Complications After Covid-19 Infection In Singapore Military Divers: A Retrospective Cohort Study.

Studies suggest that COVID-19 infections may have longer-term and more significant complications, even with mild or absent symptoms. This may predispose divers to pulmonary barotrauma, arterial gas embolisms, and reduced exercise tolerance, and impact physical and cognitive performance during diving. Military diving is physically, physiologically, and psychologically taxing on the individual. This study aims to assess the incidence of complications after COVID-19 infections in a cohort of active military divers and the incidence of diving-related injuries such as decompression sickness and barotrauma following recovery from acute COVID-19 infections. A single-center, retrospective cohort study of complications after COVID-19 infections was done in a cohort of the Republic of Singapore Navy (RSN) Naval Diving Unit (NDU) Divers and involved the collection of retrospective data for 329 military divers who were diagnosed with COVID-19 infection from 25 Mar 2020 and 13 Feb 2023. We found no clinical or subclinical complications after COVID-19 infection in our fully vaccinated, low-risk population of NDU divers after asymptomatic or mild COVID-19 infection. There were also no incidences of diving-related injuries related to COVID-19 after recovery from the acute illness. Based on the study results, it is recommended that all military divers with asymptomatic or mild COVID-19 infections return to military diving activities immediately after recovery from acute COVID-19 infection with resolution of symptoms. As existing guidelines recommend, divers with moderate to critical COVID-19 infection should be reviewed by a diving physician and undergo necessary investigations before returning to military diving.

Proposed Thalmann algorithm air diving decompression table for the Swedish Armed Forces.

The Swedish Armed Forces (SwAF) air dive tables are under revision. Currently, the air dive table from the U.S. Navy (USN) Diving Manual (DM) Rev. 6 is used with an msw-to-fsw conversion. Since 2017, the USN has been diving according to USN DM rev. 7, which incorporates updated air dive tables derived from the Thalmann Exponential Linear Decompression Algorithm (EL-DCM) with VVAL79 parameters. The SwAF decided to replicate and analyze the USN table development methodology before revising their current tables. The ambition was to potentially find a table that correlates with the desired risk of decompression sickness.  New compartmental parameters for the EL-DCM algorithm, called SWEN21B, were developed by applying maximum likelihood methods on 2,953 scientifically controlled direct ascent air dives with known outcomes of decompression sickness (DCS). The targeted probability of DCS for direct ascent air dives was ≤1% overall and ≤1‰ for neurological DCS (CNS-DCS). One hundred fifty-four wet validation dives were performed with air between 18 to 57 msw. Both direct ascent and decompression stop dives were conducted, resulting in incidences of two joint pain DCS (18 msw/59 minutes), one leg numbness CNS-DCS (51 msw/10 minutes with deco-stop), and nine marginal DCS cases, such as rashes and itching. A total of three DCS incidences, including one CNS-DCS, yield a predicted risk level (95% confidence interval) of 0.4-5.6% for DCS and 0.0-3.6% for CNS-DCS. Two out of three divers with DCS had patent foramen ovale. The SWEN21 table is recommended for the SwAF for air diving as it, after results from validation dives, suggests being within the desired risk levels for DCS and CNS-DCS.

Oxidative stress and adverse cardiovascular effects among professional divers in Egypt.

