Arterial Gas Embolism in Breath-Hold Diver.

An arterial gas embolism (AGE) is a potentially fatal complication of scuba diving that is related to insufficient exhalation during ascent. During breath-hold diving, an arterial gas embolism is unlikely because the volume of gas in the lungs generally cannot exceed the volume at the beginning of the dive. However, if a diver breathes from a gas source at any time during the dive, they are at risk for an AGE or other pulmonary overinflation syndromes (POIS). In this case report, a breath-hold diver suffered a suspected AGE due to rapidly ascending without exhalation following breathing from an air pocket at approximately 40 feet.

Buoyant ascent rate profiles for the MK10 and MK11 submarine escape and immersion equipment.

Introduction: Since the U.S. Navy transitioned from the MK10 to the MK11 submarine escape and immersion equipment (SEIE), there has been an increase in the incident rate of pulmonary barotrauma during submarine escape training. This study compares the ascent rate profiles of the MK10 and MK11 SEIE to determine if ascent rate differences between the escape suits are associated with increased pulmonary barotraumas. Methods: Buoyant ascent rates of the MK10 and MK11 SEIE were compared using weighted manikins equivalent to the 1st, 50th, and 99th percentile body weight of a submariner. Human ascents using the MK11 (n=126) were compared to human ascents in the same trainer wearing the MK10 (n=124). Results: Manikin mean ascent times were faster for the MK10 than the MK11 (5.19 seconds vs 5.28 seconds, p ≺ 0.05). Terminal velocity (Vt) was affected by manikin weight (p ≺ 0.001). Human trials confirmed the manikin results. The average mean ascent velocity for the MK10 group was 0.155 meters/ second faster than the MK11 group's mean ascent velocity (p ≺ 0.001). Mean ascent velocity was inversely correlated with all anthropometrics for the MK10 group (p ≺ 0.01). Neither height nor body mass index showed a significant association with mean ascent velocity for the MK11 group. Conclusions: The Vt of buoyant ascents is significantly affected by body weight. As the mean ascent rate of the MK11 is slower than that of the MK10, ascent rate profile differences between the suits do not appear to explain the recent increase in pulmonary barotrauma incident rates during escape training.

Pulmonary barotrauma in SCUBA diving-related fatalities: a histological and histomorphometric analysis.

Arterial gas embolism following pulmonary barotrauma occurs in 13-24% of cases of diving deaths. The study aimed to evaluate the usefulness of a histomorphometric digital analysis in the detection of air space over-distension due to pulmonary barotrauma. The study was performed on lung parenchyma specimens of 12 divers: six had died due to arterial gas embolism following pulmonary barotrauma (mean age at death of 54 years, range of 41-61 years), and six had drowned in saltwater without a diagnosis of pulmonary barotrauma (mean age at death of 54 years, range of 41-66 years) (positive controls). For negative controls, six cases of non-SCUBA divers (mean age of death of 42 years, range of 23-55 years) who died of intracerebral haemorrhage were evaluated. No significant differences were observed in the characteristics of the air spaces between control groups (positive and negative). However, differences were observed in the area occupied by air spaces and the percentage of air space area when we compared the case group to the controls (p < 0.01); and there was a slight difference in the maximum and minimum diameters of air space (p < 0.05). The mean area occupied by air spaces and the mean percentage of air space were the most useful for discriminating pulmonary barotrauma from other causes of death (100% sensitivity and 91.7% specificity). Based on our study, inclusion of an increased pattern of air spaces as a possible diagnostic criterion for pulmonary barotrauma would be useful in discerning the cause of diving death.

Hepatic venous gas secondary to pulmonary barotrauma: rat model study.

