Spontaneous pneumomediastinum and Macklin effect: Overview and appearance on computed tomography

[Pneumomediastinum as a rare complication in connective tissue disease]

Otherwise known as mediastinal emphysema, pneumomediastinum (PNM) in connective tissue diseases is a rare clinical entity. Few cases have been described in the literature. In fact, it only exceptionally complicates the evolution of connective tissue diseases. In this paper report, two cases of spontaneous PNM secondary to scleroderma and Sjogren's syndrome. Based on the data in the literature, we discuss the etiology, frequency of occurrence, and the pathophysiological mechanisms of this unusual complication.

Spontaneous Pneumomediastinum and Subcutaneous Emphysema: A Rare Complication Associated With Cocaine Consumption

Spontaneous pneumomediastinum (SPM) is a rare clinical entity typically associated with underlying pulmonary disease or trauma. However, it has also been linked to illicit drug use, with cocaine being one of the most common. We present the case of a previously healthy 23-year-old patient who arrived at the emergency department with retrosternal pain, odynophagia, dyspnea, and crepitus in the neck and chest after inhaling cocaine for three consecutive days. The patient was hemodynamically stable, with extensive subcutaneous emphysema in the neck and chest. Computed tomography of the neck and chest revealed abundant air dissecting the superficial and deep planes of the neck and mediastinum, particularly in its upper and middle portions. Additional studies included nasolaryngoscopy, which showed white material suggestive of inhaled substance use. An upper gastrointestinal endoscopy was performed to rule out perforation, which did not identify any lesions. Blood tests showed no abnormalities. Conservative management with analgesia and monitoring was initiated, resulting in the improvement of subcutaneous emphysema and pain. The patient was discharged after a two-day hospital stay. There were no complications or further visits to the institution within the following six months. This case highlights the importance of investigating a history of illicit drug use, particularly cocaine, in cases of spontaneous pneumomediastinum. Our findings support the generally benign course of this condition and the effectiveness of conservative management in the absence of complications.

Comparison of high-flow nasal cannula and conventional nasal cannula during deep sedation for endoscopic submucosal dissection: a randomized controlled trial

PURPOSE

Adequate oxygenation and airway management during deep sedation can be challenging. We investigated the effect of high-flow nasal cannula (group HF) and conventional nasal cannula (group CO) during sedation for endoscopic submucosal dissection (ESD).

METHODS

Patients undergoing ESD with deep sedation were enrolled. The primary outcome was difference in lowest oxygen saturation (SpO2) between the groups. Incidence of hypoxia (SpO2 < 90%), patients with SpO2 < 95%, hypercapnia, and airway interventions; operator satisfaction; and adverse events were recorded.

RESULTS

Thirty-two patients in each group completed the study. The mean of minimum SpO2 values was significantly higher in group HF than in group CO (96.8% ± 4.2% vs. 93.3% ± 5.3%, p = 0.005). The incidence of hypoxia was comparable between the groups (4 [12.5%] vs. 6 [18.8%], p = 0.491); however, patients with SpO2 < 95% were significantly less in group HF (5 [15.6%] vs. 18 [56.3%], p = 0.003). Incidence of hypercapnia was higher in group HF than in group CO (14 [46.7%] vs. 5 [16.7%], p = 0.013). Airway rescue interventions were significantly less common in group HF. Satisfaction of operators and post-procedural complications were comparable between the two groups. In multivariable analysis, group CO and higher body mass index were risk factors for airway managements (odds ratio [95% confidence interval]: 6.204 [1.784-21.575], p = 0.004; 1.337 [1.043-1.715], p = 0.022, respectively).

CONCLUSIONS

Compared to conventional nasal cannula, high-flow nasal cannula maintained higher minimum SpO2 value during deep sedation with propofol-remifentanil for ESD.

TRIAL REGISTRATION

Clinical Trial Registry of the Republic of Korea (KCT0006618, https://cris.nih.go.kr ; registered September 29, 2021; principal investigator: Ji Won Choi).

The Macklin Effect: An Underestimated Cause of Pneumomediastinum

The Macklin effect is a rare but potentially serious complication of pneumomediastinum, caused by the dissemination of air from the lungs into the subcutaneous tissue and mediastinum after severe chest trauma or invasive manipulation. Early recognition is crucial for proper management of the patient. A 33-year-old male skidded while riding a motorcycle, lost control of the vehicle, and crashed into a utility pole with a thoracic contusion. He was admitted to the hospital; a computed tomography (CT) of the chest and abdomen was requested, which ruled out the presence of fractures and showed air in the mediastinum and subcutaneous cellular tissue, with features suggestive of the Macklin phenomenon. After 72 hours of inpatient monitoring, the patient was discharged to the general surgery outpatient clinic. The Macklin phenomenon occurs as a result of airway rupture due to negative pressure caused by trauma or invasive mechanical ventilation. Risk factors include a higher prevalence in young males, a slender stature and above-average height, and an age range of 12 to 35 years. Early detection of the Macklin phenomenon is crucial to recognize and prevent further complications. This case demonstrated the importance of considering the Macklin effect as a cause of pneumomediastinum in patients with severe chest trauma. Diagnostic imaging plays a key role in confirming the diagnosis and planning treatment.

