A 27-Year-Old Woman with an Exacerbation of Chronic Asthma Due to Influenza A Presenting with Pneumomediastinum, Retropharyngeal Emphysema, and Subcutaneous Emphysema

Background

Spontaneous pneumomediastinum is defined by the presence of free air in the mediastinum that is not preceded by surgery, thoracic trauma, or any medical procedure [1]. The incidence of spontaneous mediastinum is increased with the presence of many predisposing factors, including, but not limited to, intrinsic lung and airway diseases (asthma, chronic obstructive lung disease, interstitial lung disease, bronchiectasis), smoking, recreational drug abuse (cocaine, marijuana, methamphetamine), and inhalation of irritants [2]. Spontaneous pneumomediastinum can also be triggered by certain precipitating factors that increase intrathoracic pressure, such as excessive vomiting, excessive coughing, acute asthma exacerbation, upper airway infections, strenuous physical exercise, labor, and forceful sneezing/inhalation [2].

Respiratory viral infections are associated with approximately 80% of acute asthma exacerbation episodes [3]. In our patient, influenza A infection was most likely the cause for acute asthma exacerbation, ultimately leading to the unique presentation of pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema.

Influenza A virus can be classified into different subtypes according to the combination of hemagglutinin (H) and neuraminidase (N) proteins that are expressed on the surface of the virus [4]. In our case, influenza A virus was detected by rapid molecular assay, which is highly sensitive and specific and can differentiate between influenza A and B; however, it cannot differentiate between influenza A subtypes as can a conventional molecular test [4].

Associated complications with pneumomediastinum include subcutaneous emphysema and retropharyngeal emphysema, which means the presence of free air within the subcutaneous tissues and retropharyngeal space, respectively. Clinical symptoms vary, depending on the involved confined space, from mild throat pain to acute airway obstruction [1].

Fortunately, in most cases, it follows a relatively benign clinical course with resolution of the symptoms with supportive measures. However, in rare cases, severe complications, including acute respiratory distress that requires intubation, pneumothorax, tension pneumomediastinum, and tension pneumopericardium, have been reported in the literature [5]. Herein, we report a 27-year-old patient with acute exacerbation of chronic asthma caused by influenza A infection who presented with spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema.

Case Report

A 27-year-old woman with a past medical history of chronic asthma presented to the Emergency Department (ED) with chest pain and shortness of breath of a 2-day duration. Her last asthma exacerbation was 3 years earlier, which was treated with prednisone and albuterol inhaler. Since that episode, she did not experience asthma symptoms or require the use of her albuterol inhaler. Additionally, she was never intubated or hospitalized due to her asthma. She was an active smoker of a half a pack daily and started smoking 8 years ago, equating to a 4-pack-year history. She had not been vaccinated for influenza or COVID-19. She described her chest pain as tightness that worsened with deep inhalation. She also reported a productive cough, with yellow sputum, subjective fever, fatigue, myalgia, nausea with 1 episode of nonbilious, nonbloody vomiting, neck fullness/swelling, throat tightness with pressure, and a sensation of bubbles she could hear and feel in her chest and neck. She noted that this exacerbation was different and out of proportion compared with her previous asthmatic attacks, and because of that she presented to the ED.

Her initial vital signs upon arrival revealed a respiratory rate of 22 breaths/min, heart rate of 106 beats/min, blood pressure of 116/77 mmHg, afebrile temperature of 36.5°C, and oxygen saturation of 94% on room air. On physical examination, she was found to have palpable crepitus of the neck, diffuse wheezes with prolonged expiratory phase in all lung fields, and a positive Hamman sign on cardiac auscultation. Chest radiograph on admission showed a frank pneumomediastinum, with gas accumulation outlining the thoracic aorta as well as extension into the superior mediastinal region and lower cervical region bilaterally, left greater than right, without presence of pneumothorax (Figure 1). She was admitted for observation, and a computed tomography scan of the chest and neck showed extensive pneumomediastinum with subcutaneous emphysema within the soft tissues of the neck, retropharyngeal emphysema, pneumopericardium, and presence of the air within the spinal canal (Figures 2–5). The patient tested positive for influenza A on a rapid influenza molecular assay.

