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Pernett F, Bergenhed P, Holmström P, Mulder E, Schagatay E. Effects of hyperventilation on oxygenation, apnea breaking points, diving response, and spleen contraction during serial static apneas. Eur J Appl Physiol 2023; 123:1809-1824. [PMID: 37060440 PMCID: PMC10363065 DOI: 10.1007/s00421-023-05202-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/07/2023] [Indexed: 04/16/2023]
Abstract
PURPOSE Hyperventilation is considered a major risk factor for hypoxic blackout during breath-hold diving, as it delays the apnea breaking point. However, little is known about how it affects oxygenation, the diving response, and spleen contraction during serial breath-holding. METHODS 18 volunteers with little or no experience in freediving performed two series of 5 apneas with cold facial immersion to maximal duration at 2-min intervals. In one series, apnea was preceded by normal breathing and in the other by 15 s of hyperventilation. End-tidal oxygen and end-tidal carbon dioxide were measured before and after every apnea, and peripheral oxygen saturation, heart rate, breathing movements, and skin blood flow were measured continuously. Spleen dimensions were measured every 15 s. RESULTS Apnea duration was longer after hyperventilation (133 vs 111 s). Hyperventilation reduced pre-apnea end-tidal CO2 (17.4 vs 29.0 mmHg) and post-apnea end-tidal CO2 (38.5 vs 40.3 mmHg), and delayed onset of involuntary breathing movements (112 vs 89 s). End-tidal O2 after apnea was lower in the hyperventilation trial (83.4 vs 89.4 mmHg) and so was the peripheral oxygen saturation nadir after apnea (90.6 vs 93.6%). During hyperventilation, the nadir peripheral oxygen saturation was lower in the last apnea than in the first (94.0% vs 86.7%). There were no differences in diving response or spleen volume reduction between conditions or across series. CONCLUSIONS Serial apneas revealed a previously undescribed aspect of hyperventilation; a progressively increased desaturation across the series, not observed after normal breathing and could heighten the risk of a blackout.
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Affiliation(s)
- Frank Pernett
- Environmental Physiology Group, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.
| | - Pontus Bergenhed
- Environmental Physiology Group, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
| | - Pontus Holmström
- Environmental Physiology Group, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
| | - Eric Mulder
- Environmental Physiology Group, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
| | - Erika Schagatay
- Environmental Physiology Group, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
- Swedish Winter Sports Research Centre, Östersund, Sweden
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Kohshi K, Denoble PJ, Tamaki H, Morimatsu Y, Ishitake T, Lemaître F. Decompression Illness in Repetitive Breath-Hold Diving: Why Ischemic Lesions Involve the Brain? Front Physiol 2021; 12:711850. [PMID: 34539434 PMCID: PMC8446421 DOI: 10.3389/fphys.2021.711850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 07/28/2021] [Indexed: 12/03/2022] Open
Abstract
Nitrogen (N2) accumulation in the blood and tissues can occur due to breath-hold (BH) diving. Post-dive venous gas emboli have been documented in commercial BH divers (Ama) after repetitive dives with short surface intervals. Hence, BH diving can theoretically cause decompression illness (DCI). “Taravana,” the diving syndrome described in Polynesian pearl divers by Cross in the 1960s, is likely DCI. It manifests mainly with cerebral involvements, especially stroke-like brain attacks with the spinal cord spared. Neuroradiological studies on Ama divers showed symptomatic and asymptomatic ischemic lesions in the cerebral cortex, subcortex, basal ganglia, brainstem, and cerebellum. These lesions localized in the external watershed areas and deep perforating arteries are compatible with cerebral arterial gas embolism. The underlying mechanisms remain to be elucidated. We consider that the most plausible mechanisms are arterialized venous gas bubbles passing through the lungs, bubbles mixed with thrombi occlude cerebral arteries and then expand from N2 influx from the occluded arteries and the brain. The first aid normobaric oxygen appears beneficial. DCI prevention strategy includes avoiding long-lasting repetitive dives for more than several hours, prolonging the surface intervals. This article provides an overview of clinical manifestations of DCI following repetitive BH dives and discusses possible mechanisms based on clinical and neuroimaging studies.
