Pneumomediastinum

Pneumomediastinum rarely leads to clinically significant complications. More commonly, the associated or precipitating condition underlying pneumomediastinum may be the cause of significant illness. Rarely, tension pneumomediastinum has been reported in which elevated mediastinal pressure leads to diminished cardiac output because of direct cardiac compression or reduced venous return. When extensive subcutaneous and mediastinal gas is present, airway compression may also occur. Jennings et al (2013) report this as a complication following blunt thoracic trauma.[2]

The generally accepted explanation for the development of pneumomediastinum is that free air tracks from ruptured alveoli along peribronchial vascular sheaths toward the hilum of the lung. From there, it extends proximally within the mediastinum.

The Macklin effect, first described in 1939, highlights the sequence of events in the development of pneumomediastinum as follows: (1) alveolar rupture, (2) air dissection along the bronchovascular sheath, and (3) free air reaching the mediastinum.

The dissection of free air may not be confined solely to the mediastinum. Zylak et al note that the mediastinum communicates with the submandibular space, the retropharyngeal space, and vascular sheaths within the neck.[3] In addition, 2 routes of communication with the retroperitoneum have been noted: via a tissue plane extending through the sternocostal attachment to the diaphragm, as well as periaortic and periesophageal fascial planes. As a result, air present within the mediastinum may dissect through these tissue planes, causing pneumopericardium, pneumothorax, subcutaneous emphysema, pneumoperitoneum, or pneumoretroperitoneum.

Carolan et al report a case of spontaneous pneumomediastinum associated with the presence of air within the cervical and thoracic spinal canal indicative of air dissection from the mediastinum, neck, and back through soft-tissue planes and the neural foramina into the spinal canal.[4] They suggest use of the term “spontaneous pneumorrhachis” for patients with this finding. Behr et al (2018) note the finding of pneumorrhachis in 5.8% of a series of 241 patients with pneumomediastinum.[5]   Pneumorrhachis was identified more frequently in patients in whom the distribution of air was seen in all three mediastinal compartments. Liu (2018) also notes that the presence of intraspinal air correlates with the severity and extent of spontaneous pneumomediastinum. Pneumorrhachis was also more common among subjects with spontaneous as opposed to secondary pneumomediastinum.[6]

In a study of 87 patients by Wong et al, the common causes of spontaneous pneumomediastinum included asthmatic exacerbation, infections (eg, pneumonia, lower respiratory tract infections), and choking.[7]  In a narrative literature review, Gasser et al (2017) identifies asthma as a co-morbidity in 22% of patients with spontaneous pneumomediastinum.  In this series, the most common triggering factors included bronchospasm (49%), cough (45%), vomiting (10%) and foreign body aspiration (8%).  The cause or associated trigger was "idiopathic" in 33%.[8]  

A large and diverse group of factors has been implicated in the development of spontaneous pneumomediastinum. Various respiratory maneuvers that have in common the development of high intrathoracic pressures may lead to pneumomediastinum. These include Valsalva maneuvers, coughing, vigorous crying, and forceful retching or vomiting.

Elevated pulmonary (alveolar) pressures

Numerous maneuvers that lead to elevated alveolar pressures may result in pneumomediastinum (see discussion of the Macklin effect in Pathophysiology).

Forceful coughing, crying, or shouting may elevate pressures. Jones et al[9]  report the development of spontaneous pneumomediastinum in a military training recruit after repeatedly shouting "Hooah!" during a motivational squad competition, highlighting that unique to the military training environment, vigorous shouting as a motivational stimulus can have barotraumatic consequences.

Vomiting, defecation, and Valsalva maneuver may elevate pulmonary alveolar pressures, as may illicit drug use, especially if associated with coughing.

Strenuous athletic activity, diving, flying, playing musical instruments, and childbirth are also potential risk factors. Sadarangani et al provide a case report of pneumomediastinum precipitated by weight lifting.[10]  Improper breathing technique during weight lifting may increase the intrathoracic pressure and the risk of pneumomediastinum. The authors note the importance of physicians and trainers who work with athletes to provide instructions regarding proper breathing techniques during weight lifting.

Spirometry has been associated with the development of pneumomediastinum in 3 individual case reports.

Respiratory illness

Obstructive lung disease (eg, asthma, bronchiolitis, foreign body aspiration, bronchopulmonary dysplasia), especially in intubated and mechanically ventilated patients, is a risk factor.