Intrahepatic gas (IHG) is commonly observed during early postmortem examinations of humans with upper or lower airway obstructions. We conducted a study to test the hypothesis that intrapulmonary gas could retrogradely spread to the hepatic vein following pulmonary barotrauma (PB). To establish a rat model of pulmonary barotrauma, we utilized a controllable pressure-vacuum pump to apply airway pressure (40, 60, or 80 mmHg). The rats were dissected directly at the end of the experiment, and histological analysis was performed through microscopic examination of the rats. Additionally, the rats were ventilated with meglumine diatrizoate under pressures of 160 and 250 mmHg to observe the signal dynamic diffusion using X-ray fluoroscopy examination. Rats exhibited classical changes associated with PB, such as alveolar rupture, pulmonary interstitial emphysema, and hemorrhage, as well as IHG characterized by the presence of gas in the hepatic vein and hepatic sinusoids. Air emboli were not observed in the liver in any of the 40 mmHg groups. However, they were observed in the liver in the 60 and 80 mmHg groups, the amount and size of air emboli in the 80 mmHg group were greater than those in the 60 mmHg group (p < 0.05). The 80 mmHg group presented radial grape-like bubbles in the centrilobular portion of the liver accompanied by congestion in the peripheral region of the hepatic lobule. X-ray fluoroscopy examination revealed a gradual enhancement of dynamic contrast medium signals from the lung to the inferior vena cava and then to the liver. Our findings indicate that pulmonary barotrauma can lead to the retrograde spread of intrapulmonary gas to the hepatic vein. When it is clear that no decomposition of the body has occurred, the presence of IHG serves as a novel indicator for the diagnosis of obstructive pulmonary disease or obstruction in the upper or lower airway.

Pulmonary Barotrauma in COVID-19 Patients With ARDS on Invasive and Non-Invasive Positive Pressure Ventilation.

BACKGROUND: We experienced a high incidence of pulmonary barotrauma among patients with coronavirus disease-2019 (COVID-19) associated acute respiratory distress syndrome (ARDS) at our institution. In current study, we sought to evaluate the incidence, clinical outcomes, and characteristics of barotrauma among COVID-19 patients receiving invasive and non-invasive positive pressure ventilation. METHODOLOGY: This retrospective cohort study included adult patients diagnosed with COVID-19 pneumonia and requiring oxygen support or positive airway pressure for ARDS who presented to our tertiary-care center from March through November, 2020. RESULTS: A total of 353 patients met our inclusion criteria, of which 232 patients who required heated high-flow nasal cannula, continuous or bilevel positive airway pressure were assigned to non-invasive group. The remaining 121 patients required invasive mechanical ventilation and were assigned to invasive group. Of the total 353 patients, 32 patients (65.6% males) with a mean age of 63 ± 11 years developed barotrauma in the form of subcutaneous emphysema, pneumothorax, or pneumomediastinum. The incidence of barotrauma was 4.74% (11/232) and 17.35% (21/121) in the non-invasive group and invasive group, respectively. The median length of hospital stay was 22 (15.7 -33.0) days with an overall mortality of 62.5% (n = 20). CONCLUSIONS: Patients with COVID-19 ARDS have a high incidence of barotrauma. Pulmonary barotrauma should be considered in patients with COVID-19 pneumonia who exhibit worsening of their respiratory disease as it is likely associated with a high mortality risk. Utilizing lung-protective ventilation strategies may reduce the risk of barotrauma.

[A case of pulmonary barotrauma complicated with cerebral arterial air embolism in a diver].

Pulmonary barotrauma is a kind of disease caused by the injury of lung tissue or blood vessel when the gas pressure of lung is too high or too lower than the external pressure of the body, which causes the air to enter the blood vessel and adjacent tissue. It could be happened in the escape of the divers with the light diving equipment or the sailors from submarine. Generally, the decompression chamber was used to treating the disease, and the minimum air pressure of 0.5 MPa recompression therapeutic schedule was used to selecting. In November 2019, a patient with pulmonary barotrauma combined with cerebral arterial gas embolism caused by improper underwater escape with light diving equipment was admitted to the General Hospital of Eastern War Zone. He was treated with 0.12 MPa oxygen inhalation recompression scheme in the oxygen chamber pressurized with air. 7 days later, the patient recovered and discharged.