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Affiliation(s)
- Kiyotaka Kohshi
- Division of Neurosurgery, Nishinihon Hospital, Kumamoto, Japan.,Department of Environmental Medicine, Kurume University School of Medicine, Kurume, Japan
| | | | - Hideki Tamaki
- Department of Environmental Medicine, Kurume University School of Medicine, Kurume, Japan.,Division of Surgery and General Medicine, Tamaki Hospital, Hagi, Japan
| | - Yoshitaka Morimatsu
- Department of Environmental Medicine, Kurume University School of Medicine, Kurume, Japan
| | - Tatsuya Ishitake
- Department of Environmental Medicine, Kurume University School of Medicine, Kurume, Japan
| | - Frédéric Lemaître
- Faculty of Sport Sciences, University of Rouen, Mont-Saint-Aignan, France.,CRIOBE USR 3278, CNRS-EPHE-UPVD, PSL, Moorea, France
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Patrician A, Dujić Ž, Spajić B, Drviš I, Ainslie PN. Breath-Hold Diving - The Physiology of Diving Deep and Returning. Front Physiol 2021; 12:639377. [PMID: 34093221 PMCID: PMC8176094 DOI: 10.3389/fphys.2021.639377] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/07/2021] [Indexed: 11/13/2022] Open
Abstract
Breath-hold diving involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. With astonishing depth records exceeding 100 m, and up to 214 m on a single breath, the human capacity for deep breath-hold diving continues to refute expectations. The physiological challenges and responses occurring during a deep dive highlight the coordinated interplay of oxygen conservation, exercise economy, and hyperbaric management. In this review, the physiology of deep diving is portrayed as it occurs across the phases of a dive: the first 20 m; passive descent; maximal depth; ascent; last 10 m, and surfacing. The acute risks of diving (i.e., pulmonary barotrauma, nitrogen narcosis, and decompression sickness) and the potential long-term medical consequences to breath-hold diving are summarized, and an emphasis on future areas of research of this unique field of physiological adaptation are provided.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Željko Dujić
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
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Patrician A, Gasho C, Spajić B, Caldwell HG, Baković-Kramaric D, Barak O, Drviš I, Dujić Ž, Ainslie PN. Case Studies in Physiology: Breath-hold diving beyond 100 meters-cardiopulmonary responses in world-champion divers. J Appl Physiol (1985) 2021; 130:1345-1350. [PMID: 33600279 DOI: 10.1152/japplphysiol.00877.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In this case study, we evaluate the unique physiological profiles of two world-champion breath-hold divers. At close to current world-record depths, the extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure are profound. As such, these professional athletes must be capable of managing such stress, to maintain performing at the forefront human capacity. In both divers, pulmonary function before and after deep dives to 102 m and 117 m in the open sea was assessed using noninvasive pulmonary gas exchange (indexed via the O2 deficit, which is analogous to the traditional alveolar to arterial oxygen difference), ultrasound B-line scores, airway resistance, and airway reactance. Hydrostatic-induced lung compression was also quantified via spirometry. Both divers successfully performed their dives. Pulmonary gas exchange efficiency was impaired in both divers at 10 min but had mostly restored within a few hours. Mild hemoptysis was transiently evident immediately following the 117-m dive, whereas both divers experienced nitrogen narcosis. Although B-lines were only elevated in one diver postdive, reductions in airway resistance and reactance occurred in both divers, suggesting that the compressive strain on the structural characteristics of the airways can persist for up to 3.5 h. Marked echocardiographic dyssynchrony was evident in one diver after 10 m of descent, which persisted until resolving at ∼77 m during ascent. In summary, despite the enormous hydrostatic and physiological stress to diving beyond 100 m on a single breath, these data provide valuable insight into the extraordinary capacity of those at the pinnacle of apneic performance.NEW & NOTEWORTHY This study shows that world-champion breath-hold divers demonstrate incredible tolerability to extreme levels of hydrostatic-induced lung compression. Immediately following dives to >100 m, there were acute impairments in pulmonary gas exchange efficiency, mild accummulation of extravascular lung fluid, noticable intrathoracic discomfort, and evident nitrogen narcosis, however, within a few hours, these had all mostly resolved.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Christopher Gasho
