Retroperitoneal fibrosis

Treatment With High-Concentration Oxygen

We present a case of persistent spontaneous pneumomediastinum precipitated by an upper respiratory infection in a patient with interstitial fibrosis associated with rheumatoid arthritis who was receiving chronic corticosteroid treatment. The persistent nature of the mediastinal emphysema over 2 months eventually required treatment with high concentrations of inhaled oxygen that resulted in rapid resolution of the pneumomediastinum without recurrence over 6 months of follow-up. This case, along with others in the medical literature, emphasizes the need for early use of high-concentration inhaled oxygen in the treatment of pneumomediastinum in high-risk patients, such as those with connective tissue disorders.

(CHEST 2000; 117:1809-1813)

Key words: oxygen therapy, pneumothorax; pulmonary fibrosis; rheumatoid arthritis; spontaneous pneumomediastinum

Spontaneous pneumomediastinum is an uncommon disorder that is usually benign and self-limited. We recently observed a patient with rheumatoid lung disease who had a persistent, symptomatic pneumomediastinum that resolved completely with the use of high concentrations of inhaled oxygen. We report this case and discuss the pathophysiology of this disorder.

CASE REPORT

The patient is a 69-year-old African-American woman who was referred for evaluation and treatment of persistent pneumomediastinum. She had a 1-year history of rheumatoid arthritis, with pulmonary fibrosis on chest radiograph. Two months prior to evaluation, she developed an upper respiratory infection with a dry cough. Approximately 2 weeks later, the patient developed the sudden onset of swelling of the right neck and face, causing complete closure of the right eye. Her voice became hoarse, leaving her unable to sing. She had mild worsening of her baseline dyspnea. A chest radiograph showed mediastinal and subcutaneous emphysema and interstitial scarring (Fig 1). She was treated conservatively with cough suppressants and was observed with repeated chest radiographs that showed slight improvement over 4 weeks. A short-term increase in prednisone was prescribed for mild worsening of shortness of breath. When her condition did not resolve, she was admitted to the hospital for further evaluation. A chest CT scan confirmed the presence of pneumomediastinum (Fig 2, 3) and a small pneumothorax. A barium swallow did not show esophageal perforation or other abnormalities. She underwent bronchoscopy that was normal, except for the presence of two small mucosal plaques that showed nonspecific inflammation on biopsy. Culture results from the bronchoscopy were negative. A purified protein derivative skin test was also negative. Over the next month, she had waxing and waning swelling of her face, neck, and chest, and a chronic, persistent cough with scant sputum production. After 2 months of nonresolving subcutaneous emphysema, she was referred to the authors for further management. At that time, she denied any shortness of breath, difficulty swallowing, or chest pain. Her most troublesome symptoms were facial swelling, including the right eyelid, such that she was unable to see with that eye, and dysphonia.

[Figures 1-3 ILLUSTRATION OMITTED]

Her medical history was remarkable for rheumatoid arthritis with pulmonary fibrosis documented on a chest radiograph for 1 year. She also had a history of paroxysmal atrial fibrillation and hypertension. Her medications included prednisone, 7.5 mg/d (average dosage over the past year was 10 mg/d). She was also taking hydrochlorothiazide, reserpine, and potassium chloride for hypertension. Her family history revealed that her father died of tuberculosis and a son died of lung cancer. She was a lifelong nonsmoker and denied the use of alcohol or illicit drugs.

On physical examination, she was in no acute distress. Her vital signs were as follows: temperature, 36.6 [degrees] C (97.8 [degrees] F); pulse, 125 beats/min; respiratory rate, 20 breaths/min; BP, 152/100 mm Hg; and arterial oxygen saturation by pulse oximetry, 94% on room air. The peak expiratory flow rate was 250 L/min. Positive physical findings included swelling and crepitus over the face, neck, chest, and right eye. She was unable to open her right eye because of the subcutaneous emphysema. The chest examination was notable for bilateral inspiratory and expiratory crackles at the bases and a positive mediastinal crunch (Hamman's sign). Cardiac examination revealed tachycardia without murmurs, rubs, or gallops. The abdomen was soft and nondistended with normal bowel sounds and no hepatosplenomegaly. The extremities showed stigmata of rheumatoid arthritis with symmetrical swelling of the proximal interphalangeal joints and limited range of motion and swelling of the metacarpal phalangeal joints bilaterally. Chest radiographs showed an increase in bibasilar interstitial markings and subcutaneous emphysema that was present since the onset of the patient's illness. A pneumothorax was not seen on these examinations. A chest CT examination from I month prior (Fig 2, 3) showed a large pneumomediastinum and a small right loculated pneumothorax. There was some irregular pleural thickening and an increase in interstitial markings in the right lung greater than in the left lung.