Professional divers are exposed to unique multifactorial hazards in their working environment and adverse cardiovascular effects such as ischemia, arrhythmia, stroke, and death are associated with professional diving. Cardiovascular events are aggravated by diving-induced oxidative stress and account for one-fourth of diving fatalities. This study aimed to measure oxidative and cardiovascular stress in a group of professional divers in Alexandria, Egypt using a panel of biomarkers. A comparative cross-sectional study was conducted between June 2017 and May 2018 at the General Naval Hospital in Alexandria. A total of 50 professional divers and a comparison group of 50 marine seafarers sharing similar maritime environments were enrolled in the study. Participants were clinically evaluated by electrocardiography (ECG) and plasma measurement of trace metals (Fe+, Cu+, and Zn+), electrolytes (Na+, K+, Ca+), and oxidative stress biomarkers (OSBMs; MDA, TAS, GST, GSH, GR, GPx, SOD, and CAT). Significant ECG abnormalities including short corrected QT interval, sinus bradycardia, left ventricular hypertrophy, early repolarization, first-degree heart block, and intraventricular conduction defect were identified among divers. Biochemical analyses revealed high mean levels of FBG [89.0 ± 12.46 vs. 100.5 ± 29.03 mg/dl], LDH-C [41.46 ± 4.01 vs. 39.34 ± 4.34 mg/dl], electrolyte imbalance [higher Na+ (9.44 ± 0.52 vs. 9.19 ± 0.60 mmol/L), and lower Ca+ (141.72 ± 3.53 and 143.26 ± 3.99 mmol/L)], disturbed trace metals [Fe+ and Zn+ (101.1 ± 38.17 vs. 147.6 ± 38.08 and 85.52 ± 27.37 vs. 116.6 ± 21.95 µm/dl, respectively), higher Cu+ (271.3 ± 75.01 vs. 100.8 ± 30.20 µm/dl)], and higher OSBMs (high MDA and reduced CAT, GPx, GSH, GR, and GST enzyme levels) among professional divers compared to the marine seafarers (t-test p < 0.05). Oxidative stress and trace metal imbalance are associated with the pathophysiology of cardiovascular disease; this association, together with electrophysiological changes of ECG may serve as biomarkers for cardiovascular risk assessment in diver periodic medical examinations.

Recurrent facial nerve baroparesis in a military diver: a case report.

Middle ear barotrauma is common in diving. However, facial nerve baroparesis is a relatively rare complication. A dehiscent facial nerve canal may be a predisposing factor to developing this complication. Although there is an increasing number of facial baroparesis cases in the literature, they are likely still under-reported. In order to avoid unnecessary recompression treatments or detrimental effects to a professional diver's career, it is important to consider this in the differential diagnosis while evaluating dive injuries. This case report describes recurrent facial baroparesis in a military diver, which manifested on contralateral sides of his face. His initial presentation was misdiagnosed as an arterial gas embolism, which led to recompression treatment and a cardiac procedure. Upon recurrence about one year later, a complete work-up was done, which included an ENT evaluation and a CT scan. Imaging demonstrated a predisposing anatomic variant bilaterally. His symptoms resolved quickly and spontaneously both times, and he has been able to return to diving.

Rescue of a submerged convulsing diver.

In 2018, the Medical Panel of the NATO Underwater Diving Working Group (UDWG) discussed the question of the rescue and management of a submerged unresponsive compressed-gas diver. The Panel reviewed the 2012 recommendation by the UHMS Diving Committee with respect to the specific recommendation in a convulsing diver using a half-face mask and separate mouthpiece, to delay surfacing until the clonic phase had subsided if the mouthpiece was in place. There is a paucity of scientific, epidemiological, experimental and observational human studies to substantiate this guidance. Experimental animal studies suggest that the likelihood of a complete airway obstruction during an ongoing seizure is low and that there is a high likelihood of surviving pulmonary barotrauma caused by complete airway closure. Airway management and control is an essential step in the management of the unresponsive diver and would be challenging to achieve in the underwater environment. Even in the military setting, it will be difficult to provide sufficient training to enable divers to handle such a situation. In this very rare scenario it is considered that emergency guidelines should be clear, concise and easy to follow. The UDWG therefore recommends that all unconscious military divers in this situation should be rescued to surface without waiting for clonic seizures to subside. Training organizations for recreational and occupational divers should consider whether this guidance should be applied for civilian divers as well.

Incidence of otic barotrauma in Canadian Armed Forces shallow-water diver candidate students 2011-2015.

