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.

Reducing Aortic Barotrauma and Vascular Extracellular Matrix Degradation by Pacemaker-Mediated QRS Widening.

Background The extent of pressure-related damage might be related to acceleration rate of the applied pressure (peak dP/dt) in the vascular system. In this study, we sought to determine whether dP/dt applied to the aortic wall (aortic dP/dt) and in turn vascular extracellular matrix degradation can be mitigated via modulation of left ventricular (LV) contractility (LV dP/dt) by pacemaker-mediated desynchronization. Methods and Results First, in 34 patients, changes in aortic dP/dt values in 3 aortic segments in response to pacemaker-mediated stepwise QRS widening leading to gradual desynchronization of the LV contraction by means of steadily changed atrioventricular delay (AVD) with temporary dual-chamber pacing was examined before and after beta-blocker (15 mg IV metoprolol) administration. Second, serum matrix metalloproteinase-9 levels were measured in the 20 patients with permanent pacemaker while they were on sinus rhythm with normal QRS width and 3 weeks after wide QRS rhythm ensured by dual pacing, dual sensing, and dual response to sensing with short AVD. LV dP/dt substantially correlated with dP/dt measured in ascending (r=0.83), descending (r=0.89), and abdominal aorta (r=0.96). QRS width strongly correlated with dP/dt measured in ascending (r=-0.95), descending (r=-0.92), and abdominal (r=-0.96) aortic segments as well. In patients with permanent pacemaker, wide QRS rhythm led to a significant reduction in serum matrix metalloproteinase-9 levels (from 142.5±32.9 pg/mL to 87.5±32.4 pg/mL [P<0.001]) at the end of 3 weeks follow-up. Conclusions QRS prolongation by short AVD dual pacing, dual sensing, and dual response to sensing results in concomitant decreases in peak dP/dt values in the LV and in all aortic segments with or without background beta-blocker administration, which in turn led to a significant reduction in circulating matrix metalloproteinase-9 levels. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT03665558.

Pulmonary Barotrauma Following Nasal High-Flow Therapy in a Patient with Bronchiolitis Obliterans Syndrome.

BACKGROUND Pulmonary barotrauma is considered as complication of the use of positive-pressure ventilations. Nasal high-flow therapy is increasingly being used as an alternative to them. Nasal high-flow therapy rarely causes pulmonary barotrauma probably because airway pressures are lower when compared with invasive mechanical ventilation. Bronchiolitis obliterans syndrome after allogenic hematopoietic stem cell transplantation is triggered by an alloimmune response in the bronchioles and causes obstruction of the bronchioles. However, the threshold of additional positive pressure has not been determined in a patient with bronchiolitis obliterans syndrome. CASE REPORT A 14-year-old female patient with acute myeloid leukemia at high risk of recurrence received an allogeneic hematopoietic stem cell transplantation from an unrelated bone marrow donor. After engraftment, she developed acute graft-versus-host disease, followed by chronic graft-versus-host disease. Ten months post-transplantation, she developed bronchiolitis obliterans syndrome. She continued to receive nasal supplemental oxygen therapy for persistent dyspnea due to bronchiolitis obliterans syndrome. At month +25, hypercapnia was noted. Therefore, we carefully initiated nasal high-flow therapy for dyspnea and adjusted the oxygen dose to maintain 90% SpO2 to avoid life-threatening apnea. The flow rate was as low as 14 to 20 L/min to avoid the risk of barotrauma and the deterioration of air trapping. Unfortunately, she died of respiratory failure at month +31 post-transplantation. A lung autopsy revealed pulmonary barotrauma. CONCLUSIONS Nasal high-flow therapy, even at low flow rates, may cause fatal pulmonary barotrauma in bronchiolitis obliterans syndrome.

Dynamic Rabbit Model of Ear Barotrauma.