A Case of Pneumomediastinum and Pneumorrhachis in a Patient With Multiple Risk Factors

Pneumomediastinum is the presence of gas (usually air) in the mediastinum, which is rare and typically benign. Pneumomediastinum is classified into primary and secondary based on etiology. Its pathophysiology is due to high intra-alveolar pressures causing alveolar rupture, which releases air that travels along bronchoalveolar sheaths into the mediastinum. Pneumomediastinum may also be concurrently seen with pneumorrhachis defined as air in the spinal canal, although this finding is rare. Here, we present the case of a 27-year-old male with a past medical history of polysubstance use and a one-week history of nausea, vomiting, and chest pain who presented with frostbite and was found to have pneumomediastinum and pneumorrhachis.

Laryngotracheal trauma-induced Macklin effect: A case report

Laryngotracheal trauma is a relatively rare traumatic injury seen particularly in young male adults. Trauma due to strangulation is one of its most frequent circumstances. However rare, pneumomediastinum is a particular complication of severe blunt neck injuries leading to alveolar ruptures. This phenomenon, described as the Macklin effect, requires early diagnosis, and its management varies from conservative to surgical treatment depending on the severity of symptoms. Our aim is to describe the case of a 21-year-old male who presented with blunt neck trauma. Clinical and imaging findings revealed subcutaneous neck emphysema and pneumomediastinum. Treatment was conservative leading to complete resolution of the injuries and the patient was discharged after 2 weeks.

Complications during Veno-Venous Extracorporeal Membrane Oxygenation in COVID-19 and Non-COVID-19 Patients with Acute Respiratory Distress Syndrome

Background: Acute respiratory distress syndrome (ARDS) presents a significant challenge in critical care settings, characterized by compromised gas exchange, necessitating in the most severe cases interventions such as veno-venous extracorporeal membrane oxygenation (vv-ECMO) when conventional therapies fail. Critically ill ARDS patients on vv-ECMO may experience several complications. Limited data exist comparing complication rates between COVID-19 and non-COVID-19 ARDS patients undergoing vv-ECMO. This retrospective observational study aimed to assess and compare complications in these patient cohorts. Methods: We retrospectively analyzed the medical records of all patients receiving vv-ECMO for ARDS between March 2020 and March 2022. We recorded the baseline characteristics, the disease course and complication (barotrauma, bleeding, thrombosis) before and after ECMO cannulation, and clinical outcomes (mechanical ventilation and ECMO duration, intensive care unit, and hospital lengths of stay and mortalities). Data were compared between COVID-19 and non-COVID-19 patients. In addition, we compared survived and deceased patients. Results: Sixty-four patients were included. COVID-19 patients (n = 25) showed higher rates of pneumothorax (28% vs. 8%, p = 0.039) with subcutaneous emphysema (24% vs. 5%, p = 0.048) and longer non-invasive ventilation duration before vv-ECMO cannulation (2 [1; 4] vs. 0 [0; 1] days, p = <0.001), compared to non-COVID-19 patients (n = 39). However, complication rates and clinical outcomes post-vv-ECMO were similar between groups. Survival analysis revealed no significant differences in pre-vv-ECMO complications, but non-surviving patients had a trend toward higher complication rates and more pleural effusions post-vv-ECMO. Conclusions: COVID-19 patients on vv-ECMO exhibit higher pneumothorax rates with subcutaneous emphysema pre-cannulation; post-cannulation complications are comparable to non-COVID-19 patients.

Air leak syndrome in animals: definition and pathogenesis

Air leak syndrome (ALS) is described in human medicine as a constellation of clinical disorders including pneumomediastinum, pneumopericardium, pulmonary interstitial emphysema, pneumothorax, pneumoperitoneum, pneumoretroperitoneum and subcutaneous emphysema. The pathogenesis of ALS depends on the anatomy of the mediastinum and its associations with thoracic, abdominal and cervical connective tissues, as well as a physical phenomenon referred to as the Macklin effect. Various animal species develop diverse combinations of these lesions, although ALS has not been recognized in animals. However, this term aids pathologists in addressing this disease compilation. The aim of this retrospective study is to illustrate examples of ALS in animals by arbitrarily selecting 13 cases in dogs, cats, pinnipeds, sea otters and harbour porpoises. ALS can be classified into three groups based on aetiology: iatrogenic, secondary or spontaneous. Iatrogenic ALS was diagnosed in two cats with tracheal laceration following endotracheal intubation. Secondary ALS was identified in two dogs, one with acute respiratory distress syndrome and the other due to grass awn migration. Secondary ALS in pinnipeds was diagnosed following severe pulmonary parasitism, uraemic pneumonia and oesophageal perforation. The other marine mammals developed ALS following trauma. Spontaneous ALS was also diagnosed in one cat and one dog without any apparent predisposing causes.

