2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):237–244. doi: 10.28920/dhm52.4.237-244. PMID: 36525681.

Hypoxia signatures in closed-circuit rebreather divers

Daniel Popa1, Craig Kutz2, Morgan Carlile2, Kaighley Brett3, Esteban A Moya4, Frank Powell4, Peter Witucki2, Richard Sadler5, Charlotte Sadler2

1 Hennepin County Medical Center, Department of Emergency Medicine, Division of Hyperbaric and Undersea Medicine, Minneapolis, MN, USA
2 UCSD Department of Emergency Medicine, Division of Hyperbaric and Undersea Medicine, San Diego, CA, USA
3 Canadian Armed Forces, Toronto, Canada
4 UCSD Department of Medicine, Division of Physiology, La Jolla, CA, USA
5 Dive Rescue International, Fort Collins, CO, USA

Corresponding author: Dr Daniel Popa, Hennepin County Medical Center, Department of Emergency Medicine, Division of Hyperbaric and Undersea Medicine, 701 Park Ave, Mail Code P1, Minneapolis, MN 55415, USA
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Keywords
Physiology; Rescue; Safety; Technical diving; Training

Abstract
(Popa D, Kutz C, Carlile M, Brett K, Moya EA, Powell F, Witucki P, Sadler R, Sadler C. Hypoxia signatures in closed-circuit rebreather divers. Diving and Hyperbaric Medicine. 2022 December 20;52(4):237–244. doi: 10.28920/dhm52.4.237-244. PMID: 36525681.)
Introduction: Faults or errors during use of closed-circuit rebreathers (CCRs) can cause hypoxia. Military aviators face a similar risk of hypoxia and undergo awareness training to determine their ‘hypoxia signature’, a personalised, reproducible set of symptoms. We aimed to establish a hypoxia signature among divers, and to investigate their ability to detect hypoxia and self-rescue while cognitively overloaded.
Methods: Eight CCR divers and 12 scuba divers underwent an initial unblinded hypoxia exposure followed by three trials; a second hypoxic trial and two normoxic trials in randomised order. Hypoxia was induced by breathing on a CCR with no oxygen supply. Subjects pedalled on a cycle ergometer while playing a neurocognitive computer game to simulate real world task loading. Subjects identified hypoxia symptoms by pointing to a board listing common hypoxia symptoms, and were instructed to perform a ‘bailout’ procedure to mimic self-rescue if they perceived hypoxia. Divers were prompted to bailout if peripheral oxygen saturation fell to 75%, or after six minutes during normoxic trials. Subsequently we interviewed subjects to determine their ability to distinguish hypoxia from normoxia.
Results: Ninety-five percent of subjects (19/20) showed agreement between unblinded and blinded hypoxia symptoms. Subjects correctly identified the gas mixture in 85% of the trials. During unblinded hypoxia, only 25% (5/20) of subjects performed unprompted bailout. Fifty-five percent of subjects (11/20) correctly performed the bailout but only when prompted, while 15% (3/20) were unable to bailout despite prompting. During blinded hypoxia 45% of subjects (9/20) performed the bailout unprompted while 15% (3/20) remained unable to bailout despite prompting.
Conclusions: Although our data support a normobaric hypoxia signature among both CCR and scuba divers under experimental conditions, most subjects were unable to recognise hypoxia in real time and perform a self-rescue unprompted, although this improved in the second hypoxia trial. These results do not support hypoxia exposure training for CCR divers.

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Publication Type: Original article

Full article available here.


2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):245−259. doi: 10.28920/dhm52.4.245-259. PMID: 36525682.

A review of accelerated decompression from heliox saturation in commercial diving emergencies

Jean-Pierre Imbert1, Jean-Yves Massimelli2, Ajit Kulkarni3, Lyubisa Matity4, Philip Bryson5

1 Divetech, 1543 ch. des vignasses, Biot, France
2 Flash Tekk Engineering, Singapore
3 Hyperbaric Solutions, Bandra East, Mumbai, India
4 Hyperbaric and Tissue Viability Unit, Gozo General Hospital, Malta
5 International SOS, Forest Grove House, Aberdeen, UK

Corresponding author: Dr Philip Bryson, International SOS, Forest Grove House, Foresterhill Road, Aberdeen, AB25 2ZP, UK
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Keywords
Decompression sickness; Diving incidents; Emergency ascent; Emergency response; Saturation diving

