1
|
Ackermann SP, Raab M, Backschat S, Smith DJC, Javelle F, Laborde S. The diving response and cardiac vagal activity: A systematic review and meta-analysis. Psychophysiology 2023; 60:e14183. [PMID: 36219506 DOI: 10.1111/psyp.14183] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 08/19/2022] [Accepted: 08/24/2022] [Indexed: 01/25/2023]
Abstract
This article aimed to synthesize the various triggers of the diving response and to perform a meta-analysis assessing their effects on cardiac vagal activity. The protocol was preregistered on PROSPERO (CRD42021231419; 01.07.2021). A systematic and meta-analytic review of cardiac vagal activity was conducted, indexed with the root mean square of successive differences (RMSSD) in the context of the diving response. The search on MEDLINE (via PubMed), Web of Science, ProQuest and PsycNet was finalized on November 6th, 2021. Studies with human participants were considered, measuring RMSSD pre- and during and/or post-exposure to at least one trigger of the diving response. Seventeen papers (n = 311) met inclusion criteria. Triggers examined include face immersion or cooling, SCUBA diving, and total body immersion into water. Compared to resting conditions, a significant moderate to large positive effect was found for RMSSD during exposure (Hedges' g = 0.59, 95% CI 0.36 to 0.82, p < .001), but not post-exposure (g = 0.11, 95% CI -0.14 to 0.36, p = .34). Among the considered moderators, total body immersion had a significantly larger effect than forehead cooling (QM = 23.46, df = 1, p < .001). No further differences were detected. Limitations were the small number of studies included, heterogenous triggers, few participants and low quality of evidence. Further research is needed to investigate the role of cardiac sympathetic activity and of the moderators.
Collapse
Affiliation(s)
- Stefan Peter Ackermann
- Department of Performance Psychology, Institute of Psychology, German Sport University Cologne, Cologne, Germany
| | - Markus Raab
- Department of Performance Psychology, Institute of Psychology, German Sport University Cologne, Cologne, Germany.,School of Applied Sciences, London South Bank University, London, UK
| | - Serena Backschat
- Department of Performance Psychology, Institute of Psychology, German Sport University Cologne, Cologne, Germany
| | - David John Charles Smith
- Department of Performance Psychology, Institute of Psychology, German Sport University Cologne, Cologne, Germany
| | - Florian Javelle
- Department of Molecular and Cellular Sports Medicine, Institute for Cardiovascular Research and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Sylvain Laborde
- Department of Performance Psychology, Institute of Psychology, German Sport University Cologne, Cologne, Germany.,UFR STAPS, EA 4260, Cesams, Normandie Université, Caen, France
| |
Collapse
|
2
|
Rass V, Ianosi BA, Lindner A, Kofler M, Schiefecker AJ, Pfausler B, Beer R, Schmutzhard E, Helbok R. Hemodynamic response during endotracheal suctioning predicts awakening and functional outcome in subarachnoid hemorrhage patients. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2020; 24:432. [PMID: 32665009 PMCID: PMC7362501 DOI: 10.1186/s13054-020-03089-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 06/12/2020] [Indexed: 01/04/2023]
Abstract
Background Endotracheal suctioning (ES) provokes a cumulative hemodynamic response by activation of sympathetic and parasympathetic circuits in the central nervous system. In this proof-of-concept study, we aimed to analyze hemodynamic changes during ES in ventilated subarachnoid hemorrhage (SAH) patients and investigated whether the associated hemodynamic changes relate to the time to arousal and functional outcome. Methods For the current observational study, 191 SAH patients admitted to the neurological intensive care unit of a tertiary hospital requiring mechanical ventilation were included. One thousand eighty ES episodes during the first 72 h of admission were analyzed. Baseline median heart rate (HR) and mean arterial pressure (MAP) were compared to peak HR and MAP during ES based on 5-min averaged data (ΔHR and ΔMAP). Multivariable analysis to assess associations between ΔHR and ΔMAP and time to arousal (time to Richmond Agitation Sedation Scale ≥ 0, RASS) and poor functional outcome (modified Rankin Scale Score > 2, mRS) was performed using generalized estimating equations. Results Patients were 59 (IQR, 50–70) years old and presented with a median admission H&H grade of 4 (IQR, 3–5). In-hospital mortality was 22% (25% at 3 months) and median time to arousal was 13 (IQR, 4–21) days. HR increased by 2.3 ± 7.1 beats per minute (bpm) from 75.1 ± 14.8 bpm at baseline. MAP increased by 3.2 ± 7.8 mmHg from baseline 80.9 ± 9.8 mmHg. In multivariable analysis, ΔHR (p < 0.001) was significantly lower in patients who regained consciousness at a later time point and a lower ΔHR was associated with poor functional 3-month outcome independent of RASS (adjOR = 0.95; 95% CI = 0.93–0.98) or midazolam dose (adjOR = 0.96; 95% CI = 0.94–0.98). ΔMAP was neither associated with the time to regain consciousness (p = 0.087) nor with functional outcome (p = 0.263). Conclusion Augmentation in heart rate may quantify the hemodynamic response during endotracheal suctioning in brain-injured patients. The value as a biomarker to early discriminate the time to arousal and functional outcome in acutely brain-injured patients needs prospective confirmation.