Macklin Effect: From Pathophysiology to Clinical Implication

Air leak syndromes (such as pneumomediastinum, pneumothorax, or subcutaneous emphysema) are frequent complications of acute respiratory distress syndrome (ARDS). Unfortunately, the development of air leaks is associated with worse outcomes. In addition, it has been hypothesized that the development of pneumomediastinum could be a marker of disease severity in patients with respiratory failure receiving noninvasive respiratory support or assisted ventilation. The so-called Macklin effect (or pulmonary interstitial emphysema) is the air dissection of the lung bronchovascular tree from peripheral to central airways following injury to distal alveoli. Ultimately, the progression of the Macklin effect leads to the development of pneumomediastinum, subcutaneous emphysema, or pneumothorax. The Macklin effect is identifiable on a chest computed tomography (CT) scan. The Macklin effect could be an accurate predictor of barotrauma in patients with ARDS (sensitivity = 89.2% [95% CI: 74.6-96.9]; specificity = 95.6% [95% CI: 90.6-98.4]), and may be a marker of disease severity. Accordingly, the detection of the Macklin effect on a chest CT scan could be used to select which patients with ARDS might benefit from different treatment algorithms, including advanced respiratory monitoring, early intubation, or, potentially, the institution of early extracorporeal support with or without invasive ventilation. In this video, the authors summarize the pathophysiology and potential clinical significance and applications of the Macklin effect in patients with acute respiratory failure.

Bilateral Pneumothorax after a Transbronchial Lung Cryobiopsy for Interstitial Lung Disease

We herein report a case of bilateral pneumothorax after a unilateral transbronchial lung cryobiopsy (TBLC). A 73-year-old man with no history of cardiothoracic surgery underwent a TBLC for the reevaluation of interstitial lung disease. Five hours later, he developed bilateral pneumothorax, pneumomediastinum, and subcutaneous emphysema. He underwent bilateral chest drainage and was discharged 18 days later. The lung biopsy specimens obtained from the TBLC contained visceral pleura and bronchial cartilage, suggesting bronchial injury as the cause of the bilateral pneumothorax.

Mechanical Ventilation during Bronchiolitis: The Macklin Effect

This is a case of barotrauma imaging (Macklin effect) after invasive mechanical ventilation in a 14-week-old newborn with complicated bronchiolitis. Teaching point: Imaging could help us improve defining the anatomical boundaries of the Macklin effect, an incompletely known anatomo-physiological entity.

Valsalva Manoeuvre-Induced Pneumothorax and Pneumomediastinum in a Covid-19 Patient with ARDS: An Unusual Mechanism for this Complication

Background

Until now, only a few cases of Valsalva-induced barotraumas (pneumothorax, pneumomediastinum and subcutaneous emphysema) have been described, and none of them among COVID-19 patients.

Case description

A man in his 50s was admitted for SARS-CoV-2-related acute respiratory distress syndrome (ARDS). Initial evolution was favourable with non-invasive ventilatory support, high-flow oxygen nasal cannula and the best supportive drugs available at the time. During the Valsalva manoeuvre while defecating, the patient reported sudden chest pain and showed a new acute hypoxemic respiratory failure due to a pneumothorax. It led to multiple complications (pulmonary embolism, haemoptysis, and cardiac arrest), and despite the best supportive care, led to the patient's death.

Discussion

The Valsalva manoeuvre can be an overlooked cause of pneumothorax in patients with COVID-19. Predisposition to barotrauma in COVID-19 patients could be explained by several factors, including the extensive use of non-invasive and invasive ventilation during the pandemic, and the histological changes observed in the lungs of those infected with COVID-19.

Conclusion

We report the first description of a Valsalva-induced barotrauma in a COVID-19 infection. We emphasise the importance of treating constipation particularly in severe COVID-19 cases, to prevent complications such as barotrauma.

