Breath-Hold Diving Injuries - A Primer for Medical Providers.

ABSTRACT: Breath-hold divers, also known as freedivers, are at risk of specific injuries that are unique from those of surface swimmers and compressed air divers. Using peer-reviewed scientific research and expert opinion, we created a guide for medical providers managing breath-hold diving injuries in the field. Hypoxia induced by prolonged apnea and increased oxygen uptake can result in an impaired mental state that can manifest as involuntary movements or full loss of consciousness. Negative pressure barotrauma secondary to airspace collapse can lead to edema and/or hemorrhage. Positive pressure barotrauma secondary to overexpansion of airspaces can result in gas embolism or air entry into tissues and organs. Inert gas loading into tissues from prolonged deep dives or repetitive shallow dives with short surface intervals can lead to decompression sickness. Inert gas narcosis at depth is commonly described as an altered state similar to that experienced by compressed air divers. Asymptomatic cardiac arrhythmias are common during apnea, normally reversing shortly after normal ventilation resumes. The methods of glossopharyngeal breathing (insufflation and exsufflation) can add to the risk of pulmonary overinflation barotrauma or loss of consciousness from decreased cardiac preload. This guide also includes information for medical providers who are tasked with providing medical support at an organized breath-hold diving event with a list of suggested equipment to facilitate diagnosis and treatment outside of the hospital setting.

Dysbarism: An Overview of an Unusual Medical Emergency.

Dysbarism is a general term which includes the signs and symptoms that can manifest when the body is subject to an increase or a decrease in the atmospheric pressure which occurs either at a rate or duration exceeding the capacity of the body to adapt safely. In the following review, we take dysbarisms into account for our analysis. Starting from the underlying physical laws, we will deal with the pathologies that can develop in the most frequently affected areas of the body, as the atmospheric pressure varies when acclimatization fails. Manifestations of dysbarism range from itching and minor pain to neurological symptoms, cardiac collapse, and death. Overall, four clinical pictures can occur: decompression illness, barotrauma, inert gas narcosis, and oxygen toxicity. We will then review the clinical manifestations and illustrate some hints of therapy. We will first introduce the two forms of decompression sickness. In the next part, we will review the barotrauma, compression, and decompression. The last three parts will be dedicated to gas embolism, inert gas narcosis, and oxygen toxicity. Such an approach is critical for the effective treatment of patients in a hostile environment, or treatment in the emergency room after exposure to extreme physical or environmental factors.

High Incidence of Barotrauma in Patients With Severe Coronavirus Disease 2019.

OBJECTIVE.: To report the high incidence of barotrauma in critically ill patients admitted to the intensive care unit (ICU) with coronavirus disease 2019 (COVID-19) and to discuss its implications. DESIGN.: Retrospective cohort study. SETTING.: ICU of an academic county hospital in Los Angeles, CA admitted from March 15-June 20, 2020. PATIENTS.: 77 patients with COVID-19 pneumonia. 75 patients met inclusion criteria. RESULTS.: 21% of patients with severe COVID-19 sustained barotrauma (33% of patients receiving IMV, 8% of patients receiving (NIV). There were no differences between the barotrauma and non-barotrauma groups regarding demographics, illness severity, or medications received, nor tidal volume or average/peak airway pressures in those receiving IMV. In the barotrauma group there was a greater proportion of patients receiving therapeutic anticoagulation (81% vs. 47%, p = 0.023) and ventilated using airway pressure release ventilation mode (13% vs. 0%, p = 0.043). Barotrauma was associated with increased likelihood of receiving a tracheostomy (OR 2.58 [0.23-4.9], p = 0.018]), longer median ICU length of stay (17 days vs. 7 days, p = 0.03), and longer median length of hospitalization (26 days vs. 14 days, p < 0.001). There was also a trend toward prolonged median duration of IMV (12.5 days vs 7 days, p = 0.13) and higher average mortality (56% vs 37%, p = 0.25). CONCLUSIONS.: Barotrauma is seen in 5-12% of patients with ARDS receiving IMV and is exceedingly rare in patients receiving NIV. We report a high incidence of barotrauma observed in critically ill patients with COVID-19 requiring either NIV or IMV. While there was a trend toward increased mortality in patients with barotrauma, this did not reach statistical significance. The increased incidence of barotrauma with COVID-19 may be a product of the pathophysiology of this disease state and a heightened inflammatory response causing rampant acute lung injury. Evidence-based medicine and lung-protective ventilation should remain the mainstay of treatment.