Collapse
Affiliation(s)
- Verena Rass
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Bogdan-Andrei Ianosi
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.,Institute of Medical Informatics, UMIT, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnoefer-Zentrum 1, 6060, Hall, Austria
| | - Anna Lindner
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Mario Kofler
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Alois J Schiefecker
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Bettina Pfausler
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Ronny Beer
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Erich Schmutzhard
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Raimund Helbok
- Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
| |
Collapse
|
3
|
Higgs A, Littley N, Chrimes N. Bradycardia during hypoxaemic airway crises. Does atropine treat the patient or the anaesthetist? Anaesthesia 2019; 74:1482-1483. [PMID: 31592552 DOI: 10.1111/anae.14823] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A Higgs
- Warrington and Halton NHS Foundation Trust, Warrington, UK
| | - N Littley
- Warrington and Halton NHS Foundation Trust, Warrington, UK
| | - N Chrimes
- Monash Medical Centre, Melbourne, Vic, Australia
| |
Collapse
|
4
|
Oyachi N, Emura T, Numano F, Tando T, Saito T, Goto Y. Non-occlusive intestinal ischemia in the ascending colon and rectum: a pediatric case occurring during encephalitis treatment. Surg Case Rep 2019; 5:23. [PMID: 30771025 PMCID: PMC6377685 DOI: 10.1186/s40792-019-0592-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 02/11/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Non-occlusive mesenteric ischemia (NOMI) is a rare and severe pathological condition that can cause intestinal necrosis without mechanical obstruction of the mesenteric artery. NOMI often develops during the treatment of severe disease in elderly patients and mostly occurs in the intestine supplied by the superior mesenteric artery (SMA). We experienced a 12-year-old patient with NOMI that was segmentally localized in the ascending colon and rectum during encephalitis treatment. CASE PRESENTATION A 12-year-old boy was hospitalized with limbic encephalitis. On day 41 after admission, he abruptly developed hypotension following diarrhea and fever, and presented abdominal distension. A computed tomography scan revealed pneumatosis intestinalis localized in the ascending colon and rectum coexisting with portal venous gas. The presence of peritoneal signs required an emergency laparotomy. Intraoperatively, skip ischemic lesions were found in the ascending colon and the rectum without bowel perforation. SMA and superior rectal arterial pulsation were present, and the patient was diagnosed with NOMI. The remaining colon, from the transverse to the sigmoid colon, appeared intact. We performed a distal ileostomy without bowel resection. Postoperative colonoscopies were carried out and revealed rectal and ascending colon stenosis with ulceration but demonstrated the patency of the two lesions. We confirmed the improvement of the transient bowel strictures; therefore, the ileal stoma was closed 14 months after the previous laparotomy. CONCLUSION NOMI can be present in childhood during encephalitis treatment and can be segmentally localized in the ascending colon and the rectum. Although NOMI is most often seen in elderly patients, we should also consider the possibility of NOMI when pediatric patients with severe illness manifest abdominal symptoms.