- Center for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Hannah G Caldwell
- Center for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | | | - Otto Barak
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Željko Dujić
- School of Medicine, University of Split, Split, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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Arieli R. Taravana, vestibular decompression illness, and autochthonous distal arterial bubbles. Respir Physiol Neurobiol 2018; 259:119-121. [PMID: 30172778 DOI: 10.1016/j.resp.2018.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 08/29/2018] [Indexed: 11/16/2022]
Abstract
Decompression bubbles can develop only from pre-existing gas micronuclei. These are the nanobubbles which appear on active hydrophobic spots (AHS) found on the luminal aspect of all blood vessels. Following decompression, with the propagation of blood along the arterial tree, diffusion parameters cause increased transfer of nitrogen from the tissue into the artery, and more so if perfusion is low. Taravana is a neurological form of decompression illness (DCI) prevalent in repeated breath-hold diving. A nanobubble on an AHS in a distal artery of the brain may receive an influx of nitrogen after each dive until it occludes the arterial blood flow. The vestibular organ has very low perfusion compared with the brain and the cochlea of the inner ear. We suggest that a nanobbubble on an AHS in the distal artery of the vestibular organ will receive a high influx of nitrogen from the surrounding tissue after decompression due to the low nitrogen clearance, thus expanding to cause vestibular DCI.
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Affiliation(s)
- Ran Arieli
- The Israel Naval Medical Institute, Haifa, Israel; Eliachar Research Laboratory, Western Galilee Medical Centre, Nahariya, Israel.
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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.
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Fernández A, Edwards JF, Rodríguez F, Espinosa de los Monteros A, Herráez P, Castro P, Jaber JR, Martín V, Arbelo M. “Gas and Fat Embolic Syndrome” Involving a Mass Stranding of Beaked Whales (Family Ziphiidae) Exposed to Anthropogenic Sonar Signals. Vet Pathol 2016; 42:446-57. [PMID: 16006604 DOI: 10.1354/vp.42-4-446] [Citation(s) in RCA: 203] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.
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Affiliation(s)
- A Fernández
- Unit of Histology and Pathology, Institute for Animal Health, Veterinary School, University of Las Palmas de Gran Canaria, Spain.
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Abstract
This article establishes the basic mathematical models and the principles and assumptions used for inert gas transfer within body tissues-first, for a single compartment model and then for a multicompartment model. From these, and other more complex mathematical models, the transport of inert gases between lungs, blood, and other tissues is derived and compared to known experimental studies in both animals and humans. Some aspects of airway and lung transfer are particularly important to the uptake and elimination of inert gases, and these aspects of gas transport in tissues are briefly described. The most frequently used inert gases are those that are administered in anesthesia, and the specific issues relating to the uptake, transport, and elimination of these gases and vapors are dealt with in some detail showing how their transfer depends on various physical and chemical attributes, particularly their solubilities in blood and different tissues. Absorption characteristics of inert gases from within gas cavities or tissue bubbles are described, and the effects other inhaled gas mixtures have on the composition of these gas cavities are discussed. Very brief consideration is given to the effects of hyper- and hypobaric conditions on inert gas transport.
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Affiliation(s)
- A Barry Baker
- Department of Anaesthesia, University of Sydney, NSW, Australia.