Respiratory tract infections, especially if associated with asthma, may predispose a patient to the development of a pneumomediastinum. Fearon et al and Vazquez et al report cases in which pneumomediastinum is associated with mycoplasma lower respiratory tract infection.[11, 12]  An association of severe spontaneous pneumomediastinum and laryngotracheitis in a young patient with asthma was reported by Lin et al, suggesting the need to consider spontaneous pneumomediastinum in the differential diagnosis of any patient presenting with cervical emphysema and signs of respiratory tract infection, especially in association with asthma.[13]

Hasegawa et al reported spontaneous pneumomediastinum complicating pneumonia in children infected with the 2009 pandemic influenza A (H1N1) virus.[14]

Spontaneous pneumomediastinum that is unrelated to positive pressure ventilation has been reported as a complication of severe COVID-19 pneumonia.[15, 16] Most cases resolve spontaneously with conservative management.

Foreign body aspiration has been reported in association with pneumomediastinum.

Organ injury

Penetrating or blunt injury to the thorax may cause air leak syndromes including pneumomediastinum. The etiology is thought to be related to the Macklin effect. Rezende-Neto et al reported that occult pneumomediastinum occurred in approximately 6% of all trauma patients with blunt chest injuries.[17]  Patients with pneumomediastinum were more severely injured than those without as indexed by higher injury severity scores (ISS). However, none of the patients with occult pneumomediastinum had aerodigestive tract injuries and follow up chest CT scans demonstrated complete resolution of the pneumomediastinum in all cases.

Tracheobronchial rupture, esophageal injury, or perforation of a hollow abdominal viscus may lead to free mediastinal air.

Miscellaneous medical conditions

Pneumomediastinum has been reported in association with convulsions, tooth extraction, and dermatomyositis.

United States statistics

The epidemiology of pneumomediastinum reflects that of the associated disease states, when present.

Spontaneous pneumomediastinum is an uncommon condition. A review by Chalumeau et al summarized the available literature.[18] Based on previous studies, they determined a prevalence of spontaneous pneumomediastinum ranging from 1 per 800 to 1 per 42,000 pediatric patients presenting to a hospital emergency department. Stack et al reported a 0.3% incidence of pneumomediastinum in association with asthma presenting to their institution over a 10-year period.[19] The mean age of affected patients was 11 years. No sex differences were observed in this cohort. Another study by Vianello et al that included 45 patients with severe acute asthma exacerbation found that 11.1% (five patients) were diagnosed with pneumomediastinum.[20]  

A study from Nashville, Tennessee, reported the frequency of extra-abdominal gas in a series of patients undergoing laparoscopic esophageal surgery. Forty-seven percent of patients (N = 45) had evidence of extra-abdominal air on chest radiography. Of these, 86% had a pneumomediastinum. Pneumomediastinum persisted at least 1 postoperative day in two thirds of these cases. However, no mortality or morbidity was attributable to the presence of pneumomediastinum.

In a series of patients with sepsis-induced acute respiratory distress syndrome (ARDS), air leaks of any type, excluding pneumothorax, occurred in 3.7% of patients.[21] Ventilator pressures and volumes delivered were not correlated with the development of air leak.

In a series of adult patients presenting with blunt chest trauma, as many as 10% had evidence of pneumomediastinum. A study by Muckart et al that included 389 patients with blunt thoracic trauma reported a minimal incidence (5.9% for pneumomediastinum) of pneumomediastinum or pneumopericardium following blunt thoracic trauma.[22]

International statistics

A study by Briassoulis et al from Athens, Greece, evaluating the frequency of air leaks in children receiving mechanical ventilation reported a prevalence of 27%.[23] However, they did not report the prevalence of specific types of air leak.

Esayag et al reported an Israeli series of 13 patients with spontaneous pneumomediastinum.[24] This group represented 1 in 41,600 referrals to the emergency room and 1 in 15,500 hospitalizations. The median age of the patients was 19 years (range 2–72 y). Males comprised 77% of this group.

A case series from the Children's Medical Center, China Medical University in Taiwan reported by Lee et al defined an incidence of spontaneous pneumomediastinum in children of 1:8,302 patient visits to the pediatric emergency department.[25] They observed a bimodal distribution, with cases occurring in children younger than 4 years old and in adolescents aged 15-18 years. Males outnumbered females by a ratio of 4:1.