The patient was given a prescription for 100% oxygen by nonrebreathing face mask, which she was instructed to use 12 h/d at home over the next 2 weeks. After approximately 7 days, the subcutaneous emphysema had completely resolved and the patient's voice returned to normal. The patient used the oxygen for 3 additional days and then discontinued the treatment. Over 6 months following this treatment, she has had no recurrence of her subcutaneous emphysema.

DISCUSSION

Pneumomediastinum was first recognized as a medical entity by Laennec who reported it as a consequence of trauma in 1819.[1] Spontaneous pneumomediastinum was described for the first time in the Sewall lecture in 1939 by Louis Hamman.[2] The unmistakable sign that bears Hamman's name is characterized by a "curious loud bubbling, crackling sound in synchrony with the heart beat." In 1944, the link between the clinical entity and its underlying pathophysiology was surmised by Macklin and Macklin.[3] From an elegant series of laboratory studies, they concluded that spontaneous pneumomediastinum was the result of barotrauma, where disruption of alveolar structures led to dissection of air up the bronchovascular sheath into the superficial cervical and retroperitoneal spaces. From this and other studies, they correctly conjectured that the pressure surrounding the bronchovascular sheaths is lower than alveolar pressure, and that the difference between alveolar and the peribronchovascular pressure increases with increasing lung volume.[4] This theory was very nicely demonstrated in a 1996 case report[5] of a woman undergoing partial liquid ventilation who subsequently developed barotrauma. The radiopaque perfluorocarbon that leaked from the alveoli was visualized tracking along the same anatomic pathway described by Macklin and Macklin.[3] The CT scan on our patient also clearly demonstrates the distribution of air along these pathways (Fig 2, 3).

Spontaneous pneumomediastinum is an uncommon disorder representing between 1 in 12,000 to 1 in 30,000 hospital admissions.[6,7] The diagnosis generally implies the absence of other causes of air in the mediastinum, such as that caused by gas-producing organisms or rupture of the oropharynx or esophagus. Two case series in the literature identify 42 cases.[6,8] The typical patient is a young male adult.[6,8] Maneuvers that usually precede spontaneous pneumomediastinum are those that involve an increase in lung volume followed by an dramatic increase in pleural pressure, such as coughing, sneezing, vomiting, or parturition.[9,10] Spontaneous pneumomediastinum has also been described in association with the use of illicit drugs such as marijuana or crack cocaine, where the inhalational maneuver is a total lung capacity inhalation followed by a Valsalva maneuver.[9-12] We speculate that cocaine inhalation may be particularly prone to cause spontaneous mediastinum because the constriction of the pulmonary blood vessels would further lower the pressure in the bronchovascular bundle. Other causes of spontaneous pneumomediastinum include diabetic ketoacidosis, which causes hyperpnea and vomiting; asthma, which causes coughing and hyperinflation; and vigorous athletic activity.[13-15] Unusual causes of spontaneous pneumomediastinum include paraquat intoxication and trombone playing.[16,17] In the current case, we attribute the spontaneous pneumomediastinum to the patient's cough, which was the result of a minor upper respiratory infection.

The most common presenting symptoms include retrosternal chest pain with radiation to the neck or back, dyspnea, and dysphonia.[6,8] Less common presentations include throat discomfort, dysphagia, and odynophagia.[6,8,18,19] The signs are subcutaneous emphysema, the absence of cardiac dullness to percussion, and Hamman's sign.[10] Worrisome signs of increased mediastinal pressure that suggest tamponade physiology or tension pneumothorax include cyanosis, neck vein distention, and circulatory collapse. Our patient presented with mild dyspnea and dysphonia and demonstrated subcutaneous emphysema and Hamman's sign.