Rare pulmonary barotrauma after explosive decompression: a case report.

BACKGROUND: Pneumothorax as a consequence of pulmonary barotrauma during explosive decompression military crew training in a hypobaric chamber is an extremely rare and sparsely diagnosed complication. Extensive bilateral tissue damage is even more unexpected. CASE PRESENTATION: A 26-year-old active duty Air Force pilot was performing an explosive decompression simulation from 8000 ft. (2438.4 m) to 25,000 ft. (7620 m) in a 1.5 s interval. The training was interrupted due to the pilot's apparent health complications. After transfer to the emergency department, a CT scan showed bilateral lung barotrauma with emphysema. CONCLUSIONS: The case report shows extensive emphysema and pneumothorax after a rapid decompression done for training purposes. It is a possible but rare complication. The cause remains unclear, with suspicion of a predisposed lung disease.

A case of a critically injured diver with multiorgan failure and severe pulmonary overinflation syndrome in a resource-limited setting.

A diver practicing controlled emergency ascent training on the island of Guam suffered bilateral pneumothorax, pneumomediastinum, coronary arterial gas embolism, and developed multiple organ dysfunction syndrome. Due to limitations of available resources he was medically managed in the intensive care unit until he could be transferred to University of California San Diego for definitive management. We provide an account of our management of the patient, the pathophysiology of injury as well as a review of the safety of recreational diving skills training, current standards of practice and potential pitfalls when considering proper management of a critically injured diver.

Pulmonary barotrauma during hookah diving: a case report.

When commercial sea harvesters have dive accidents, it is sometimes difficult to obtain an accurate dive history and make a definitive diagnosis. We report a sea harvest diver who dived to collect sea snails (Rapana venosa) by using a hookah dive system. He experienced mediastinal and subcutaneous emphysema due to interruption of breathing airflow. Thoracic computed tomography performed one year prior to the accident revealed paramediastinal subpleural blebs on both lung apices. Emphysema was resolved by administering normobaric oxygen.

Pulmonary barotrauma: assessment and investigation in divers.

Decompression illness (DCI) is an uncommon problem but can be significant in terms of morbidity and, very rarely, mortality. The mechanisms of DCI are pulmonary barotrauma and decompression sickness due to inert gas supersaturation. After the initial management phase, identification of predisposing factors is important to help advise divers regarding future risk and avoidance. Here we present four cases of DCI where pulmonary barotrauma was the likely causative mechanism. We highlight the important features in assessment for pulmonary barotrauma and advising divers on the risk of a recurrence.

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.

Neurological complications of underwater diving.

The diver's nervous system is extremely sensitive to high ambient pressure, which is the sum of atmospheric and hydrostatic pressure. Neurological complications associated with diving are a difficult diagnostic and therapeutic challenge. They occur in both commercial and recreational diving and are connected with increasing interest in the sport of diving. Hence it is very important to know the possible complications associated with this kind of sport. Complications of the nervous system may result from decompression sickness, pulmonary barotrauma associated with cerebral arterial air embolism (AGE), otic and sinus barotrauma, high pressure neurological syndrome (HPNS) and undesirable effect of gases used for breathing. The purpose of this review is to discuss the range of neurological symptoms that can occur during diving accidents and also the role of patent foramen ovale (PFO) and internal carotid artery (ICA) dissection in pathogenesis of stroke in divers.

Decompression illness: a comprehensive overview.