Sex- and age-related demographics

In a series of pneumomediastinum occurring in persons with asthma, there was a very slight male predominance in the prevalence of spontaneous pneumomediastinum. Other series confirm this excess of male cases. Damore and Dayan reported 29 cases of pneumomediastinum over a 10-year period unrelated to trauma, intubation, or surgical procedures; 69% of patients were male.[26] Some have suggested that a body habitus favoring a tall thin build is an additional risk factor for the development of spontaneous pneumomediastinum. The mechanisms underlying this association are unclear. Traumatic pneumomediastinum is more common in males, reflecting the male predominance among those who experience trauma and accidents.

The peak prevalence of spontaneous pneumomediastinum is seen in the second to fourth decades of life. This presumably reflects involvement in activities that increase the risk for developing pneumomediastinum, such as diving or marked physical exertion (eg, athletic activities, weight lifting). Moreover, the force of an individual's cough, vomit, and Valsalva maneuvers (all of which may lead to pneumomediastinum) attenuates with age, accounting for the decline in the prevalence of pneumomediastinum with age.

The age distribution for pneumomediastinum occurring in conjunction with specific disease processes reflects the age profile of the particular disease.

Although recurrent pneumomediastinum is a risk, the pneumomediastinum is almost invariably benign, with morbidity or mortality principally attributable to the associated or precipitating condition.

Morbidity/mortality

The mortality and morbidity associated with pneumomediastinum are generally attributable to underlying disease states. Spontaneous pneumomediastinum is usually a self-limited condition that rarely produces significant or life-threatening symptoms.

The mortality rate associated with pneumomediastinum may be as high as 50-70% as seen in Boerhaave syndrome (esophageal rupture following vomiting). The development of air leak, according to Weg et al, is not associated with an increased mortality rate in patients with sepsis-induced ARDS.[21]  Other predisposing conditions associated with high mortality rates include trauma (blunt and penetrating, especially high velocity injury), asthma, and tracheobronchial perforation.

The most common morbidities attributable to pneumomediastinum are symptoms such as chest pain, voice change, and cough. Rarely, tension pneumomediastinum may result in decreased cardiac output. Laryngeal compression leading to stridor has been reported. Gas embolism has rarely been reported.

Complications

Associated air leaks

Other air leak syndromes (in particular, pneumothorax) may be observed in conjunction with pneumomediastinum.

Subcutaneous emphysema is commonly noted, although it is not usually associated with serious complications.

Tension pneumomediastinum

Although rare, tension pneumomediastinum may occur, leading to compression of the great veins, compromising venous return, which may result in hypotension and hypoxemia secondary to ventilation/perfusion mismatch.

Mediastinitis

Pneumomediastinum following massive vomiting may be associated with Boerhaave syndrome; developing mediastinitis is a risk.

Associated conditions

Complications may arise from associated conditions such as asthma, a foreign body, or drug ingestion.

Advise the patient to avoid high-risk activities. Instructions include the following:

• Avoid strenuous athletic activities, particularly those involving Valsalva maneuvers such as weight lifting.

• Avoid playing woodwind instruments.

• Avoid barotrauma from activities such as flying, parachuting, or scuba diving.

• Maintain good asthma control. Ensure that influenza and pertussis vaccinations are current.

• Avoid smoking and inhalation of illicit drugs.

For patient education resources, see the Lungs Center, as well as Emphysema and Chest Pain.

In Damore's series, the most common symptoms seen with pneumomediastinum (PM) were subcutaneous emphysema (76% of patients) and neck or chest pain (38% of patients).[26]   In a narrative literature review of 216 patients, Gasser et al (2017) note that chest pain (55%), neck pain or sore throat (53%) and dyspnea (41%) were the most frequently identified symptoms.[8]  

Chest pain

In spontaneous pneumomediastinum (SPM), pain is said to be a feature in 50-90% of cases.[27, 28] Typically, it is retrosternal in location and worsened by inspiratory maneuvers. The pain may radiate to the shoulders or back suggesting the possibility of myocardial infarction or pericarditis, under the appropriate clinical circumstances.

Chest pain was a presenting feature in 27% of persons with asthma and pneumomediastinum in one series. However, in a pediatric series of asthma patients presenting with chest pain (Majerus 2018), the chest x-ray yielded a positive finding, including pneumomediastinum in 11% of patients.[29]

Okada et al (2014) report a series of 20 patients with SPM, all of whom had evidence of PM on chest computed tomography (CT).[30] Symptoms reported by these patients included chest pain occurring in 75%, dysphagia in 50%, and dyspnea in 40%.