INTRODUCTION: While otic barotrauma (OBT) is a common condition experienced by divers, data related to military divers is limited. This study aimed to determine the incidence of OBT in Canadian armed forces (CAF) shallow-water diver (SWD) students trained through the Fleet Dive Unit (Atlantic) (FDU[A]) between 2011-2015. METHODS: A retrospective cohort evaluation was performed. The study group consisted of all SWD candidates who embarked on an SWD course through FDU(A) between 2011-2015. A total of 241 subjects comprised the final data analysis. RESULTS: A total of 56 individuals (23.2%) suffered 60 instances of OBT, yielding an incidence density rate of 8.68 per 1,000 person-days on course. A total of 73 diving days (10.44 per 1,000 planned person-course days, or 4.87 diving days per course) were lost due to OBT. Of the reported OBT cases, 18% resulted in cessation of training, 72% in temporary removal from diving. There was no statistically significant association between sex, history of environmental allergies, previous dive qualification, age or rank and the development of OBT. CONCLUSIONS: This study reveals that OBT is prevalent among CAF SWD candidates, with operational impact due to missed diving days. This study is limited, and further prospective study is recommended.

A historical review of the U.S. Navy's busiest recompression chamber in the Pacific theater with a current perspective on caring for civilian divers within its area of responsibility: short communication.

On the island Nation of Guam, the United States Department of Defense has stationed military personnel from every service branch. Guam is utilized as a strategic waypoint for the U.S. military in the Pacific theater. As the largest service branch in the region, the Navy has placed a few Diving Medical Officers in Guam to collectively manage and treat patients with recompression therapy. Guam is also a popular tourist destination, with multiple recreational diving companies certifying individuals who are looking to take advantage of the beautiful warm water and exotic marine life. Unfortunately, with an increase in training and certifying inexperienced divers, came an increase in the operational tempo of the U.S. Navy's recompression chamber on Guam. The recompression chamber on Naval Base Guam (NBG) has been treating patients since 1971. With the only multiplace chamber in the Mariana Islands, Diving Medical Officers, with the accompanying chamber staff, treat military personnel, active-duty sponsored patients and civilian patients. Treating civilian patients by military providers through military treatment facilities presents multiple issues that must be addressed in an effort to provide efficient quality medical care. This article reviews the records, documents, and activity of the NBG chamber over the last four decades. Through the obtained data the information provides projected financial reimbursement from civilian patients. The article also sheds light on areas of needed improvement with regard to data collection, third-party financial collection efforts and the necessity of an inclusive electronic health record (EHR) for military and civilian patients.

Role of tympanocentesis in the prevention of middle ear barotrauma induced by fast buoyant ascent escape from 200 m underwater.

Introduction: We aimed to study middle ear barotrauma caused by fast compression followed by buoyant ascent escape from 200 m underwater and its effect on the auditory system, and to validate the preventive effect of tympanocentesis on middle ear barotrauma. Methods: Twenty Sprague Dawley rats were divided into two groups: rats in group A underwent a simulated fast buoyant ascent escape from a depth of 200 m, while those in group B underwent tympanocentesis before the procedure described for group A. Ear endoscopy, acoustic conductance, and auditory brainstem response (ABR) tests were conducted before and after the procedure to evaluate the severity of middle ear barotrauma and auditory function in both groups. Additionally, histopathological examination of the middle ear in both groups was conducted to evaluate the severity of middle ear barotrauma by observing submucosal haemorrhage. Results: None of the ears in either group showed any abnormalities before the experiment. In group A, middle ear barotrauma was universally observed after the simulation procedure. The tympanograms of all ears were initially type A and became type B after the procedure. Further, after the simulation, the hearing thresholds at different frequencies (4, 8, 16, 24, and 32 kHz) assessed by ABR significantly increased compared to those before the procedure. In group B, no middle ear barotrauma was observed, and the hearing threshold at each frequency did not change significantly compared with post-puncturing. After dissecting the middle ear, gross pathological observations were consistent with the above results. Microscopically, blood accumulation and submucosal haemorrhage in the middle ear cavity were observed in group A but not in group B. Conclusions: Fast buoyant ascent from 200 m underwater can cause middle ear barotrauma, resulting in hearing loss. Tympanic membrane puncture can effectively prevent middle ear barotrauma caused by the rapid buoyant ascent escape procedure.

