Eur J Cardiothorac Surg 2004;25:852-855
© 2004 Elsevier Science NL
Current assessment and management of spontaneous pneumomediastinum: experience in 24 adult patients
George J. Koulliasa,
Dimitris P. Korkolisa*,
Xu Jie Wangb,
Graeme L. Hammonda
a Section of Cardiothoracic Surgery, Yale-New Haven Hospital, Yale University School of Medicine, New Haven, CT, USA
b St Mary's Hospital, Yale University School of Medicine, New Haven, CT, USA
Received 22 December 2003;
received in revised form 24 January 2004;
accepted 28 January 2004.
* Corresponding author. Address: 22 Socratous Str, 1st Floor, Kifissia 14561, Athens, Greece. Tel.: +30-210-8083743/6937-307272; fax: +30-210-8012-689
e-mail: dkorkolis_2000{at}yahoo.com
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Abstract
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Objectives: Spontaneous pneumomediastinum (SPM) is an uncommon, benign, self-limited disorder that usually occurs in young adults without any apparent precipitating factor or disease. The purpose of this study was to review our experience in dealing with this entity and detail a reasonable course of assessment and management. Methods: A retrospective case series was conducted to identify adult patients with SPM who were diagnosed and treated in a single institution between 1993 and 2000. Results: Twenty-four patients were identified who included 18 men and 6 women with a mean age of 17.5 years. Acute onset chest pain was the predominant symptom at presentation. Only half of the patients developed clinically evident subcutaneous emphysema. The most frequent precipitating factor was a history of illegal drug abuse seen in 25% of patients. Other factors included asthmatic bronchospasm, physical activity and violent coughing or vomiting. Chest radiography and computerized tomography (CT) were diagnostic in all cases with CT scan revealing six cases with associated pulmonary abnormalities. Esophagogram and flexible bronchoscopy were selectively used. Twelve patients (50%) were admitted to the hospital. Their mean hospital stay was 2 days. All patients were conservatively treated. In a follow-up of 310 years no complications or recurrences were observed. Conclusions: SPM follows alveolar rupture in the pulmonary interstitium. It shows a rising incidence in young drug users. It has a wide range of clinical features necessitating a high index of suspicion. Chest X-ray and CT scan should be always performed. Hospitalization and aggressive approach should be limited. SPM responds well to conservative treatment and follows a benign natural course.
Key Words: Pneumomediastinum Spontaneous pneumomediastinum Mediastinal emphysema
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1. Introduction
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Spontaneous pneumomediastinum (SPM) is an uncommon and benign clinical disorder that usually occurs in young adult males without an apparent precipitating factor or disease [1,2]. Because of its relative infrequency, its subtle presentation, as well as the existing limited experience, the diagnosis of SPM can be easily missed, whereas the necessary assessment and proper management are still unclear [3].
The purpose of this study was to review a single institution's clinical experience with SPM and to detail a reasonable course of evaluation and treatment.
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2. Materials and methods
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Between 1993 and 2000, all adult cases of SPM diagnosed and treated by the Department of Cardiothoracic Surgery in Yale-New Haven Hospital, CT, USA, were investigated. Only those cases of pneumomediastinum that occurred spontaneously and in patients older than 12 years of age were reviewed. SPM was defined as cases in which pneumomediastinum did not occur in the setting of positive-pressure ventilation or gross trauma. Patients who may have developed pneumomediastinum in the setting of a possible Valsalva maneuver or with inhalation drug use were considered to be spontaneous.
All SPM case records were carefully reviewed in respect to the demographic data, symptoms, clinical findings at presentation, precipitating factors, diagnostic workup performed, offered treatment, length of hospital stay, as well as natural course and outcome. Precipitating factors reviewed included a recent or remote history of drug abuse, the performance of a Valsalva-type maneuver and a recent history of physical activity. In addition, cigarette smoking and other pulmonary-related medical problems were recorded. Charts were specifically reviewed for the presence or absence of subcutaneous emphysema or bronchospasm in the clinical evaluation. Chest radiograph and computerized tomography (CT) scan results were analyzed, whereas the use of additional diagnostic tests, such as esophagogram and flexible bronchoscopy, were justified and recorded. Reasons for admission, possible complications, length of hospital stay and course of the disease were taken under consideration.
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3. Results
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Twenty-four adult patients meeting the criteria for SPM were identified. They were 18 men and 6 women with a mean age of 17.5 years (range between 15 and 26 years). Body build and smoking habits were not significantly different from the general population.
At the time of initial evaluation, all patients had one or more symptoms that could be related to the presence of a pneumomediastinum. Acute onset retrosternal chest pain was the predominant symptom seen in 66.6% of cases. Persistent cough was apparent in 41.6% and discomfort related to their neck or throat (e.g. sore throat, dysphagia) was described in 33.3% of patients. Only two patients (8.3%) were complaining of dyspnea or shortness of breath, on presentation (Table 1).