Collapse
Affiliation(s)
- Noboru Oyachi
- Department of Pediatric Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Yamanashi, 400-8506, Japan.
| | - Takaki Emura
- Department of Pediatric Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Yamanashi, 400-8506, Japan
| | - Fuminori Numano
- Department of Pediatric Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Yamanashi, 400-8506, Japan
| | - Tomoko Tando
- Department of Pediatrics, Yamanashi Prefectural Central Hospital, Kofu, Japan
| | - Tomohiro Saito
- Department of Pediatrics, Yamanashi Prefectural Central Hospital, Kofu, Japan
| | - Yusuke Goto
- Department of Pediatrics, Yamanashi Prefectural Central Hospital, Kofu, Japan
| |
Collapse
|
5
|
Abstract
Breath-hold diving is practiced by recreational divers, seafood divers, military divers, and competitive athletes. It involves highly integrated physiology and extreme responses. This article reviews human breath-hold diving physiology beginning with an historical overview followed by a summary of foundational research and a survey of some contemporary issues. Immersion and cardiovascular adjustments promote a blood shift into the heart and chest vasculature. Autonomic responses include diving bradycardia, peripheral vasoconstriction, and splenic contraction, which help conserve oxygen. Competitive divers use a technique of lung hyperinflation that raises initial volume and airway pressure to facilitate longer apnea times and greater depths. Gas compression at depth leads to sequential alveolar collapse. Airway pressure decreases with depth and becomes negative relative to ambient due to limited chest compliance at low lung volumes, raising the risk of pulmonary injury called "squeeze," characterized by postdive coughing, wheezing, and hemoptysis. Hypoxia and hypercapnia influence the terminal breakpoint beyond which voluntary apnea cannot be sustained. Ascent blackout due to hypoxia is a danger during long breath-holds, and has become common amongst high-level competitors who can suppress their urge to breathe. Decompression sickness due to nitrogen accumulation causing bubble formation can occur after multiple repetitive dives, or after single deep dives during depth record attempts. Humans experience responses similar to those seen in diving mammals, but to a lesser degree. The deepest sled-assisted breath-hold dive was to 214 m. Factors that might determine ultimate human depth capabilities are discussed. © 2018 American Physiological Society. Compr Physiol 8:585-630, 2018.
Collapse
|
6
|
Integrity of Cerebellar Fastigial Nucleus Intrinsic Neurons Is Critical for the Global Ischemic Preconditioning. Brain Sci 2017; 7:brainsci7100121. [PMID: 28934119 PMCID: PMC5664048 DOI: 10.3390/brainsci7100121] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 09/15/2017] [Accepted: 09/18/2017] [Indexed: 01/25/2023] Open
Abstract
Excitation of intrinsic neurons of cerebellar fastigial nucleus (FN) renders brain tolerant to local and global ischemia. This effect reaches a maximum 72 h after the stimulation and lasts over 10 days. Comparable neuroprotection is observed following sublethal global brain ischemia, a phenomenon known as preconditioning. We hypothesized that FN may participate in the mechanisms of ischemic preconditioning as a part of the intrinsic neuroprotective mechanism. To explore potential significance of FN neurons in brain ischemic tolerance we lesioned intrinsic FN neurons with excitotoxin ibotenic acid five days before exposure to 20 min four-vessel occlusion (4-VO) global ischemia while analyzing neuronal damage in Cornu Ammoni area 1 (CA1) hippocampal area one week later. In FN-lesioned animals, loss of CA1 cells was higher by 22% compared to control (phosphate buffered saline (PBS)-injected) animals. Moreover, lesion of FN neurons increased morbidity following global ischemia by 50%. Ablation of FN neurons also reversed salvaging effects of five-minute ischemic preconditioning on CA1 neurons and morbidity, while ablation of cerebellar dentate nucleus neurons did not change effect of ischemic preconditioning. We conclude that FN is an important part of intrinsic neuroprotective system, which participates in ischemic preconditioning and may participate in naturally occurring neuroprotection, such as "diving response".