Altered Sympathoadrenal Activity Following Cold-Water Diving.

INTRODUCTION: Little data exist on the effect of extremely cold-water diving on thermo-metabolic hormone secretion. Moreover, the impact of repetitive dives on the stress response is unknown. The purpose of this study was to determine the effects of two daily bouts of cold-water diving on the hormonal and metabolic profile of elite military personnel and to measure the stress response. METHODS: Healthy, male, Norwegian Special Forces operators (n = 5) volunteered for this study. Physiological and hormone data were analyzed prior to and following twice-daily Arctic dives (3.3°C). RESULTS: Core temperature was maintained (p > .05), whereas skin temperature was significantly reduced over the course of each dive (p < .01). Pairwise comparisons revealed adrenocorticotropic hormone (ACTH) and cortisol concentration significantly decreased across both dives and days (p < .001). Adrenaline and noradrenaline significantly increased across both time and day (p < .001). Leptin, testosterone, and IGF-1 significantly decreased over time but recovered between days. CONCLUSION: The main findings of this effort are that there is a rapid sympathetic-adreno-medullary (SAM/SNS) response to cold-water diving and a suppression of the hypothalamic-pituitary-adrenal (HPA) axis and hormones related to repair and recovery. While the sample size was too small to determine the role of SAM/SNS, HPA, and thyroid hormone effect on thermoregulation, it addresses a gap in our understanding of physiological adaptions that occurs in extreme environments.

Pulmonary oxygen toxicity breath markers after heliox diving to 81 metres.

Pulmonary oxygen toxicity (POT), an adverse reaction to an elevated partial pressure of oxygen in the lungs, can develop as a result of prolonged hyperbaric hyperoxic conditions. Initially starting with tracheal discomfort, it results in pulmonary symptoms and ultimately lung fibrosis. Previous studies identified several volatile organic compounds (VOCs) in exhaled breath indicative of POT after various wet and dry hyperbaric hypoxic exposures, predominantly in laboratory settings. This study examined VOCs after exposures to 81 metres of seawater by three navy divers during operational heliox diving. Univariate testing did not yield significant results. However, targeted multivariate analysis of POT-associated VOCs identified significant (P = 0.004) changes of dodecane, tetradecane, octane, methylcyclohexane, and butyl acetate during the 4 h post-dive sampling period. No airway symptoms or discomfort were reported. This study demonstrates that breath sampling can be performed in the field, and VOCs indicative of oxygen toxicity are exhaled without clinical symptoms of POT, strengthening the belief that POT develops on a subclinical-to-symptomatic spectrum. However, this study was performed during an actual diving operation and therefore various confounders were introduced, which were excluded in previous laboratory studies. Future studies could focus on optimising sampling protocols for field use to ensure uniformity and reproducibility, and on establishing dose-response relationships.

The lower limit for FEV1/FVC in dive medical assessments: a retrospective study.

