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.

PROMISING DIRECTIONS OF SCIENTIFIC AND PEDAGOGICAL WORK OF THE DEPARTMENT OF OCCUPATIONAL MEDICINE, AVIATION, SPACE AND DIVING MEDICINE

The main promising directions of research activities of the department and pedagogical work with the use of new forms of professional training of specialists in the field of occupational medicine based on the concept of lifelong education and a competence-based approach are presented. The department develops "biomedicine of the future" with the involvement of the latest achievements in the field of medical biochemistry, molecular biology, bioengineering, biotechnology, medical radiobiology. The department carries out the development and implementation of programs of higher professional education for students and residents of Sechenov University and students of the DPO system, taking into account the approaches of personalized and evidence-based medicine. The department has introduced new educational technologies (blended learning), is developing modern on-line services and modular programs.

Sinus barotrauma in diving

Introduction: Sinus barotrauma is a common occurrence in diving and subaquatic medicine, potentially compromising dive safety. To gain a more thorough understanding of the condition, an in-depth investigation is justified. Methods: This was a survey study. An anonymous, electronic questionnaire was distributed to 7,060 recipients: professional divers of the Finnish Border Guard, the Finnish Rescue Services, and the Finnish Heritage agency, as well as recreational divers registered as members of the Finnish Divers’ Association reachable by email (roughly two-thirds of all members and recreational divers in Finland). Primary outcomes were self-reported prevalence, clinical characteristics, and health effects of sinus barotrauma while diving. Secondary outcomes were adjusted odds ratios (OR) for frequency of sinus barotrauma with respect to possible risk factors. Results: In total, 1,881 respondents participated in the study (response rate 27%). A total of 49% of the respondents had experienced sinus barotrauma while diving and of those affected, 32% had used medications to alleviate their symptoms. The factors associated with sinus barotrauma were pollen allergies (OR 1.59; 95% CI 1.10–2.29), regular smoking (OR 2.04; 95% CI 1.07–3.91) and a high number of upper respiratory tract infections per year (≥ 3 vs. < 3 infections per year: OR 2.76; 95% CI 1.79–4.24). Conclusions: Sinus barotrauma is the second most common condition encountered in diving medicine, having affected 49% of the respondents. Possible risk factors include allergies to pollen, regular smoking, and a high number of URTIs per year.

Retrospective review of enquiries to the Québec diving medicine call centre: 2004 through 2018

Introduction: The Centre de Médecine de Plongée du Québec (CMPQ) established a bilingual 24-hour dive emergency call line and diving medicine information service in 2004. The toll-free number (888-835-7121) works throughout Canada. Calls and emails ([email protected]) are answered by a CMPQ coordinator or on-call hyperbaric physicians and other consultants as needed. We reviewed 15 years of activity. Methods: Details of phone calls and email enquiries to the centre were reviewed individually and compiled into a database. Data were analysed to characterise contact volume and issues addressed. Contacts were categorised into five groups: information only (INF); medical opinion required (MOP); medical issue after the critical period of urgency had passed (PUR); current urgent but not immediate life-threatening issue (NLT); and immediate life- or health-threatening issue (ILT). Data presented as mean (standard deviation) or percentage. Results: A total of 3,232 contacts were made from May 2004 through December 2018: 19 (SD 8) per month [215 (70) per year]. Primary issues of concern were: emergency planning (20%); technical (not medical/physiology) questions (16%); otorhinolaryngological (12%); and decompression sickness-related (7%). Categorisation was 52% INF, 28% MOP, 13% PUR, 7% NLT, and 0.1% ILT, with 0.2% lacking sufficient detail to categorise. The nature of the diving activity of interest was determined in 67% of cases: 48% (n = 1,039) professional; 46% (n = 1,008) recreational; and 1% (n = 11) breath-hold. Conclusions: The call centre serves as a resource to the community, providing information on health and safety for diving in addition to being available to assist with emergent needs.

Decompressive Pathology in Cetaceans Based on an Experimental Pathological Model

Decompression sickness (DCS) is a widely known clinical syndrome in human medicine, mainly in divers, related to the formation of intravascular and extravascular gas bubbles. Gas embolism and decompression-like sickness have also been described in wild animals, such as cetaceans. It was hypothesized that adaptations to the marine environment protected them from DCS, but in 2003, decompression-like sickness was described for the first time in beaked whales, challenging this dogma. Since then, several episodes of mass strandings of beaked whales coincidental in time and space with naval maneuvers have been recorded and diagnosed with DCS. The diagnosis of human DCS is based on the presence of clinical symptoms and the detection of gas embolism by ultrasound, but in cetaceans, the diagnosis is limited to forensic investigations. For this reason, it is necessary to resort to experimental animal models to support the pathological diagnosis of DCS in cetaceans. The objective of this study is to validate the pathological results of cetaceans through an experimental rabbit model wherein a complete and detailed histopathological analysis was performed. Gross and histopathological results were very similar in the experimental animal model compared to stranded cetaceans with DCS, with the presence of gas embolism systemically distributed as well as emphysema and hemorrhages as primary lesions in different organs. The experimental data reinforces the pathological findings found in cetaceans with DCS as well as the hypothesis that individuality plays an essential role in DCS, as it has previously been proposed in animal models and human diving medicine.