Collapse
|
7
|
Golanov EV, Shiflett JM, Britz GW. Diving Response in Rats: Role of the Subthalamic Vasodilator Area. Front Neurol 2016; 7:157. [PMID: 27708614 PMCID: PMC5030511 DOI: 10.3389/fneur.2016.00157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/08/2016] [Indexed: 11/29/2022] Open
Abstract
Diving response (DR) is a powerful integrative response targeted toward survival of the hypoxic/anoxic conditions. Being present in all animals and humans, it allows to survive adverse conditions like diving. Earlier, we discovered that forehead stimulation affords neuroprotective effect, decreasing infarction volume triggered by permanent occlusion of the middle cerebral artery in rats. We hypothesized that cold stimulation of the forehead induces DR in rats, which, in turn, exerts neuroprotection. We compared autonomic [AP, heart rate (HR), cerebral blood flow (CBF)] and EEG responses to the known DR-triggering stimulus, ammonia stimulation of the nasal mucosa, cold stimulation of the forehead, and cold stimulation of the glabrous skin of the tail base in anesthetized rats. Responses in AP, HR, CBF, and EEG to cold stimulation of the forehead and ammonia vapors instillation into the nasal cavity were comparable and differed significantly from responses to the cold stimulation of the tail base. Excitotoxic lesion of the subthalamic vasodilator area (SVA), which is known to participate in CBF regulation and to afford neuroprotection upon excitation, failed to affect autonomic components of the DR evoked by forehead cold stimulation or nasal mucosa ammonia stimulation. We conclude that cold stimulation of the forehead triggers physiological response comparable to the response evoked by ammonia vapor instillation into nasal cavity, which is considered as stimulus triggering protective DR. These observations may explain the neuroprotective effect of the forehead stimulation. Data demonstrate that SVA does not directly participate in the autonomic adjustments accompanying DR; however, it is involved in diving-evoked modulation of EEG. We suggest that forehead stimulation can be employed as a stimulus capable of triggering oxygen-conserving DR and can be used for neuroprotective therapy.
Collapse
Affiliation(s)
- Eugene V. Golanov
- Department of Neurosurgery, The Houston Methodist Hospital, Houston, TX, USA
- Department of Neurosurgery, University of Mississippi Medical Center, Jackson, MS, USA
| | - James M. Shiflett
- Department of Neurosurgery, University of Mississippi Medical Center, Jackson, MS, USA
| | - Gavin W. Britz
- Department of Neurosurgery, The Houston Methodist Hospital, Houston, TX, USA
| |
Collapse
|
8
|
|
9
|
Ostergaard L, Rudiger A, Wellmann S, Gammella E, Beck-Schimmer B, Struck J, Maggiorini M, Gassmann M. Arginine-vasopressin marker copeptin is a sensitive plasma surrogate of hypoxic exposure. HYPOXIA 2014; 2:143-151. [PMID: 27774473 PMCID: PMC5045063 DOI: 10.2147/hp.s57894] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Background A reduced oxygen supply puts patients at risk of tissue hypoxia, organ damage, and even death. In response, several changes are activated that allow for at least partial adaptation, thereby increasing the chances of survival. We aimed to investigate whether the arginine vasopressin marker, copeptin, can be used as a marker of the degree of acclimatization/adaptation in rats exposed to hypoxia. Methods Sprague-Dawley rats were exposed to 10% oxygen for up to 48 hours. Arterial and right ventricular pressures were measured, and blood gas analysis was performed at set time points. Pulmonary changes were investigated by bronchoalveolar lavage, wet and dry weight measurements, and lung histology. Using a newly developed specific rat copeptin luminescence immunoassay, the regulation of vasopressin in response to hypoxia was studied, as was atrial natriuretic peptide (ANP) by detecting mid-regional proANP. Results With a decreasing oxygen supply, the rats rapidly became cyanotic and inactive. Despite continued exposure to 10% oxygen, all animals recuperated within 16 hours and ultimately survived. Their systemic blood pressure fell with acute (5 minutes) hypoxia but was partially recovered over time. In contrast, right ventricular pressures increased with acute (5 minutes) hypoxia and normalized after 16 hours. No signs of pulmonary inflammation or edema were found despite prolonged hypoxia. Whereas copeptin levels increased significantly after acute (5 minutes) hypoxia and then returned to near baseline after 16 hours, mid-regional proANP levels were even further increased after 16 hours of exposure to hypoxia. Conclusion Plasma copeptin is a sensitive marker of acute (5 minutes) exposure to severe hypoxia, and subsequent regulation can indicate recovery. Copeptin levels can therefore reflect clinical and physiological changes in response to hypoxia and indicate recovery from ongoing hypoxic exposure.