Abstract
(Imbert J-P, Massimelli J-Y, Kulkarni A, Matity L, Bryson P. A review of accelerated decompression from heliox saturation in commercial diving emergencies. Diving and Hyperbaric Medicine. 2022 December 20;52(4):245−259. doi: 10.28920/dhm52.4.245-259. PMID: 36525682.)
Introduction: Saturation diving is a specialised method of intervention in offshore commercial diving. Emergencies may require the crew to be evacuated from the diving support vessel. Because saturation divers generally need several days to reach surface, the emergency evacuation of divers is based on dedicated hyperbaric rescue systems. There are still potential situations for which these systems cannot be used or deployed, and where an emergency decompression provides an alternative solution.
Methods: Our objective was to describe historical cases and assess the benefit of emergency decompressions, with the collection of data from the authors’ direct experience and networks, providing witness or first-hand information.
Results: We documented three cases of emergency decompression following bell evacuations, and six cases of accelerated decompression performed in the chamber or hyperbaric rescue chamber. Review of these cases showed: 1) the complicated nature of such emergencies that make decisions difficult; 2) the variety of solutions implemented; and 3) the surprisingly safe and successful outcomes of several operations. Analysis of the accelerated decompression occurrences allowed derivation of the options used; upward initial excursion, increased chamber partial pressure of oxygen associated to increased ascent rates, and inert gas switching. We identified four published procedures for accelerated decompression.
Conclusions: Despite modern hyperbaric rescue systems, accelerated decompression remains an essential tool in case of emergency. The diving industry needs clear guidance on what can be achieved, depending on the saturation depth and the level of emergency.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

Full article available here.


2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):260−270. doi: 10.28920/dhm52.4.260-270. PMID: 36525683.

Effects of high oxygen tension on healthy volunteer microcirculation

Nicolas Cousin1, Julien Goutay1, Patrick Girardie1, Raphaël Favory1, Elodie Drumez2, Daniel Mathieu1, Julien Poissy1, Erika Parmentier1, Thibault Duburcq1

1 Pôle de réanimation, hôpital Roger Salengro, CHU Lille, Lille, France
2 Unité de méthodologie – biostatistique et data management, CHU Lille, Lille, France

Corresponding author: Dr Thibault Duburcq, Centre Hospitalier Universitaire de Lille, Hôpital Roger Salengro – Centre de réanimation, Avenue du Professeur Emile Laine , 59037 LILLE Cedex, France
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Keywords
Hyperbaric oxygen treatment; Hyperoxia; Laser Doppler flowmetry; Near-infrared spectroscopy; Perfusion

Abstract
(Cousin N, Goutay J, Girardie P, Favory R, Drumez E, Mathieu D, Poissy J, Parmentier E, Duburcq. Effects of high oxygen tension on healthy volunteer microcirculation. Diving and Hyperbaric Medicine. 2022 December 20;52(4):260−270. doi: 10.28920/dhm52.4.260-270. PMID: 36525683.)
Introduction: Previous studies have highlighted hyperoxia-induced microcirculation modifications, but few have focused on hyperbaric oxygen (HBO) effects. Our primary objective was to explore hyperbaric hyperoxia effects on the microcirculation of healthy volunteers and investigate whether these modifications are adaptative or not.
Methods: This single centre, open-label study included 15 healthy volunteers. Measurements were performed under five conditions: T0) baseline value (normobaric normoxia); T1) hyperbaric normoxia; T2) hyperbaric hyperoxia; T3) normobaric hyperoxia; T4) return to normobaric normoxia. Microcirculatory data were gathered via laser Doppler, near-infrared spectroscopy and transcutaneous oximetry (PtcO2). Vascular-occlusion tests were performed at each step. We used transthoracic echocardiography and standard monitoring for haemodynamic investigation.
Results: Maximal alterations were observed under hyperbaric hyperoxia which led, in comparison with baseline, to arterial hypertension (mean arterial pressure 105 (SD 12) mmHg vs 95 (11), P < 0.001) and bradycardia (55 (7) beats·min-1 vs 66 (8), P < 0.001) while cardiac output remained unchanged. Hyperbaric hyperoxia also led to microcirculatory vasoconstriction (rest flow 63 (74) vs 143 (73) perfusion units, P < 0.05) in response to increased PtcO2 (104.0 (45.9) kPa vs 6.3 (2.4), P < 0.0001); and a decrease in laser Doppler parameters indicating vascular reserve (peak flow 125 (89) vs 233 (79) perfusion units, P < 0.05). Microvascular reactivity was preserved in every condition.
Conclusions: Hyperoxia significantly modifies healthy volunteer microcirculation especially during HBO exposure. The rise in PtcO2 promotes an adaptative vasoconstrictive response to protect cellular integrity. Microvascular reactivity remains unaltered and vascular reserve is mobilised in proportion to the extent of the ischaemic stimulus.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

Full article available here.


2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):271−276. doi: 10.28920/dhm52.4.271-276. PMID: 36525684.

