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.

Spontaneous pneumomediastinum in anti-MDA5-positive dermatomyositis: Prevalence, risk factors, and prognosis.

OBJECTIVE: To depict the clinical panorama of spontaneous pneumomediastinum (SPM) in anti-MDA5 antibody-positive dermatomyositis (anti-MDA5+ DM). METHODS: A total of 1352 patients with idiopathic inflammatory myopathy (IIM), including 384 anti-MDA5+ DM patients were retrospectively enrolled. The clinical profiles of anti-MDA5+ DM-associated SPM were analyzed. RESULTS: We identified that 9.4 % (36/384) of anti-MDA5+ DM patients were complicated with SPM, which was significantly higher than that of non-anti-MDA5+ DM and other IIM subtypes (P all <0.001). SPM developed at a median of 5.5 (3.0, 12.0) months after anti-MDA5+ DM onset. Anti-MDA5+ DM patients complicated with SPM showed a significantly higher frequency of fever, dyspnea, and pulmonary infection including viral and fungal infections compared to those without SPM (P all < 0.05). Cytomegalovirus (CMV) and fungal infections were identified to be independent risk factors for SPM development in the anti-MDA5+ DM. SPM and non-SPM patients in our anti-MDA5+ DM cohort showed comparable short-term and long-term survival (P = 0.236). Furthermore, in the SPM group, we found that the non-survivors had a lower peripheral lymphocyte count, higher LDH level, and higher frequency of intensification of immunosuppressive treatment (IST) than survivors. The elevated LDH level and intensification of IST were independent risk factors for increased mortality in anti-MDA5+ DM-associated SPM patients. CONCLUSIONS: Nearly one-tenth of patients with anti-MDA5+ DM develop SPM. Both CMV and fungal infections are risk factors for SPM occurrence. The development of SPM does not worsen the prognosis of anti-MDA5+ DM patients, and the intensification of IST does harm to the SPM prognosis.

Pneumopericardium following severe thoracic trauma.

BACKGROUND: Traumatic pneumopericardium (PPC) is a rare clinical entity associated with chest trauma, resulting from a pleuropericardial connection in the presence of a pneumothorax, interstitial air tracking along the pulmonary perivascular sheaths from ruptured alveoli to the pericardium, or direct trachea-bronchial-pericardial communication.  Our objectives were to describe the modern management approach to PPC and to identify variables that could improve survival with severe thoracic injury. METHODS: We conducted a retrospective study of the trauma registry between 2015 and 2022 at a Level I verified adult trauma center for all patients with PPC. Demographics, injury patterns, and treatment characteristics were compared between blunt and penetrating trauma. This study focused on the management strategies and the physiologic status regarding PPC and the development of tension physiology. The main outcome measure was operative versus nonoperative management. RESULTS: Over a seven-year period, there were 46,389 trauma admissions, of which 488 patients had pneumomediastinum. Eighteen patients were identified with PPC at admission. Median age was 39.5 years (range, 18-77 years), predominantly male (n = 16, 89 %), Black (n = 12, 67 %), and the majority from blunt trauma (78 %). Half had subcutaneous emphysema on presentation while 39 % had recognizable pneumomediastinum on chest x-ray. Tube thoracostomy was the most common intervention in this cohort (89 %). Despite tube thoracostomy, tension PPC was observed in three patients, two mandating emergent pericardial windows for progression to tension physiology, and the remaining requiring reconstruction of a blunt tracheal disruption. The majority of PPC patients recovered with expectant management (83 %), and no deaths were directly related to PPC. CONCLUSIONS: Traumatic PPC is a rare radiographic finding with the majority successfully managed conservatively in a monitored ICU setting. These patients often have severe thoracic injury with concomitant injuries requiring thoracostomy alone; however, emergent surgical intervention may be required when PPC progresses to tension physiology to improve overall survival.

Spontaneous pneumomediastinum associated with subcutaneous emphysema, pneumopericardium and pneumothorax: a rare association complicating measles.

A unique case of severe measles complicated by multiple features of gas accumulation is described, on the ground of the available literature evidences. Complications from measles have been reported in every organ system and they may vary by age and underlying conditions. Pneumomediastinum is usually associated with subcutaneous emphysema and pneumopericardium, but rarely associated with pneumothorax. We report extremely rare simultaneous occurrence of self-limiting pneumomediastinum, pneumopericardium, subcutaneous neck and chest region emphysema, and pneumothorax, in a 19-year-old girl with measles. A review of the literature has documented only one previous report of spontaneous pneumomediastinum, subcutaneous emphysema and pneumothorax in the course of measles, and no previous cases reported the association of pneumomediastinum, subcutaneous emphysema, pneumopericardium and pneumothorax complicating measles.

