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.

COVID-19: A Possible Cause of Spontaneous Pneumoperitoneum

Introduction

Pneumoperitoneum is the presence of air within the peritoneal cavity and is mostly caused by organ rupture. Spontaneous pneumoperitoneum accounts 5% to 15% of the cases and occurs in the absence of organ damage. The pulmonary origin of pneumoperitoneum is unusual, and probably associated with mechanical ventilation and alveolar leak. In patients with coronavirus disease 2019 (COVID-19) there are some reports of air leak, like pneumothorax, pneumomediastinum, pneumoperitoneum, and subcutaneous emphysema.

Case presentation

We present the case of a 70-year-old man with COVID-19 pneumonia admitted to the Intensive Care Unit (ICU). Since admission he was on Non-Invasive Ventilation (NIV), without improvement, needing Invasive Mechanical Ventilation (IMV) due to severe respiratory failure. Five days after IMV despite protective lung ventilation, massive spontaneous subcutaneous emphysema, pneumomediastinum and pneumoperitoneum were diagnosed. Besides initial conservative management 12 hours later, the patient developed abdominal compartment syndrome requiring percutaneous needle decompression.

Conclusions

Pneumoperitoneum can be considered a rare complication of COVID-19 pneumonia and its management, resulting not only from the viral pulmonary but also from secondary causes. Conservative management should be usually enough. However, in the presence of abdominal compartment syndrome prompt recognition and treatment are crucial and eventually lifesaving.

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.

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.

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.

"Pneumomediastinum: A marker of severity in Covid-19 disease"

Objective

The goal of this study was to look at the incidence, risk factors, clinical characteristics, and radiological aspects of COVID-19 patients who developed pneumomediastinum and compare these features between those who died and those who survived.

Materials and methods

This retrospective observational study included COVID-19 patients having pneumomediastinum on CT from May 2020 to May 2021 in a COVID-19 care hospital. 1st wave patients were considered between the period of May 2020 to January 2021 and those in the second wave between February 2021 to May 2021. The clinical details were analyzed by a consultant intensivist and CT scans were read by a team of 6 resident radiologists and 5 experienced radiologists. Demographic data, co-morbidities, clinical parameters, hemodynamic markers, radiological involvement and associated complications were analyzed.

Results

During the study period, 10,605 COVID-19 patients were admitted to our hospital of which 5689 underwent CT scan. 66 patients were detected to have pneumomediastinum on CT; 26 of them in the first wave and 40 in the second wave. Out of 66, 28 patients were admitted to ICU, 9 during the first wave and 18 during the second wave. The overall incidence of developing pneumomediastinum was 1.16%. Incidence in the 1st wave was 1.0% and in the 2nd wave was 1.29%. The overall mortality rate in admitted COVID-19 patients was 12.83% while it was 43.9% in COVID-19 patients who developed pneumomediastinum. Incidence of pneumomediastinum and pneumothorax was high in patients with extensive parenchymal involvement. 59/66 (89%) cases of pneumomediastinum had severe CT score on imaging.

Conclusion

We conclude that pneumomediastinum is a marker of poor prognosis. Timely diagnosis of interstitial emphysema or pneumomediastinum will aid in planning early protective ventilation strategies and timely intervention of complications.

Unusual subcutaneous emphysema extending to the limbs following blunt chest injury

Subcutaneous emphysema can be traumatic, infectious, iatrogenic, or spontaneous. Traumatic subcutaneous emphysema of the upper limb is not infrequent following trauma to that limb. However, the subcutaneous emphysema of the limbs following trauma to a site other than the limb is seldom reported. A 45-year-old male was referred from a private hospital to a tertiary care hospital with right-sided multiple rib fractures and pneumothorax following chest injury. The patient was having acidotic breathing on examination, and crepitus was present over the bilateral chest and bilateral upper and lower limbs, suggesting subcutaneous emphysema. Right and left intercostal drainage tubes were inserted at our hospital. The patient died in the emergency after a few hours of treatment. The X-ray performed at the autopsy revealed extensive bilateral upper and lower limb subcutaneous emphysema. The deceased had multiple rib fractures over the right side with fractured ends of the two ribs piercing the pleural cavity, causing tears in the lung parenchyma. The cause of death was attributed to the chest injury and its sequelae. Such rapidly expanding subcutaneous emphysema can be a sign of underlying severe chest injury. Prompt insertion of the intercostal drainage tube could be the lifesaving procedure in such cases.