BACKGROUND: Establishing animal models of ear barotrauma (EB) to provide evaluation criteria for Eustachian tube dysfunction.METHODS: Using expansive sponges, 70 rabbits' right pharyngeal openings of the auditory tubes were blocked to cause dysfunction in the right Eustachian tubes. The right tympanic cavities of 65 rabbits were the Model Group (Subgroups 1-13) and these rabbits' left tympanic cavities were the Nonblockage Group. Hypobaric chamber tests (HCTs) at various vertical speeds (100 m · s-1, 75 m · s-1, 50 m · s-1, and 15 m · s-1) and altitudes (13,123 ft and 6562 ft) were conducted. The remaining five rabbits' right tympanic cavities were the Control Group and no HCTs were conducted. After HCTs, observations were made on rabbits' behavioral changes, oto-endoscope and tympanometry results, and pathological changes of the tympanic mucosae.RESULTS: 1) Rabbits in Subgroups 1-12 demonstrated EB, while Subgroup 13 and the Control Group did not. 2) Histopathology showed EB caused by rapid ascent/descent at 100 m · s-1 was more severe than that of 75 m · s-1 and 50 m · s-1 (P < 0.01), and that there were no significant differences in EB caused by rapid ascent/descent at 75 m · s-1 and 50 m · s-1 (P > 0.05). There were no significant differences in pathological injuries at the altitudes of 6562 ft and 13,123 ft (P > 0.05). 3) Based on tympanic membrane structures, tympanometry, and histopathological results, rabbits' EB can be classified into mild, moderate, and severe.DISCUSSION: EB's dynamic models could be established through HCTs on rabbits with Eustachian tube dysfunction.Wang B, Xu X, Lin J, Jin Z. Dynamic rabbit model of ear barotrauma. Aerosp Med Hum Perform. 2019; 90(8):696-702.

Diving Headache.

This review will focus on the most recent information regarding the ICHD-3 definition of diving headache as well as other important causes of diving headache that are not listed in the ICHD-3 classification system. The paper will discuss etiology, diagnosis, and management of these disorders, focusing, when possible, on the newest research available. ICHD-3 diving headache is due to hypercapnia and is treated accordingly with oxygen. Other causes of diving headache range from decompression sickness to external compression headache to primary headache disorders, such as migraine. Correctly determining the underlying cause of the diving headache is critical to management and relies on history taking and physical exam. The pathophysiology of newly described types of diving headache, such as diving ascent headache, remains under investigation but may be related to other homeostatic headache causes, such as airplane headache. Further investigation may yield more information regarding management as well as possible insight into other headache disorders.

A Free Diver with Hemoptysis and Chest Pain.

[Full article available at http://rimed.org/rimedicaljournal-2019-02.asp].

Effects of Breath-Hold Deep Diving on the Pulmonary System.

This short review focuses on pulmonary injury in breath-hold (BH) divers. When practicing their extreme leisure sport, they are exposed to increased pressure on pulmonary gas volumes, hypoxia, and increased partial gas pressures. Increasing ambient pressures do present a serious problem to BH deep divers, because the semi-rigid thorax prevents the deformation required by the Boyle-Mariotte law. As a result, a negative-pressure barotrauma (lung squeeze) with acute hemoptysis is not uncommon. Respiratory maneuvers such as glossopharyngeal insufflation (GI) and glossopharyngeal exsufflation (GE) are practiced to prevent lung squeeze and to permit equalizing the paranasal sinuses and the middle ear. GI not only impairs venous return, thereby provoking hypotension and even fainting, but also produces intrathoracic pressures likely to induce pulmonary barotrauma that is speculated to induce long-term injury. GE, in turn, further increases the already negative intrapulmonary pressure, thereby favoring alveolar collapse (atelectasis). Finally, hypoxia seemingly not only induces brain injury but initiates the opening of intrapulmonary shunts. These pathways are large enough to permit transpulmonary passage of venous N2 bubbles, making stroke-like phenomena in deep BH divers possible.

Tympanometric evaluation of Eustachian tube function in Polish scuba divers.

BACKGROUND: Scuba divers are subjected to relatively high ambient pressures while descending. Equalizing maneuvers (e.g., Valsalva) are necessary to open the Eustachian tube (ET) and allow air into the middle ear (ME) cavity. Insufficient opening of the ET leads to ME barotrauma, which is the most common injury related to scuba diving. The study aims were to assess the incidence of ME barotrauma and to compare tympanometric parameters and stapedial reflexes in scuba divers and non-diving individuals. MATERIAL AND METHODS:: 60 scuba divers participated in the study; control consisted of 90 non-diving volunteers without a history of otolaryngologic problems. All participants were examined with the use of otoscopy and tympanometry with evaluation of ipsilateral stapedial reflexes. The group studied was surveyed regarding occurrence of ME barotrauma and diving competence. RESULTS: 51.7% of the divers experienced ME barotrauma, the most common symptoms being earache and hearing loss. Comparison of the group studied and control revealed significantly lower ME pressure and compliance in scuba divers. In scuba divers with ME barotrauma, longer time from injury correlates directly with greater ME pressure and compliance, indicating tissue recovery. At 4,000Hz 100dB percentage of present stapedial reflexes among scuba divers was significantly lower than in controls; moreover, a greater number of dives correlated inversely with percentage of present stapedial reflexes at 4000Hz 100dB. The reduced thresholds at high intensities suggest a negative effect of scuba diving on hearing. CONCLUSIONS: ME pressure and compliance, however still within the norm, are significantly lower in scuba divers than in non-diving healthy volunteers. This may be attributed to a subclinical form of barotrauma.