Dyspnea

Dyspnea may reflect associated illnesses such as asthma, a coexistent pneumothorax, or rarely a tension pneumomediastinum.

Fever

Low-grade fever may be present. Fever may occur following cytokine release that is associated with air leak. However, mediastinitis or infectious/inflammatory disorders should be included in the differential diagnosis when fever is present.

Dysphonia

Walsh-Kelly and Kelly reported a 14-year-old girl with pneumomediastinum whose only presenting symptom was dysphonia.[31]

Throat pain

Patients may present with symptoms of throat pain. In some cases, pneumomediastinum may follow relatively innocuous oropharyngeal trauma that presents as mouth or throat pain. In one series,[32] evaluating the head and neck manifestations of spontaneous pneumomediastinum, the primary initial symptoms were neck swelling, neck pain, and odynophagia.

Jaw pain

Jaw pain has occasionally been reported.

Miscellaneous

Dysphagia, neck swelling, and torticollis all have been reported in association with spontaneous pneumomediastinum.

Triggering factors

Bullaro suggests that triggering factors may be identified in 70-90% of patients with spontaneous pneumomediastinum.[33] Attempt to identify precipitating factors, such as the Valsalva maneuver, illicit drug ingestion, vigorous vomiting or cough, or activities that may lead to barotrauma (eg, scuba diving, flying). The forceful cough of asthma is one of the most common triggers of spontaneous pneumomediastinum in children and, for some, may be an initial presenting symptom or sign.

One report suggested an association between belching in a heavy drinker and the development of Boerhaave syndrome (esophageal rupture following vomiting). Patients with cyclical vomiting may also be at increased risk of developing pneumomediastinum.

Pneumomediastinum may be observed in pediatric patients (usually female) with anorexia nervosa. Hochlehnert et al note that starvation and malnutrition may predispose to structural changes within the lung interstitium, leading to the formation of bullae, emphysema, and bronchiectasis, which adds to the risk of spontaneous pneumomediastinum following vomiting.[34]

Hyperpnea in association with diabetic ketoacidosis may cause pneumomediastinum.[35]

Catamenial pneumomediastinum has been reported. A woman with endometriosis developed retrosternal chest pain at the time of menstruation and was found to have subcutaneous emphysema. A pneumomediastinum was noted on chest radiography. SPM has also been reported among mothers following labor and delivery.[36]

Drug history

In school-aged or adolescent patients, a comprehensive drug history should be taken, including a history of smoking and drinking (to elicit pneumomediastinum associated with vomiting). Ask the patient specifically about inhalation of illicit drugs, chemical compounds, or commercial aerosols.

A report from the Partnership For a Drug Free America notes that the practice of sniffing or "huffing" vapors from ordinary products like glue, spray paint, nail polish remover, and gasoline in order to get high is once again gaining popularity. The report notes that approximately 20% of US teenagers admit to getting high by inhaling common household products, with few teens understanding the dangers of this practice.

Huffing has been reported among elementary school–aged children. Parents may recognize signs of inhalant abuse, such as chemical odors on children's hands or clothes, spray cans or soaked rags in their rooms, and physical and behavioral signs, such as a dazed appearance, red or irritated eyes or nose, irritability, or problems at school.

A parents' guide is published on the Partnership for a Drug Free America's Web site.

The pulmonary toxicities of inhalant abuse are generally due to asphyxia or direct chemical pneumonitis. However, air leak is possible. In a series that included adults, Perna et al reported the most common predisposing factor was consumption of cocaine seen in 55%.[37] The pattern of cocaine use was that of occasional use (as opposed to regular or long-term abuse), typically occurring a few hours before presenting symptoms.

Subcutaneous air

Although not pathognomic of pneumomediastinum, the presence of subcutaneous crepitations suggests free air is present within the thoracic cavity.

Stack and Caputo reported finding subcutaneous emphysema in 73% of patients presenting with asthma subsequently found to have pneumomediastinum.[19]  The positive predictive value of this sign for pneumomediastinum in their series was 100%.

