(Chest. 2000;117:1809-1813.)
© 2000
American College of Chest Physicians
Persistent Pneumomediastinum in Interstitial Fibrosis Associated With Rheumatoid Arthritis*
Treatment With High-Concentration Oxygen
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.
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{at}welch.jhu.edu
 |
Abstract
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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.
Key Words: oxygen therapy • pneumothorax • pulmonary fibrosis • rheumatoid arthritis • spontaneous pneumomediastinum
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Introduction
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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.
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Case Report
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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.
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Figure 1.. Chest radiograph showing mediastinal air causing
an area of radiolucency around the aorta, pulmonary artery, and
pericardium. Subcutaneous emphysema is present in the neck and anterior
chest.
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Figure 2.. Chest CT shows the mediastinal air tracking along
the bronchovascular bundles, causing the bronchus intermedius and left
main pulmonary artery and vein to be prominently visualized. Patchy
interstitial scarring is present in the lung periphery. Subcutaneous
emphysema is present in the deep fascia beneath the right breast.
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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°C (97.8°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 1 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.
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Figure 3.. Chest CT at the level of the aortic arch shows air
surrounding the trachea and esophagus. A small lateral pneumothorax is
present on the right side. Subcutaneous emphysema is present on the
right upper chest and the left lateral chest.
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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.
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Discussion
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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 report5
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
10
11
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
14
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
21
22
23
There have been three cases of
spontaneous pneumomediastinum and bilateral pneumothoraces associated
with systemic lupus.24
25
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
Fraser22
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
7
8
In this case, the pneumomediastinum
lasted for 2 months before treatment was instituted. Prolonged or
recurrent pneumomediastinum appears to be more common in patients with
underlying collagen diseases.21
22
23
Matsuda et
al27
reported fatalities in 11 of 21 published cases of
pneumomediastinum associated with dermatomyositis in his review. Most
reviews of this topic advocate no specific treatment and do not advise
hospitalization.6
7
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
29
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.
Received for publication April 27, 1999.
Accepted for publication December 9, 1999.
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TOP
Abstract
Introduction