LEARNING POINTS

Pneumothorax is a common complication of severe COVID-19 infection, but Valsalva manoeuvre-induced pneumothorax in COVID-19 patients has never been reported previously.Particular care should be taken to prevent and treat constipation in hospitalised patients as it may cause a wide range of complications, including barotraumatism.The extensive use of non-invasive and invasive ventilation may play a role in barotrauma, but causal association has not been proven.

Computed tomography imaging-guided parasternal approach drainage for children with tension pneumomediastinum: a case series

PURPOSE

Tension pneumomediastinum is a rare and dangerous complication in children that can be fatal, and timely detection and treatment are critical. The aim of this study was to evaluate the safety and feasibility of computed tomography (CT) imaging-guided parasternal approach drainage for tension pneumomediastinum in children.

METHODS

From June 2018 to February 2023, we consecutively enrolled 19 children with tension pneumomediastinum in our institution. A pigtail catheter was inserted into the anterior mediastinum by a CT imaging-guided parasternal approach. The catheter was connected to a negative-pressure water seal bottle to drain the pneumomediastinum. Clinical data and outcomes were summarized.

RESULTS

The mean age was 3.1 ± 3.4 years, the mean weight was 15 ± 9.1 kg, the mean procedure time was 11.8 ± 2.4 min, and the drainage time was 6.7 ± 3.4 days. No major complications were identified, such as haemothorax, catheter displacement, or mediastinal infection. Effective drainage was obtained in all patients as assessed by comparing images and ventilatory parameters, and no additional surgical treatment was needed. There was no recurrence during the follow-up, which was more than 2 months. In our data, two children with COVID-19 were discharged from the hospital after effective drainage and other clinical treatment.

CONCLUSION

CT-guided parasternal approach drainage is safe, minimally invasive, and effective for children with tension pneumomediastinum.

Pneumorrhachis secondary to exacerbation of asthma: A case report and literature review

Pneumorrhachis is defined by the presence of air within the spinal cord. Spontaneous pneumorrhachis secondary to exacerbation of asthma is rare, and its management is rarely discussed. We present a case of spontaneous pneumorrhachis in the context of a viral exacerbation of asthma, followed by a systematic literature review of all available cases of pneumorrhachis in asthma exacerbation. A total of 25 case studies reported pneumorrhachis in 28 asthma patients, all of whom presented with concomitant pneumomediastinum. Investigation and exclusion for other potential aetiologies of pneumorrhachis such as trauma or infection occurred to varying extents and may depend on clinical presentation and degree of suspicion. No other contributing aetiologies were demonstrated in this review, and no patients required specific intervention for pneumorrhachis. Whilst pneumorrhachis is generally benign, management should revolve around standard care of asthma exacerbation, attention to potentially life-threatening differential diagnoses, and supportive care.

Barotrauma in patients with severe coronavirus disease 2019-retrospective observational study

Background

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Although it is known that the COVID-19 acute respiratory distress syndrome (ARDS) is associated with higher incidence of pulmonary barotrauma, unique mechanisms causing the aforementioned complication are still to be investigated. The goal of this research was to investigate the incidence of barotrauma among COVID-19 patients treated in the intensive care unit (ICU) and to examine different clinical outcomes among those subjects.

Methods

This retrospective observational cohort study included adult COVID-19 patients admitted to ICU from September 1, 2020, to February 28, 2022. All admitted subjects received invasive respiratory support. Subjects were divided into two groups based on occurrence of pulmonary barotrauma. Data were collected from available electronical medical records.

Results

In the study period, a total of 900 subjects met inclusion criteria. Pulmonary barotrauma occurred in 88 (9.8%) of them. Subcutaneous emphysema developed in 73 (83%), pneumomediastinum in 68 (77.3%) and pneumothorax in 54 (61.4%) subjects. A small group of subjects developed less common complications like pneumoperitoneum (8 subjects, 9.1%) and pneumopericardium (2 subjects, 2.3%). Survival rate was higher in control than in barotrauma group [396 (48.8%) vs. 22 (25.0%), P<0.05]. There was also a significant difference between two groups in PaO2/FiO2 ratio on admission, duration of non-invasive respiratory support before mechanical ventilation, duration of mechanical ventilation and duration of ICU and hospital stay, all in favour of control group.

Conclusions

Development of barotrauma in patients with severe forms of COVID-19 disease and in need of respiratory support is associated with longer ICU and hospital stay as well as lower survival rates at hospital discharge. Further efforts are needed in understanding mechanism in developing barotrauma and finding new prevention and treatment options.

COVID-19-associated lung weakness (CALW): Systematic review and meta-analysis

OBJECTIVES

To assess mortality and different clinical factors derived from the development of atraumatic pneumothorax (PNX) and/or pneumomediastinum (PNMD) in critically ill patients as a consequence of COVID-19-associated lung weakness (CALW).

