor that can manifest for different reasons in the fetus and neonate. Though the fetus and neonate have different hypoxia sensing mechanisms and respond differently to acute hypoxia, both responses prevent deviations to respiratory and other developmental processes. Intermittent and chronic hypoxia pose much greater threats to the normal developmental respiratory processes. Gestational intermittent hypoxia, due to maternal sleep-disordered breathing and sleep apnea, increases eupneic breathing and decreases the hypoxic ventilatory response associated with impaired gasping and autoresuscitation postnatally. Chronic fetal hypoxia, due to biologic or environmental (i.e. high-altitude) factors, is implicated in fetal growth restriction and preterm birth causing a decrease in the postnatal hypoxic ventilatory responses with increases in irregular eupneic breathing. Mechanisms driving these changes include delayed chemoreceptor development, catecholaminergic activity, abnormal myelination, increased astrocyte proliferation in the dorsal respiratory group, among others. Long-term high-altitude residents demonstrate favorable adaptations to chronic hypoxia as do their offspring. Neonatal intermittent hypoxia is common among preterm infants due to immature respiratory systems and thus, display a reduced drive to breathe and apneas due to insufficient hypoxic sensitivity. However, ongoing intermittent hypoxia can enhance hypoxic sensitivity causing ventilatory overshoots followed by apnea; the number of apneas is positively correlated with degree of hypoxic sensitivity in preterm infants. Chronic neonatal hypoxia may arise from fetal complications like maternal smoking or from postnatal cardiovascular problems, causing blunting of the hypoxic ventilatory responses throughout at least adolescence due to attenuation of carotid body fibers responses to hypoxia with potential roles of brainstem serotonin, microglia, and inflammation, though these effects depend on the age in which chronic hypoxia initiates. Fetal and neonatal intermittent and chronic hypoxia are implicated in preterm birth and complicate the respiratory system through their direct effects on hypoxia sensing mechanisms and interruptions to the normal developmental processes. Thus, precise regulation of oxygen homeostasis is crucial for normal development of the respiratory control network. © 2021 American Physiological Society. Compr Physiol 11:1653-1677, 2021.
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Affiliation(s)
- Gary C. Mouradian
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Satyan Lakshminrusimha
- Department of Pediatrics, UC Davis Children’s Hospital, UC Davis Health, UC Davis, Davis, California, USA
| | - Girija G. Konduri
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
- Children’s Research Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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10
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Garcia AJ, Viemari JC, Khuu MA. Respiratory rhythm generation, hypoxia, and oxidative stress-Implications for development. Respir Physiol Neurobiol 2019; 270:103259. [PMID: 31369874 DOI: 10.1016/j.resp.2019.103259] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 07/15/2019] [Accepted: 07/24/2019] [Indexed: 02/07/2023]
Abstract
Encountered in a number of clinical conditions, repeated hypoxia/reoxygenation during the neonatal period can pose both a threat to immediate survival as well as a diminished quality of living later in life. This review focuses on our current understanding of central respiratory rhythm generation and the role that hypoxia and reoxygenation play in influencing rhythmogenesis. Here, we examine the stereotypical response of the inspiratory rhythm from the preBötzinger complex (preBötC), basic neuronal mechanisms that support rhythm generation during the peri-hypoxic interval, and the physiological consequences of inspiratory network responsivity to hypoxia and reoxygenation, acute and chronic intermittent hypoxia, and oxidative stress. These topics are examined in the context of Sudden Infant Death Syndrome, apneas of prematurity, and neonatal abstinence syndrome.
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Affiliation(s)
- Alfredo J Garcia
- Institute for Integrative Physiology, Section of Emergency Medicine, The University of Chicago, Chicago, 60637, IL, United States
| | - Jean Charles Viemari
- Institut de Neurosciences de la Timone, P3M team, UMR7289 CNRS & AMU, Faculté de Médecine de la Timone, 27 Bd Jean Moulin, Marseille, 13005, France
| | - Maggie A Khuu
- Institute for Integrative Physiology, Section of Emergency Medicine, The University of Chicago, Chicago, 60637, IL, United States
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11
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Kouakam C, Stephan-Blanchard E, Léké A, Kongolo G, Haraux E, Delanaud S, Telliez F, Chardon K. The hypoxic test in preterm neonates reinvestigated. Pediatr Pulmonol 2018; 53:483-491. [PMID: 29136344 DOI: 10.1002/ppul.23907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 10/17/2017] [Indexed: 01/15/2023]
Abstract
AIM We currently lack a suitable gold-standard method for implementation on modern equipment to assess peripheral chemoreceptor sensitivity. The aim of the present study was to develop an accurate and reproducible method for assessing peripheral chemoreceptors sensitivity in sleeping preterm neonates. METHODS A poïkilocapnic hypoxic test was performed twice during rapid eye movement sleep (REM sleep) and non-rapid eye movement sleep (nonREM sleep). The infant breathed hypoxic gas (15% O2 ) for 60 s. The ventilatory response to hypoxia was assessed by comparing minute ventilation during the control period (21% O2 ) with successive 4-cycles sequences during hypoxia. We detected the first statistically significant increase in minute ventilation and recorded the corresponding response time. RESULTS During normoxia, minute ventilation was higher during REM sleep than in nonREM sleep (428.1 mL · min-1 · kg-1 [307.7-633.6]; 388.8 mL · min-1 · kg-1 [264.7-608.0], respectively; P = 0.001). After hypoxia, minute ventilation increased in both REM and nonREM sleep. The response was significantly higher in REM than in nonREM (25.3% [10.8-80.0] and 16.8% [7.5-33.2], respectively; P = 0.005). The intraclass correlation coefficients for all respiratory parameters were above 0.90. CONCLUSION We have developed a highly reliable method for assessing peripheral chemoreceptors sensitivity at the response time to hypoxia. In the future, researchers could use this method to assess the involvement of peripheral chemoreceptors in infants who experience chronic hypoxia (e.g. in bronchopulmonary dysplasia and recurrent apnea).