Spontaneous Pneumomediastinum Secondary to Undiagnosed Asthma in Military Adult.

Spontaneous pneumomediastinum (SPM) is a rare but described complication of exercise-induced bronchoconstriction (EIB), more commonly observed in children with asthma. We present a 23-year-old active duty military male and avid distance runner who developed progressive radiating retrosternal chest pain preceded by wheezing and coughing paroxysm. A chest computed tomography revealed extensive pneumomediastinum. SPM results from increased intrathoracic pressure with alveolar rupture and subsequent tracking of air between fascial planes. Like most cases of SPM, our patient remained hemodynamically stable and responded well to conservative therapies with complete resolution. After thorough evaluation, undiagnosed asthma was determined to be the inciting etiology. The patient is now well controlled and symptom free on a daily low-dose inhaled corticosteroid without SPM reoccurrence. In young adult patients presenting with SPM, EIB and asthma should be considered on the differential diagnosis as appropriate medical therapy will improve symptoms and reduce risk of reoccurrence.

The clinical characteristics of subcutaneous and mediastinal emphysema in anti-melanoma differentiation-associated 5 positive dermatomyositis associated with interstitial lung disease.

OBJECTIVES: To investigate the clinical characteristics of subcutaneous emphysema (SE) and mediastinal emphysema (ME) occurring in patients with anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis associated with interstitial lung disease (anti-MDA5-positive DM-ILD). METHODS: In this retrospective study, a total of 117 anti-MDA5-positive DM-ILD patients were admitted to our hospital. All patients underwent an assessment of autoantibodies, serum ferritin levels, and lung high-resolution CT scans. RESULTS: In patients with anti-MDA5-positive DM-ILD, the incidence of SE/ME was found to be 11.1%, which was significantly higher compared to patients with anti-synthetase syndrome (p<0.01). The mortality rate among anti-MDA5-positive DM-ILD patients with SE/ME was significantly higher than those without SE/ME (p=0.0022). There was no statistically significant difference in the occurrence of SE/ME between patients with positive anti-Ro-52 antibodies and those with negative anti-Ro-52 antibodies (p=0.18). Patients with higher serum ferritin levels (1000 ng/ml ≤serum ferritin ≤1500 ng/ml) had a higher likelihood of developing SE/ME compared to patients with lower serum ferritin levels (serum ferritin <500 ng/ml) (p<0.01). Among 13 anti-MDA5-positive DM-ILD patients with SE/ME, six (46.2%) developed SE/ME within 1 month of being diagnosed and 53.8% of patients underwent positive pressure ventilation prior to the onset of SE/ME. CONCLUSIONS: We found that SE/ME is not uncommon in anti-MDA5-positive DM-ILD and is an important factor associated with poor patient prognosis. The occurrence of SE/ME is correlated with high levels of serum ferritin and is not related to anti-Ro-52 antibodies. Rheumatologists should pay close attention to SE/ME caused by positive pressure ventilation in anti-MDA5-positive DM-ILD patients.

High-Altitude Pulmonary Edema Combined with Spontaneous Pneumomediastinum: A Case Report.

Background: High-altitude pulmonary edema (HAPE) is a serious life-threatening disease that occurs after rapid ascent to high altitude; its main early-stage presentations include fatigue, headache, low-grade fever, dyspnea, and cough. X-ray and computed tomography (CT) images show pulmonary shadows and patches, which may be localized (initial right lung field predomination) or generalized to the bilateral lung base. Case Presentation: In this report, we present a case of a 25-year-old man diagnosed with HAPE combined with spontaneous pneumomediastinum. After a quick descent and effective medical treatment, this patient made a full recovery. The case may provide helpful information for the prevention and treatment of this disease since an increased number of people, especially young men, currently travel and work at high altitudes. Conclusion: After accurate clinical diagnosis with the help of CT or X-ray, immediate descent and appropriate oxygen supplementation are the most effective treatments for HAPE at high altitude.

Pneumomediastinum: Experience with 87 Patients.