INTRODUCTION: Interpreting pulmonary function test (PFT) results requires a valid reference set and a cut-off differentiating pathological from physiological pulmonary function; the lower limit of normal (LLN). However, in diving medicine it is unclear whether an LLN of 2.5% (LLN-2.5) or 5% (LLN-5) in healthy subjects constitutes an appropriate cut-off. METHODS: All PFTs performed at the Royal Netherlands Navy Diving Medical Centre between 1 January 2015 and 1 January 2021 resulting in a forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and/or FEV1/FVC with a Z-score between -1.64 (LLN-5) and -1.96 (LLN-2.5) were included. Records were screened for additional tests, referral to a pulmonary specialist, results of radiological imaging, and fitness to dive. RESULTS: Analysis of 2,108 assessments in 814 subjects showed that 83 subjects, 74 men and nine women, mean age 32.4 (SD 8.2) years and height 182 (7.0) cm, had an FVC, FEV1 and/or FEV1/FVC with Z-scores between -1.64 and -1.96. Of these 83 subjects, 35 (42%) underwent additional tests, 77 (93%) were referred to a pulmonary specialist and 31 (37%) underwent high-resolution CT-imaging. Ten subjects (12%) were declared 'unfit to dive' for various reasons. Information from their medical history could have identified these individuals. CONCLUSIONS: Use of LLN-2.5 rather than LLN-5 for FEV1/FVC in asymptomatic individuals reduces additional investigations and referrals to a pulmonary specialist without missing important diagnoses, provided a thorough medical history is taken. Adoption of LLN-2.5 could save resources spent on diving medical assessments and protect subjects from harmful side effects associated with additional investigations, while maintaining an equal level of safety.

Pulmonary barotrauma with cerebral arterial gas embolism from a depth of 0.75-1.2 metres of fresh water or less: A case report.

During underwater vehicle escape training with compressed air, a fit 26-year-old soldier suffered pulmonary barotrauma with cerebral arterial gas embolism after surfacing from a depth of 0.75-1.2 metres of freshwater or less. She presented with an altered level of consciousness. Rapid neurological examination noted slurred speech, a sensory deficit and right hemiparesis. Eleven hours after the accident, hyperbaric oxygen treatment was initiated using US Navy Treatment Table 6. The soldier almost completely recovered after repeated hyperbaric oxygen treatment. Given the very shallow depth this is an unusual case with only two similar case reports published previously.

Manned validation of a US Navy Diving Manual, Revision 7, VVal-79 schedule for short bottom time, deep air decompression diving.

INTRODUCTION: The US Navy air decompression table was promulgated in 2008, and a revised version, calculated with the VVal-79 Thalmann algorithm, was promulgated in 2016. The Swedish Armed Forces conducted a laboratory dive trial using the 2008 air decompression table and 32 dives to 40 metres' seawater for 20 minutes bottom time resulted in two cases of decompression sickness (DCS) and high venous gas emboli (VGE) grades. These results motivated an examination of current US Navy air decompression schedules. METHODS: An air decompression schedule to 132 feet seawater (fsw; 506 kPa) for 20 minutes bottom time with a 9-minute stop at 20 fsw was computed with the VVal-79 Thalmann algorithm. Dives were conducted in 29°C water in the ocean simulation facility at the Navy Experimental Diving Unit. Divers dressed in shorts and t-shirts performed approximately 90 watts cycle ergometer work on the bottom and rested during decompression. VGE were monitored with 2-D echocardiography at 20-minute intervals for two hours post-dive. RESULTS: Ninety-six man-dives were completed, resulting in no cases of DCS. The median (IQR) peak VGE grades were 3 (2-3) at rest and 3 (3-3) with limb flexion. VGE grades remained elevated two hours post-dive with median grades 1 (1-3) at rest and 3 (1-3) with movement. CONCLUSIONS: Testing of a short, deep air decompression schedule computed with the VVal-79 Thalmann algorithm, tested under diving conditions similar to earlier US Navy dive trials, resulted in a low incidence of DCS.

Evaluating the thermal protection provided by a 2‒3 mm wet suit during fin diving in shallow water with a temperature of 16‒20°C.