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Affiliation(s)
- Christelle Kouakam
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France
| | | | - André Léké
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France.,Department of Neonatal Medicine, University Hospital, Amiens, France
| | - Guy Kongolo
- Department of Pediatric Intensive Care Unit, University Hospital, Amiens, France
| | - Elodie Haraux
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France.,Department of Pediatric Surgery, University Hospital, Amiens, France
| | - Stéphane Delanaud
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France
| | - Frédéric Telliez
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France
| | - Karen Chardon
- PériTox-INERIS laboratory UMR_I 01, Jules Verne University of Picardy, Amiens, France
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12
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Ali K, Rosser T, Bhat R, Wolff K, Hannam S, Rafferty GF, Greenough A. Antenatal smoking and substance-misuse, infant and newborn response to hypoxia. Pediatr Pulmonol 2017; 52:650-655. [PMID: 27723956 DOI: 10.1002/ppul.23620] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 09/22/2016] [Accepted: 09/27/2016] [Indexed: 11/10/2022]
Abstract
OBJECTIVES To determine at the peak age for sudden infant death syndrome (SIDS) the ventilatory response to hypoxia of infants whose mothers substance misused in pregnancy (SM infants), or smoked during pregnancy (S mothers) and controls whose mothers neither substance misused or smoked. In addition, we compared the ventilatory response to hypoxia during the neonatal period and peak age of SIDS. WORKING HYPOTHESIS Infants of S or SM mothers compared to control infants would have a poorer ventilatory response to hypoxia at the peak age of SIDS. STUDY DESIGN Prospective, observational study. PATIENT-SUBJECT SELECTION Twelve S; 12 SM and 11 control infants were assessed at 6-12 weeks of age and in the neonatal period. METHODOLOGY Changes in minute volume, oxygen saturation, heart rate, and end tidal carbon dioxide levels on switching from breathing room air to 15% oxygen were assessed. Maternal and infant urine samples were tested for cotinine, cannabinoids, opiates, amphetamines, methadone, cocaine, and benzodiazepines. RESULTS The S and SM infants had a greater decline in minute volume (P = 0.037, P = 0.016, respectively) and oxygen saturation (P = 0.031) compared to controls. In all groups, the magnitude of decline in minute volume in response to hypoxia was higher in the neonatal period compared to at 6-12 weeks (P < 0.001). CONCLUSIONS Both maternal substance misuse and smoking were associated with an impaired response to a hypoxic challenge at the peak age for SIDS. The hypoxic ventilatory decline was more marked in the neonatal period compared to the peak age for SIDS indicating a maturational effect. Pediatr Pulmonol. 2017;52:650-655. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Kamal Ali
- Neonatal Intensive Care Unit, King's College Hospital NHS Foundation Trust, London, United Kingdom
| | - Thomas Rosser
- Division of Asthma, Allergy and Lung Biology, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, United Kingdom
| | - Ravindra Bhat
- Neonatal Intensive Care Unit, King's College Hospital NHS Foundation Trust, London, United Kingdom
| | - Kim Wolff
- Addiction Sciences Unit, King's College London, London, United Kingdom
| | - Simon Hannam
- Division of Asthma, Allergy and Lung Biology, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, United Kingdom
| | - Gerrard F Rafferty
- Division of Asthma, Allergy and Lung Biology, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, United Kingdom
| | - Anne Greenough
- Neonatal Intensive Care Unit, King's College Hospital NHS Foundation Trust, London, United Kingdom.,Division of Asthma, Allergy and Lung Biology, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, United Kingdom.,National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom
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13
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Trachsel D, Svendsen J, Erb T, von Ungern-Sternberg B. Effects of anaesthesia on paediatric lung function. Br J Anaesth 2016; 117:151-63. [DOI: 10.1093/bja/aew173] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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14
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Koos BJ, Rajaee A, Ibe B, Guerra C, Kruger L. Thalamic mediation of hypoxic respiratory depression in lambs. Am J Physiol Regul Integr Comp Physiol 2016; 310:R586-95. [PMID: 26818057 PMCID: PMC4867384 DOI: 10.1152/ajpregu.00412.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/27/2016] [Indexed: 11/22/2022]
Abstract
Immaturity of respiratory controllers in preterm infants dispose to recurrent apnea and oxygen deprivation. Accompanying reductions in brain oxygen tensions evoke respiratory depression, potentially exacerbating hypoxemia. Central respiratory depression during moderate hypoxia is revealed in the ventilatory decline following initial augmentation. This study determined whether the thalamic parafascicular nuclear (Pf) complex involved in adult nociception and sensorimotor regulation (Bentivoglio M, Balerecia G, Kruger L. Prog Brain Res 87: 53-80, 1991) also becomes a postnatal controller of hypoxic ventilatory decline. Respiratory responses to moderate isocapnic hypoxia were studied in conscious lambs. Hypoxic ventilatory decline was compared with peak augmentation. Pf and/or adjacent thalamic structures were destroyed by the neuron-specific toxin ibotenic acid (IB). IB lesions involving the thalamic Pf abolished hypoxic ventilatory decline. Lesions of adjacent thalamic nuclei that spared Pf and control injections of vehicle failed to blunt hypoxic respiratory depression. Our findings reveal that the thalamic Pf region is a critical controller of hypoxic ventilatory depression and thus a key target for exploring molecular concomitants of forebrain pathways regulating hypoxic ventilatory depression in early development.
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Affiliation(s)
- Brian J Koos
- Department of Obstetrics & Gynecology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California;
| | - Arezoo Rajaee
- Department of Obstetrics & Gynecology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
| | - Basil Ibe
- Department of Pediatrics, C. W. Steers Biological Resource Center, Los Angeles Biomedical Research Institute, Harbor-University of California Los Angeles Medical Center, Torrance, California; and
| | - Catalina Guerra
- C. W. Steers Biological Resource Center, Los Angeles Biomedical Research Institute, Harbor-University of California Los Angeles Medical Center, Torrance, California
| | - Lawrence Kruger
- Department of Neurobiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
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Abstract
Hypoxic episodes are troublesome components of bronchopulmonary dysplasia (BPD) in preterm infants. Immature respiratory control seems to be the major contributor, superimposed on abnormal respiratory function. Relatively short respiratory pauses may precipitate desaturation and bradycardia. This population is predisposed to pulmonary hypertension; it is likely that pulmonary vasoconstriction also plays a role. The natural history has been well-characterized in the preterm population at risk for BPD; however, the consequences are less clear. Proposed associations of intermittent hypoxia include retinopathy of prematurity, sleep disordered breathing, and neurodevelopmental delay. Future study should address whether these associations are causal relationships.
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Affiliation(s)
- Richard J. Martin
- Case Western Reserve University School of Medicine, Rainbow Babies & Children’s Hospital, 11100 Euclid Avenue, Suite RBC 3100, Cleveland, Ohio 44106-6010, Ph: 216-844-3387/Fax: 216-844-3380
| | - Juliann M. Di Fiore
- Case Western Reserve University, Rainbow Babies & Children’s Hospital, 11100 Euclid Avenue, Suite RBC 3100, Cleveland, Ohio 44106-6010, Ph: 216-368-1245/Fax: 216-844-3380
| | - Michele C. Walsh
- Case Western Reserve University School of Medicine, Rainbow Babies & Children’s Hospital, 11100 Euclid Avenue, Suite RBC 3100, Cleveland, Ohio 44106-6010, Ph: 216-844-3759/Fax: 216-844-3380
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16
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MacLean JE, Fitzgerald DA, Waters KA. Developmental changes in sleep and breathing across infancy and childhood. Paediatr Respir Rev 2015; 16:276-84. [PMID: 26364005 DOI: 10.1016/j.prrv.2015.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 08/06/2015] [Indexed: 11/24/2022]
Abstract
Sleep and breathing are physiological processes that begin in utero and undergo progressive change. While the major period of change for both sleep and breathing occurs during the months after birth, considered a period of vulnerability, more subtle changes continue to occur throughout childhood. The systems that control sleep and breathing develop separately, but sleep represents an activity state during which breathing and breathing control is significantly altered. Infants and young children may spend up to 12 hours a day sleeping; therefore, the effects of sleep on breathing are fundamental to understanding both processes in childhood. This review summarizes the current literature relevant to understanding the normal development of sleep and breathing across infancy and childhood.