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9
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Lemaitre F, Fahlman A, Gardette B, Kohshi K. Decompression sickness in breath-hold divers: A review. J Sports Sci 2009; 27:1519-34. [DOI: 10.1080/02640410903121351] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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10
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Fitz-Clarke JR. Lung compression effects on gas exchange in human breath-hold diving. Respir Physiol Neurobiol 2009; 165:221-8. [DOI: 10.1016/j.resp.2008.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 11/17/2008] [Accepted: 12/13/2008] [Indexed: 10/21/2022]
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Lindholm P, Lundgren CEG. The physiology and pathophysiology of human breath-hold diving. J Appl Physiol (1985) 2008; 106:284-92. [PMID: 18974367 DOI: 10.1152/japplphysiol.90991.2008] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive. However, a remarkable, and so far poorly understood, variation in individual disposition for such problems exists. Mortality connected with breath-hold diving is primarily concentrated to less well-trained recreational divers and competitive spearfishermen who fall victim to hypoxia. Particularly vulnerable are probably also individuals with preexisting cardiac problems and possibly, essentially healthy divers who may have suffered severe alternobaric vertigo as a complication to inadequate pressure equilibration of the middle ears. The specific topics discussed include the diving response and its expression by the cardiovascular system, which exhibits hypertension, bradycardia, oxygen conservation, arrhythmias, and contraction of the spleen. The respiratory system is challenged by compression of the lungs with barotrauma of descent, intrapulmonary hemorrhage, edema, and the effects of glossopharyngeal insufflation and exsufflation. Various mechanisms associated with hypoxia and loss of consciousness are discussed, including hyperventilation, ascent blackout, fasting, and excessive postexercise O(2) consumption. The potential for high nitrogen pressure in the lungs to cause decompression sickness and N(2) narcosis is also illuminated.
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Affiliation(s)
- Peter Lindholm
- Department of Physiology and Pharmacology, Karolinska Insitutet, Stockholm, Sweden.
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12
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Abstract
Despite convincing evidence of a relationship between breath-hold diving and decompression sickness (DCS), the causal connection is only slowly being accepted. Only the more recent textbooks have acknowledged the risks of repetitive breath-hold diving. We compare four groups of breath-hold divers: (1) Japanese and Korean amas and other divers from the Pacific area, (2) instructors at naval training facilities, (3) spear fishers, and (4) free-dive athletes. While the number of amas is likely decreasing, and Scandinavian Navy training facilities recorded only a few accidents, the number of spear fishers suffering accidents is on the rise, in particular during championships or using scooters. Finally, national and international associations (e.g., International Association of Free Drives [IAFD] or Association Internationale pour Le Developpment De L'Apnee [AIDA]) promote free-diving championships including deep diving categories such as constant weight, variable weight, and no limit. A number of free-diving athletes, training for or participating in competitions, are increasingly accident prone as the world record is presently set at a depth of 171 m. This review presents data found after searching Medline and ISI Web of Science and using appropriate Internet search engines (e.g., Google). We report some 90 cases in which DCS occurred after repetitive breath-hold dives. Even today, the risk of suffering from DCS after repetitive breath-hold diving is often not acknowledged. We strongly suggest that breath-hold divers and their advisors and physicians be made aware of the possibility of DCS and of the appropriate therapeutic measures to be taken when DCS is suspected. Because the risk of suffering from DCS increases depending on depth, bottom time, rate of ascent, and duration of surface intervals, some approaches to assess the risks are presented. Regrettably, none of these approaches is widely accepted. We propose therefore the development of easily manageable algorithms for the prevention of those avoidable accidents.
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Affiliation(s)
- J D Schipke
- Research Group Experimental Surgery, University Hospital Duesseldorf, Germany.
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Kohshi K, Katoh T, Abe H, Okudera T. Neurological Diving Accidents in Japanese Breath‐Hold Divers: A Preliminary Report. J Occup Health 2006. [DOI: 10.1539/joh.43.56] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Kiyotaka Kohshi
- Department of Neurosurgery
- Division of Hyperbaric MedicineUniversity Hospital of Occupational and Environmental Health
| | - Takahiko Katoh
- Department of Health Information ScienceSchool of Health Sciences, University of Occupational and Environmental Health
| | | | - Toshio Okudera
- Department of RadiologyAkita Research Institute of Brain and Blood Vessels
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14
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Abstract
Apnea diving is a fascinating example of applied physiology. The record for apnea diving as an extreme sport is 171 meters, 8:58 minutes. The short time beneath the surface induces profound cardiovascular and respiratory effects. Variations of blood-gas tensions result from the interaction of metabolism and the rapid sequence of compression and decompression. Decompression sickness is possible. Apnea divers can reach depths beyond the theoretic physiologic limit by using the lung-packing maneuver. Apnea divers exhibit a fall in heart rate, which can be trained and is an oxygen-conserving effect, but increases the incidence of ventricular arrhythmia.
