On physical examination, he is noted to be a well-developed, well-nourished male in no acute distress. He does not appear to be tachypneic or cyanotic. The vital signs show a temperature of 98.1°F (36.7°C), a blood pressure of 94/58 mm Hg, a heart rate of 67 bpm, a respiratory rate of 20 breaths/min, and an oxygen saturation of 95% while breathing room air. No jugular venous distention is noted, and the patient has a normal respiratory effort. The lungs are clear to auscultation bilaterally, without any wheezes, rales, or rhonchi. The heart examination reveals a regular rate and rhythm, with normal S1 and S2 heart sounds and no murmurs, rubs, or gallops. The abdomen is soft, nontender, and nondistended. His extremities do not exhibit any clubbing, cyanosis, or edema. No subcutaneous crepitus is appreciated on examination of the skin.
The initial laboratory findings show a white blood cell (WBC) count of 11.0 × 103/μL (11.0 × 109/L; normal range, 3.8-10.9 × 103/μL), with neutrophils at 73.9% (0.73; normal range, 41.8%-77%), a hemoglobin of 15.1 g/dL (9.37 mmol/L; normal range, 13.6-17.3 g/dL), a hematocrit of 44.0% (0.44; normal range, 39.8-50.7%), and platelets of 263 × 103/μL (263 × 109/L; normal range, 141-401 × 103/μL). The basic metabolic panel is normal. A urine toxicology screen is negative. The erythrocyte sedimentation rate (ESR) is 5 mm/hr (normal range, <15>
Questions answered incorrectly will be highlighted.
Hint: Look closely at the heart and surrounding structures.
Discussion
Figure 2b.
The chest radiograph showed linear and curvilinear radiolucencies in the anterior mediastinum and possibly pericardium suggestive of pneumomediastinum and minimal pneumopericardium. A computed tomography (CT) scan of the chest was subsequently obtained, which confirmed the presence of pneumomediastinum (see Figures 2a and 2b) and pneumopericardium, with air tracking superiorly along the right carotid sheath (not included on the images provided). There was no evidence of pneumothorax, bullous changes, or bronchopleural fistula. The remaining portions of the lungs were normal, with no areas of focal consolidation or pleural effusion. The esophagus and trachea appeared normal. There was no mediastinal or hilar lymphadenopathy. The vascular and bone structures had no abnormalities. A diagnosis of pneumomediastinum and pneumopericardium was established based on the imaging studies, and the patient was admitted to the hospital for observation.
Spontaneous pneumomediastinum is defined as the presence of free air in the mediastinum without any apparent precipitating cause. Secondary pneumomediastinum is caused by certain events, such as trauma, infections in the intrathoracic or oropharyngeal spaces, or disruption of the aerodigestive tract. Spontaneous pneumomediastinum is a rare, usually self-limited disease primarily affecting young men. More than 75% of reported cases occur in males, with a mean age of 20 years. The incidence of spontaneous pneumomediastinum has not been clearly established because the only published reports available are case studies or small case series. Newcomb and Clark reported an incidence of 1 in 29,670 emergency department presentations, whereas the figure observed in the study by Macia et al was 1 in 44,511. Other sources have found the incidence of spontaneous pneumomediastinum to be between 1 in 800 and 1 in 42,000 hospital admissions. The incidence of this disease could be underestimated, given that it frequently goes unrecognized. The clinical presentation of spontaneous pneumomediastinum can often be subtle, and the diagnosis is sometimes missed or delayed.[1-7]
The most commonly proposed cause of pneumomediastinum is alveolar rupture, which occurs in the presence of elevated intra-alveolar pressure or damage to the alveolar walls. An increased pressure gradient between the intra-alveolar and interstitial spaces leads to air leakage from small alveolar openings and ruptured alveoli into the perivascular spaces, which leads to interstitial emphysema. The pressure gradient then favors dissection of air along the vascular sheaths toward the hilum. Air can then decompress into the subcutaneous tissues and the deep cervical spaces, eventually spreading into the pericardial space and leading to pneumopericardium. Dissection of free air into the pericardial space is a common complication of barotrauma in neonates, but it is quite rare in adults, in whom the apposition of the pericardial layers is very tight.[1-3,7]
Various conditions can cause elevation of intra-alveolar pressure, including airway obstruction (eg, mucous plugging in an asthmatic or a foreign body), mechanical ventilation, blunt trauma, coughing, emesis, or the Valsalva maneuver (eg, during parturition). Certain conditions that can cause damage to the alveolar walls include pneumonitis, emphysema, lung fibrosis, and adult respiratory distress syndrome (ARDS).[1-4]
In order to make a diagnosis of spontaneous pneumomediastinum, the clinician must rule out causes of secondary pneumomediastinum. This is particularly vital because alternative causes of pneumomediastinum are potentially life-threatening. It is important to determine if the patient has had recent dental surgery and/or procedures of the upper digestive tract, as well as evaluate for underlying conditions that can lead to pneumomediastinum, such as gas-producing infections in the head, neck, and abdomen, or neoplasms disrupting the mucosal integrity of the esophagus. Esophageal rupture must be ruled out by obtaining an esophagram when indicated. Events or conditions known to precipitate spontaneous pneumomediastinum include vomiting (especially retching), asthma exacerbation, coughing, or physical activity.[1,3,5,7]