Decompression illness is a collective term for two maladies (decompression sickness [DCS] and arterial gas embolism [AGE]) that may arise during or after surfacing from compressed gas diving. Bubbles are the presumed primary vector of injury in both disorders, but the respective sources of bubbles are distinct. In DCS bubbles form primarily from inert gas that becomes dissolved in tissues over the course of a compressed gas dive. During and after ascent ('decompression'), if the pressure of this dissolved gas exceeds ambient pressure small bubbles may form in the extravascular space or in tissue blood vessels, thereafter passing into the venous circulation. In AGE, if compressed gas is trapped in the lungs during ascent, pulmonary barotrauma may introduce bubbles directly into the pulmonary veins and thence to the systemic arterial circulation. In both settings, bubbles may provoke ischaemic, inflammatory, and mechanical injury to tissues and their associated microcirculation. While AGE typically presents with stroke-like manifestations referrable to cerebral involvement, DCS can affect many organs including the brain, spinal cord, inner ear, musculoskeletal tissue, cardiopulmonary system and skin, and potential symptoms are protean in both nature and severity. This comprehensive overview addresses the pathophysiology, manifestations, prevention and treatment of both disorders.

Spontaneous Pneumomediastinum Induced by a Combination of Flu-A Infection and E-cigarettes: A Case Report.

Pneumomediastinum (PM) and subcutaneous emphysema are characterized by extra-alveolar air within the mediastinum and subcutaneous tissue. PM may occur spontaneously or due to trauma or an underlying airway disease. Spontaneous pneumomediastinum (SPM) may be caused by intractable vomiting, forceful coughing, child birthing, or performing a Valsalva maneuver. However, there are limited studies or case reports that present a combination of influenza A infection and electronic cigarette (e-cigarette)-induced SPM. This case report presents SPM in a previously healthy 20-year-old female with untreated influenza A infection and a history of e-cigarette use who presented to the emergency department with fever, cough, chest pain, dyspnea, and vomiting. Her physical examination was significant for neck tenderness, subcutaneous neck crepitus, and increased respiratory effort. Diagnostic evaluation included a chest X-ray and chest computed tomography that revealed PM with subcutaneous emphysema extending into the neck, as well as a negative Gastrografin study. She was treated conservatively and discharged after two days, with a follow-up scheduled at a pulmonary clinic. This case report highlights the need for a detailed substance use history, particularly e-cigarette use, when determining the etiology of SPM in a previously healthy patient. Management for SPM is conservative and should include addressing underlying etiologies with special attention to cessation and education of e-cigarettes and illicit substances.

Pneumomediastinum in COVID-19: Risk factors and outcomes from a multicentre case-control study.

BACKGROUND: An increased incidence of pneumomediastinum has been observed among patients hospitalized with coronavirus disease 2019 (COVID-19) pneumonia. The study aimed to identify risk factors for COVID-19-associated pneumomediastinum and investigate the impact of pneumomediastinum on clinical outcomes. METHODS: In this multicentre retrospective case-control study, we included consecutive patients with COVID-19 pneumonia and pneumomediastinum hospitalized from March 2020 to July 2020 at ten centres; then, we identified a similarly sized control group of consecutive patients hospitalized with COVID-19 pneumonia and respiratory failure who did not develop pneumomediastinum during the same period. Clinical, laboratory, and radiological characteristics, as well as respiratory support and outcomes, were collected and compared between the two groups. Risk factors of pneumomediastinum were assessed by multivariable logistic analysis. RESULTS: Overall 139 patients with pneumomediastinum and 153 without pneumomediastinum were analysed. Lung involvement ≥75 %, consolidations, body mass index (BMI) < 22 kg/m2, C-reactive protein (CRP) > 150 mg/L, D-dimer >3000 ng/mL FEUs, and smoking exposure >20 pack-year were all independently correlated with the occurrence of pneumomediastinum. Patients with pneumomediastinum had a longer hospital stay (mean ± SD 31.2 ± 20.2 days vs 19.6 ± 14.2, p < 0.001), higher intubation rate (73/139, 52.5 % vs 27/153, 17.6 %, p < 0.001), and in-hospital mortality (68/139, 48.9 % vs 36/153, 23.5 %, p < 0.001) compared to controls. CONCLUSIONS: Extensive lung parenchyma involvement, consolidations, low BMI, high inflammatory markers, and tobacco exposure are associated with a greater risk of pneumomediastinum in COVID-19 pneumonia. This complication significantly worsens the outcomes.