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Affiliation(s)
- Claus-Martin Muth
- Sektion Anaesthesiologische Pathophysiologie und Verfahrensentwicklung, Universitaetsklinikum, Parkstrasse 11, D-89073 Ulm (Donau), Germany.
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Kohshi K, Katoh T, Abe H, Wong RM. [Central nervous system involvement in patients with decompression illness]. SANGYO EISEIGAKU ZASSHI = JOURNAL OF OCCUPATIONAL HEALTH 2003; 45:97-104. [PMID: 12833851 DOI: 10.1539/sangyoeisei.45.97] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dysbarism or decompression illness (DCI), a general term applied to all pathological changes secondary to altered environmental pressure, has two forms decompression sickness (DCS) and arterial gas embolism (AGE) after pulmonary barotrauma. Cerebral and spinal disorders have been symptomatically categorized as AGE and DCS, respectively. Magnetic resonance images (MRIs) of divers with DCI showed multiple cerebral infarction in the terminal and border zones of the brain arteries. In addition, there were no differences between MRI findings for compressed air and breath-hold divers. Although the pathogenesis of the brain is not well understood, we propose that arterialized bubbles passing through the lungs and heart involved the brain. From the mechanisms of bubble formation, however, this disorder has been classified as DCS. We propose that there is a difference between clinical and mechanical diagnoses in the criteria of brain DCI. In contrast to brain injury, the spinal cord is involved only in compressed air divers, and is caused by disturbed venous circulation due to bubbles in the epidural space. The best approach to prevent diving accidents is to make known the problems for professional and amateur divers.
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Affiliation(s)
- Kiyotaka Kohshi
- Department of Neurosurgery, Division of Hyperbaric Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
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Baumgartner RW, Frick A, Kremer C, Oechslin E, Russi E, Turina J, Georgiadis D. Microembolic signal counts increase during hyperbaric exposure in patients with prosthetic heart valves. J Thorac Cardiovasc Surg 2001; 122:1142-6. [PMID: 11726888 DOI: 10.1067/mtc.2001.117282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Patients with prosthetic heart valves have an increased risk of thromboembolic events, and transcranial Doppler sonography reveals microembolic signals. Whereas microembolic signals were initially assumed to be of particulate matter, recent studies suggest that they are partially gaseous in origin. If this is true, alteration of environmental pressure should change microembolic signal counts. We undertook this study to evaluate the influence of hyperbaric exposure on microembolic signal counts in persons with prosthetic heart valves. METHODS AND RESULTS Microembolic signal counts were monitored by transcranial Doppler sonography of both middle cerebral arteries under normobaria (normobaria 1), 2 subsequent periods of hyperbaria (2.5 and 1.75 bar), and a second period of normobaria (normobaria 2) in 15 patients with prosthetic heart valves. Each monitoring period lasted 30 minutes. Compression and decompression rates were 0.1 bar/min. Microembolic signal counts increased from 20 (12-78) at normobaria 1 to 79 (30-165) at 2.5 bar (P <.01 vs normobaria 1 and 2), decreased to 44 (18-128) at 1.75 bar (P <.01 vs normobaria 1 and 2.5 bar; P <.001 vs normobaria 2), and returned to 20 (8-96) at normobaria 2 (values are medians and 95% confidence intervals). CONCLUSIONS Our results strongly suggest that gaseous bubbles are underlying material for part of the microembolic signals detected in patients with prosthetic heart valves.
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