Sphenoid sinus barotrauma in diving: case series and review of the literature.

About 50% of scuba divers have suffered from barotrauma of the ears and about one-third from barotrauma of paranasal sinuses. The sphenoid sinuses are rarely involved. Vital structures, as internal carotid artery and optic nerve, adjoin the sphenoid sinus. Thus, barotrauma could lead to serious neurologic disorders, including blindness. After searching the literature (Medline) and other sources (Internet), we present some cases of sphenoid sinus barotrauma, because these injuries may be underreported and misdiagnosed due to the lack of awareness and knowledge. Therefore, information is provided, e.g. on anatomical and pathophysiological features. Divers and physicians should have in mind that occasional headache during or after diving sometimes signals serious neurological disorders like vision loss. We show that injuries can develop from both negative and positive pressures in the sinuses. Because visual recovery depends on prompt diagnosis and proper therapy, physicians like otolaryngologists, ophthalmologists and neurologists need to closely collaborate.

Scuba diving death: Always due to drowning? Two forensic cases and a review of the literature.

Scuba diving is an increasingly common recreational activity. We describe the physiopathology of barotrauma in two cases where death was caused by pulmonary barotrauma while diving. An inspection and autopsy were carried out in both cases. The autopsy data were supported by post-mortem radiological investigation. Histological and toxicological analyses were also carried out, and dive computer and tank manometer analysis performed. In both cases, the cause of death was attributable to arterial gas embolism, resulting from pulmonary barotrauma subsequent to pulmonary over-distension. The dive computer analysis and the tank manometer allowed us to understand what happened underwater. In our opinion, a multidisciplinary approach is crucial in order to clarify the cause of death. Some pathological conditions and risk factors should be considered before diving.

Influence of repetitive diving in saltwater on pressure equalization and Eustachian tube function in recreational scuba divers.

INTRODUCTION: We investigated in a prospective, observational trial the feasibility of using the Eustachian tube function test (ETFT) to measure the effect of repetitive pressure exposure during open seawater dives on Eustachian tube function. METHODS: The study included 28 adult divers during six consecutive days of diving in the Red Sea. Participants underwent otoscopy and ETFT before the first dive, between each dive and after the last dive. ETFT included regular tympanometry (R-tymp), tympanometry after Valsalva (V-tymp) and after swallowing (S-tymp). The R-tymp was obtained as 'baseline' peak pressure. After a Valsalva, the peak pressure should shift (positively), revealing a positive shift of the tympanic membrane. This pressure shift is defined here as R-VdP. The changes in compliance and peak pressure were recorded and correlated with otoscopic findings and diving experience. Middle ear barotrauma was scored using the Edmonds modified TEED scale. RESULTS: The 28 participants performed 437 dives. Positive shift of pressure in the middle ear was evident with significant changes from day one to day three (P < 0.0001). Divers with barotrauma showed significantly lower values of R-tymp peak pressure and significantly higher negative R-VdP, compared to divers with normal otoscopic findings (P < 0.05). Diving experience significantly correlated with R-tymp peak pressure and prevalence of middle ear barotrauma. CONCLUSION: Significant changes in middle ear pressure and pressure equalization from repeated pressure exposure in saltwater were seen using ETFT. Repetitive, multi-day diving led to significantly decreased compliance and increased R-tymp peak pressure (overpressure) in the middle ear. Most profound changes were observed in less and intermediate experienced divers.

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.

Rescue therapeutic strategy combining ultra-protective mechanical ventilation with extracorporeal CO2 removal membrane in near-fatal asthma with severe pulmonary barotraumas: A case report.