INTRODUCTION: The purpose of the study was to evaluate the thermal protection provided by a 2-3 mm surfing wet suit during at least two hours of fin diving in shallow water with a temperature of 16-20°C. We examined the effect of wearing the suit while diving in cold water on cognitive performance, muscle strength, and hand motor function. METHODS: Subjects were six male well-trained rebreather divers, 19-23 years old, acclimatised to cold. They attended the laboratory on three separate occasions, when we conducted the experiment at one of three temperatures, 16, 18, and 20°C. Core temperature (gastrointestinal system), skin temperature, oxygen consumption, and cold perception were evaluated during the test. Before and immediately after the dives, subjects performed a series of cognitive, manual dexterity, and muscle strength tests. RESULTS: Core temperature decreased by 0.35-0.81°C over the two hours at all three water temperatures. No subject reached a core temperature below 35°C. The decrease in upper body skin temperature during the two hour dive ranged between 5.97 and 8.41°C (P < 0.05). Two hours diving in 16-20°C water resulted in a significant increase in the time taken to perform the task of unlinking and reassembling four shackles (∼30% longer, P < 0.05). No effect was found on the cognitive or muscle strength tests. CONCLUSIONS: A 2-3 mm wet suit provides adequate thermal protection in trained and cold-acclimatised young males engaged in active diving in shallow water with a temperature of 16°C and above.

Longitudinal screening of hearing threshold in navy divers: is diving really a hazard?

INTRODUCTION: Hearing loss (HL) is common in the adult working population. It is widely assumed that diving is a risk factor for HL. However, studies with sufficient follow-up comparing HL in divers to non-divers are limited. This study aimed to assess the hearing threshold (HT) of Royal Netherlands Navy divers who had been diving for more than 15 years and to compare it to the ISO standard 7029:2017 reference table. METHODS: In this 25-year retrospective cohort study the Royal Netherlands Navy Diving Medical Centre audited the medical records of 1,117 Navy divers. Yearly dive medical assessments were performed according to professional standards, including audiometry. HTs were compared to the ISO 7029:2017 reference table, including Z-distribution, using paired t-tests. RESULTS: Thirty-five divers were included who had been diving for 15 years or longer. The HT increased significantly in nine of the 16 measured frequencies, while the Z-score decreased significantly in nine of the 16 tested frequencies (eight in both ears). In the 25-year follow-up the pattern was more obvious, with one significantly increased HT, and 10 significantly decreased Z-scores. DISCUSSION: The absolute HT increases after 15 years of military diving, but less than would be expected from normal age-related deterioration. Moreover, when comparing Z-scores, this sample of divers actually hear better than non-divers. We conclude that military diving is not an increased risk for HL compared to regular occupational hazards and suggest withdrawing the requirement for routine yearly audiometric evaluation as part of a dive medical examination.

Modern assessment of pulmonary function in divers cannot rely on old reference values.

INTRODUCTION: Pulmonary function testing (PFT) is an important part of dive medical examinations. Depending on the standard used to assess fitness to dive, different reference sets and fixed cut-off points are used. Reference values are part of an ongoing debate regarding the validity and accuracy related to different age groups, sex and ethnic backgrounds. The Global Lung Initiative (GLI) has provided an all-age reference set which corrects for sex and ethnicity (GLI-2012); this has had substantial impact on pulmonary medicine. METHOD: We present an algorithm that can be used to standardise analysis of PFT in divers using the GLI-2012 reference set. Differences in the analysis of PFT between the ECSC/ERS-1993 and the GLI-2012 reference values are illustrated by means of three case reports. CONCLUSION: Using a valid database of reference values increases accuracy and might prevent additional medical investigations and/or incorrect assessment of fitness to dive. Although our algorithm needs further evaluation to ensure its validity, the preliminary results are promising. Whatever algorithm is used, we urge dive medical physicians to consider using valid reference sets when analysing PFT for assessment of fitness to dive.

Personality and behavioural outcomes in diving: current status and recommendations for future research.

This paper provides a brief overview of the shift from studies describing the personality profiles of divers to studies exploring associations between personality variables and diving performance in terms of behavioural outcomes. The personality associations that were investigated include performance during training, panic proneness, diving injuries, susceptibility to inert gas narcosis, and the behaviour of tourist divers. The paper concludes with a number of suggested directions for further research on personality and diving that may provide tangible benefits in terms of both enhanced safety and improved performance underwater.