Pneumomediastinum has also been found to be associated with inhalational drug use. Theoretically, this has been thought to be caused by barotrauma from prolonged forceful breath holding. Cocaine and marijuana users perform a Valsalva-type maneuver during deep inhalation of the respective substance (often through a water pipe), leading to an increase in intra-alveolar pressure and subsequent alveolar rupture. There is no evidence of a direct pharmacological effect of illicit drugs on spontaneous pneumomediastinum.[1-4]
Patients with spontaneous pneumomediastinum most commonly present with complaints of chest pain, dyspnea, and neck pain or discomfort. Chest pain is the most common symptom, and it typically presents as an acute, retrosternal, pleuritic pain that may radiate to the neck, back, or shoulders. Other, less common symptoms include odynophagia, dysphagia, dysphonia, cough, back pain, or abdominal pain. Physical examination may reveal signs of respiratory distress, subcutaneous emphysema, and the Hamman sign, which is pathognomonic for pneumomediastinum. The Hamman sign refers to crunching, crackling, or bubbling sounds that are synchronous with the heart beat on auscultation. This signifies air in the mediastinum. The prevalence of the Hamman sign is highly variable; however, subcutaneous emphysema, mainly at the neck, is a more frequent finding that is seen in 40% to 100% of cases.[1-5,7]
The differential diagnosis of spontaneous pneumomediastinum is broad and includes musculoskeletal disorders, acute coronary syndrome, pericarditis, pneumothorax, pulmonary embolism, tracheobronchial tree rupture, and Boerhaave syndrome. Tracheobronchial tree rupture and Boerhaave syndrome are potentially life-threatening conditions. Boerhaave syndrome can be ruled out with a contrast-enhanced esophagogram if it is suspected and, if tracheobronchial tree rupture is suspected, it can be ruled out with a bronchoscopy.[1-3]
The diagnosis of pneumomediastinum is confirmed by obtaining posteroanterior and lateral chest radiographs. Posteroanterior chest radiographs typically reveal radiolucency between the left heart border and the mediastinal pleura. A lateral view should always be obtained because, if only a posteroanterior radiograph is taken, the diagnosis will be missed in up to 50% of cases. When air is limited in quantity, the only sign of pneumomediastinum on plain chest radiography may be a radiolucent band (hyperlucency) in the retrosternal area, which can only be seen in the lateral view. Up to 30% of patients with spontaneous pneumomediastinum present with a normal radiograph; therefore, if the clinical suspicion is high, a CT scan of the chest can be obtained in those cases in which the diagnosis is unclear.[1-3]
Spontaneous pneumomediastinum is almost always a benign, self-limited condition. The treatment consists of supportive measures, including rest, oxygen, and analgesics. Breathing 100% oxygen helps to enhance reabsorption of the free air by increasing the gradient of nitrogen between the alveoli and the tissues. Antibiotic therapy is not required for spontaneous pneumomediastinum. Patients respond well to supportive treatment and pain typically resolves within 1-2 days. Follow-up chest radiography should be obtained within 12-24 hours. The chest radiograph findings usually return to normal within a week. Significant complications are virtually nonexistent, and most published series have not reported any cases of recurrence.
Figure 3b.
In the case of this patient, he was admitted to the hospital for observation and supportive treatment was initiated with supplemental oxygen and analgesics. The patient had a normal complete evaluation by an ear, nose, and throat (ENT) surgeon. In addition, a CT scan of the neck was obtained and was found to be normal. A repeat CT scan of the chest obtained the day after admission showed no interval progression in the pneumomediastinum and pneumopericardium. The patient's pain and shortness of breath resolved within 24 hours, and the patient was subsequently discharged to home after a 2-day hospital stay. A CT scan of the chest performed 3 days after discharge showed mild improvement in the pneumomediastinum and resolution of the pneumopericardium (see Figures 3a and 3b). At the time of discharge, the patient was instructed to refrain from future drug use and smoking, and to avoid air travel or prolonged stays at high altitudes for 1 month. Physical activity was not restricted except for scuba diving, which he was directed not to do for at least 6 months. These suggestions are based on the theoretical risk for recurrence of spontaneous pneumomediastinum. The actual rate and risk factors for recurrence are not known, so recommendations on avoidance of potential high risk activities must be individualized based on patient factors and known information about the recurrence of pneumothorax.
e. None of above
Source : http://cme.medscape.com/viewarticle/702661
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