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Affiliation(s)
- Joanna E MacLean
- Division of Respiratory Medicine, Department of Pediatrics, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, AB, Canada; Discipline of Paediatrics & Child Health, Sydney Medical School, University of Sydney, Australia; Department of Respiratory Medicine, The Children's Hospital at Westmead, Sydney, NSW, Australia.
| | - Dominic A Fitzgerald
- Discipline of Paediatrics & Child Health, Sydney Medical School, University of Sydney, Australia; Department of Respiratory Medicine, The Children's Hospital at Westmead, Sydney, NSW, Australia
| | - Karen A Waters
- Discipline of Paediatrics & Child Health, Sydney Medical School, University of Sydney, Australia; Department of Respiratory Medicine, The Children's Hospital at Westmead, Sydney, NSW, Australia
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Horne RSC, Nixon GM. The role of physiological studies and apnoea monitoring in infants. Paediatr Respir Rev 2014; 15:312-8. [PMID: 25304428 DOI: 10.1016/j.prrv.2014.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 09/15/2014] [Indexed: 11/18/2022]
Abstract
There is evidence that failure of cardio-respiratory control mechanisms plays a role in the final event of the Sudden Infant Death Syndrome (SIDS). Physiological studies during sleep in both healthy term born infants and those at increased risk for SIDS have been widely used to investigate how the major risk and protective factors for SIDS identified from epidemiological studies might alter infant physiology. Clinical polysomnography (PSG) in infants who eventually succumbed to SIDS however demonstrated abnormalities that were neither sufficiently distinctive nor predictive to support routine use of PSG for infants at risk for SIDS. PSG findings have also been shown to be not predictive of recurrence of Apparent Life Threatening Events (ALTE) and thus international guidelines state that PSG is not indicated for routine evaluation in infants with an uncomplicated ALTE, although PSG may be indicated when there is clinical evidence of a sleep related breathing disorder. A decision to undertake home apnoea monitoring should consider the potential advantages and disadvantages of monitoring for that individual, in the knowledge that there is no evidence of the efficacy of such devices in preventing SIDS.
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Affiliation(s)
- Rosemary S C Horne
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Department of Paediatrics, Monash University, Level 5, Monash Medical Centre, 246 Clayton Rd, Clayton, Victoria, Australia 3168.
| | - Gillian M Nixon
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Department of Paediatrics, Monash University, Level 5, Monash Medical Centre, 246 Clayton Rd, Clayton, Victoria, Australia 3168
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18
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Abstract
During the first year of life and particularly the first 6 months autonomic control of the cardio-respiratory system is still undergoing maturation and infants are at risk of cardio-respiratory instability. These instabilities are most marked during sleep, which is important as infants spend the majority of each 24 hours in sleep. Sleep state has a marked effect on the cardio-respiratory system with instabilities being more common in active sleep compared to quiet sleep. Responses to hypoxia are also immature during infancy and may make young infants more vulnerable to cardio-respiratory instability. It has been proposed that an inability to respond appropriately to a life threatening event underpins the Sudden Infant Death Syndrome (SIDS). The major risk factors for SIDS, prone sleeping and maternal smoking, both impair cardio-respiratory control in normal healthy term infants.
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Affiliation(s)
- Rosemary S C Horne
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Level 5, Monash Medical Centre, 246 Clayton Rd, Clayton, Victoria, Australia 3168.
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19
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The physiological determinants of sudden infant death syndrome. Respir Physiol Neurobiol 2013; 189:288-300. [PMID: 23735486 DOI: 10.1016/j.resp.2013.05.032] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/19/2013] [Accepted: 05/27/2013] [Indexed: 01/08/2023]
Abstract
It is well-established that environmental and biological risk factors contribute to Sudden Infant Death Syndrome (SIDS). There is also growing consensus that SIDS requires the intersection of multiple risk factors that result in the failure of an infant to overcome cardio-respiratory challenges. Thus, the critical next steps in understanding SIDS are to unravel the physiological determinants that actually cause the sudden death, to synthesize how these determinants are affected by the known risk factors, and to develop novel ideas for SIDS prevention. In this review, we will examine current and emerging perspectives related to cardio-respiratory dysfunctions in SIDS. Specifically, we will review: (1) the role of the preBötzinger complex (preBötC) as a multi-functional network that is critically involved in the failure to adequately respond to hypoxic and hypercapnic challenges; (2) the potential involvement of the preBötC in the gender and age distributions that are characteristic for SIDS; (3) the link between SIDS and prematurity; and (4) the potential relationship between SIDS, auditory function, and central chemosensitivity. Each section underscores the importance of marrying the epidemiological and pathological data to experimental data in order to understand the physiological determinants of this syndrome. We hope that a better understanding will lead to novel ways to reduce the risk to succumb to SIDS.
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20
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Apnea of prematurity--perfect storm. Respir Physiol Neurobiol 2013; 189:213-22. [PMID: 23727228 DOI: 10.1016/j.resp.2013.05.026] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Revised: 05/17/2013] [Accepted: 05/21/2013] [Indexed: 12/23/2022]
Abstract
With increased survival of preterm infants as young as 23 weeks gestation, maintaining adequate respiration and corresponding oxygenation represents a clinical challenge in this unique patient cohort. Respiratory instability characterized by apnea and periodic breathing occurs in premature infants because of immature development of the respiratory network. While short respiratory pauses and apnea may be of minimal consequence if oxygenation is maintained, they can be problematic if accompanied by chronic intermittent hypoxemia. Underdevelopment of the lung and the resultant lung injury that occurs in this population concurrent with respiratory instability creates the perfect storm leading to frequent episodes of profound and recurrent hypoxemia. Chronic intermittent hypoxemia contributes to the immediate and long term co-morbidities that occur in this population. In this review we discuss the pathophysiology leading to the perfect storm, diagnostic assessment of breathing instability in this unique population and therapeutic interventions that aim to stabilize breathing without contributing to tissue injury.
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Garcia AJ, Koschnitzky JE, Dashevskiy T, Ramirez JM. Cardiorespiratory coupling in health and disease. Auton Neurosci 2013; 175:26-37. [PMID: 23497744 DOI: 10.1016/j.autneu.2013.02.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/21/2013] [Accepted: 02/08/2013] [Indexed: 10/27/2022]
Abstract
Cardiac and respiratory activities are intricately linked both functionally as well as anatomically through highly overlapping brainstem networks controlling these autonomic physiologies that are essential for survival. Cardiorespiratory coupling (CRC) has many potential benefits creating synergies that promote healthy physiology. However, when such coupling deteriorates autonomic dysautonomia may ensue. Unfortunately there is still an incomplete mechanistic understanding of both normal and pathophysiological interactions that respectively give rise to CRC and cardiorespiratory dysautonomia. Moreover, there is also a need for better quantitative methods to assess CRC. This review addresses the current understanding of CRC by discussing: (1) the neurobiological basis of respiratory sinus arrhythmia (RSA); (2) various disease states involving cardiorespiratory dysautonomia; and (3) methodologies measuring heart rate variability and RSA.