RATIONALE: Mechanical ventilation of severe acute asthma is still considered a challenging issue, mainly because of the gas trapping phenomenon with the potential for life-threatening barotraumatic pulmonary complications. PATIENT CONCERNS: Herein, we describe 2 consecutive cases of near-fatal asthma for whom the recommended protective mechanical ventilation approach using low tidal volume of 6 mL/kg and small levels of PEEP was rapidly compromised by giant pneumomediastinum with extensive subcutaneousemphysema. DIAGNOSES: Near fatal asthma. INTERVENTION: A rescue therapeutic strategy combining extracorporeal CO2 removal membrane with ultra-protective extremely low tidal volume (3 mL/kg) ventilation was applied. OUTCOMES: Both patients survived hospital discharge. LESSONS: These 2 cases indicate that ECCO2R associated with ultra-protective ventilation could be an alternative to surgery in case of life-threatening barotrauma occurring under mechanical ventilation.

The future of mechanical ventilation: lessons from the present and the past.

The adverse effects of mechanical ventilation in acute respiratory distress syndrome (ARDS) arise from two main causes: unphysiological increases of transpulmonary pressure and unphysiological increases/decreases of pleural pressure during positive or negative pressure ventilation. The transpulmonary pressure-related side effects primarily account for ventilator-induced lung injury (VILI) while the pleural pressure-related side effects primarily account for hemodynamic alterations. The changes of transpulmonary pressure and pleural pressure resulting from a given applied driving pressure depend on the relative elastances of the lung and chest wall. The term 'volutrauma' should refer to excessive strain, while 'barotrauma' should refer to excessive stress. Strains exceeding 1.5, corresponding to a stress above ~20 cmH2O in humans, are severely damaging in experimental animals. Apart from high tidal volumes and high transpulmonary pressures, the respiratory rate and inspiratory flow may also play roles in the genesis of VILI. We do not know which fraction of mortality is attributable to VILI with ventilation comparable to that reported in recent clinical practice surveys (tidal volume ~7.5 ml/kg, positive end-expiratory pressure (PEEP) ~8 cmH2O, rate ~20 bpm, associated mortality ~35%). Therefore, a more complete and individually personalized understanding of ARDS lung mechanics and its interaction with the ventilator is needed to improve future care. Knowledge of functional lung size would allow the quantitative estimation of strain. The determination of lung inhomogeneity/stress raisers would help assess local stresses; the measurement of lung recruitability would guide PEEP selection to optimize lung size and homogeneity. Finding a safety threshold for mechanical power, normalized to functional lung volume and tissue heterogeneity, may help precisely define the safety limits of ventilating the individual in question. When a mechanical ventilation set cannot be found to avoid an excessive risk of VILI, alternative methods (such as the artificial lung) should be considered.

Onset of barotrauma injuries related to number of pile driving strike exposures in hybrid striped bass.

Previous studies exploring injury response to pile driving in fishes presented exposure paradigms (>900 strikes) that emulated circumstances where fish would not leave an area being ensonified. Those studies did not, however, address the question of how many strikes are needed before injuries appear. Thus, the number of strikes paired with a constant single strike sound exposure level (SELss) that can cause injuries is not yet clear. In order to examine this question, hybrid striped bass (white bass Morone chrysops × striped bass Morone saxatilis) were exposed to 8-384 strikes in three different SELss treatments that generated different cumulative sound exposure level values. The treatment with the highest SELss values caused swim bladder injuries in fish exposed to as few as eight pile strikes. These results have important implications for pile driving operations where SELss values meet or exceed the exposure levels used in this study.

Eustachian tube evaluation in aviators.

The aim of the study is to evaluate the Eustachian tube functionality in a group of aviators to underline a subclinical dysfunction and the related risk of ear fullness or barotitis. Hypobaric chamber allows to simulate the pressure variation of the flight. This prospective study enrolled 42 aviation pilots, members of the Italian Air Force, to whom were evaluated Eustachian tube functionality by Tubomanometry, patients subjective assessments concerning feasibility of Valsalva's and Toynbee's clinical symptoms, tympanometry, and objective Valsalva before and after exposure to hypobaric chamber. The new Eustachian tube score (ETS-7) was also calculated for each pilot before and after exposure to hypobaric chamber. Results of our examination showed that: before chamber exposition, in 92.8 % of pilots, an ETS-7 of eight or more was found bilaterally. In three (7.2 %) cases, a unilateral ETS-7 ≤ 7 was found and two of those had a positive history. After undergoing the hypobaric chamber session, the evaluation of ETS-7 showed only 19 % of pilots with an ETD score ≤7, in particular three bilateral and five unilateral cases. Three of those pilots were clinically positive: two airmen reported persistent fullness, while the other one had a barotitis. Therefore, the combined use of TMM and ETS-7 before and after hypobaric chamber exposure appears to be a reliable method for assessing the functional capacity of the Eustachian tube in aviators, the stressful effect of flight on it, to exclude subjects at increased risk of ear pain, fullness, or barotrauma.