OBJECTIVE: The aim of the present series was first to present our experience in the management of 37 patients with spontaneous pneumomediastinum (SPM), and further to indicate the necessity of identifying true SPM cases as they are currently inadequately defined. METHODS: This is a single-center, retrospective study, conducted in a university hospital. Consecutive adult patients with pneumomediastinum (PM) between January 2009 and March 2020 were involved in the series. The data about age, gender, symptoms, signs, treatment, length of hospital stay (LOS), and in-hospital mortality were evaluated. RESULTS: In total, 87 cases with pneumomediastinum (37 with spontaneous and 50 with secondary PM) were analyzed. Patients in both groups were of similar ages (P=0.4). Sufferers with secondary PM were more likely to have: an associated pneumothorax (19% vs 58%, P<0.05), a chest tube placed (18.9% vs 58%, P<0.05), an associated pleural effusion (0% vs 18%, P<0.05). They presented with a longer LOS (3.9 vs 5.3 days, P<0.05), and were more likely to die (0% vs 10%, P<0.05). Additionally they showed a higher prevalence of radiologic subcutaneous emphysema (49% vs 74%, P<0.05). CONCLUSION: Spontaneous pneumomediastinum is an onset of clinical importance with a low mortality rate, short LOS and good longterm prognosis. It often presents with chest pain, dyspnea and/or subcutaneous emphysema. However, secondary causes of mediastinal air must be ruled out, due to their potential devastating outcome if not diagnosed promptly. A consensus aimed at an update of the classification guidelines is more than indispensable.

Case report of a child with spontaneous pneumomediastinum and subcutaneous emphysema.

Hamman's syndrome is a rare clinical entity that presents with spontaneous pneumomediastinum and subcutaneous emphysema. It is most commonly diagnosed in young men and pregnant women, and is rare in children. We report the case of a female toddler who presented to an emergency department with fever, cough and shortness of breath. Imaging studies revealed subcutaneous emphysema and pneumomediastinum. The patient was diagnosed with Hamman's syndrome after ruling out other possibilities. We discuss the underlying mechanisms of the disease, the diagnostic criteria and the treatment options. The purpose of this case report is to improve clinicians' awareness of the existence of this rare clinical entity in paediatric patients.

Primary spontaneous pneumomediastinum: 237 cases in a single-center experience over a 10-year period and assessment of factors related with recurrence.

OBJECTIVE: To evaluate the precipitating factors and symptoms of primary spontaneous pneumomediastinum (PSPM) and to assess the factors related with recurrent spontaneous pneumomediastinum (RSPM). METHODS: From 2010 to 2021, 237 PSPM patients were included in this retrospective study. Clinical information including in-hospital periods, morbidity, mortality, presenting symptoms, precipitating events, smoking, and asthma history was obtained. The patients with smoking history were subdivided into "ex-smoker" or "current smoker". The severity of asthma was categorized into "mild intermittent", "mild persistent", "moderate persistent", or "severe persistent". During follow-up, patients with RSPM were classified into "recurrence" group and the others were into "no recurrence" group. Multivariate regression analysis was used to elucidate the associated factors with RSPM. RESULTS: The mean age of study patients (men: women = 222: 15) was 23.4 years and mean period of hospital stay was 7.5 days. There was no mortality and morbidity. Most frequent symptom and precipitating factor were acute chest pain (n = 211, 89.0%) and cough (n = 72, 30.4%), respectively. RSPM occurred in 11 patients (4.6%). The proportion of patients with smoking (72.8% vs. 37.1%, p = 0.010) or asthma (81.8% vs. 39.8%, p<0.001) was significantly higher in "recurrence" group than "no recurrence" group. On multivariate analysis, asthma was the only factor associated with RSPM (mild intermittent/persistent, OR = 7.092, p = 0.047; moderate persistent, OR = 8.000, p = 0.011). CONCLUSION: PSPM is a benign disease with no morbidity and mortality. Asthma may be the associated factor with RSPM; thus, despite the low rate of recurrence, patients with asthma should be informed about the chance of RSPM.

Clinical significance of para-carinal air cysts in patients with pleuroparenchymal fibroelastosis: The relationship with pneumomediastinum and pneumothorax.