Decompressing rescue personnel during Australian submarine rescue operations.

INTRODUCTION: Personnel rescuing survivors from a pressurized, distressed Royal Australian Navy (RAN) submarine may themselves accumulate a decompression obligation, which may exceed the bottom time limits of the Defense and Civil Institute of Environmental Medicine (DCIEM) Air and In-Water Oxygen Decompression tables (DCIEM Table 1 and 2) presently used by the RAN. This study compared DCIEM Table 2 with alternative decompression tables with longer bottom times: United States Navy XVALSS_DISSUB 7, VVAL-18M and Royal Navy 14 Modified tables. METHODS: Estimated probability of decompression sickness (PDCS), the units pulmonary oxygen toxicity dose (UPTD), the volume of oxygen required and the total decompression time were calculated for hypothetical single and repetitive exposures to 253 kPa air pressure for various bottom times and prescribed decompression schedules. RESULTS: Compared to DCIEM Table 2, XVALSS_DISSUB 7 single and repetitive schedules had lower estimated PDCS, which came at the cost of longer oxygen decompressions. For single exposures, DCIEM schedules had PDCS estimates ranging from 1.8% to 6.4% with 0 to 101 UPTD and XVALSS_DISSUB 7 schedules had PDCS of less than 3.1%, with 36 to 350 UPTD. CONCLUSIONS: The XVALSS_DISSUB 7 table was specifically designed for submarine rescue and, unlike DCIEM Table 2, has schedules for the estimated maximum required bottom times at 253 kPa. Adopting these tables may negate the requirement for saturation decompression of rescue personnel exceeding DCIEM limits.

Decompressing recompression chamber attendants during Australian submarine rescue operations.

INTRODUCTION: Inside chamber attendants rescuing survivors from a pressurised, distressed submarine may themselves accumulate a decompression obligation which may exceed the limits of Defense and Civil Institute of Environmental Medicine tables presently used by the Royal Australian Navy. This study assessed the probability of decompression sickness (PDCS) for medical attendants supervising survivors undergoing oxygen-accelerated saturation decompression according to the National Oceanic and Atmospheric Administration (NOAA) 17.11 table. METHODS: Estimated probability of decompression sickness (PDCS), the units pulmonary oxygen toxicity dose (UPTD) and the volume of oxygen required were calculated for attendants breathing air during the NOAA table compared with the introduction of various periods of oxygen breathing. RESULTS: The PDCS in medical attendants breathing air whilst supervising survivors receiving NOAA decompression is up to 4.5%. For the longest predicted profile (830 minutes at 253 kPa) oxygen breathing at 30, 60 and 90 minutes at 132 kPa partial pressure of oxygen reduced the air-breathing-associated PDCS to less than 3.1 %, 2.1% and 1.4% respectively. CONCLUSIONS: The probability of at least one incident of DCS among attendants, with consequent strain on resources, is high if attendants breathe air throughout their exposure. The introduction of 90 minutes of oxygen breathing greatly reduces the probability of this interruption to rescue operations.

Periorbital emphysema after a wet chamber dive.

Although periorbital emphysema (PE) is commonly associated with orbital fractures, it may develop without any fracture or significant trauma in circumstances such as post-surgery, infection, forceful nose blowing, sneezing, and weight lifting. We report on a healthy military diver who developed PE following a wet chamber dive. A diagnosis of PE secondary to sinus barotrauma was reached. He was treated conservatively without medication and his symptoms recovered completely within 10 days. To the best of our knowledge, only five cases of diving-related PE have been reported in the literature. Analysis of these cases and ours revealed that facial trauma, repeated forceful Valsalva manoeuvres and recent upper respiratory tract infection are probable risk factors for diving-related PE.