Pneumomediastinum Associated with COVID-19: A Case Series

Coronavirus disease 2019 (COVID-19), caused by the new coronavirus SARSCoV-2, is an infectious disease that has caused an increase in hospitalizations for pneumonia; the spectrum of clinical presentation is variable. One such presentation, pneumomediastinum (PM), is defined as the presence of air or some other gas in the mediastinum. It is a rare condition, usually benign and self-limited; it has been seen in patients with COVID-19. Although most cases are, as explained above, self limited and in addition, can be managed conservatively, close monitoring is recommended, as PM can cause life-threatening hemodynamic and respiratory disturbances. We present a case series of 4 patients with SARS CoV-2 infection, in whom PM was found, and who were admitted to the Regional Hospital of High Specialty of the Yucatan Peninsula during the period of May 2020 through August 2020.

Spontaneous pneumomediastinum in COVID-19 patients. Case series

Spontaneous pneumomediastinum is defined as the presence of free air within the mediastinum without an apparent cause such as chest trauma. It is a benign, self-limiting condition that is conservatively treated. Clinical diagnosis is based on two symptoms: chest pain and dyspnea; and on a particular sign: subcutaneous emphysema. It has been reported in patients with influenza A (H1N1) and severe acute respiratory syndrome; however, it has been rarely observed in COVID-19 patients. In this work, we describe six male patients with COVID-19, aged between 27 and 82 years, who presented with spontaneous pneumomediastinum and subcutaneous emphysema; both conditions were completely resorbed with conservative management.

Spontaneous pneumomediastinum and COVID-19 pneumonia: Report of three cases with emphasis on CT imaging

Spontaneous pneumomediastinum is a rare complication of coronavirus disease 2019. The published literature consists mainly of case reports and small case series. There are still many questions regarding the pathogenesis, the prognostic significance and the implications on patient management. In our hospital, 3 coronavirus disease 2019 patients developed spontaneous pneumomediastinum: 1 on admission at the emergency department and the other 2 during hospitalization. In this study we describe their clinical course and computed tomography (CT) findings. All of them had severe disease according to the total severity score on admission CT. The management of pneumomediastinum was conservative and follow-up CT showed resolution in all patients. As the correlation between extension of parenchymal lung lesions and development of pneumomediastinum is still under investigation, we highlight the importance of reporting the severity score on chest CT in order to obtain more comparable results between different studies. Furthermore, in this tragic circumstance we also had the opportunity to familiarize ourselves with the otherwise uncommon occurrence of air along the bronchovascular sheaths (Macklin effect) and evaluate the ability of CT to detect it.

Pneumomediastinum in COVID-19 disease: Outcomes and relation to the Macklin effect

AIM

Pneumomediastinum (PM) is associated with several etiologies and mechanisms. Although it has been described more than 100 years ago, the literature is limited to small retrospective studies. This study aimed to follow patients with coronavirus disease (COVID-19) that developed PM during hospitalization and describe their clinical and radiological evolution.

METHODS

A prospective cohort was developed with patients with PM, excluding those with aerodigestive trauma, inside a hospital COVID-19 dedicated hospital. Clinical variables including onset of symptoms, hemodynamic instability, associated complications, the need of interventions, and disease course were all recorded. Also, radiological findings such as the presence of the Macklin effect, extension of lung involvement by COVID-19, and characteristics of the PM were analyzed.

RESULTS

Twenty-one patients with non-traumatic PM were followed, resulting in an overall incidence of 0.5% during the study period. Seven (33%) patients had associated pneumothorax and malignant/tension PM was observed in three (14%) cases. The Macklin effect could be found in 11 patients (52%) and the majority of them had more than 50% of lung involvement due to COVID-19. The mortality rate was 49%; however, no deaths were directly related to the PM.

CONCLUSIONS

PM incidence is probably increased in the severe acute respiratory syndrome caused by COVID-19, especially in those with greater involvement of the lungs, and the Macklin effect may be an important underlying mechanism of this complication. Usually, PM has a benign course, but complications like tension/malignant PM may occur requiring prompt detection and intervention.

Predictors of Pneumothorax/Pneumomediastinum in Mechanically Ventilated COVID-19 Patients

Objective

To determine the incidence, predictors, and outcome of pneumothorax (PNX)/pneumomediastinum (PMD) in coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS).

Design

Observational study.

Setting

Tertiary-care university hospital.