The Hamman sign

This sign, which some authors have suggested is pathognomic of pneumomediastinum, consists of precordial systolic crepitations and diminution of heart sounds. Sahni et al (2013) in their meta-analysis estimate that this sign is detected in only 20% of patients with SPM.[38]

Damore and Dayan reported a prevalence of 10% in his series.[26]

Associated pneumothorax

The presence of a pneumothorax should be clinically suspected in individuals with respiratory distress, asymmetry of breath sounds, and hypoxemia. Banki et al (2013) report that pneumothorax was identified in 14% of their patients with SPM.[39]

Other diseases

Associated conditions that may predispose to pneumomediastinum, particularly asthma, should be sought.

Oxygen saturation

Pulse oximetry is mandatory in all children with suspected pneumomediastinum.

In a series of children with asthma presenting to an emergency department, those with pneumomediastinum had a significant difference in oxyhemoglobin saturation (90% vs 94% of those without pneumomediastinum, P = 0.03).

The following studies are indicated in suspected cases of pneumomediastinum (PM):

ABG

ABG should be checked in individuals presenting with respiratory distress.

Depending on the severity of the underlying respiratory compromise, the blood gas may be normal or may reveal hypoxia, hypocarbia, or hypercarbia.

Cardiac enzymes

Evidence of myocardial infarction should be sought in individuals with chest pain of unclear etiology. Myocardial infarction is very rare in children. However, it has been seen in patients with the coronary vasculitis of Kawasaki syndrome and with congenital coronary artery anomalies.

Toxicology

Blood or urine should be tested for the presence of illicit drugs when indicated by history or physical examination.

Chest radiography

Chest radiography usually (although not invariably) reveals a pneumomediastinum. Chest radiography reveals air within the mediastinal space. Coexisting disease (eg, pneumothorax, pneumoperitoneum, pneumoretroperitoneum of pneumopericardium) may also be evident.

Radiolucent streaks representing free air may be observed tracking along the margins of the heart, within the retrosternal space, or surrounding the trachea. Typical features of pneumomediastinum seen on chest radiography are caused by air outlining normal anatomic structures as it tracks from the mediastinum producing the thymic sail sign, "ring around the artery" sign, tubular artery sign, double bronchial wall sign, continuous diaphragm sign, and the extrapleural sign (see the image below, which is a chest radiograph demonstrating pneumomediastinum as well as subcutaneous emphysema in a female with asthma intubated for respiratory failure).

The chest radiograph is taken from an adolescent girl with status asthmaticus who was intubated for respiratory failure. A rim of air consistent with a pneumomediastinum may be observed along the upper left border of the heart. Subcutaneous air is observed in the soft tissues of the neck. She required very high peak inspiratory pressures (50 cm H2), which in conjunction with marked air trapping due to her asthma, caused alveolar rupture, allowing air to track to the mediastinum. A central venous line was placed.

Radiographic signs are as follows:

• Ring around the artery (tubular artery): A radiolucent area is observed surrounding the right pulmonary artery when viewed on a lateral chest radiograph.

• Thymic sail sign: In infants with pneumomediastinum, the thymic lobes are shifted upwards resembling a full sail. This has been referred to the "spinnaker-sail" sign.[40, 41]

• Continuous diaphragm sign: Free air is present between the pericardium and diaphragm, causing the central parts of the diaphragm to become apparent.

Wong et al (2013) report that lateral neck soft-tissue radiographs demonstrated abnormal air collections in 9 of 10 patients who had normal chest radiographs.[7] They suggest that the addition of lateral neck radiographs may help to identify some patients with SPM in whom chest radiographs are normal.

Chest CT scanning

Chest CT scanning has 2 major roles in the diagnosis of pneumomediastinum.

Chest CT scanning may be used to diagnose pneumomediastinum not visualized on chest radiography. A study from Japan describes the use of chest CT scanning in diagnosing small pneumomediastinum not visible on chest radiography. In a series of 33 patients diagnosed with spontaneous pneumomediastinum (SPM) on the basis of clinical presentation and/or chest radiography findings, chest CT scanning revealed pneumomediastinum in 3 patients in whom the chest radiography findings were unremarkable. The authors concluded that chest radiography alone may result in a missed diagnosis in 10% of patients presenting with pneumomediastinum. In a series of 20 patients with SPM and evidence of mediastinal air collections on chest CT, chest radiographs were interpreted as normal in 20% (Okada 2014).