During the hospitalization, she was treated with intravenous methylprednisolone, ipratropium bromide/albuterol inhalations, and supplemental oxygen therapy, in addition to oseltamivir for influenza A treatment. Spirometry was not performed during this hospital stay. After 3 days, her symptoms improved significantly, and a chest radiograph showed significant improvement; she was discharged on the third day, with close follow-up with the pulmonary clinic.

Discussion

In this case report, we present a unique and rare synchronous presentation of pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema in a 27-year-old female patient who presented with acute exacerbation of well-controlled asthma caused by influenza A infection. This case highlights the need for additional caution in patients presenting with asthma exacerbation caused by respiratory viral infections displaying signs or symptoms of suspected extra-alveolar air.

Spontaneous pneumomediastinum is an uncommon clinical finding that has been reported to be more prevalent among a younger population. The incidence rate of spontaneous pneumomediastinum is 1 in 25 000 between the ages of 5 and 34 years, with young male patients accounting for 75% of the cases [6].

The spontaneous pneumomediastinum was first described by Hamman in 1939, when he identified subcutaneous emphysema in a postpartum patient [7]. The pathophysiology was delineated by Macklin in 1944, in his experimental animal model; his work showed that a sudden rise in intra-alveolar pressure causes alveolar damage and rupture, with the leakage and the migration of air from alveolar spaces toward the hilum and mediastinum alongside the pulmonary vasculature. Once the air reaches the mediastinum, it travels along the tissue planes and can reach the face, neck, retropharyngeal, retroperitoneal, and even epidural area [5]. In our case, the air leaked from the ruptured alveoli into mediastinal, sub-cutaneous structures in the neck, retropharyngeal areas, and the spinal canal at the thoracic level, causing spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema.

The most common presenting symptom is chest pain, which occurred in 75% of cases, followed by shortness of breath (49%), cough (36%), and neck pain (36%). Other less common symptoms include dysphagia, odynophagia, lightheadedness, weakness, dysphonia, and back pain [8]. On clinical examination, subcutaneous emphysema was present in 58% of cases, according to the systemic review of 210 patients with spontaneous pneumomediastinum [8]. However, the Hamman sign, which is a substernal crunching sound synchronous with heart systole and heard over the precordium, was observed in 18% of patients with spontaneous pneumomediastinum [8].

Spontaneous pneumomediastinum associated with asthma exacerbation and respiratory viral infections has been reported in the literature. In 2019, Okafor et al described a 22-year-old patient with a past medical history of asthma who presented with asthma exacerbation, with negative influenza and respiratory syncytial virus on a polymerase chain reaction test, and was found to have extensive spontaneous pneumomediastinum that extended into the neck, the pericardium, around the esophagus, and into the spinal canal [9]. In 2020, Khan et al described a 23-year-old asthmatic patient who developed spontaneous pneumomediastinum secondary to asthma exacerbation in the setting of rhinovirus infection; his pneumomediastinum extended into his neck and retropharyngeal space [10]. Both cases showed improvement with supportive measures only [9,10]. In the present case, we describe a 27-year-old female asthmatic patient who presented with acute respiratory distress secondary to asthma exacerbation caused by influenza A infection that progressed to spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema, which resolved with supportive care and treatment of asthma.