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Affiliation(s)
- Alfredo J Garcia
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
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22
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MacLean JE, Tan S, Fitzgerald DA, Waters KA. Assessing ventilatory control in infants at high risk of sleep disordered breathing: a study of infants with cleft lip and/or palate. Pediatr Pulmonol 2013; 48:265-73. [PMID: 22528960 DOI: 10.1002/ppul.22568] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 04/01/2012] [Indexed: 11/10/2022]
Abstract
Neonatal exposure to intermittent hypoxia results in altered ventilatory response to subsequent hypoxia in animal models. The effect of similar exposure in human infants is unknown. Our objective was to determine the impact of sleep disordered breathing (SDB) in early infancy on ventilatory response in infants. We recruited consecutive infants with cleft lip and/or palate (CL/P) to undergo ventilatory response testing using exposure to a hypoxic (15% O(2) ) gas mixture during sleep. This population is at high risk of SDB because of smaller airway caliber and abnormal palatal muscle attachments predisposing them to airway obstruction of ranging severity from birth. Ventilatory responses were compared between infants with a low apnea-hypopnea index (AHI; AHI < 15 events/hr) and a high AHI (AHI ≥ 15 events/hr). Testing was successfully completed in 22 of 23 infants who underwent testing at 4.4 ± 4.8 months. Infants with high AHI had lower weight z-scores, higher number of oxygen desaturation events during sleep, but similar oxygen saturation (S(p) O(2) ) nadir compared to infants with low AHI. The pattern of ventilatory response to hypoxia differed between the two groups; infants with high AHI had an earlier ventilatory decline and a blunted maximal ventilatory response to hypoxia. Infants with a high AHI use a different strategy to augment ventilation in response to hypoxia; while infants with a low AHI initially increased respiratory rate, tidal volume was the first parameter to increase in infants with high AHI. These results demonstrate that SDB in infancy is associated with altered ventilatory response to hypoxia.
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Affiliation(s)
- Joanna E MacLean
- Division of Respiratory Medicine, Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada.
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23
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Physiologic basis for intermittent hypoxic episodes in preterm infants. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 758:351-8. [PMID: 23080182 DOI: 10.1007/978-94-007-4584-1_47] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intermittent hypoxic episodes are typically a consequence of immature respiratory control and remain a troublesome challenge for the neonatologist. Furthermore, their frequency and magnitude are commonly underestimated by clinically employed pulse oximeter settings. In extremely low birth weight infants the incidence of intermittent hypoxia [IH] progressively increases over the first 4 weeks of postnatal life, with a subsequent plateau followed by a slow decline beginning at weeks six to eight. Over this period of unstable respiratory control, increased oxygen-sensitive peripheral chemoreceptor activity has been associated with a higher incidence of apnea of prematurity. In contrast, infants with bronchopulmonary dysplasia [chronic neonatal lung disease] exhibit decreased peripheral chemosensitivity, although the effect on respiratory stability in this population is unclear. Such episodic hypoxia/reoxygenation in early life has the potential to sustain a proinflammatory cascade with resultant multisystem, including respiratory, morbidity. Therapeutic approaches for intermittent hypoxic episodes comprise careful titration of baseline or supplemental inspired oxygen as well as xanthine therapy to prevent apnea of prematurity. Characterization of the pathophysiologic basis for such intermittent hypoxic episodes and their consequences during early life is necessary to provide an evidence-based approach to their management.
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24
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Abstract
In infants and children with chronic respiratory disease, hypoxia is a potential risk of aircraft travel. Although guidelines have been published to assist clinicians in assessing an individual's fitness to fly, they are not wholly evidence based. In addition, most evidence relates to adults with chronic obstructive pulmonary disease and thus cannot be extrapolated to children and infants. This review summarises the current literature as it applies to infants and children potentially at risk during air travel. Current evidence suggests that the gold standard for assessing fitness to fly, the hypoxia flight simulation test, may not be accurate in predicting in flight hypoxia in infants and children with respiratory disease. Further research is needed to determine the best methods of assessing safety of flight in infants and children.
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Affiliation(s)
- Adelaide Withers
- Respiratory Medicine, Princess Margaret Hospital, Perth, Australia.
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25
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Abstract
Apnea of prematurity (AOP) is a significant clinical problem manifested by an unstable respiratory rhythm reflecting the immaturity of respiratory control systems. This review will address the pathogenesis of and treatment strategies for AOP. Although the neuronal mechanisms leading to apnea are still not well understood, recent decades have provided better insight into the generation of the respiratory rhythm and its modulation in the neonate. Ventilatory responses to hypoxia and hypercarbia are impaired and inhibitory reflexes are exaggerated in the neonate. These unique vulnerabilities predispose the neonate to the development of apnea. Treatment strategies attempt to stabilize the respiratory rhythm. Caffeine remains the primary pharmacological treatment modality and is presumed to work through blockade of adenosine receptors A(1) and A(2). Recent evidences suggest that A(2A) receptors may have a greater role than previously thought. AOP typically resolves with maturation suggesting increased myelination of the brainstem.
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Affiliation(s)
- O P Mathew
- Section of Neonatology, Department of Pediatrics, Medical College of Georgia, Augusta, GA 30912-3740, USA.
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26
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Osona Rodríguez de Torres B, Asensio de la Cruz O, Peña Zarza JA, Figuerola Mulet J, Aguilar Fernández AJ. [Recommendations for management of patients with lung disease planning a flight or high altitude travel]. An Pediatr (Barc) 2011; 75:64.e1-11. [PMID: 21429828 DOI: 10.1016/j.anpedi.2010.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 12/01/2010] [Accepted: 12/13/2010] [Indexed: 11/17/2022] Open
Abstract
Every year a large number of children travel by plane and/or to places with high altitudes. Most of these journeys occur without incident. Immigration and recent socioeconomic changes have also increased the number of patients with cardiopulmonary disease who travel. Environmental changes in these places, especially lower oxygen, can lead to a risk of significant adverse events. The paediatrician must be aware of the diseases that are susceptible to complications, as well as the necessary preliminary studies and recommendations for treatment in these circumstances. The Techniques Group of the Spanish Society of Paediatric Chest Diseases undertook to design a document reviewing the literature on the subject, providing some useful recommendations in the management of these patients.
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Abstract
Most abnormalities of ventilatory control in infants are due to immaturity or abnormal development of ventilatory control. This includes a broad range, from rare disorders like congenital central hypoventilation syndrome to common problems such as apnoea of prematurity. Development of the ventilatory control system, including central respiratory rhythmogenesis and central and peripheral chemoreception, begins early in gestation and continues for weeks or months after birth. Development of the neural components of central rhythmogenesis and their highly complex interconnectivity results from complex, timing-sensitive interactions between patterning and other genes, transcription factors and neurotrophic factors. At birth, nearly all aspects of ventilatory control remain immature, especially in preterm infants; and postnatal maturation can be altered by hypoxia, toxins and other stressors. Clinical care may be greatly enhanced by increased awareness of ventilatory control maturation and related disorders.
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Affiliation(s)
- John L Carroll
- University of Arkansas for Medical Sciences, Department of Pediatrics, Division of Pulmonary Medicine, Arkansas Children's Hospital, Little Rock, Arkansas 72212, USA.