Participants

One hundred sixteen consecutive critically ill, invasively ventilated patients with COVID-19 ARDS.

Interventions

The authors collected demographic, mechanical ventilation, imaging, laboratory, and outcome data. Primary outcome was the incidence of PNX/PMD. Multiple logistic regression analyses were performed to identify predictors of PNX/PMD.

Measurements and Main Results

PNX/PMD occurred in a total of 28 patients (24.1%), with 22 patients developing PNX (19.0%) and 13 developing PMD (11.2%). Mean time to development of PNX/PMD was 14 ± 11 days from intubation. The authors found no significant difference in mechanical ventilation parameters between patients who developed PNX/PMD and those who did not. Mechanical ventilation parameters were within recommended limits for protective ventilation in both groups. Ninety-five percent of patients with PNX/PMD had the Macklin effect (linear collections of air contiguous to the bronchovascular sheaths) on a baseline computed tomography scan, and tended to have a higher lung involvement at intensive care unit (ICU) admission (Radiographic Assessment of Lung Edema score 32.2 ± 13.4 v 18.7 ± 9.8 in patients without PNX/PMD, p = 0.08). Time from symptom onset to intubation and time from total bilirubin on day two after ICU admission were the only independent predictors of PNX/PMD. Mortality was 60.7% in patients who developed PNX/PMD versus 38.6% in those who did not (p = 0.04).

Conclusion

PNX/PMD occurs frequently in COVID-19 patients with ARDS requiring mechanical ventilation, and is associated with increased mortality. Development of PNX/PMD seems to occur despite use of protective mechanical ventilation and has a radiologic predictor sign.

Fatal bilateral pneumothorax and generalized emphysema following contraindicated speaking-valve application

We report a case of a contraindicated attachment of a speaking valve to a tracheal tube with an inflated cuff, which rapidly resulted in the patient's death. The attached one-way valve allowed unrestrained inspiration through the tracheal tube but prevented physiological expiration. The increased pulmonary pressure resulted in alveolar rupture and replaced expiration with a steady release of air into the peribronchial sheaths and the mediastinum, resulting in what is commonly known as the Macklin effect. From the mediastinum, air inflated both pleural cavities, the peritoneum, and the subcutaneous tissue of the entire body. No gas was found in the blood vessels, the brain, the bones, or in the inner organs. The entire air volume was estimated by radiological segmentation to be more than 25 l. This implies continuous inspiration, while expiration turned into an aberrant pulmonary decompression by whole-body gas-enclosure. Death ultimately resulted from asphyxia following bilateral (tension) pneumothorax.

Anorexia nervosa with massive pulmonary air leak and extraordinary propagation

A rare case combining pneumothorax, pneumomediastinum, pneumopericardium, pneumoperitoneum, pneumorrhachis, air in retroperitoneum and extensive subcutaneous emphysema simultaneously in a severely anorectic male with BMI 9.2 (22.8 kg) and multiple vomitings is presented. This unusual condition was treated successfully with conservative medical approach in a specialized somatic unit for anorexia nervosa.

Scary gas: a spectrum of soft tissue gas encountered in the axial body (part II)

Ectopic gas in the mediastinum, subperitoneal abdomen, and superficial soft tissues is concerning and can be seen in the setting of trauma, iatrogenic injuries, infection, and inflammation. It can spread along different dissection pathways and may present remotely from the involved organ as described in part one. Recognition of ectopic gas on imaging and differentiating it from other causes of benign gas is very important as these conditions associated with ectopic gas can lead to rapid patient deterioration and usually require urgent surgery. In part two, the different causes of ectopic and benign gas in the torso are reviewed as well as the imaging features that can help to narrow the differential diagnosis.

Tension pneumopericardium in blunt thoracic trauma

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Tension pneumopericardium is a cause of shock in thoracic trauma.

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It should be regarded in hemodynamically unstable patients with blunt chest trauma.

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Immediate pericardium decompression may save the patient’s life.

Introduction

Pneumopericardium, defined as the presence of gas in the pericardial sac, is a rare condition caused mostly by trauma. Tension pneumopericardium is a cause of hemodynamic instability; hence, it consists in a life-threatening situation and should be regarded in blunt chest trauma.