BACKGROUND: Para-tracheal or para-carinal air cysts (PACs) are often asymptomatic and usually detected incidentally by methods such as computed tomography. Their clinical significance is unclear in patients with pleuroparenchymal fibroelastosis (PPFE). METHODS: We evaluated the clinical significance of PACs in PPFE and their relationship with pneumomediastinum or pneumothorax. RESULTS: In total, 50 patients had PPFE and 34 (68%) had PACs. Most PACs were para-carinal (n = 30). A para-tracheal air cyst was detected in only nine patients, which included five patients having both para-carinal and para-tracheal air cysts. Overall median survival was 24.7 months. Survival was not significantly different between the patients with [PACs(+)] and without PACs (P = 0.268). A high frequency (64%) of the complication of pneumomediastinum or pneumothorax occurred in the overall population during follow-up. Pneumomediastinum/pneumothorax occurred significantly more frequently in patients with PACs(+) than in those without (76.5% vs. 37.5%; P = 0.012). PACs(+) was the only significant risk factor for pneumomediastinum/pneumothorax. CONCLUSIONS: Our data showed that PACs commonly occur in patients with PPFE, and most PACs were para-carinal air cysts. Additionally, PACs(+) was a significant risk factor for pneumomediastinum/pneumothorax; therefore, clinicians should be more aware of these complications during follow-up examination, particular in PACs(+) patients with PPFE.

COVID-19-Related Pleural Diseases.

Coronavirus disease 2019 (COVID-19)-related pleural diseases are now well recognized. Since the beginning of the pandemic, increasing cases of pleural diseases including pneumothorax, pneumomediastinum, and pleural effusion with severe COVID-19 infection have attracted the attention of physicians and are not incidental or due to barotrauma. The complicated course of COVID-19 illness highlights the complex pathophysiological underpinnings of pleural complications. The management of patients with pneumothorax and pneumomediastinum is challenging as the majority require assisted ventilation; physicians therefore appear to have a low threshold to intervene. Conversely, pleural effusion cases, although sharing some similar patient characteristics with pneumothorax and pneumomediastinum, are in general managed more conservatively. The evidence suggests that patients with COVID-19-related pleural diseases, either due to air leak or effusion, have more severe disease with a worse prognosis. This implies that prompt recognition of these complications and targeted management are key to improve outcomes.

[Hamman's syndrome in SARS-CoV-2 pneumonia]. / Síndrome de Hamman en neumonía por SARS-CoV-2.

Hamman's syndrome, or spontaneous pneumomediastinum, is the presence of air in the mediastinum without a history of previous pulmonary pathology, chest trauma or iatrogenesis. It has been described as a rare complication in patients with COVID-19 pneumonia. It is postulated that an increase in airway pressure associated with diffuse alveolar damage caused by the virus produces an air leak into the mediastinum. Chest pain and dyspnea associated with subcutaneous emphysema should make the treating physician suspicious. We introduce a 79-year-old patient who, during hospitalization for pneumonia secondary to COVID-19, suddenly developed dyspnea, chest pain, coughing spells and bronchospasm with the discovery of spontaneous pneumomediastinum on chest tomography. He evolved favorably with bronchodilator treatment and temporary oxygen therapy. Hamman's syndrome is a rare cause of respiratory failure progression in patients with COVID-19 pneumonia. Its recognition is crucial to implement the appropriate treatment.

El síndrome de Hamman, o neumomediastino espontáneo, es la presencia de aire en mediastino en pacientes sin antecedentes de enfermedad pulmonar previa, trauma torácico o iatrogenia. Se ha descrito como una complicación rara en pacientes con neumonía por COVID-19. Se postula que un aumento en la presión de la vía aérea asociado a daño alveolar difuso generado por el virus, producen una fuga de aire hacia el mediastino. El dolor torácico y disnea, asociado a enfisema subcutáneo, deben hacer sospechar al médico tratante. Presentamos un paciente de 79 años que durante su internación por neumonía secundaria al virus SARS-CoV-2 evolucionó súbitamente con disnea, dolor torácico, accesos de tos y broncoespasmo con hallazgo de neumomediastino espontáneo en la tomografía de tórax. Evolucionó favorablemente con tratamiento broncodilatador y oxigenoterapia. El síndrome de Hamman es una causa poco frecuente de progresión de insuficiencia respiratoria en pacientes con neumonía por COVID-19. Su identificación es crucial para implementar el tratamiento adecuado.

Pneumoperitoneum, pneumomediastinum and subcutaneous emphysema following argon plasma coagulation treatment of colonic angioectasia.