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28
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Bloch-Salisbury E, Hall MH, Sharma P, Boyd T, Bednarek F, Paydarfar D. Heritability of apnea of prematurity: a retrospective twin study. Pediatrics 2010; 126:e779-87. [PMID: 20837586 DOI: 10.1542/peds.2010-0084] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Apnea of prematurity (AOP) is a disturbance in respiratory rhythm defined by idiopathic pauses in breathing that reduce blood oxygen levels and/or heart rate. It is a major clinical problem among preterm infants. OBJECTIVES The primary goal of this study was to estimate the genetic susceptibility to AOP in a cohort of preterm twins. A secondary aim was to identify risk factors associated with AOP in this cohort. METHODS A single-center, retrospective study (2000-2008) was performed by using data from 317 premature twin pairs (<36 weeks' gestational age). Heritability estimates were determined by comparing intrapair AOP concordance between 56 monozygotic and 161 dizygotic twin pairs by using structural equation modeling. Risk factors of AOP among a cohort of 543 premature twins were assessed by using mixed-effects logistic regression. RESULTS The heritability of AOP was 87% (95% confidence interval [CI]: 0.64-0.97) among same-gender twins. A gender-dependent model revealed that genetic factors accounted for 99% of the variance in male twins (95% CI: 0.89-1.00) and 78% of the variance in female twins (95% CI: 0.49-0.94). Significant risk factors for AOP were low gestational age (P<.001), cesarean delivery (P=.017), and conception through assisted reproductive technologies (P=.008). CONCLUSIONS These findings suggest that AOP has an important genetic basis underlying this developmental-related disorder of respiratory control. Future genomic studies may provide information on pathophysiological mechanisms that underlie AOP.
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Affiliation(s)
- Elisabeth Bloch-Salisbury
- Department of Neurology, University of Massachusetts Medical School, 55 Lake Ave N, Worcester, MA 01655, USA.
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Apnea of prematurity: What can observational studies tell us about pathophysiology? Sleep Med 2010; 11:701-7. [DOI: 10.1016/j.sleep.2009.11.016] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 10/30/2009] [Accepted: 11/04/2009] [Indexed: 11/21/2022]
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Teppema LJ, Dahan A. The Ventilatory Response to Hypoxia in Mammals: Mechanisms, Measurement, and Analysis. Physiol Rev 2010; 90:675-754. [DOI: 10.1152/physrev.00012.2009] [Citation(s) in RCA: 257] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The respiratory response to hypoxia in mammals develops from an inhibition of breathing movements in utero into a sustained increase in ventilation in the adult. This ventilatory response to hypoxia (HVR) in mammals is the subject of this review. The period immediately after birth contains a critical time window in which environmental factors can cause long-term changes in the structural and functional properties of the respiratory system, resulting in an altered HVR phenotype. Both neonatal chronic and chronic intermittent hypoxia, but also chronic hyperoxia, can induce such plastic changes, the nature of which depends on the time pattern and duration of the exposure (acute or chronic, episodic or not, etc.). At adult age, exposure to chronic hypoxic paradigms induces adjustments in the HVR that seem reversible when the respiratory system is fully matured. These changes are orchestrated by transcription factors of which hypoxia-inducible factor 1 has been identified as the master regulator. We discuss the mechanisms underlying the HVR and its adaptations to chronic changes in ambient oxygen concentration, with emphasis on the carotid bodies that contain oxygen sensors and initiate the response, and on the contribution of central neurotransmitters and brain stem regions. We also briefly summarize the techniques used in small animals and in humans to measure the HVR and discuss the specific difficulties encountered in its measurement and analysis.
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Affiliation(s)
- Luc J. Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
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32
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Arousal response to hypoxia in newborns: Insights from animal models. Biol Psychol 2010; 84:39-45. [DOI: 10.1016/j.biopsycho.2009.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 11/30/2009] [Accepted: 12/02/2009] [Indexed: 11/24/2022]
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Steggerda JA, Mayer CA, Martin RJ, Wilson CG. Effect of intermittent hypercapnia on respiratory control in rat pups. Neonatology 2010; 97:117-23. [PMID: 19752577 PMCID: PMC3696363 DOI: 10.1159/000237222] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 01/13/2009] [Indexed: 11/19/2022]
Abstract
Preterm infants are subject to fluctuations in blood gas status associated with immature respiratory control. Intermittent hypoxia during early postnatal life has been shown to increase chemoreceptor sensitivity and destabilize the breathing pattern; however, intermittent hypercapnia remains poorly studied. Therefore, to test the hypothesis that intermittent hypercapnia results in altered respiratory control, we examined the effects of daily exposure to intermittent hypercapnia on the ventilatory response to subsequent hypercapnic and hypoxic exposure in neonatal rat pups. Exposure cycles consisted of 5 min of intermittent hypercapnia (5% CO(2), 21% O(2), balance N(2)) followed by 10 min of normoxia. Rat pups were exposed to 18 exposure cycles each day for 1 week, from postnatal day 7 to 14. We analyzed diaphragm electromyograms (EMGs) from pups exposed to subsequent acute hypercapnic (5% CO(2)) and hypoxic (12% O(2)) challenges. In response to a subsequent hypercapnia challenge, there was no significant difference in the ventilatory response between control and intermittent hypercapnia-exposed groups. In contrast, intermittent hypercapnia-exposed rat pups showed an enhanced ventilatory response to hypoxic challenge with an increase in minute EMG to 118 +/- 14% of baseline versus 107 +/- 13% for control pups (p < 0.05). We speculate that prior hypercapnic exposure may increase peripheral chemoreceptor response to subsequent hypoxic exposures and result in perturbed neonatal respiratory control.
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Affiliation(s)
- Justin A Steggerda
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, USA
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34
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Wong-Riley MTT, Liu Q. Neurochemical and physiological correlates of a critical period of respiratory development in the rat. Respir Physiol Neurobiol 2009; 164:28-37. [PMID: 18524695 DOI: 10.1016/j.resp.2008.04.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 04/22/2008] [Accepted: 04/22/2008] [Indexed: 01/27/2023]
Abstract
Despite its vital importance to life, respiration is not mature at birth in mammals, but rather, it undergoes a great deal of growth, refinement, and adjustments postnatally. Many adjustments do not follow smooth paths, but assume abrupt changes during certain postnatal periods that may render the animal less capable of responding to respiratory stressors. The present review focuses on neurochemical and physiological correlates of a critical period of respiratory development in the rat. In addition to an imbalanced expression of reduced excitatory and enhanced inhibitory neurotransmitters, a switch in the expressions of gamma-aminobutyric acid (GABA)A receptor subunits from alpha3 to alpha1 occurs around postnatal day (P)12 in the pre-Bötzinger nucleus and the ventrolateral subnucleus of the solitary tract nucleus. Possible subunit switches in a number of other neurotransmitter receptors are discussed. These neurochemical changes are paralleled by ventilatory adjustments at the end of the second postnatal week. At P13 and under normoxia, respiratory frequency reaches its peak before assuming a gradual fall, and both tidal volume and minute ventilation exhibit a significant rise prior to a plateau or a gradual decline until P21. The response to acute hypoxia is markedly reduced between P12 and P16, being lowest at P13. Thus, the end of the second postnatal week can be considered as a critical period of respiratory development, during which multiple neurochemical and physiological adjustments and switches are orchestrated at the same time, rendering the system extremely dynamic but, at the same time, vulnerable to externally imposed perturbations and insults. The critical period embodies a time of multi-system, multifaceted growth and adjustments. It is a plastic, transitional period that is also a part of the normal development of the respiratory system.