Case report

A 51-year-old male was victim of a 4 m fall and burial. He was stable upon admission and presented a simple pneumopericardium and pneumomediastinum on CT. While being submitted to an upper digestive endoscopy he presented respiratory failure and had to be intubated, suddenly evolving to shock. He was promptly referred to the operating room; a pericardial window confirmed tension pneumopericardium and immediately hemodynamic stability was restored. A pericardial drain was placed and kept for 15 days. He was discharged at the 18th day post-trauma after a satisfactory recovery at the trauma ICU.

Discussion

Blunt thoracic trauma causes pneumopericardium by various mechanisms. Tension pneumopericardium is a possible outcome, probably related to positive-pressure ventilation. It leads to hemodynamic instability and requires immediate decompression and placement of a pericardial drain.

Case report]

BACKGROUND

Pneumomediastinum is the presence of free air around mediastinal structures, which may be spontaneous or secondary, and can occur in 10% of patients with blunt chest trauma, with the Macklin effect being its main pathophysiology.

CLINICAL CASE

A 21 year old male, hit by motor vehicle, with alvéolopalatal fracture and blunt chest trauma, who, 72 hrs after admission, shows subcutaneous emphysema in the anterior chest. A simple tomography of the chest and abdomen was performed, finding a pneumomediastinum, bilateral pulmonary contusions and pneumoperitoneum. Oesophageal, tracheobronchial or intra-abdominal viscera injuries were ruled out, establishing the cause of pneumomediastinum and pneumoperitoneum due to the Macklin effect. This required conservative management in intensive care unit, with a favourable clinical course and discharged after a 10 day hospital stay.

DISCUSSION

Macklin effect is caused by dissection of air medially along the bronchoalveolar sheath (interstitial emphysema), secondary to alveolar breakdown and extending into mediastinal and other anatomical structures (pneumoperitoneum). It has been documented in blunt trauma, as well as in acute asthma, positive pressure ventilation, or after Valsalva manoeuvres. The imaging method of choice is computed tomography, and its characteristic findings, interstitial emphysema adhering to a bronchus and pulmonary blood vessel.

CONCLUSIONS

In the presence of pneumomediastinum and pneumoperitoneum is necessary to rule out oesophageal and tracheobronchial injury before establishing the Macklin effect as its cause. The diagnosis is made with computed tomography and managed conservatively.

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

Spontaneous pneumomediastinum (SPM) is described as free air or gas located within the mediastinum that is not associated with any noticeable cause such as chest trauma. SPM has been associated with many conditions and triggers, including bronchial asthma, diabetic ketoacidosis, forceful straining during exercise, inhalation of drugs, as well as other activities associated with the Valsalva maneuver. The Macklin effect appears on thoracic computed tomography (CT) as linear collections of air contiguous to the bronchovascular sheaths. With the recent availability of multidetector-row CT, the Macklin effect has been seen in the clinical setting more frequently than expected. The aim of this review article is to describe the CT imaging spectrum of the Macklin effect in patients with SPM, focusing on the common appearance of the Macklin effect, pneumorrhachis, and persistent SPM with pneumatocele.

Diagnosis and treatment of patients with spontaneous pneumomediastinum. Respir Investig. 2014;52:36-40. [PMID: 24388369 DOI: 10.1016/j.resinv.2013.06.001]

BACKGROUND

Although many patients complaining of chest pain visit the emergency department, very few are diagnosed with spontaneous pneumomediastinum (SPM). We present the management of 20 patients with SPM.

METHODS

We retrospectively analyzed the clinical features, past history, chest X-rays (CXRs), 64-slice helical computed tomography (CT) images, and clinical course of 20 patients with SPM (19 men and 1 woman) who visited the emergency department of the Tokyo Metropolitan Bokutoh Hospital between 2005 and 2010.

RESULTS

SPM predominantly resulted from physical exertion during such activities as sports and weight lifting (8 patients). The most common complaint was chest pain (15 patients), followed by dysphagia (10 patients), and dyspnea (8 patients). Subcutaneous emphysema was detected in 9 patients. The mean body mass index of the patients was 20.8±1.4kg/m(2). Although CXR findings of pneumomediastinum were absent in 5 patients, CT showed findings of the Macklin effect in all patients-interstitial gas was observed in the perihilar area in all patients and in the peripheral lung area in 9 patients (45%). Ten patients were hospitalized. The others received ambulatory care in the form of analgesics without antibiotics. All patients fully recovered without complications.

CONCLUSIONS

Our results showed that 64-slice helical CT is more reliable than CXRs for diagnosing SPM. Moreover, some patients with SPM can be treated without hospitalization, thus decreasing medical expenses for these patients.