DESIGN

Systematic review with meta-analysis.

SETTING

Intensive Care Unit (ICU).

PARTICIPANTS

Original research evaluating patients, with or without the need for protective invasive mechanical ventilation (IMV), with a diagnosis of COVID-19, who developed atraumatic PNX or PNMD on admission or during hospital stay.

INTERVENTIONS

Data of interest were obtained from each article and analyzed and assessed by the Newcastle-Ottawa Scale. The risk of the variables of interest was assessed with data derived from studies including patients who developed atraumatic PNX or PNMD.

MAIN VARIABLES OF INTEREST

Mortality, mean ICU stay and mean PaO2/FiO2 at diagnosis.

RESULTS

Information was collected from 12 longitudinal studies. Data from a total of 4901 patients were included in the meta-analysis. A total of 1629 patients had an episode of atraumatic PNX and 253 patients had an episode of atraumatic PNMD. Despite the finding of significantly strong associations, the great heterogeneity between studies implies that the interpretation of results should be made with caution.

CONCLUSIONS

Mortality among COVID-19 patients was higher in those who developed atraumatic PNX and/or PNMD compared to those who did not. The mean PaO2/FiO2 index was lower in patients who developed atraumatic PNX and/or PNMD. We propose grouping these cases under the term COVID-19-associated lung weakness (CALW).

Acute Airway Compromise Due to Spontaneous Pneumomediastinum in COVID-19 Infection and Subsequent Rapid Formation of Pulmonary Subpleural Bullae: A Case Report

Spontaneous pneumomediastinum (SPM), an increasingly documented complication of COVID-19 infection, usually presents with retrosternal chest pain and dyspnea but can present atypically. In this case, an exceptionally rare presentation could have led to inappropriate management and a poor outcome. Here, a previously healthy 41-year-old Afro-Caribbean male non-smoker presents with acute airway compromise due to SPM. Conservative management proved effective, with anxiolysis to mitigate patient self-induced lung injury (PSILI) and oxygen supplementation via a non-rebreather mask to increase the resolution rate till the patient stabilized over the following days. The sequelae of the lung insult were noted in subsequent imaging, showing the formation of many subpleural bullae. Our case demonstrates the need for a high index of suspicion for pneumomediastinum among teams caring for COVID-19 cases. It also highlights the potential need for follow-up for further research on pulmonary sequelae.

Comparison of high-flow nasal cannula and conventional nasal cannula during sedation for endoscopic submucosal dissection: a retrospective study

Background

The high-flow nasal cannula (HFNC) is a relatively recent method that provides high-flow, heated, humidified gas delivery.

Objectives

We compared HFNC (group HF) and conventional nasal cannula (NC) (group CO) during deep sedation with propofol and remifentanil for endoscopic submucosal dissection (ESD).

Design

Single-center, retrospective observational cohort study.

Methods

In this study, a total of 159 cases were analyzed (group CO, 71 and group HF, 88). We collected the data from electronic medical records from September 2020 to June 2021. The lowest oxygen saturation (SpO2), incidence of hypoxia (SpO2 < 90%), rescue interventions, and adverse events between the two groups were investigated.

Results

There were significant differences between the two groups in lowest SpO2 and incidence of hypoxia [group CO versus group HF; 90.3 ± 9.7% versus 95.7 ± 9.0%, 25 (35.2%) versus 10 (11.4%); p < 0.001, p < 0.001; respectively]. Among the rescue interventions, the number of jaw thrust, patient stimulation, O2 flow increase, and nasal airway insertion were significantly higher in the CO group than in the HF group. However, postprocedural chest X-ray showed higher rates of abnormal findings (atelectasis, aspiration, and pneumoperitoneum) in group HF than in group CO [group CO: 8 (11.3%) versus group HF: 26 (29.5%), p = 0.005]. In multivariable analysis, besides group CO, difficult type of lesion was the risk factor for hypoxia.

Conclusions

Compared to the conventional NC, HFNC provided adequate oxygenation and a stable procedure without significant adverse events during sedation for ESD. However, caution is needed to avoid complications associated with deep sedation and difficult type of lesions.

Complications associated with incorrect use of nasal CPAP

Nasal continuous positive airway pressure (nCPAP) is a safe, effective, non-invasive respiratory modality to deliver positive end expiratory pressure in neonates. Many studies have established its associated improved respiratory outcomes without increase in major morbidities associated with preterm neonates. In contrast, there is paucity in literature addressing complications such as nasal injury, abdominal distention, air leak syndromes (especially pneumothorax), hearing loss, heat and chemical burns, swallowing and aspiration of small components of the nasal interface and delay in escalation of respiratory support associated with the use of nCPAP, most frequently due to its incorrect use. This is a comprehensive review that seeks to address the different complications that are associated with the incorrect use of nCPAP highlighting that these are operator-related and not device-related.