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Affiliation(s)
- Margaret T T Wong-Riley
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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Abstract
Apnea of prematurity (AOP) remains a major clinical problem in present day neonatology that warrants frequent evaluations and imposes challenges in therapeutic strategies. Although the pathogenesis of AOP is poorly understood, it is probably a manifestation of physiologic immaturity of breathing control rather than a pathologic disorder. Immature breathing responses to hypoxia, hypercapnia and exaggerated inhibitory pulmonary reflexes in preterm infants might also contribute to the occurrence or severity of AOP. Recent data suggest a role for genetic predisposition. Although typically resolve with maturation, the role of bradycardia and desaturation episodes associated with AOP in the development of sleep disorder breathing and neurodevelopmental delay needs further clarification. Pharmacological treatment with methylxanthines and CPAP remain the mainstay for treatment of AOP. However, recent studies have implicated central inhibitory neuromodulators including prostaglandins, GABA and adenosine in its pathogenesis, the fact that might provide future specific targets for treatment. This review will summarize new insights involving these issues as well as others involving the pathogenesis, treatment strategies and consequences of apnea in premature infants.
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Affiliation(s)
- Jalal M Abu-Shaweesh
- Rainbow Babies & Children's Hospital, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106-6010, USA
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VERBEEK MARJANMA, RICHARDSON HEIDIL, PARSLOW PETERM, WALKER ADRIANM, HARDING RICHARD, HORNE ROSEMARYSC. Arousal and ventilatory responses to mild hypoxia in sleeping preterm infants. J Sleep Res 2008; 17:344-53. [DOI: 10.1111/j.1365-2869.2008.00653.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Resnick SM, Hall GL, Simmer KN, Stick SM, Sharp MJ. The Hypoxia Challenge Test Does Not Accurately Predict Hypoxia in Flight in Ex-Preterm Neonates. Chest 2008; 133:1161-6. [DOI: 10.1378/chest.07-2375] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Bollen B, Bouslama M, Matrot B, D'Hooge R, Van den Bergh O, Gallego J. Learned defense response to hypoxia in newborn mice. Neurosci Lett 2007; 420:268-72. [PMID: 17532570 DOI: 10.1016/j.neulet.2007.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 04/24/2007] [Accepted: 05/06/2007] [Indexed: 11/16/2022]
Abstract
In newborns, hypoxia elicits defensive behaviors including awakening from sleep, body movements and crying. An inability to produce this defense response is a risk factor for sudden infant death syndrome and other respiratory control disorders. In this study, we examined the possibility that the defense response to hypoxia in newborns is partly determined by early exposure to hypoxia. We explored this possibility in 6-day-old mice, which resemble human preterm infants of approximately 25-30 weeks' gestational age. Ultrasonic vocalizations (USVs) were recorded as a marker for the defense response to hypoxia. In a conditioning experiment, newborn mice were exposed to two artificial odors (conditioned stimuli, CS). For acquisition (two trials), pups were exposed to one odor (CS+) in a hypoxic gas mixture (10% O2, which was the unconditioned stimulus, US) and to another odor (CS-) in air. Then, the pups were exposed to each odor while breathing air. Newborn mice produced significantly more USVs when exposed to the odor previously paired with hypoxia than to the control odor. Thus, associative learning may shape the defense response to hypoxia in newborns.
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Affiliation(s)
- Bieke Bollen
- INSERM, U676, Robert-Debré Teaching Hospital, 75019 Paris, France, and Laboratory of Biological Psychology, Department of Psychology, University of Leuven, B-3000 Leuven, Belgium
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Richardson HL, Parslow PM, Walker AM, Harding R, Horne RSC. Maturation of the initial ventilatory response to hypoxia in sleeping infants. J Sleep Res 2007; 16:117-27. [PMID: 17309771 DOI: 10.1111/j.1365-2869.2007.00575.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In infants most previous studies of the hypoxic ventilatory response (HVR) have been conducted only during quiet sleep (QS) and arousal responses have not been considered. Our aim was to quantify the maturation of the HVR in term infants during both active sleep (AS) and QS over the first 6 months of life. Daytime polysomnography was performed on 15 healthy term infants at 2-5 weeks, 2-3 and 5-6 months after birth and infants were challenged with hypoxia (15% O2, balance N2). Tests in AS always resulted in arousal; in QS tests infants either aroused or did not arouse. A biphasic HVR was observed in non arousing tests at all three ages studied. The fall in SpO2 was more rapid in arousal tests at all three ages. At 2-5 weeks, in non-arousing QS tests, there was a greater fall in respiratory frequency (f) despite a smaller fall in SpO2 compared with 2-3 and 5-6 months. When infants aroused there was no difference in the HVR between sleep states or with postnatal age. However, when infants failed to arouse from QS, arterial desaturation was less in the younger infants despite a poorer HVR. We suggest that arousal in response to hypoxia, particularly in AS, is a vital survival mechanism throughout the first 6 months of life.
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Affiliation(s)
- Heidi L Richardson
- Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Melbourne, Vic., Australia
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Darnall RA, Ariagno RL, Kinney HC. The late preterm infant and the control of breathing, sleep, and brainstem development: a review. Clin Perinatol 2006; 33:883-914; abstract x. [PMID: 17148011 DOI: 10.1016/j.clp.2006.10.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The brainstem development of infants born between 33 and 38 weeks' gestation is less mature than that of a full-term infant. During late gestation, there are dramatic and nonlinear developmental changes in the brainstem. This translates into immaturity of upper airway and lung volume control, laryngeal reflexes, chemical control of breathing, and sleep mechanisms. Ten percent of late preterm infants have significant apnea of prematurity and they frequently have delays in establishing coordination of feeding and breathing. Unfortunately, there is a paucity of clinical, physiologic, neuroanatomic, and neurochemical data in this specific group of infants. Research focused on this group of infants will not only further our understanding of brainstem maturation during this high risk period, but will help develop focused plans for their management.