Ho et al[42] report a series comparing the radiologic findings of patients diagnosed with spontaneous pneumomediastinum to those with secondary pneumomediastinum associated with a central airways defect, esophageal rupture, or recent intervention in the airway or esophagus. They note that on multidetector CT (MDCT), spontaneous pneumomediastinum patients were more likely to have air in the anterior mediastinum (97% vs 61%, P< .001) and pulmonary interstitial emphysema (57% vs 4%, P< .001) and less likely to show subdiaphragmatic air (0% vs 32%, P< .001), pleural effusions (9% vs 61%, P< .001), and acute pulmonary airspace opacities (14% vs 50%, P = .003) when compared with patients with secondary pneumomediastinum.

CT scanning may provide additional diagnostic information regarding the presence of coexisting illness, such as perforated esophagus. Dissanaike et al noted that major injuries to the aerodigestive tract were readily identified on chest CT scans performed in adult patients with blunt trauma and pneumomediastinum.[43]

A study by Lee et al characterized CT findings associated with mortality in patients with pneumomediastinum due to blunt trauma. The study found that pneumomediastinum is uncommon in patients with injury from blunt trauma, however, CT findings of posterior pneumomediastinum, air in all mediastinal compartments, and concurrent hemothorax are associated with increased mortality.[44]

Contrast radiography

Contrast studies have been recommended when esophageal perforation is suspected in some patients with PM.

Wu et al (2013) compared chest CT to contrast fluoroscopic esophagogram among patients with pneumomediastinum evident on CT who were referred for an emergent contrast study.[45] A positive result for esophageal perforation on CT was defined as evidence of esophageal injury or periesophageal infiltration that coexisted with periesophageal air. A positive fluoroscopic study result was defined as oral contrast medium leakage from the esophagus. The sensitivity and negative predictive value (NPV) were 100% for CT compared with fluoroscopic contrast esophagogram. Thus, the sensitivity and NPV of CT were either superior or equal to those of fluoroscopic esophagography for identifying esophageal perforation. These study results suggest that contrast esophagograms are unnecessary in patients with pneumomediastinum when CT is negative for esophageal perforation.

MRI

The routine use of MRI in the diagnostic evaluation of pneumomediastinum has not been reported. However, Castellote et al reports the sensitivity of MRI in detection of free air as well as other forms of intrathoracic pathology.[46]

Ultrasonography

Megremis et al details the use of ultrasonography in the detection of pneumomediastinum.[47]

Spirometry

Spirometry or measurements of peak expiratory flow should not be undertaken in patients with pneumomediastinum because the increased alveolar pressures may further exacerbate the air leak.

Electrocardiography

An ECG may be performed to evaluate for myocardial infarction, pericarditis, and myocarditis. Decreased voltage, ST segment depression, and nonspecific T-wave changes may be noted as indications of these potential disease processes.

Diagnostic or therapeutic procedures are generally not necessary. Placement of a chest tube should not be attempted unless an accompanying symptomatic pneumothorax is present.

Bronchoscopy is indicated if a tracheobronchial perforation is suspected, which may occasionally be observed following blunt chest trauma. Neal et al observed that pneumomediastinum after blunt trauma in clinically stable children is rarely associated with significant underlying injury to the tracheobronchial tree.[48] In addition to trauma indications, bronchoscopy may assist with localization and removal of foreign bodies as well as the evaluation of endobronchial lesions that may occur in association with pneumomediastinum.[49]

Haam et al report a series in which all patients with spontaneous pneumomediastinum undergoing contrast studies of the esophagus or esophagoscopy had normal studies.[50] These authors suggest that these studies are indicated only if an esophageal perforation is suspected or signs of mediastinitis are present.

Medical therapy depends on the clinical status of the patient. In general, most children with pneumomediastinum (PM) are asymptomatic, and the natural course is for the pneumomediastinum to spontaneously resolve.

Mechanical ventilation

Although mechanical ventilation (MV) may cause air leaks, including pneumomediastinum, continuing the MV and even escalating respiratory support may be necessary depending on the severity of the underlying respiratory distress and the degree of compromise caused by the air leak. Principle objectives include the use of the lowest pressures or tidal volumes necessary to achieve satisfactory carbon dioxide removal and oxygenation. Permissive hypercapnia, a ventilatory strategy that is based on maintaining adequate oxygenation and blood pH while allowing high partial pressure of carbon dioxide, allows for ventilatory support while minimizing barotrauma.

Case reports have described the successful use of high-frequency oscillatory ventilation (HFOV) in a child with acute respiratory distress syndrome (ARDS) and pneumomediastinum.

Asynchronous independent lung ventilation has been reported as a therapy for pneumomediastinum.