The Macklin effect closely correlates with pneumomediastinum in acutely ill intubated patients with COVID-19 infection

PURPOSE

Patients with COVID-19 infection are frequently found to have pulmonary barotrauma. Recent work has identified the Macklin effect as a radiographic sign that often occurs in patients with COVID-19 and may correlate with barotrauma.

METHODS

We evaluated chest CT scans in COVID-19 positive mechanically ventilated patients for the Macklin effect and any type of pulmonary barotrauma. Patient charts were reviewed to identify demographic and clinical characteristics.

RESULTS

The Macklin effect on chest CT scan was identified in a total of 10/75 (13.3%) COVID-19 positive mechanically ventilated patients; 9 developed barotrauma. Patients with the Macklin effect on chest CT scan had a 90% rate of pneumomediastinum (p < 0.001) and a trend toward a higher rate of pneumothorax (60%, p = 0.09). Pneumothorax was most frequently omolateral to the site of the Macklin effect (83.3%).

CONCLUSION

The Macklin effect may be a strong radiographic biomarker for pulmonary barotrauma, most strongly correlating with pneumomediastinum. Studies in ARDS patients without COVID-19 are needed to validate this sign in a broader population. If validated in a broad population, future critical care treatment algorithms may include the Macklin sign for clinical decision making and prognostication.

[COVID-19-associated lung weakness (CALW): Systematic review and meta-analysis]

Objectives

To assess mortality and different clinical factors derived from the development of atraumatic pneumothorax (PNX) and/or pneumomediastinum (PNMD) in critically ill patients as a consequence of COVID-19-associated lung weakness (CALW).

Design

Systematic review with meta-analysis.

Setting

Intensive care unit (ICU).

Participants

Original research evaluating patients, with or without the need for protective invasive mechanical ventilation (IMV), with a diagnosis of COVID-19 who had developed atraumatic PNX or PNMD on admission or during their hospital stay.

Interventions

Data of interest were obtained from each article and analysed and assessed by the Newcastle-Ottawa Scale. The risk of the variables of interest was assessed by data derived from studies including patients who developed atraumatic PNX or PNMD.

Main variables of interest

Mortality, mean ICU length of stay and mean PaO₂/FiO₂ at diagnosis.

Results

Data were collected from 12 longitudinal studies. Data from a total of 4,901 patients were included in the meta-analysis. A total of 1,629 patients had an episode of atraumatic PNX and 253 patients had an episode of atraumatic PNMD. Despite finding significantly strong associations, the high heterogeneity between studies means that interpretation of the results should be made with caution.

Conclusions

Mortality of COVID-19 patients was higher in those who developed atraumatic PNX and/or PNMD compared to those who did not. The mean PaO2/FiO2 index was lower in patients who developed atraumatic PNX and/or PNMD. We propose to group these cases under the term CAPD.

Spontaneous pneumomediastinum and macklin effect: Three rare case reports with computed tomography findings

Spontaneous pneumomediastinum (SPM) is defined as free air or gas in the mediastinum that is not associated with an obvious cause such as chest trauma. The SPM results from acutely elevated intra-alveolar pressure: The high-pressure gradient between the distal alveoli and the pulmonary interstitium leads to alveolar rupture. This causes free gas to separate through the peribronchovascular fascial sheaths (interstitial emphysema) into the hilum and then into the mediastinum. Once the gas is in the mediastinum, it can travel up to the cervical soft tissues (even the retroperitoneum) producing subcutaneous emphysema. The Macklin effect appears on thoracic computed tomography (CT) as linear air collections adjacent to bronchovascular sheaths. This case report presents CT findings of SPM due to the Macklin effect in three cases and a brief literature review on this subject.

Pneumomediastinum in COVID-19 disease: Clinical review with emphasis on emergency management

Pneumomediastinum can be primary (spontaneous) or secondary to iatrogenic, traumatic, and non-traumatic causes. The incidence of spontaneous and secondary pneumomediastinum is higher in patients with coronavirus disease 2019 (COVID-19) compared to the general population. So, pneumomediastinum should be considered in the differential diagnosis of any patient with COVID-19 presenting with chest pain and breathlessness. A high level of suspicion is required to diagnose this condition promptly. Unlike in other disease conditions, pneumomediastinum in COVID-19 has a complicated course with higher mortality in intubated patients. No guidelines exist for managing pneumomediastinum patients with COVID-19. Therefore, emergency physicians should be aware of the various treatment modalities besides conservative management for pneumomediastinum and life-saving interventions for tension pneumomediastinum.