Emergency Medicine Cases in Underwater and Hyperbaric Environments: The Use of in situ Simulation as a Learning Technique

IntroductionHyperbaric chambers and underwater environments are challenging and at risk of serious accidents. Personnel aiming to assist patients and subjects should be appropriately trained, and several courses have been established all over the world. In healthcare, simulation is an effective learning technique. However, there have been few peer-reviewed articles published in the medical literature describing its use in diving and hyperbaric medicine.MethodsWe implemented the curriculum of the Master’s degree in hyperbaric and diving medicine held at the University of Padova with emergency medicine seminars created by the faculty and validated by external experts. These seminars integrated traditional lectures and eight in situ simulation scenarios.ResultsFor the hyperbaric medicine seminar, simulations were carried out inside a real hyperbaric chamber at the ATIP Hyperbaric Treatment Centre, only using air and reproducing compression noise without pressurization to avoid damages to the manikins. The four scenarios consisted of hyperoxic seizures, pneumothorax, hypoglycemia, and sudden cardiac arrest. Furthermore, we added a hands-on session to instruct participants to prepare an intubated patient undergoing hyperbaric oxygen treatment with a checklist and simulating the patient transfer inside and outside the hyperbaric chamber. The diving medicine seminar was held at the Y-40 The Deep Joy pool in Montegrotto Terme (Italy), also involving SCUBA/breath-hold diving (BHD) instructors to rescue subjects from the water. These diving medicine scenarios consisted of neurologic syndrome (“taravana/samba”) in BHD, drowning of a breath-hold diver, pulmonary barotrauma in BHD, and decompression illness in a SCUBA diver.ConclusionWith this experience, we report the integration of simulation in the curriculum of a teaching course in diving and hyperbaric medicine. Future studies should be performed to investigate learning advantages, concept retention, and satisfaction of participants.

Broad individual immersion-scattering of respiratory compliance likely substantiates dissimilar breathing mechanics

Head-out water immersion alters respiratory compliance which underpins defining pressure at a “Lung centroid” and the breathing “Static Lung Load”. In diving medicine as in designing dive-breathing devices a single value of lung centroid pressure is presumed as everyone’s standard. On the contrary, we considered that immersed respiratory compliance is disparate among a homogenous adult group (young, healthy, sporty). We wanted to substantiate this ample scattering for two reasons: (i) it may question the European standard used in designing dive-breathing devices; (ii) it may contribute to understand the diverse individual figures of immersed work of breathing. Resting spirometric measurements of lung volumes and the pressure–volume curve of the respiratory system were assessed for 18 subjects in two body positions (upright Up, and supine Sup). Measurements were taken in air (Air) and with subjects immersed up to the sternal notch (Imm). Compliance of the respiratory system (Crs) was calculated from pressure–volume curves for each condition. A median 60.45% reduction in Crs was recorded between Up-Air and Up-Imm (1.68 vs 0.66 L/kPa), with individual reductions ranging from 16.8 to 82.7%. We hypothesize that the previously disregarded scattering of immersion-reduced respiratory compliance might participate to substantial differences in immersed work of breathing.

Diving medical officers as hospitalists: a case of arterial gas embolism following a routine GI procedure

Arterial gas embolism is a well-described and frequently seen injury encountered in both civilian and military diving operations. It is becoming increasingly reported and potentially increasingly more common in the hospital environment as a complication of more frequent gastroenterology procedures. We present a case of a 49-year-old, active-duty female who developed significant left-sided neurological deficits manifesting as diffuse left-sided weakness, subjective confusion, and severe headache following esophagogastroduodenoscopy. With increased clinical suspicion for arterial gas embolism, the patient was evaluated by the hyperbaric medicine team at our facility and subsequently treated to near-resolution of symptoms by multiple hyperbaric oxygen treatments. This case highlights the importance of considering this rare complication during or following common invasive procedures. Furthermore, the unique training and experience of physicians with expertise in diving medicine and their ability to recognize these types of injury in the hospital setting highlights the importance of continued training in these fields within Military Medicine in addition to civilian Undersea and Hyperbaric Medicine fellowships.