Nitrogen washout with inhalation of 100% oxygen has been suggested as a possible therapy for pneumomediastinum. The actual indications for this procedure are unclear.

Adequate analgesia is necessary in children with pain.

Surgical intervention has rarely been described in pneumomediastinum. Its use is reserved for pneumomediastinum leading to marked cardiorespiratory compromise or circumstances of defined esophageal or tracheal tear. However, Cunningham et al (2013) present case outcomes in 2 pediatric patients with tracheal injury managed conservatively, suggesting that this may be a treatment option in some cases.[51]

The use of mediastinoscopy in alleviating life-threatening pneumomediastinum has been reported in a small number of cases.

Percutaneous placement of mediastinal drainage tubes has been reported. Chau et al describe percutaneous decompression of tension pneumomediastinum under fluoroscopic guidance using a drainage catheter and Heimlich valve in a 2-year-old girl with dermatomyositis and lung involvement.[52] CT-guided placement may also be considered.

Diet

No special diet is indicated.

Activity

Patients should avoid strenuous physical activity until resolution of the pneumomediastinum has occurred.

No medical therapy is indicated. Associated conditions (eg, asthma, gastroesophageal reflux disease [GERD]) should be aggressively treated.

The patient should avoid risk factors associated with the development of pneumomediastinum. However, published evidence to support the following guidelines is sparse, and the following recommendations are in large part drawn from those relating to pneumothorax.

Physical activities associated with the development of pneumomediastinum (eg, weight lifting, scuba diving, playing wind instruments) should be minimized. Indeed, extrapolating from the data relating to air leaks and scuba diving, a history of pneumomediastinum should be considered an absolute contraindication to diving. The authors suggest abstaining from other activities listed above for a minimum period of 6 months. If pneumomediastinum recurs, avoidance of these activities permanently would be advisable.

Medical conditions associated with the development of pneumomediastinum should be treated aggressively. These include asthma and recurrent vomiting (eg, from gastroesophageal reflux disease [GERD], chemotherapy, cyclic vomiting, bulimia).[53]

Pneumomediastinum has been reported in association with childbirth (vaginal delivery).

Children at risk for pneumomediastinum or with a history of developing pneumomediastinum should be fully vaccinated, including vaccinations for pertussis and influenza.

A retrospective study characterized the outcomes of pediatric spontaneous pneumomediastinum and proposed a management pathway. In a series of 96 pediatric patients, it was noted that 92% of patients with PM were hospitalized. Length of stay for non-ICU patients was 1 day, and 3 days for ICU admissions. Follow-up imaging was obtained in 81% of patients but did not alter management decision-making. The study concluded that spontaneous pneumomediastinum without associated comorbidities can be managed with expectant outpatient observation without further imaging. Children with asthma should be treated independent of spontaneous pneumomediastinum.[54]

Patients should be closely monitored (clinically and with pulse oximetry or cardiorespiratory monitors) to anticipate development of more serious complications associated with pneumomediastinum (PM), such as tension pneumomediastinum, pneumothorax, or pneumopericardium. The patient should avoid strenuous physical activity; forced expiratory maneuvers such as spirometry or pulmonary function testing should also be avoided. If esophageal perforation has occurred, the risk of developing mediastinitis is very high. These patients should be observed very closely for evolving fever and signs of worsening respiratory distress or systemic sepsis.

Esophageal perforation, with the attendant risk of developing mediastinitis, may require treatment with broad-spectrum antibiotics.

No specific medical therapy is indicated for the prevention or treatment of pneumomediastinum. As noted above, associated conditions should be treated aggressively.

Those with a history of pneumomediastinum may benefit from antitussives during coughing spells.

Intensive care

Patients with severe respiratory distress, increasing oxygen requirements, other air leak syndromes, or signs of cardiovascular compromise may require transfer to a pediatric intensive care unit for further monitoring and management.

Pediatric tertiary care

If the patient has cardiorespiratory compromise or a serious condition associated with a pneumomediastinum (eg, esophageal perforation), transfer to a pediatric tertiary care facility may be necessary.

Avoidance of high-risk behavior

High-risk behavior includes strenuous athletic activities, scuba diving, weight lifting, and playing wind instruments.

Paroxysmal coughing, screaming, and crying may all result in pneumomediastinum.

Inhalation of both legal drugs (cigarettes) and illicit drugs (eg, cocaine, marijuana) should be avoided.