INTRODUCTION: The paper presents unusual symptoms as a complication of therapeutic colonoscopy. CASE REPORT: A 70-year-old polymorbid female patient in chronic dialysis program underwent argon plasma coagulation treatment of leaking angioectasias in the cecum and ascending colon. Shortly after the procedure she presented with shortness of breath and subcutaneous emphysema of the neck which was initially misdiagnosed as swelling. Further tests revealed pneumoperitoneum, subcutaneous emphysema and pneumomediastinum. Considering the high risks for our patient (comorbidities, obesity), a laparoscopic approach was indicated. During laparoscopy neither peritonitis nor intestinal perforation were found. The patient recovered without complications after further complex treatment. CONCLUSION: Shortness of breath and subcutaneous emphysema are not typically among the first symptoms of colonoscopic perforation. Our case confirms that we should bear this complication in mind and when suspected, the diagnostic process should be started without delay.

Chest Tightness with Cycling Turned Out To Be Pneumomediastinum.

BACKGROUND Pneumomediastinum, or mediastinal emphysema, means air present inside the mediastinum. It usually presents with symptoms of chest pain and shortness of breath. Examination can be significant for crepitus along the neck area. There are many risk factors associated with pneumomediastinum, including asthma and COVID-19. Most cases of pneumomediastinum improve with conservative management, and surgery (mediastinotomy) is reserved for complicated cases with tension pneumomediastinum. CASE REPORT This is the case of a 23-year-old man who presented with chest tightness after 3.5 h of cycling. The patient did have a prior history of clinically stable asthma, with no recent exacerbation, and denied any other associative factors. Imaging was significant for pneumomediastinum. The patient was admitted for observation in the hospital and treated with supportive care, without any surgical intervention. The patient had appropriate improvement in his symptoms in 24 h. Repeat imaging showed improvement in the pneumomediastinum, and the patient was discharged to outpatient follow-up. CONCLUSIONS Our case presents a unique link between cycling and pneumomediastinum. Prolonged cycling may emerge as a risk factor for this complication. People with a previous history of pneumomediastinum should be careful to review other risk factors prior to planning long-distance bicycling. Physicians need to keep this differential diagnosis in mind when encountering a patient with similar symptoms so that a timely diagnosis is made.

The Impact of Obesity on Early Complications Following Tracheostomy: An Evaluation of a Nationwide Registry.

INTRODUCTION: The obesity epidemic is an important public health problem in the United States. Previous studies have revealed the association between obesity and various surgical complications. Tracheostomy which is an important lifesaving procedure may prove technically challenging in an obese patient. This study sought to evaluate the association between obesity and early complications following standard tracheostomy using a national registry. METHODS: Adult patients who underwent tracheostomy from 2007 to 2017 were analyzed using the Nationwide Inpatient Sample (NIS). The population was stratified into obese and non-obese groups. Early complications following standard tracheostomy were identified and compared between the two groups. Multivariable logistic regression analyses were performed to assess the association between obesity and early complications following tracheostomy. RESULTS: Data pertaining to 205 032 adult patients were evaluated. Obese patients accounted for 12.1% (n = 21 816) of the entire cohort. The most common complication in the cohort was perioperative bleeding (4316 [2.1%]). A total of 1382 (0.67%), 949 (0.46%), and 134 (0.07%) patients developed pneumothorax/pneumomediastinum, stoma/surgical site infection, and tracheal injury following standard tracheostomy, respectively. There was no difference in the odds of tracheal injury, perioperative bleeding, and pneumomediastinum/pneumothorax following standard tracheostomy in the obese and non-obese group in multivariable analysis. However, obesity was associated with 60% increased odds of developing stoma/surgical site infection following standard tracheostomy (OR 1.60 [1.33-1.92], P < 0.01). CONCLUSION: Obesity is associated with an increased risk of developing stoma/surgical site infection following standard tracheostomy. This adds to the growing need for measures to help curb the obesity epidemic in a bid to improve surgical outcomes.

Pneumomediastinum complicating diabetic ketoacidosis.

Pneumomediastinum is an uncommon finding in patients with diabetic ketoacidosis (DKA) and may occur spontaneously or secondary to an effort rupture of the oesophagus. Excluding oesophageal rupture is important, as delaying treatment increases the risk of mortality. We discuss a case of DKA complicated by vomiting, pneumomediastinum, pneumopericardium and air in the epidural space. Instead of fluoroscopic oesophagography, chest CT was used to investigate oesophageal rupture. We present an overview of case reports and retrospective studies illustrating the utility of chest CT in the investigation of oesophageal rupture over fluoroscopic oesophagography.

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.