Collapse
Affiliation(s)
- Louise Ostergaard
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zürich; Zürich Center for Integrative Human Physiology
| | | | - Sven Wellmann
- Zürich Center for Integrative Human Physiology; Division of Neonatology, University Hospital Zürich, Zürich; Department of Neonatology, University Children's Hospital Basel, Basel, Switzerland
| | - Elena Gammella
- Department of Human Morphology and Biomedical Science, University of Milan, Milan, Italy
| | | | - Joachim Struck
- Research Department, B⋅R⋅A⋅H⋅M⋅S Biomarkers, Thermo Fisher Scientific, Hennigsdorf, Germany
| | - Marco Maggiorini
- Zürich Center for Integrative Human Physiology; Medical Intensive Care Unit, University Hospital Zürich, Zürich, Switzerland
| | - Max Gassmann
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zürich; Zürich Center for Integrative Human Physiology; Universidad Peruana Cayetano Heredia, Lima, Peru
| |
Collapse
|
10
|
Campbell ML. Assessing Respiratory Distress When the Patient Cannot Report Dyspnea. Nurs Clin North Am 2010; 45:363-73. [DOI: 10.1016/j.cnur.2010.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
11
|
Respiratory distress: a model of responses and behaviors to an asphyxial threat for patients who are unable to self-report. Heart Lung 2008; 37:54-60. [PMID: 18206527 DOI: 10.1016/j.hrtlng.2007.05.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Accepted: 05/29/2007] [Indexed: 11/22/2022]
Abstract
Respiratory distress is the suffering that results from asphyxiation, and is characterized by observable behaviors. Standard measures of dyspnea rely on the patient's ability to self-report. However, not all patients who experience dyspnea are able to self-report because of temporary impairments or declining cognition, making them vulnerable to under-recognition and undertreatment of their distress. Hence, there is a need for a multidimensional behavioral assessment of respiratory distress. A synthesis of scientific literature contributed to the development of this model of respiratory distress behaviors. The proposed model relies on primitive, subcortical, emotional, and autonomic neurologic systems that are rapidly triggered in response to an asphyxial threat to sustain survival. The near-immediate activation of autonomic and fear responses from subcortical brain areas produces observable and measurable behaviors. This proposed model has clinical and scientific usefulness, if testing characterizes and confirms one or more patterns of patient behaviors, in response to an asphyxial threat.
Collapse
|
12
|
Campbell ML. Fear and pulmonary stress behaviors to an asphyxial threat across cognitive states. Res Nurs Health 2007; 30:572-83. [DOI: 10.1002/nur.20212] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
13
|
|
14
|
Abstract
Dyspnea is a subjective experience that can be reported by the patient. Respiratory distress is an observable corollary, and represents the physical or emotional suffering that results from the experience of dyspnea. Recognizing and understanding this subjective phenomenon poses a challenge to intensive care unit (ICU) clinicians when caring for the patient who is dying in the ICU. Dyspnea and cognitive impairment are highly prevalent in the terminally ill ICU patient. A Respiratory Distress Observation Model may provide a theoretical foundation for the assessment of this phenomenon that is grounded in emotional and autonomic domains of neurologic function. Treatment of dyspnea and respiratory distress relies on nonpharmacologic interventions and opioids and sedatives. As with pain, the treatment of dyspnea and respiratory distress relies on close evaluation of the patient and treatment to satisfactory effect. Empirical evidence suggests that quality care with control of distressing symptoms does not hasten death. Withholding opioids or sedatives in the face of unrelieved dyspnea or respiratory distress has no moral foundation.