Only 12 patients (50%) had clinically evident subcutaneous emphysema, even after the radiographic findings of SPM were noted. Bronchospasm was detected in four patients implying a possible asthmatic component.
After careful investigation, predisposing agents for the development of SPM could be identified in most patients. The most frequent precipitating factor was a history of illegal drug abuse (cocaine and heroin), which was noted in six patients (25%). Other factors included acute bronchial asthma in four patients (16.6%), non-contact physical activity (tennis, weightlifting) in four (16.6%), violent coughing (including a case of idiopathic pulmonary fibrosis) in four (16.6%), recent performance of contact-sports (football, wrestling) in two (8.3%) and a vigorous vomiting episode in two patients (8.3%). In the remaining two patients (8.3%) no predisposing factor was found and SPM developed entirely at rest (Table 2).
Every patient had a chest radiograph and a subsequent chest CT scan as part of the initial diagnostic assessment. Both of these were always diagnostic for pneumomediastinum. They also showed the presence of pneumothorax in two patients. CT scan, in addition, revealed further information about an associated pulmonary infection in four patients and evidence of suspected pulmonary tuberculosis in two patients. An esophagogram and a flexible bronchoscopy were undertaken in 12 (50%) and 10 patients (41.6%), respectively. These studies were only performed to exclude the possibility of esophageal or tracheobronchial rupture, in cases with a highly suspicious setting, such as contact sports, violent coughing or vomiting and drug abuse. However, no splanchnic perforation was found.
All patients had antibiotic prophylaxis given for the prevention of mediastinitis. This consisted of a third-generation cephalosporin, such as ceftriaxone. Broader coverage with the addition of clindamycin was used when the possibility of splanchnic perforation was high and when the presentation was accompanied by fever or leukocytosis, in a delayed and suspicious setting. Nevertheless, these agents were discontinued shortly, thereafter.
Half of our patients were admitted to the hospital, whereas the remaining were released and followed-up in an outpatient basis. Reasons for admission included control of bronchospasm and cough in four patients (33.3%), treatment of associated infection in four (33.3%), management of concurrent pneumothorax in two (16.6%) and evaluation of suspected tuberculosis in two patients (16.6%).
All patients were managed with bed rest, pain control, follow-up chest X-ray, work-up for asthma and oxygen therapy. Oxygen therapy helped with the absorbance of mediastinal air and led to rapid resolution of SPM. One patient with pneumothorax had a temporary Heimlich valve placed, whereas the diagnosis of tuberculosis in the other two was excluded.
The mean hospital stay was 2 days (range between 1 and 5 days). No complications were seen. Patients were discharged when fully evaluated and asymptomatic, even with some residual radiographic findings of pneumomediastinum. In a follow-up period of 310 years, no recurrence of SPM was noted and no re-admission for the same reason was recorded.
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4. Discussion
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Pneumomediastinum, as a medical entity, has been originally recognized since 1819, when it was accurately described by Laennec [4] in the setting of trauma injuries. Hamman [1] was the first to report primary or SPM in 1939. His description of audible crepitation occurring with the heartbeat on chest auscultation is known as the Hamman's sign. According to Macklin and Macklin [5] in 1944, SPM results from the rupture of terminal alveoli into the lung interstitium as a consequence of a pressure gradient existing between the periphery of the lung and the hilum. This rupture causes air to dissect along the pulmonary vasculature towards the hilum. The gas then dissects centrally along the bronchoalveolar trunks, the peribronchial space or within the lymphatics to reach the mediastinum [6]. Data from animal experiments indicate that the intrapulmonary pressure, the alveolararterial pressure gradient, the degree of alveolar expansion, as well as the presence of pulmonary parenchymal pathology plays prominent roles in alveolar rupture [5]. It has been also confirmed in histological studies that air can dissect along the perivascular connective tissue into the pulmonary parenchyma resulting in interstitial emphysema [7].
In the international literature, SPM has been linked to many causes such as bronchial asthma [8], diabetic ketoacidosis [9], forceful straining during exercise [10], inhalation of drugs [11], childbirth [12], severe cough or vomiting [13], as well as other activities associated with the Valsalva maneuver [14].