Retropharyngeal emphysema is a rare complication associated with spontaneous pneumomediastinum. It has been previously described as a rare complication of a dental procedure [11]. However, the accumulating air in the mediastinum can leak into the retropharyngeal area, causing retropharyngeal emphysema. In 2004, Smith and Hsu described 4 cases of retropharyngeal emphysema secondary to spontaneous pneumomediastinum that were resolved with supportive measures [12]. However, retropharyngeal emphysema is not necessarily a benign condition, as patients can develop more significant airway obstruction. Lee et al described a 12-year-old asthmatic patient that presented with signs of acute airway obstruction secondary to spontaneous retropharyngeal emphysema and pneumomediastinum [13]. Skogvoll et al described a previously healthy 2.5-year-old child who developed acute airway obstruction secondary to retropharyngeal emphysema associated with rhinovirus infection that led to respiratory failure and intubation [14]. Cohn et al described a 13-year-old asthmatic patient who required intubation due to airway obstruction secondary to spontaneous pneumomediastinum with retropharyngeal emphysema [15].

To the best of our knowledge, only 1 case in the literature has reported spontaneous pneumomediastinum leading to retropharyngeal emphysema secondary to an acute asthma exacerbation triggered by influenza A infection. Niehaus et al described a 27-year-old woman with poorly controlled asthma who presented in respiratory distress secondary to massive pneumomediastinum and retropharyngeal emphysema as a rare complication of acute asthma exacerbation secondary to influenza A infection [16]. In the present case, we describe a 27-year- old female patient with well-controlled asthma who presented with chest pain, shortness of breath, and throat pressure and was found to have spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema secondary to acute asthma exacerbation in the setting of influenza A infection. Our case demonstrates a rare complication of a combination of 2 common conditions, and the patient improved significantly with supportive measures.

Other serious complications of spontaneous pneumomediastinum are secondary pneumothorax, tension pneumomediastinum, and tension pneumopericardium. Leakage of air into the pleural cavity can lead to the formation of subpleural bullae; the rupture of these bullae causes secondary pneumothorax [5]. Additionally, accumulation of the air and pressure in the pleural cavity can lead to compression of adjacent intrathoracic structures, causing tension pneumomediastinum or tension pneumopericardium [17].

Spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema diagnosis can first be confirmed by chest radiograph. On routine chest radiographs, lucent streaks or bubbles of gas that outline the mediastinal structures, elevate the mediastinal pleura, and extend into the chest wall or the neck can be visualized [18]. Lateral neck radiograph is more sensitive than the routine posteroanterior chest films (sensitivity 95.2% vs 89.1%) and, therefore, should be performed for symptomatic patients in whom pneumomediastinum is suggested [18]. Computed tomography is superior in detecting pneumomediastinum, subcutaneous emphysema, retropharyngeal emphysema, tracheal or esophageal injury, and lung disease; however, it is not indicated in the general evaluation of spontaneous pneumomediastinum in patients without clinical evidence of underlying lung disease [18].

Spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema usually follow a benign course, and the management in most cases is conservative. Most patients admitted to hospital are treated with rest, analgesia, bronchodilators, and oxygen therapy, and spontaneous resolution is usually achieved in 2 to 7 days. The mechanism of pure oxygen therapy is by increasing the diffusion pressure of nitrogen in the interstitium, which promotes the rapid absorption of free air [8]. In the present case, the patient was treated with methylprednisolone and ipratropium bromide/albuterol inhalations for asthma control and oseltamivir for influenza A treatment. Her symptoms were resolved with this treatment and she was discharged after 3 days, with close follow-up.

Conclusions

We report a case of an adult with well-controlled asthma presenting with spontaneous pneumomediastinum, subcutaneous emphysema, and retropharyngeal emphysema as a complication of acute exacerbation of chronic asthma secondary to influenza A, demonstrating a rare complication of 2 common conditions. Although complications are associated with relatively benign clinical courses, severe complications have been reported in the literature. This case increases the awareness of these complications and highlights the importance of considering them in any young asthmatic patient presenting with acute asthma exacerbation, especially in the setting of respiratory viral infections, and showing signs of suspected extra-alveolar air or dyspnea not improving with medical therapy.