Delayed treatment for decompression illness: factors associated with long treatment delays and treatment outcome

Sofia A Sokolowski1, Anne K Räisänen-Sokolowski2,3, Laura J Tuominen2,4, Richard V Lundell2,5 

1 University of Eastern Finland, Kuopio, Finland
2 Department of Pathology, Helsinki University, Helsinki, Finland
3 HUSLAB, Pathology, Helsinki University Hospital, Helsinki, Finland 
4 Department of Anaesthesia, Tampere University Hospital, Tampere, Finland
5 Diving Medical Centre, Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland

Corresponding author: Dr Richard V Lundell, Diving Medical Centre, Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland
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Keywords
Decompression sickness; Hyperbaric oxygen treatment; Epidemiology; First aid oxygen; Remote locations; Treatment sequelae

Abstract
(Sokolowski SA, Räisänen-Sokolowski AK, Tuominen LJ, Lundell RV. Delayed treatment for decompression illness: factors associated with long treatment delays and treatment outcome. Diving and Hyperbaric Medicine. 2022 December 20;52(4):271−276. doi: 10.28920/dhm52.4.271-276. PMID: 36525684.)
Introduction: Effectiveness of delayed hyperbaric oxygen treatment (HBOT) for decompression illness (DCI) and factors affecting treatment delays have not been studied in large groups of patients.
Methods: This retrospective study included 546 DCI patients treated in Finland in the years 1999–2018 and investigated factors associated with recompression delay and outcome. Treatment outcome was defined as fully recovered or presence of residual symptoms on completion of HBOT. The symptoms, use of first aid oxygen, number of recompression treatments needed and characteristics of the study cohort were also addressed.
Results: Delayed HBOT (> 48 h) remained effective with final outcomes similar to those treated within 48 h. Cardio-pulmonary symptoms were associated with a shorter treatment delay (median 15 h vs 28 h without cardiopulmonary symptoms, P < 0.001), whereas mild sensory symptoms were associated with a longer delay (48 vs 24 h, P < 0.001). A shorter delay was also associated with only one required HBOT treatment (median 24 h vs 34 h for those requiring multiple recompressions) (P = 0.002). Tinnitus and hearing impairment were associated with a higher proportion of incomplete recoveries (78 and 73% respectively, P < 0.001), whereas a smaller proportion of cases with tingling/itching (15%, P = 0.03), nausea (27%, P = 0.03), motor weakness (33%, P = 0.05) and visual disturbances (36%, P = 0.04) exhibited residual symptoms. Patients with severe symptoms had a significantly shorter delay than those with mild symptoms (median 24 h vs 36 h respectively, P < 0.001), and a lower incidence of complete recovery.
Conclusions: Delayed HBOT remains an effective and useful intervention. A shorter delay to recompression is associated with fewer recompressions required to achieve recovery or recovery plateau.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

Full article available here.


2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):277−280. doi: 10.28920/dhm52.4.277-280. PMID: 36525685.

Descriptive study of decompression illness in a hyperbaric medicine centre in Bangkok, Thailand from 2015 to 2021

Pitchaya Chevasutho1, Hansa Premmaneesakul2, Atipong Sujiratana2

1 Occupational Medicine Center, Chonburi Hospital, Chonburi, Thailand
2 Maritime Medicine Division, Somdech Phra Pinklao Hospital, Naval Medical Department, Bangkok, Thailand

Corresponding author: Dr Pitchaya Chevasutho, Occupational Medicine Center, Chonburi Hospital, 69 Moo 2, Sukhumvit Rd, Chonburi, Thailand 20000
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Keywords
Arterial gas embolism; Decompression sickness; Diving incidents; Hyperbaric oxygen treatment

Abstract
(Chevasutho P, Premmaneesakul H, Sujiratana A. Descriptive study of decompression illness in a hyperbaric medicine centre in Bangkok, Thailand from 2015 to 2021. Diving and Hyperbaric Medicine. 2022 December 20;52(4):277−280. doi: 10.28920/dhm52.4.277-280. PMID: 36525685.)
Introduction: This study aimed to determine the characteristics of decompression illness patients and their treatment outcomes, at the Center of Hyperbaric Medicine, Somdech Phra Pinklao Hospital, one of the largest centres in Thailand.
Methods: Past medical records of patients with decompression illness from 2015 to 2021 were retrieved and analysed.
Results: Ninety-eight records of diving-related illness from 97 divers were reviewed. Most of the divers were male (n = 50), Thai (n = 86), and were certified at least open water or equivalent (n = 88). On-site first aid oxygen inhalation was provided to 17 divers. Decompression sickness (DCS) cases were characterised according to organ systems involved. The most prominent organ system involved was neurological (57%), followed by mixed organs (28%), musculoskeletal (13%), and pulmonary (2%). There were three cases of arterial gas embolism (AGE). Median presentation delay was three days. Ninety patients were treated with 
US Navy Treatment Table 6. At the end of their hyperbaric oxygen treatment, most divers (65%) recovered completely.
Conclusions: Despite oxygen first aid being given infrequently and long delays before definitive treatment, treatment outcome was satisfactory. Basic knowledge and awareness of diving-related illnesses should be promoted among divers and related personnel in Thailand along with further studies.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

Full article available here.