Pneumomediastinum is a rare complication of systemic autoimmune diseases. Most of the reported associations have been with dermatomyositis.[20-23] There have been three cases of spontaneous pneumomediastinum and bilateral pneumothoraces associated with systemic lupus.[24-26] Our case is the first one involving rheumatoid arthritis with rheumatoid lung disease. Like the present case, all of the patients in the literature with collagen vascular disease have also shown evidence of interstitial pulmonary fibrosis.[27] Interstitial fibrosis is well recognized as a predisposing factor for pneumothorax, but is less widely recognized as a predisposition to pneumomediastinum.[22,27] Cicuttini and Fraser[22] have hypothesized that the alveolar rupture is secondary either to interstitial fibrosis or pulmonary infarctions resulting from vasculitis. Other factors that may predispose the patient with interstitial lung disease to spontaneous pneumomediastinum are the negative pleural and interstitial pressures that result from the reduced lung compliance when the lungs are expanded, and the inhomogeneous nature of the disease, which may lead to overdistension of normal lung tissue.

Although the triggering event in the present case was not unusual, the prolonged clinical course was unusual. Spontaneous pneumomediastinum typically resorbs within a period of 1 to 2 weeks without treatment, and rarely recurs.[6-8] In this case, the pneumomediastinum lasted for 2 months before treatment was instituted. Prolonged or recurrent pneumomediastinum appears to be more common ia patients with underlying collagen diseases.[21-23] Matsuda et al[27] reported fatalities in 11 of 21 published cases of pneumomediastinum associated with dermatomyosiris in his review. Most reviews of this topic advocate no specific treatment and do not advise hospitalization.[6-8,28] We think that a more aggressive approach is warranted in high-risk patients. Thus, when spontaneous pneumomediastinum occurs in patients with underlying interstitial lung disease, we recommend close observation, possible hospitalization, and the use of inhaled oxygen treatment.

In the current case, we treated with a high concentration of oxygen. This has been widely recommended for resorption of pneumothorax and has been considered theoretically helpful for subcutaneous gas collections for many years.[10,28-30] Subcutaneous and mediastinal emphysema is resorbed into tissues by diffusion along a partial pressure gradient. With breathing 100% oxygen, nitrogen is washed out of the blood, thus increasing the gradient for absorption of the gas by a factor of fivefold to 10-fold.[29] In the present case, the inhalation of high concentrations of oxygen not only led to resorption of the subcutaneous gas, but was associated with prevention of recurrence. The persistence of the subcutaneous emphysema reflects a steady state between the leakage of air from the terminal airspaces and the absorption of air from the tissues. When the subcutaneous emphysema was resorbed in this case, there was no recurrence. We speculate that the site of tissue leakage must have been preserved by the presence of the interstitial gas. When the gas was allowed to resorb, then the tissue planes at the site of the rupture would have been allowed to oppose each other leading to healing of the air leak. The chronic use of prednisone in this case and other cases of collagen vascular disease associated pneumomediastinum may have contributed to the failure of the tissues to heal promptly.

In summary, we report a case of persistent spontaneous pneumomediastinum in a patient with rheumatoid lung disease. The subcutaneous emphysema resolved promptly after institution of high-concentration oxygen therapy. We recommend that patients with interstitial lung disease and underlying collagen disease who develop this disorder be observed closely and treated with high-concentration oxygen because of the high rates of persistence and complication.

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Anshul Patel, BS; Branko Kesler, MD; and Robert A. Wise, MD, FCCP

(*) From Johns Hopkins University, School of Medicine at the Johns Hopkins Asthma and Allergy Center, Division of Pulmonary and Critical Care Medicine, Baltimore, MD.

Manuscript received April 27, 1999; revision accepted December 9, 1999.

Correspondence to: Robert A. Wise, MD, FCCP, Johns Hopkins University, School of Medicine at the Johns Hopkins Asthma and Allergy Center, Division of Pulmonary and Critical Care Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224; e-mail: rwise@welch.jhu.edu

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