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.

Intraoperative use of low volume ventilation to decrease postoperative mortality, mechanical ventilation, lengths of stay and lung injury in adults without acute lung injury.

BACKGROUND: Since the 2000s, there has been a trend towards decreasing tidal volumes for positive pressure ventilation during surgery. This an update of a review first published in 2015, trying to determine if lower tidal volumes are beneficial or harmful for patients. OBJECTIVES: To assess the benefit of intraoperative use of low tidal volume ventilation (less than 10 mL/kg of predicted body weight) compared with high tidal volumes (10 mL/kg or greater) to decrease postoperative complications in adults without acute lung injury. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2017, Issue 5), MEDLINE (OvidSP) (from 1946 to 19 May 2017), Embase (OvidSP) (from 1974 to 19 May 2017) and six trial registries. We screened the reference lists of all studies retained and of recent meta-analysis related to the topic during data extraction. We also screened conference proceedings of anaesthesiology societies, published in two major anaesthesiology journals. The search was rerun 3 January 2018. SELECTION CRITERIA: We included all parallel randomized controlled trials (RCTs) that evaluated the effect of low tidal volumes (defined as less than 10 mL/kg) on any of our selected outcomes in adults undergoing any type of surgery. We did not retain studies with participants requiring one-lung ventilation. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the quality of the retained studies with the Cochrane 'Risk of bias' tool. We analysed data with both fixed-effect (I2 statistic less than 25%) or random-effects (I2 statistic greater than 25%) models based on the degree of heterogeneity. When there was an effect, we calculated a number needed to treat for an additional beneficial outcome (NNTB) using the odds ratio. When there was no effect, we calculated the optimum information size. MAIN RESULTS: We included seven new RCTs (536 participants) in the update.In total, we included 19 studies in the review (776 participants in the low tidal volume group and 772 in the high volume group). There are four studies awaiting classification and three are ongoing. All included studies were at some risk of bias. Participants were scheduled for abdominal surgery, heart surgery, pulmonary thromboendarterectomy, spinal surgery and knee surgery. Low tidal volumes used in the studies varied from 6 mL/kg to 8.1 mL/kg while high tidal volumes varied from 10 mL/kg to 12 mL/kg.Based on 12 studies including 1207 participants, the effects of low volume ventilation on 0- to 30-day mortality were uncertain (risk ratio (RR) 0.80, 95% confidence interval (CI) 0.42 to 1.53; I2 = 0%; low-quality evidence). Based on seven studies including 778 participants, lower tidal volumes probably reduced postoperative pneumonia (RR 0.45, 95% CI 0.25 to 0.82; I2 = 0%; moderate-quality evidence; NNTB 24, 95% CI 16 to 160), and it probably reduced the need for non-invasive postoperative ventilatory support based on three studies including 506 participants (RR 0.31, 95% CI 0.15 to 0.64; moderate-quality evidence; NNTB 13, 95% CI 11 to 24). Based on 11 studies including 957 participants, low tidal volumes during surgery probably decreased the need for postoperative invasive ventilatory support (RR 0.33, 95% CI 0.14 to 0.77; I2 = 0%; NNTB 39, 95% CI 30 to 166; moderate-quality evidence). Based on five studies including 898 participants, there may be little or no difference in the intensive care unit length of stay (standardized mean difference (SMD) -0.06, 95% CI -0.22 to 0.10; I2 = 33%; low-quality evidence). Based on 14 studies including 1297 participants, low tidal volumes may have reduced hospital length of stay by about 0.8 days (SMD -0.15, 95% CI -0.29 to 0.00; I2 = 27%; low-quality evidence). Based on five studies including 708 participants, the effects of low volume ventilation on barotrauma (pneumothorax) were uncertain (RR 1.77, 95% CI 0.52 to 5.99; I2 = 0%; very low-quality evidence). AUTHORS' CONCLUSIONS: We found moderate-quality evidence that low tidal volumes (defined as less than 10 mL/kg) decreases pneumonia and the need for postoperative ventilatory support (invasive and non-invasive). We found no difference in the risk of barotrauma (pneumothorax), but the number of participants included does not allow us to make definitive statement on this. The four studies in 'Studies awaiting classification' may alter the conclusions of the review once assessed.