2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):281−285. doi: 10.28920/dhm52.4.281-285. PMID: 36525686.

Agreement between ultrasonic bubble grades using a handheld self-positioning Doppler product and 2D cardiac ultrasound

Oscar Plogmark1,2, Carl Hjelte1,2,3, Magnus Ekström1, Oskar Frånberg2,4

1 Lund University, Faculty of Medicine, Department of Clinical Sciences Lund, Respiratory Medicine and Allergology, Lund, Sweden
2 Swedish Armed Forces Diving and Naval Medicine Center, Swedish Armed Forces, Karlskrona, Sweden
3 Sahlgrenska University Hospital, Anesthesia and Intensive Care. Gothenburg, Sweden
4 Blekinge Institute of Technology, Department of Mathematics and Natural Science, Karlskrona, Sweden

Corresponding author: Oscar Plogmark, Sten Bergmans väg 21, 121 46 Johanneshov, Sweden
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Keywords
Decompression; Decompression illness; Decompression sickness; Diving research; Echocardiography; Ultrasound; Venous gas emboli

Abstract
(Plogmark O, Hjelte C, Ekström M, Frånberg O. Agreement between ultrasonic bubble grades using a handheld self-positioning Doppler product and 2D cardiac ultrasound. Diving and Hyperbaric Medicine. 2022 December 20;52(4):281−285. doi: 10.28920/dhm52.4.281-285. PMID: 36525686.)
Introduction: Intravascular bubble load after decompression can be detected and scored using ultrasound techniques that measure venous gas emboli (VGE). The aim of this study was to analyse the agreement between ultrasonic bubble grades from a handheld self-positioning product, the O’DiveTM, and cardiac 2D ultrasound after decompression.
Methods: VGE were graded with both bilateral subclavian vein Doppler ultrasound (modified Spencer scale) and 2D cardiac images (Eftedal Brubakk scale). Agreement was analysed using weighted kappa (Kw). Analysis with Kw was made for all paired grades, including measurements with and without zero grades, and for each method’s highest grades after each dive.
Results: A total of 152 dives yielded 1,113 paired measurements. The Kw agreement between ultrasound VGE grades produced by cardiac 2D images and those from the O’Dive was ‘fair’; when zero grades were excluded the agreement was ‘poor’. The O’Dive was found to have a lower sensitivity to detect VGE compared to 2D cardiac image scoring.
Conclusions: Compared to 2D cardiac image ultrasound, the O’Dive yielded generally lower VGE grades, which resulted in a low level of agreement (fair to poor) with Kw.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

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2022 December;52(4) 

Diving Hyperb Med. 2022 December 20;52(4):286−288. doi: 10.28920/dhm52.4.286-288. PMID: 36525687.

Electric shock leading to acute lung injury in a scuba diver

Kelly Johnson-Arbor

Department of Plastic and Reconstructive Surgery, MedStar Georgetown University Hospital, Washington DC, USA

Corresponding author: Dr Kelly Johnson-Arbor, Department of Plastic and Reconstructive Surgery, MedStar Georgetown University Hospital, 3800 Reservoir Road NW, Washington DC, 20007, USA
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Keywords
Burns; Diving; Electric injuries; Salt water aspiration

Abstract
(Johnson-Arbor K. Electric shock leading to acute lung injury in a scuba diver. Diving and Hyperbaric Medicine. 2022 December 20;52(4):286−288. doi: 10.28920/dhm52.4.286-288. PMID: 36525687.)
Introduction: Electrical injuries are a rarely reported complication of scuba diving.
Case report: A 33-year-old woman wore a 12-volt heated shirt designed for motorcycling, powered by a canister light battery, while scuba diving. A leak in her drysuit allowed water to make contact with an electrified connector from the heated shirt, and she experienced painful electrical shocks. She was able to disconnect the power source and finish the dive, but she developed progressive fevers and dyspnoea several hours later. She was diagnosed with acute lung injury and treated with bronchodilators. Her symptoms resolved over subsequent weeks.
Discussion: Acute lung injury is rarely reported after low voltage electrical injury. In this case, the use of a heated shirt that was not intended for underwater activities heightened the patient’s risk for electric shock that likely resulted in aspiration of sea water and subsequent acute lung injury. To reduce risk of injury, divers should use equipment that is designed for underwater submersion. Medical professionals who treat the diving population should be aware that divers may use modified equipment that increases the risk of diving-related complications.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

Publication Type: Original article

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