Miller and colleagues [15] were the first to report SPM in the setting of inhalation of an illicit drug (i.e. marijuana). Mattox [16] subsequently reported a series of patients with SPM who were frequent users of marijuana and heroin. More recently, SPM has been reported in association with inhaling nitrous oxide [17], smoking free-base [18] or crack-cocaine [19] and ecstasy abuse [20]. There are still questions as to whether SPM seen with inhalation drug used is caused by the same barotrauma-related mechanism or whether it is caused by the direct toxic action of heat and the strong vasoconstrictive action of the inhaled substances [14]. Valsalva-type manipulations are quite common among users of cocaine or marijuana when they routinely perform a forceful breath-holding type maneuver during inhalation of the respective substance. In our series of 24 patients with SPM, recent or remote history of illegal drug abuse was the most frequent predisposing factor, accounting for 25% of cases. It is, therefore, thought that the current incidence of SPM is considerably more common than was previously believed. In addition, there is a reason to expect that, in the era of inhalation drug use, cases of SPM will most likely increase in frequency, particularly in younger individuals. The disturbing young age of these patients has been shown in our series as well as in others [21,22]. In contrast, no correlation with a particular somatotype, as in the case of spontaneous pneumothorax, was observed.
The clinical presentation of SPM can often be subtle and the diagnosis sometimes missed or delayed [13]. Every patient in our series presented with one or more symptoms that could be directly or indirectly related to the presence of a pneumomediastinum. A high-index of suspicion is, therefore, necessary for its prompt diagnosis. Chest pain has been usually found to be the predominant symptom [13,22]. Symptoms such as cough, dyspnea or dysphagia have been also reported [13,22,23].
Subcutaneous emphysema, either in the neck or chest, although characteristic for SPM, has only been noted in half of our patients, even after radiologic documentation. The presence of subcutaneous emphysema in SPM is not stable and varies from 40 to 100%, in different reports [14,21,22].
The initial differential diagnosis of SPM assessed by a thoracic surgeon should be broad and includes cardiac, pulmonary, musculoskeletal and esophageal causes (Table 3). The majority of these causes can be safely excluded with a thorough history, detailed physical examination, electrocardiographic evaluation, as well as radiographic or endoscopic assessment, as indicated.
It is certain that chest radiograph remains the standard for making the diagnosis of SPM. Chest X-ray was diagnostic in all our cases, whereas similar results have been reported by others [21,22]. It has been emphasized, however, that without a lateral film, the diagnosis will be missed in approximately half of the cases; hence when air is limited in quantity the only sign of pneumomediastinum on plain chest radiography may be a line or band of transradiancy in the retrosternal area, which can only be seen in the lateral view [23]. In contrast, the diagnosis of SPM can be easily made at CT scan because the anatomical location of the air is evident on cross-sectional display. Kaneki et al. [24] showed that chest X-ray alone could poorly detect approximately 30% of SPM and that CT scan was needed to make the final diagnosis in these cases. In addition, CT scan should always be used in clinically suspicious cases and when an underlying cause or an associated pulmonary disease is to be elucidated [25]. This was true in our patients with associated infection and suspected tuberculosis. In the present study, because of availability and decreased cost, we used chest CT scan in all of our patients. Further diagnostic assessment with esophageal contrast study or flexible endoscopy carries a small but not negligible risk and is not always necessary. These tests should be performed in the setting of delayed presentation, contact sports, violent coughing or strong suspicion of drug abuse, particularly in the presence of fever, sweating or leukocytosis, as well as in cases with any diagnostic doubt [13].
The issue of prophylactic antibiotic coverage in SPM is contradictory. All patients in our study received at least one dose of a third-generation cephalosporin. That seems reasonable, particularly in highly suspicious cases and until any additional workup is completed. Although recent reports from smaller series [13,21,22] advocate immediate admission or expedite diagnostic approach, we found that SPM does not usually require aggressive intervention or hospitalization. Patients who were admitted developed no complications, such as tension pneumomediastinum, delayed pneumothorax or airway compromise, and were safely discharged within a few days. In addition, none of those treated in an outpatient basis showed exacerbation or future recurrence. With the increase in the incidence of SPM, the financial savings of avoiding hospitalization for these patients should be appreciated. Taking into consideration the benign nature of this entity, only cases, where the diagnosis is in question, the underlying disease needs specific treatment or the possibility of an organ perforation cannot be ruled out, should be considered for further diagnostic workup and admission.
In conclusion, SPM is an uncommon and self-limited clinical entity. It follows alveolar rupture into the pulmonary interstitium and is produced by an acute episode of high-intrathoracic pressure. It usually occurs in young adults with a rising frequency in illegal drug users. Although chest pain is the predominant symptom, SPM shows a wide range of clinical features, necessitating a thorough differential diagnosis and a high-index of suspicion. Chest radiography may not always be sufficient, whereas CT scan, with its decreasing cost and increasing availability, offers both the confirmation of the diagnosis and the assessment of any associated causes or abnormalities, and should be used. Hospitalization and aggressive approach should be limited and individualized. SPM has a benign natural course and responds well to conservative treatment.
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