Clinical use of Macklin-like radiological sign (Macklin effect): A systematic review

INTRODUCTION

Recent studies suggested that Macklin sign is a predictor of barotrauma in patients with acute respiratory distress syndrome (ARDS). We performed a systematic review to further characterize the clinical role of Macklin.

METHODS

PubMed, Scopus, Cochrane Central Register and Embase were searched for studies reporting data on Macklin. Studies without data on chest CT, pediatric studies, non-human and cadaver studies, case reports and series including <5 patients were excluded. The primary objective was to assess the number of patients with Macklin sign and barotrauma. Secondary objectives were: occurrence of Macklin in different populations, clinical use of Macklin, prognostic impact of Macklin.

RESULTS

Seven studies enrolling 979 patients were included. Macklin was present in 4-22% of COVID-19 patients. It was associated with barotrauma in 124/138 (89.8%) of cases. Macklin sign preceded barotrauma in 65/69 cases (94.2%) 3-8 days in advance. Four studies used Macklin as pathophysiological explanation for barotrauma, two studies as a predictor of barotrauma and one as a decision-making tool. Two studies suggested that Macklin is a strong predictor of barotrauma in ARDS patients and one study used Macklin sign to candidate high-risk ARDS patients to awake extracorporeal membrane oxygenation (ECMO). A possible correlation between Macklin and worse prognosis was suggested in two studies on COVID-19 and blunt chest trauma.

CONCLUSIONS

Increasing evidence suggests that Macklin sign anticipate barotrauma in patients with ARDS and there are initial reports on use of Macklin as a decision-making tool. Further studies investigating the role of Macklin sign in ARDS are justified.

Clinical Features of COVID-19 and Differentiation from Other Causes of CAP

Community-acquired pneumonia (CAP) is a significant cause of morbidity and mortality, one of the most common reasons for infection-related death worldwide. Causes of CAP include numerous viral, bacterial, and fungal pathogens, though frequently no specific organism is found. Beginning in 2019, the COVID-19 pandemic has caused incredible morbidity and mortality. COVID-19 has many features typical of CAP such as fever, respiratory distress, and cough, and can be difficult to distinguish from other types of CAP. Here, we highlight unique clinical features of COVID-19 pneumonia such as olfactory and gustatory dysfunction, lymphopenia, and distinct imaging appearance.

Dedicated esophageal imaging may be unnecessary in marijuana-associated spontaneous pneumomediastinum: Findings from a retrospective cohort study

Background

Marijuana use has become more common since its legalization, as have reports of marijuana-associated spontaneous pneumomediastinum. Non-spontaneous causes such as esophageal perforation are often ruled out on presentation due to the severe consequences of untreated disease. Here we seek to characterize the presentation of marijuana-associated spontaneous pneumomediastinum and explore whether esophageal imaging is necessary in the setting of an often benign course and rising healthcare costs.

Materials and Methods

Retrospective review was performed for all 18-55 year old patients evaluated at a tertiary care hospital between 1/1/2008 and 12/31/2018 for pneumomediastinum. Iatrogenic and traumatic causes were excluded. Patients were divided into marijuana and control groups.

Results

30 patients met criteria, with 13 patients in the marijuana group. The most common presenting symptoms were chest pain/discomfort and shortness of breath. Other symptoms included neck/throat pain, wheezing, and back pain. Emesis was more common in the control group but cough was equally prevalent. Leukocytosis was present in most patients. Four out of eight of computed tomography esophagarams in the control group showed a leak requiring intervention, while only one out of five in the marijuana group showed even a possible subtle extravasation of contrast but this patient ultimately was managed conservatively given the clinical picture. All standard esophagrams were negative. All marijuana patients were managed without intervention.

Discussion

Marijuana-associated spontaneous pneumomediastinum appears to have a more benign clinical course compared to non-spontaneous pneumomediastinum. Esophageal imaging did not change management for any marijuana cases. Perhaps such imaging could be deferred if clinical presentation of pneumomediastinum in the setting of marijuana use is not suggestive of esophageal perforation. Further research into this area is certainly worth pursuing.

A Case Series of Spontaneous Pneumomediastinum With/Without Pneumothorax in COVID-19

With the previous worldwide initial coronavirus disease 2019 (COVID-19) pandemic, a notable rise in spontaneous pneumomediastinum with/without pneumothorax (SPP) has been noted. Most cases were initially reported as complications secondary to barotrauma from mechanical ventilation (MV) with COVID-19. However, with the Delta strain, starting from December 2020, there have been multiple reports of SPP. The SPP is an uncommon complication outside use of assisted ventilation with either noninvasive positive pressure ventilation (NIPPV) or MV. COVID-19 has been linked to higher incidence of SPP without use of NIPPV or MV. We present a series of 5 cases with a polymerase chain reaction-confirmed COVID-19 diagnostic testing whose hospital course was complicated by SPP unrelated to the use of either NIPPV or MV.