Collapse
Affiliation(s)
- Margaret L Campbell
- Palliative Care Service, Nursing Administration, Detroit Receiving Hospital, 4201 St. Antoine Boulevard, Detroit, MI 48201, USA.
| |
Collapse
|
15
|
Molfino N. Evolución funcional del pulmón y síntomas respiratorios. Arch Bronconeumol 2004. [DOI: 10.1016/s0300-2896(04)75566-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
16
|
Singer D. Neonatal tolerance to hypoxia: a comparative-physiological approach. Comp Biochem Physiol A Mol Integr Physiol 1999; 123:221-34. [PMID: 10501017 DOI: 10.1016/s1095-6433(99)00057-4] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Newborn mammals exhibit a number of physiological reactions which differ from normal adult physiology and are often regarded as signs of immaturity. However, when looked upon from a comparative point of view, it becomes obvious that some of these 'physiological peculiarities' bear striking similarity to adaptation mechanisms known from hypoxia-tolerant animals and may thus contribute to the well-established, yet poorly understood, phenomenon of neonatal hypoxia tolerance. As the mammalian fetus lives at oxygen partial pressures corresponding to 8000 m altitude, the first line of perinatal hypoxia defense consists of long-term adaptations to limited intrauterine oxygen supply: (1) improved O2 transport by fetal acclimatization to high altitude, (2) reduced metabolic rate by hibernation-like deviation from metabolic size allometry, (3) diminished cerebral vulnerability by functional analogies to diving turtle brain, and (4) enhanced metabolic flexibility by optional repartitioning of energy supply from growth to maintenance metabolism. In the case of birth asphyxia, these background mechanisms are complemented by short-term responses to acute oxygen lack: (1) reduction of body temperature as in natural torpor, (2) reduction of heart rate and redistribution of circulation as in diving mammals, (3) reduction of respiration rate typical of 'hypoxic hypometabolism', and (4) reduction of blood pH according to the concept of 'acidotic torpidity'. Although anaerobic metabolism is improved in neonatal mammals by increased glycogen stores, reduced metabolic demands, and sustained wash-out of acid metabolites, neonatal hypoxia tolerance seems to be primarily based on the ability to maintain tissue aerobiosis as long as possible. This is even reflected by isoenzyme patterns which do not consistently favour anaerobic glycolysis and, thus, are reminiscent of the 'lactate paradox' found in high altitude adaptation. Altogether, from a biological point of view, the perinatal period appears as a source of adaptive mechanisms that can be refound, in varying combinations, in many survival strategies. From a clinical point of view, the interplay of long- and short-term mechanisms offers a novel approach to estimation of the newborn's ability to withstand temporary oxygen lack. However, most of these mechanisms are not unambiguous and, above all, not unlimited in their protective effect so that they do not release obstetricians or neonatologists from their obligation to counteract fetal or neonatal hypoxia without delay.
Collapse
Affiliation(s)
- D Singer
- Department of Pediatrics, University Clinics, Goettingen, Germany
| |
Collapse
|
17
|
Gooden BA. Mechanism of the human diving response. INTEGRATIVE PHYSIOLOGICAL AND BEHAVIORAL SCIENCE : THE OFFICIAL JOURNAL OF THE PAVLOVIAN SOCIETY 1994; 29:6-16. [PMID: 8018553 DOI: 10.1007/bf02691277] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The diving response in human beings is characterized by breath-holding, slowing of the heart rate (diving bradycardia), reduction of limb blood flow and a gradual rise in the mean arterial blood pressure. The bradycardia results from increased parasympathetic stimulus to the cardiac pacemaker. The reduction in limb blood flow is due to vasoconstriction resulting from increased activity of the sympathetic nerves supplying arteries in the arms and legs. Essentially the response is produced by the combination of water touching the face and either voluntary or involuntary (reflex) arrest of breathing. The nervous inputs and outputs for the response are coordinated in the brain stem by the respiratory, vasomotor and cardioinhibitory "centers." The diving response in human beings can be modified by many factors but the most important are water temperature, oxygen tension in the arterial blood and emotional factors.
Collapse
Affiliation(s)
- B A Gooden
- Department of Physiology and Pharmacology, Queen's Medical Centre, University of Nottingham, U.K
| |
Collapse
|