History
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.
Physical Examination
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).
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This chest radiograph (posteroanterior and lateral view) is from a 3-year-old girl with a history of prematurity, chronic lung disease, and asthma who presented with a viral pneumonitis and persistent cough. On the posteroanterior view, a pneumomediastinum (arrow) is noted. Also, extensive subcutaneous air is observed.
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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.
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On the lateral radiograph from the patient in Media file 2, anterior mediastinal air is observed. Left lower lobe atelectasis is also present. The child was asymptomatic and was discharged 2 days later.
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Chest radiographs in anteroposterior (AP) and lateral projections obtained in a 9-year-old girl with wheezing and pneumonitis. The arrows highlight the "spinnaker sail sign" in which free mediastinal air lifts the thymus off of the heart and major vessels.
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Subcutaneous emphysema and pneumothorax.