Repetitive freshwater diving: risk factors and prevalence of barotrauma.

OBJECTIVE: The aim was to investigate the influence of repetitive scuba diving in fresh water on the middle ear mucosa. The prevalence of middle ear barotrauma (MEB) and risk factors for MEB were evaluated. STUDY DESIGN: Prospective cohort study, Level of evidence 1b. METHODS: During three days, 23 divers made 144 repetitive dives in a freshwater lake. Participants underwent otoscopic examinations and were questioned about ENT-related complaints in the morning before the first dive, in between the dives and after the last dive. Otoscopic findings were documented and classified according to the TEED scale (0 = normal eardrum to 4 = perforation), for the right and the left ear separately. RESULTS: In total, 416 examinations were performed. ENT-related complaints during diving, mostly failed pressure equalization (74%), were reported after 10% of all dives. Most common pathology was MEB (TEED 1-3, 26%). Valsalva maneuver was possible during all exams. Significant increase of MEB (TEED⟩0) occurred with an increasing cumulative number of dives per day (P ⟨ .0001). Diving depth significantly influenced the MEB distribution (P = .035). MEB with higher TEED levels (2 and 3) was present only in the less experienced and intermediate divers. With increasing TEED level, more participants reported ENT-related problems (P ⟨ .0001). However, 74.4% of divers with MEB were still asymptomatic. CONCLUSION: During three days of diving, the MEB prevalence increased with a cumulative number of dives per day. The major risk factors were diving depth and diving experience. Higher TEED level correlated with an increasing number of subjective ENT-related disorders during diving.

Alternobaric vertigo and facial baroparesis caused by scuba diving and relieved by chewing pineapple: a case report.

Equalization of middle ear pressure is an important consideration for scuba divers. When middle ear pressure is asymmetric, a diver may experience alternobaric vertigo. Moreover, individuals with an underlying temporal bone dehiscence are predisposed to facial baroparesis. An understanding on behalf of fellow divers and emergency responders to recognize and differentiate facial baroparesis from decompression illness is critical. Misdiagnosis may lead to inappropriate treatment or unwarranted stoppage of diving. There have been a few dozen reported cases of facial baroparesis in the literature, but few have included firsthand accounts. This report describes an incidence of unilateral facial baroparesis preceded by alternobaric vertigo, with commentary from divers who witnessed the individual experiencing the facial paresis. The facial weakness in this case resolved within 15 minutes after the diver chewed on fresh pineapple. This report suggests that alternobaric vertigo may be a harbinger of facial baroparesis. Upon resurfacing divers should consider prophylactic measures that help to dilate the Eustachian tube such as chewing, yawning and swallowing in order to minimize the risk of middle ear pressure-induced vertigo or facial paresis.

Sudden Death in a Diver: A Diagnostic Conundrum.