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Affiliation(s)
- Robert A Darnall
- Department of Physiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
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Liu Q, Lowry TF, Wong-Riley MTT. Postnatal changes in ventilation during normoxia and acute hypoxia in the rat: implication for a sensitive period. J Physiol 2006; 577:957-70. [PMID: 17038423 PMCID: PMC1890370 DOI: 10.1113/jphysiol.2006.121970] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Previously, we found heightened expression of inhibitory neurochemicals and depressed expression of excitatory neurochemicals with a sudden drop in metabolic activity around postnatal day (P) 12 in rat brainstem respiratory nuclei, suggesting that this period is a critical window during which respiratory control or regulation may be distinctly different. To test this hypothesis, the hypoxic ventilatory responses (HVR) to 10% oxygen were tested in rats every day from P0 to P21. Our data indicate that (1) during normoxia (N), breathing frequency (f) increased with age, peaking at P13, followed by a gradual decline, whereas both tidal volume (V(T)) and minute ventilation (.V(E) ) significantly increased in the second postnatal week, followed by a progressive increase in V(T) and a relative plateau in .V(E); (2) during 5 min of hypoxia (H), .V(E) exhibited a biphasic response from P3 onward. Significantly, the ratio of .V(E)(H) to .V(E)(N) was generally > 1 during development, except for P13-16, when it was < 1 after the first 1-2 min, with the lowest value at P13; (3) the H : N ratio for f, V(T) and .V(E) during the first 30 s and the last minute of hypoxia all showed a distinct dip at P13, after which the V(T) and .V(E) values rose again, while the f values declined through P21; and (4) the H : N ratios for f, V(T) and .V(E) averaged over 5 min of hypoxia all exhibited a sudden fall at P13. The f ratio remained low thereafter, while those for V(T) and .V(E) increased again with age until P21. Thus, hypoxic ventilatory response is influenced by both f and V(T) before P13, but predominantly by V(T) after P13. The striking changes in normoxic ventilation as well as HVR at or around P13, together with our previous neurochemical and metabolic data, strongly suggests that the end of the second postnatal week is a critical period of development for brainstem respiratory nuclei in the rat.
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Affiliation(s)
- Qiuli Liu
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Richardson HL, Parslow PM, Walker AM, Harding R, Horne RSC. Variability of the initial phase of the ventilatory response to hypoxia in sleeping infants. Pediatr Res 2006; 59:700-4. [PMID: 16627885 DOI: 10.1203/01.pdr.0000214978.94064.66] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most of the available data on the hypoxic ventilatory response (HVR) in infants has been obtained in quiet sleep (QS), and only one study has made repeated tests in the same infant. We aimed to gain a more complete knowledge of the maturation and consistency of the initial phase of the HVR by performing multiple tests in both QS and active sleep (AS) over the first 6 mo of life in term infants. Fifteen healthy term infants were studied with daytime polysomnography longitudinally at 2-5 wk, 2-3 mo, and 5-6 mo after birth. Each infant received multiple hypoxic (15% O2, balance N2) challenges (three or more) in both AS and QS. In AS, infants consistently aroused to hypoxia; however, in QS, infants both aroused and failed to arouse. The initial phase of the HVR varied considerably between infants with the changes in ventilation/kg [SD of inspired minute ventilation per kilogram of body weight (V(I)/kg)] being more variable during AS than QS at all three ages and overall decreasing with postnatal age in both sleep states. The variability between replicate V(I)/kg measurements was also significantly greater in AS compared with QS at 2-5 wk postnatal age. There was no evidence of habituation to repeated hypoxic tests in either sleep state. Our study has demonstrated that the initial phase of the HVR is variable both between and within term infants in both AS and QS, with responses being markedly more variable during AS, and becoming more consistent with increasing postnatal age. By performing only one test or by failing to account for arousal responses, previous studies may not have detected the natural variation of the infant HVR.
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Affiliation(s)
- Heidi L Richardson
- Ritchie Centre for Baby Health Research, Monash University, Clayton, Victoria 3168, Australia
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Horne RSC, Parslow PM, Harding R. Postnatal development of ventilatory and arousal responses to hypoxia in human infants. Respir Physiol Neurobiol 2005; 149:257-71. [PMID: 15876558 DOI: 10.1016/j.resp.2005.03.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 02/15/2005] [Accepted: 03/14/2005] [Indexed: 11/18/2022]
Abstract
During the first year of life there is significant maturation of the hypoxic ventilatory response (HVR) in human infants. Compared with adults, healthy term infants have an immature HVR until at least 6 months of age. There are few studies in infants on the effects of sleep state on the HVR but these suggest that at early postnatal ages there is initially no sleep-state related difference; this is followed by a developmental trend towards the adult situation in which the response is depressed in REM sleep compared with NREM. Maternal cigarette smoking is a major risk factor for SIDS and the mechanism for this may involve a depressed HVR in the exposed infant; however studies are limited and the wide variation in cigarette consumption makes interpretation of results difficult. Arousal responses to hypoxia are of vital importance and a failure to arouse has been implicated in SIDS. Sleeping infants frequently fail to arouse in response to hypoxia in QS, whereas in AS they invariably arouse; furthermore arousal latency is longer in QS compared with AS. The oxygen saturation at which infants arouse is not different between sleep states, suggesting that desaturation is more rapid in AS. In QS younger infants arouse more readily than at older ages and arousal is depressed by maternal smoking. These findings suggest that depression of the arousal response to hypoxia in AS may have life-threatening consequences. Infants at increased risk for SIDS have been shown to have both depressed ventilatory and arousal responses to hypoxia, thus they may be at even greater risk.
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Affiliation(s)
- Rosemary S C Horne
- Ritchie Centre for Baby Health Research, Monash University, Level 5, Monash Medical Centre, 246 Clayton Road, Clayton, Vic. 3168, Australia.
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Kinkead R, Genest SE, Gulemetova R, Lajeunesse Y, Laforest S, Drolet G, Bairam A. Neonatal maternal separation and early life programming of the hypoxic ventilatory response in rats. Respir Physiol Neurobiol 2005; 149:313-24. [PMID: 15894516 DOI: 10.1016/j.resp.2005.04.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Revised: 04/14/2005] [Accepted: 04/14/2005] [Indexed: 11/29/2022]
Abstract
The neonatal period is critical for central nervous system (CNS) development. Recent studies have shown that this basic neurobiological principle also applies to the neural circuits regulating respiratory activity as exposure to excessive or insufficient chemosensory stimuli during early life can have long-lasting consequences on the performance of this vital system. Although the tactile, olfactory, and auditory stimuli that the mother provides to her offspring during the neonatal period are not directly relevant to respiratory homeostasis, they likely contribute to respiratory control development. This review outlines the rationale for the link between maternal stimuli and programming of the hypoxic ventilatory response during early life, and presents recent results obtained in rats indicating that experimental disruption of mother-pup interaction during this critical period elicits significant phenotypic plasticity of the hypoxic ventilatory response.
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Affiliation(s)
- Richard Kinkead
- Pediatrics, Centre de Recherche Hospitalier Universitaire de Québec, Université Laval, Québec, Qué., Canada.
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45
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Abstract
The neural control of respiratory airflow via the vocal fold is characterized by inspiratory abduction and postinspiratory (early expiratory) adduction causing decreases and increases in glottal resistance, respectively. The postinspiratory increase in glottal resistance plays a major role in braking the speed of expiratory airflow, to act against the high recoil pressure of the neonatal rat lung. In the present study, we investigated changes in upper airway patency during severe hypoxia in neonatal rats. We measured dynamic changes in subglottal pressure during normoxic and hypoxic conditions in an arterially perfused brainstem preparation in which we could control gas tensions accurately. Initially, hypoxia (5% O(2), 5% CO(2), and 90% nitrogen) produced an excitatory response in phrenic nerve activity accompanied by augmentation of both inspiratory-related glottal dilation and postinspiratory glottal constriction. Later, during the early stages of hypoxia-induced respiratory depression and initiation of gasping, we observed a massive reduction of the respiratory modulation of glottal resistance. In most preparations, this was transient and replaced by a paradoxic inspiratory-related glottal constriction. We propose that during severe hypoxia in the in situ preparation, paradoxic inspiratory glottal constriction can be observed during gasping, and this may impair ventilation despite the persistence of rhythmic contractions of the respiratory muscles. The latter is of clinical interest, because this may relate to the finding of cot death victims who died as a result of upper airway obstruction but without apparent apnea or rebreathing.