Spontaneous pneumomediastinum in COVID‐19 patients: two cases

Coronavirus disease 2019 (COVID-19) has become a massive epidemic affecting millions of people worldwide. The common radiological findings of COVID-19 are peripheral ground glass or consolidative opacities, but pneumomediastinum is a very rare finding of COVID-19, especially in patients not receiving mechanical ventilation support. Our aim was to present cases of spontaneous pneumomediastinum in two patients with COVID-19 and to discuss the potential mechanism underlying it.

Isolated pneumomediastinum in severe category COVID-19 patients admitted in ICU: a case series

Background

Pneumomediastinum is a rare complication associated with acute respiratory distress syndrome secondary to other viral pneumonias. However, it has been on a rise in COVID-19 patients with severe disease.

Case presentation

We present three cases to highlight that isolated pneumomediastinum can complicate the course of illness in patients on non-invasive ventilation. In our case series, two COVID-19 diagnosed cases with no previous history of intubation developed pneumomediastinum. They were managed conservatively with a successful outcome. The third patient developed PM with subcutaneous emphysema post-intubation, although managed conservatively succumbed to the disease.

Conclusions

Clinicians need to be alert to the development of such a complication in the event of sudden onset dyspnoea with chest pain. Conservative management, with low pressure settings on the ventilator results in gradual improvement of patient.

Spontaneous prevertebral emphysema following weight training in a 21-year-old female

Subcutaneous emphysema (SCE) of the head, neck and mediastinum most commonly arises due to penetrating trauma and iatrogenic events facilitating air entry into these spaces [1]. Spontaneous SCE can emerge due to a pressure gradient between the intra-alveolar air and surrounding structures, causing alveolar rupture and dissection of the peribronchovascular sheath. This is known as the Macklin effect. Potential consequences include pneumomediastinum, pneumothorax, facial emphysema and pneumoracchis [1]. We aim to describe a case of SCE in a 21-year-old female presenting to the emergency department (ED) after weight training. A 21-year-old female presented to the ED with a sore throat and dysphagia after weight lifting in the gym 6 h earlier. Training involved repeat Valsalva manoeuvres. She experienced sharp pain with onset over an hour, worse with swallowing. She had a history of gastro-oesophageal reflux disease. Vital signs, local examination and systemic examination were unremarkable. The diagnosis was made with soft tissue neck X-ray, demonstrating emphysema within the prevertebral space extending from the skull base to the first thoracic vertebra (Fig. 1). Her chest X-ray showed no pneumothorax or pneumomediastinum. No intervention was required beyond analgesia, and she was discharged from the ED. She was advised to avoid heavy lifting and diving. A follow-up radiograph showed resolution of the SCE. This case is an important rare entity and highlights for clinicians that pain after physical exercise may involve injuries extending beyond the area directly trained.

Pneumomediastinum and Pneumopericardium as Uncommon Complications of COVID-19 Infection: A Review Article

There is an emerging body of literature describing an increasing incidence of pneumomediastinum and, to a lesser extent, pneumopericardium as a complication of COVID-19. However, the literature lacks information regarding patients' characteristics and a general view of this unusual condition. The purpose of this paper is to summarize the current literature on this phenomenon. In this study, we summarize the risk factors/etiology, imaging modalities, management, and prognosis of known cases in the literature. In total, 48 articles were included in the study, ranging from case reports to case series. Most patients were male (83.3%). The overall mortality rate was 27.1% and the recovery rate was 62.5%.

Pneumomediastinum as patient self-inflicted lung injury in patients with acute respiratory distress syndrome due to COVID-19: a case series

Background

In patients with coronavirus disease (COVID-19) due to severe acute respiratory syndrome coronavirus 2 infection, pneumomediastinum has been increasingly reported in cases of noninvasive oxygen therapy, including high-flow nasal cannula, and invasive mechanical ventilation. However, its pathogenesis is still not understood.

Case Presentation

We report two cases of pneumomediastinum in acute respiratory distress syndrome (ARDS) caused by COVID-19. In both cases, control of spontaneous breathing with neuromuscular blocking agents resulted in resolution of pneumoperitoneum.

Conclusion

The improvement of pneumomediastinum with control of spontaneous breathing suggested patient self-inflicted lung injury as a possible mechanism in this case series. In ARDS cases with pneumomediastinum, in addition to controlling plateau pressure with conventional lung protective ventilation, spontaneous breathing should be controlled if the patient's inspiratory effort is suspected to be strong.