We discuss the case of an experienced diver who ran out of air during his final ascent while scuba diving. He lost consciousness rapidly after surfacing and despite immediate cardiopulmonary resuscitation, could not be revived. On arrival at the emergency department he was noted to have copious amounts of blood in his upper airway and had developed extensive subcutaneous emphysema. Large amounts of air were observed in the central circulation following a postmortem computerized tomography scan as well as pneumomediastinum, a small right-sided hemothorax, and extensive subcutaneous emphysema. We discuss several potential pathophysiological mechanisms that might explain these findings. Finally, we end with a recommendation for an expedient whole-body postmortem computerized tomography scan and autopsy by a suitably qualified pathologist in the investigation of all dive-related fatalities, where possible.

Pneumopericardium in the Neonate.

Pneumopericardium occurs when air accumulates in the pericardial sac surrounding the heart and is one of the rarest forms of air leaks in neonates. Because of various advances in neonatal care, including gentler modes of ventilation, surfactant replacement, and antenatal steroids, the incidence of pneumopericardium has decreased. Despite the decrease in incidence of pneumopericardium, most cases arise in premature infants with a history of respiratory distress and mechanical ventilation. Evidence has shown that the incidence is inversely related to birth weight and that pneumopericardium has high mortality and morbidity rates.

Ear, nose and throat and non-acoustic barotrauma.

The organs of the ear, nose and throat (ENT) contain air- or gas-filled cavities, which make them sensitive to pressure changes. There is a specific pathophysiology involved when these structures are exposed to non-acoustic press ure changes, which are usually not traumatic in normals. The concepts of pathophysiology, diagnosis and treatment of these traumas in an emergency setting are reviewed.

Intraoperative use of low volume ventilation to decrease postoperative mortality, mechanical ventilation, lengths of stay and lung injury in patients without acute lung injury.

BACKGROUND: During the last decade, there has been a trend towards decreasing tidal volumes for positive pressure ventilation during surgery. It is not known whether this new trend is beneficial or harmful for patients. OBJECTIVES: To assess the benefit of intraoperative use of low tidal volume ventilation (< 10 mL/kg of predicted body weight) to decrease postoperative complications. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 9), MEDLINE (OvidSP) (from 1946 to 5 September 2014) and EMBASE (OvidSP) (from 1974 to 5 September 2014). SELECTION CRITERIA: We included all parallel randomized controlled trials (RCTs) that evaluated the effect of low tidal volumes (defined as < 10 mL/kg) on any of our selected outcomes in adult participants undergoing any type of surgery. We did not retain studies with participants requiring one-lung ventilation. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the quality of the retained studies with the Cochrane 'Risk of bias' tool. We analysed data with both fixed-effect (I(2) statistic < 25%) or random-effects (I(2) statistic > 25%) models based on the degree of heterogeneity. When there was an effect, we calculated a number needed to treat for an additional beneficial outcome (NNTB) using the odds ratio. When there was no effect, we calculated the optimal size information. MAIN RESULTS: We included 12 studies in the review. In total these studies detailed 1012 participants (499 participants in the low tidal volume group and 513 in the high volume group). All studies included were at risk of bias as defined by the Cochrane tool. Based on nine studies including 899 participants, we found no difference in 0- to 30-day mortality between low and high tidal volume groups (risk ratio (RR) 0.79, 95% confidence interval (CI) 0.40 to 1.54; I(2) statistic 0%; low quality evidence). Based on four studies including 601 participants undergoing abdominal or spinal surgery, we found a lower incidence of postoperative pneumonia in the lower tidal volume group (RR 0.44, 95% CI 0.20 to 0.99; I(2) statistic 19%; moderate quality evidence; NNTB 19, 95% CI 14 to 169). Based on two studies including 428 participants, low tidal volumes decreased the need for non-invasive postoperative ventilatory support (RR 0.31, 95% CI 0.15 to 0.64; moderate quality evidence; NNTB 11, 95% CI 9 to 19). Based on eight studies including 814 participants, low tidal volumes during surgery decreased the need for postoperative invasive ventilatory support (RR 0.33, 95% CI 0.14 to 0.80; I(2) statistic 0%; NNTB 36, 95% CI 27 to 202; moderate quality evidence). Based on three studies including 650 participants, we found no difference in the intensive care unit length of stay (standardized mean difference (SMD) -0.01, 95% CI -0.22 to 0.20; I(2) statistic = 42%; moderate quality evidence). Based on eight studies including 846 participants, we did not find a difference in hospital length of stay (SMD -0.16, 95% CI -0.40 to 0.07; I(2) statistic 52%; moderate quality evidence). A meta-regression showed that the effect size increased proportionally to the peak pressure measured at the end of surgery in the high volume group. We did not find a difference in the risk of pneumothorax (RR 2.01, 95% CI 0.51 to 7.95; I(2) statistic 0%; low quality evidence). AUTHORS' CONCLUSIONS: Low tidal volumes (defined as < 10 mL/kg) should be used preferentially during surgery. They decrease the need for postoperative ventilatory support (invasive and non-invasive). Further research is required to determine the maximum peak pressure of ventilation that should be allowed during surgery.