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Affiliation(s)
- Mathias Dutschmann
- Department of Physiology, University of Göttingen, 37076 Göttingen, Germany.
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46
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Abstract
Apnea, the cessation of respiratory airflow, can begin in many preterm infants in the first week of life and can last until the day of discharge or beyond. This article provides an overview of the complex anatomic, physiological, and developmental mechanisms related to immaturity of both the central nervous system and musculature of the pulmonary system, that contribute to apnea of prematurity. Apnea of prematurity is a diagnosis of exclusion; an array of other conditions and stimuli can also cause apnea, including infections, pulmonary disease, and intracranial pathology. The standard clinical management of apnea, including cutaneous stimulation, methylxanthine therapy, and continuous positive airway pressure or ventilatory support, are discussed as well as newer investigational therapies, such as olfactory stimulation. Emerging evidence on the long-term neurodevelopmental impact of apnea is reviewed. Nursing measures to prevent and manage apnea are reviewed with an emphasis on parent education and preparation for discharge. Apnea resolves in most preterm infants as they approach term corrected gestational age; however, if it does not, options include continued hospitalization or, for infants with stable apnea, discharge with a home apnea monitor.
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MESH Headings
- Apnea/diagnosis
- Apnea/mortality
- Apnea/nursing
- Central Nervous System Stimulants/therapeutic use
- Combined Modality Therapy
- Continuity of Patient Care
- Drug Therapy, Combination
- Female
- Follow-Up Studies
- Gestational Age
- Home Nursing
- Humans
- Infant, Newborn
- Infant, Premature, Diseases/diagnosis
- Infant, Premature, Diseases/mortality
- Infant, Premature, Diseases/nursing
- Infant, Very Low Birth Weight
- Intensive Care Units, Neonatal
- Male
- Monitoring, Ambulatory/instrumentation
- Monitoring, Ambulatory/methods
- Neonatal Nursing/standards
- Neonatal Nursing/trends
- Nurse's Role
- Positive-Pressure Respiration
- Risk Assessment
- Severity of Illness Index
- Survival Rate
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47
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Walsh MC, Yao Q, Gettner P, Hale E, Collins M, Hensman A, Everette R, Peters N, Miller N, Muran G, Auten K, Newman N, Rowan G, Grisby C, Arnell K, Miller L, Ball B, McDavid G. Impact of a physiologic definition on bronchopulmonary dysplasia rates. Pediatrics 2004; 114:1305-11. [PMID: 15520112 DOI: 10.1542/peds.2004-0204] [Citation(s) in RCA: 450] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Bronchopulmonary dysplasia (BPD) is the endpoint of many intervention trials in neonatology, yet the outcome measure when based solely on oxygen administration may be confounded by differing criteria for oxygen administration between physicians. We previously reported a technique to standardize the definition of BPD between sites by using a timed room-air challenge in selected infants. We hypothesized that a physiologic definition of BPD would reduce the variation in observed rates of BPD among different neonatal centers. Methodology. A total of 1598 consecutive inborn premature infants (501-1249 g birth weight) who remained hospitalized at 36 weeks' postmenstrual age were prospectively assessed and assigned an outcome with both a clinical definition and physiologic definition of BPD. The clinical definition of BPD was oxygen supplementation at exactly 36 weeks' postmenstrual age. The physiologic definition of BPD was assigned at 36 +/- 1 weeks' postmenstrual age and included 2 distinct subpopulations. First, neonates on positive pressure support or receiving >30% supplemental oxygen with saturations between 90% and 96% were assigned the outcome BPD and not tested further. Second, those receiving < or =30% oxygen or effective oxygen >30% with saturations >96% underwent a room-air challenge with continuous observation and oxygen-saturation monitoring. Outcomes of the room-air challenge were "no BPD" (saturations > or =90% during weaning and in room air for 30 minutes) or "BPD" (saturation <90%). At the conclusion of the room-air challenge, all infants were returned to their baseline oxygen levels. Safety (apnea, bradycardia, increased oxygen use) and outcomes of the physiologic definition versus the clinical definition were assessed. RESULTS A total of 560 (35.0%) neonates were diagnosed with BPD by the clinical definition of oxygen use at 36 weeks' postmenstrual age. The physiologic definition diagnosed BPD in 398 (25.0%) neonates in the cohort. All infants were safely studied. There were marked differences in the impact of the definition on BPD rates between centers (mean reduction: 10%; range: 0-44%). Sixteen centers had a decrease in their BPD rate, and 1 center had no change in their rate. CONCLUSIONS The physiologic definition of BPD reduced the overall rate of BPD and reduced the variation among centers. Significant center differences in the impact of the physiologic definition were seen, and differences remained even with the use of this standardized definition. The magnitude of the change in BPD rate is comparable to the magnitude of treatment effects seen in some clinical trials in BPD. The physiologic definition of BPD facilitates the measurement of BPD as an outcome in clinical trials and the comparison between and within centers over time.
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Affiliation(s)
- Michele C Walsh
- Rainbow Babies and Childrens Hospital, Department of Pediatrics, Case Case Western Reserve University, 11100 Euclid Ave, Mailstop 6010, Cleveland, OH 44106, USA.
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48
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Abstract
Respiratory control in the fetus and neonate is quite immature when compared to that of adults. This immaturity involves all facets of respiration including respiratory responses to hypoxia, hypercapnia, an exaggerated apnoeic response to laryngeal stimulation and immature responses to activation of pulmonary afferents. The net result of this immaturity of breathing responses is the vulnerability of neonates and especially preterm infants to apnoea and respiratory pauses. The mechanisms behind immature control of breathing are not fully understood, but seem to originate from a predominance of inhibitory input early in life on respiratory centres. The relative contribution of up-regulation of inhibitory pathways versus down-regulation of excitatory ones is not clear. Multiple neurotransmitters have been implicated in the regulation of breathing in mammals and some of them are discussed in this chapter.
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Affiliation(s)
- Jalal M Abu-Shaweesh
- Department of Pediatrics, Case Western Reserve University, 11000 Euclid Ave, Cleveland, OH 44106, USA.
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49
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Affiliation(s)
- Richard J Martin
- Rainbow Babies & Children's Hospital, University Hospitals of Cleveland, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-6010, USA
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50
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Abstract
Increasing numbers of infants and children journey by aeroplane, or travel to high altitude destinations, for example, on holiday or as part of a population migration. Most are healthy, although increasingly children may be transported by aeroplane or helicopter specifically to obtain treatment for severe illness or injury. It is therefore useful to review the effects of altitude, and their relevance to children who undertake flights or travel to, or at high altitudes, particularly those with acute and chronic medical conditions.
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Affiliation(s)
- M P Samuels
- Academic Department of Paediatrics, University Hospital of North Staffordshire, Stoke on Trent ST4 6QG, UK.
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