An unusual, life-threatening complication of EBUS-TBNA: Pneumoperitoneum.

Endobronchial ultrasound-guided with transbronchial needle aspiration (EBUS-TBNA) is a safe procedure. We present an unusual life-threatening complication after EBUS-TBNA in a 43-year-old female. She underwent EBUS-TBNA for enlarged lymph nodes evaluation. After EBUS-TBNA, a progressively worsening abdominal distension was observed. In computed tomography, subcutaneous emphysema, bilateral pneumothorax, pneumomediastinum and pneumoperitoneum were detected. This complication was successfully treated with chest tube insertion and bedside abdominal decompression. Even though EBUS-TBNA is considered to bear a low risk, the possibility of complication occurrence must be taken into account and clinicians must be more cautious about pulmonary barotrauma, especially when EBUS-TBNA is performed.

Incidence and outcomes following pulmonary barotrauma in COVID-19 ventilated and non-ventilated patients with acute respiratory failure: A retrospective study.

Background and Objectives: : Alveolar rupture following increased transalveolar pressure on positive pressure ventilation is associated with pulmonary barotrauma (PB). The spectrum varies from pneumothorax, pneumomediastinum, pneumopericardium, pneumoperitoneum, retro-pneumoperitoneum and subcutaneous emphysema. We studied the incidence of PB and their clinical characteristics in patients with coronavirus disease 19 (COVID-19)-associated acute respiratory failure. Methods: Patients aged >18 years with COVID-19-associated acute respiratory distress syndrome were included in the study. We recorded demographics (age, gender, comorbidities), severity scores (APACHE II on admission, SOFA on the day of barotrauma), type of PB and outcomes at discharge from the hospital. Patient characteristics are descriptively reported. Survival analysis was done using Kaplan-Meier survival tests after classifying by various factors. Survival was compared using the log-rank test. Results: Thirty-five patients experienced PB. Eighty per cent of patients in this cohort were males with mean age of 55.89 years. The commonest comorbidities were diabetes mellitus and hypertension. Twelve spontaneously breathing patients developed barotrauma. Eight patients experienced sequential events. In all, 18 patients required insertion of pigtail catheters. The median survival time in patients was 37 days (95% CI: 25-49 days). The overall survival rate was 34.3%. Mean serum ferritin levels were six times upper limit of normal in deceased, reflecting the severity of lung involvement. Conclusion: A high incidence of PB was noted following severe acute respiratory syndrome coronavirus (SARS CoV-2) infection even in the non-ventilated patients, a consequence of SARS CoV-2 effects on the pulmonary parenchyma causing widespread lung injury.

Cerebral arterial gas embolism (CAGE) during open water scuba certification training whilst practising a controlled emergency swimming ascent.

We report the case of a 23-year-old male novice diver who sustained cerebral arterial gas embolism (CAGE) during his open water certification training whilst practising a free ascent as part of the course. He developed immediate but transient neurological symptoms that had resolved on arrival to hospital. Radiological imaging of his chest showed small bilateral pneumothoraces, pneumopericardium and pneumomediastinum. In view of this he was treated with high flow normobaric oxygen rather than recompression, because of the risk of development of tension pneumothorax upon chamber decompression. There was no relapse of his neurological symptoms with this regimen. The utility and safety of free ascent training for recreational divers is discussed, as is whether a pneumothorax should be vented prior to recompression, as well as return to diving following pulmonary barotrauma.

Pulmonary Barotrauma After Diving Without Breathing Equipment.

A case of a 19-year-old male with mediastinal and subcutaneous emphysema consistent with pulmonary barotrauma after diving is reported. He presented with facial swelling, voice change, chest pain, and shortness of breath after multiple dives between 8 and 12 feet deep without underwater breathing equipment in a river. Relevant radiology, including radiographs and computed tomography (CT imaging), and a discussion of pulmonary barotrauma are presented.