Diving medicine.

Exposure to the undersea environment has unique effects on normal physiology and can result in unique disorders that require an understanding of the effects of pressure and inert gas supersaturation on organ function and knowledge of the appropriate therapies, which can include recompression in a hyperbaric chamber. The effects of Boyle's law result in changes in volume of gas-containing spaces when exposed to the increased pressure underwater. These effects can cause middle ear and sinus injury and lung barotrauma due to lung overexpansion during ascent from depth. Disorders related to diving have unique presentations, and an understanding of the high-pressure environment is needed to properly diagnose and manage these disorders. Breathing compressed air underwater results in increased dissolved inert gas in tissues and organs. On ascent after a diving exposure, the dissolved gas can achieve a supersaturated state and can form gas bubbles in blood and tissues, with resulting tissue and organ damage. Decompression sickness can involve the musculoskeletal system, skin, inner ear, brain, and spinal cord, with characteristic signs and symptoms. Usual therapy is recompression in a hyperbaric chamber following well-established protocols. Many recreational diving candidates seek medical clearance for diving, and healthcare providers must be knowledgeable of the environmental exposure and its effects on physiologic function to properly assess individuals for fitness to dive. This review provides a basis for understanding the diving environment and its accompanying disorders and provides a basis for assessment of fitness for diving.

The O'Neill grading system for evaluation of the tympanic membrane: A practical approach for clinical hyperbaric patients.

Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are the two most common complications of clinical hyperbaric oxygen (HBO2) treatment. The current grading system, the Teed's Classification, was first described in 1944 with modifications to this system over the years, but none are specific for the evaluation and treatment of patients undergoing clinical HBO2 therapy. Currently, the standard of care is a baseline otoscopic examination performed prior to starting HBO2 therapy. Repeat otoscopy is required for patients having ETD, pain or other symptoms during the compression and/or decompression phase of the treatment. Results from these examinations are used to determine the proper course of treatment for the ETD or MEB. The Teed's classification was not intended to correlate with the consistency of diagnosis, the clinical approach to relieving symptoms or the treatment of the inflicted trauma. It is not a practical tool for the modern hyperbaric team. We describe a newer grading system, the O'Neill Grading System (OGS), which allows simple, practical and consistent classification of ETD and MEB by all members of the clinical hyperbaric medicine team. Based on the O'Neill Grade assigned, evidence supported suggestions for appropriate actions and medical interventions are offered.

Barotrauma: Tooth under Pressure.

With the growing number of air passengers, flight attendants, leisure pilots, as well as military and airline pilots, dentists may encounter physiological and pathological phenomena precipitated by high altitude. With the introduction of the self-contained breathing apparatus (SCUBA), many of these manifestations caused by changes in atmospheric pressure were reported in association with diving as well. Limited literature exists on this subject. Hence, this article aims to review literature concerning the classification, etiology and manifestations of barodontalgia, as well as important clinical considerations for its management.