The impact of a pulmonary recruitment maneuver to reduce post-laparoscopic shoulder pain: A randomized controlled trial.

OBJECTIVE: A pulmonary recruitment maneuver (PRM) can effectively reduce post-laparoscopic shoulder pain (PLSP). However, a high-pressure PRM may cause pulmonary barotrauma. This study aimed to evaluate the efficacy and safety of a PRM using two different maximum inspiratory pressures (40 and 60cmH2O) for reducing PLSP. STUDY DESIGN: Patients undergoing gynecologic laparoscopy were randomly allocated to a control group (n=30), a 40 cmH2O PRM group (n=30), and a 60 cmH2O PRM group (n=30). In the control group, residual carbon dioxide was removed by passive exsufflation through the port site. In the two intervention groups, the PRM consisting of five manual pulmonary inflations was performed at the end of surgery with a maximum pressure of 40 cmH2O or 60 cmH2O, respectively. Shoulder pain and wound pain were recorded using a visual analogue scale at 24 and 48h postoperatively. RESULTS: Wound pain scores at 24 and 48h post-surgery were not different between the three groups. The PLSP scores in the two intervention groups were significantly lower than that seen in the control group at 24 and 48h postoperatively (P=0.006 and P<0.001, respectively). However, there were no statistically significant differences in the PLSP scores between the two intervention groups. CONCLUSION: A low-pressure PRM (40cmH2O) is as effective as a high-pressure PRM (60cmH2O) for removing residual gas from the peritoneal cavity. PRM using a maximal inspiratory pressure of 40cmH2O is safe and efficacious for the reduction of PLSP.

Airway pressure release ventilation during ex vivo lung perfusion attenuates injury.

OBJECTIVE: Critical organ shortages have resulted in ex vivo lung perfusion gaining clinical acceptance for lung evaluation and rehabilitation to expand the use of donation after circulatory death organs for lung transplantation. We hypothesized that an innovative use of airway pressure release ventilation during ex vivo lung perfusion improves lung function after transplantation. METHODS: Two groups (n = 4 animals/group) of porcine donation after circulatory death donor lungs were procured after hypoxic cardiac arrest and a 2-hour period of warm ischemia, followed by a 4-hour period of ex vivo lung perfusion rehabilitation with standard conventional volume-based ventilation or pressure-based airway pressure release ventilation. Left lungs were subsequently transplanted into recipient animals and reperfused for 4 hours. Blood gases for partial pressure of oxygen/inspired oxygen fraction ratios, airway pressures for calculation of compliance, and percent wet weight gain during ex vivo lung perfusion and reperfusion were measured. RESULTS: Airway pressure release ventilation during ex vivo lung perfusion significantly improved left lung oxygenation at 2 hours (561.5 ± 83.9 mm Hg vs 341.1 ± 136.1 mm Hg) and 4 hours (569.1 ± 18.3 mm Hg vs 463.5 ± 78.4 mm Hg). Likewise, compliance was significantly higher at 2 hours (26.0 ± 5.2 mL/cm H2O vs 15.0 ± 4.6 mL/cm H2O) and 4 hours (30.6 ± 1.3 mL/cm H2O vs 17.7 ± 5.9 mL/cm H2O) after transplantation. Finally, airway pressure release ventilation significantly reduced lung edema development on ex vivo lung perfusion on the basis of percentage of weight gain (36.9% ± 14.6% vs 73.9% ± 4.9%). There was no difference in additional edema accumulation 4 hours after reperfusion. CONCLUSIONS: Pressure-directed airway pressure release ventilation strategy during ex vivo lung perfusion improves the rehabilitation of severely injured donation after circulatory death lungs. After transplant, these lungs demonstrate superior lung-specific oxygenation and dynamic compliance compared with lungs ventilated with standard conventional ventilation. This strategy, if implemented into clinical ex vivo lung perfusion protocols, could advance the field of donation after circulatory death lung rehabilitation to expand the lung donor pool.