Clinical signs of barotrauma in golden perch, Macquaria ambigua (Richardson), and associated effects on post-release mortality and health.

This study assessed the effects of different retrieval depths (2, 10 or 20 m), surface intervals (none or 15 min) and release methods (untreated, vented or recompressed) on the incidence of external and internal clinical signs of barotrauma (ECSB and ICSB) and post-release mortality in golden perch, Macquaria ambigua (Richardson). Fish were assessed for ECSB before and after surface intervals and either monitored for mortality over 3 days in two deep cages or killed for internal examination. When all fish were left untreated, short-term mortality increased with retrieval depth from 0% and 4.2% among 2 and 10-m fish, respectively, to 19.2% among 20-m fish; while surface interval only affected the incidence of two ECSB (excess buoyancy and a prolapsed cloaca). Mortality was also greater among 20-m fish that were subjected to a 15-min surface interval and left untreated (22.2%) or vented (22.2%) than those that were recompressed (5.6%). Of the ECSB, only exophthalmia was associated with increased mortality, with half of the affected fish dying. However, many fish retrieved from 10 and 20 m also sustained numerous ICSB, including compressed gonads or vital organs and ruptured or collapsed, haemorrhaging swimbladders that remained deflated for up to 3 days after release.

Facial baroparesis: a critical differential diagnosis for scuba diving accidents--case report.

Facial nerve baroparesis is a rare and potentially under-reported complication of scuba diving. A diver, after surfacing from a shallow dive, developed isolated left-sided facial palsy accompanied by pain and decreased hearing in the left ear. No other signs or symptoms attributable to a scuba diving accident were detected. Forty minutes later, he heard a "pop" in the affected ear, after which all symptoms quickly resolved. Repeat neurological and ear examinations were normal. He showed no residual or new symptoms 24 hours later. The differential diagnosis of facial neurological deficit after diving includes decompression sickness, cerebral air embolism due to pulmonary barotrauma, facial nerve barotrauma and common conditions such as stroke and Bell's palsy. It is important to recognize the condition since recompression treatment can further damage the facial nerve.

Initial review of the U.S. Navy's pressurized submarine escape training outcomes.

The U.S. Navy reinstituted pressurized submarine escape training (PSET) for submarine sailors in 2009 after a nearly 30-year absence. This training addresses escape from a disabled submarine at depth with the use of the Beaufort, Ltd. Mk 10 Submarine Escape and Immersion Equipment (SEIE) suit. Training is classified as "high-risk" due to previous U.S. and foreign navy experience with training-associated morbidity and mortality, particularly from diving-related illness. To reduce risk, medical screening procedures are performed. During the first 39 months of training, 7,025 students screened for PSET with 32% completing all phases, including two pressurized ascents. The most common reason for screening disqualification was presence of upper respiratory congestion. During training, middle ear barotrauma was responsible for 53% of attrition, primarily during the test of pressure.

[Aerosinusitis. Part 2: Diagnosis, therapy and recommencement of flight duties]. / Aerosinusitis. Teil 2: Diagnostik, Therapie und Wiederaufnahme der Flugtätigkeit.

Aerosinusitis more frequently affects the frontal sinus than the maxillary sinus and mostly occurs during descent. Sinonasal diseases and anatomic variations leading to obstruction of paranasal sinus ventilation favor the development of aerosinusitis. This Continuing Medical Education (CME) article is based on selective literature searches of the PubMed database (search terms: "aerosinusitis", "barosinusitis", "barotrauma" AND "sinus", "barotrauma" AND "sinusitis", "sinusitis" AND "flying" OR "aviator"). Additionally, currently available monographs and further articles that could be identified based on the publication reviews were also included. In part 2, diagnostic measures, drug therapy, balloon dilatation and endoscopic sinus surgery are presented, along with a discussion regarding when flight attendants and pilots are able to resume their work. Endoscopic surgery to expand the natural drainage pathways of the affected sinuses with minimal surgical trauma to the healthy mucous membranes is largely successful.