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Pneumomediastinum, Emergency Medicine

Basics

Description

- Presence of free air or gas within the mediastinum (mediastinal emphysema) - May originate from esophagus, lungs, or bronchial tree (aerodigestive process) - May occur spontaneously (primary pneumomediastinum) or as result of trauma, surgery, or other pathologic processes (secondary pneumomediastinum) - Spontaneous pneumomediastinum: - Caused by extrapleural tracheobronchial injury: - Increased intra-alveolar pressure, low perivascular pressures, or both - Terminal alveolar rupture into the lung interstitium and bronchovascular tissue sheath - Dissection of air into the hilum and subsequently the mediastinum along a pressure gradient - Mediastinal air then dissects into the fascial planes, most commonly into the tissues of the neck.

- Primary or spontaneous pneumomediastinum: - Associated with forced Valsalva maneuvers: - Forceful vomiting - Forceful straining during exercise - Straining during defecation - Coughing/sneezing - Intense screaming - Labor and delivery - Playing wind instruments - Pulmonary function testing - Anorexia nervosa - Obesity - Pre-existing lung disorders (interstitial lung disease, pulmonary fibrosis, pneumonitis) - Illicit inhalation drug use (marijuana, cocaine, methamphetamine) - Tobacco abuse

- Secondary pneumomediastinum: - Secondary to thoracic barotrauma - Common traumatic mechanisms: - Motor vehicle collision - Fall - Blows to chest or neck - Recent esophageal/tracheobronchial instrumentation

- Chest pain (most common symptom in multiple series): - Sharp - Pleuritic - Retrosternal - Radiating to back and arms - Often positional

- CXR: - Most valuable initial test - Important to include lateral view because mediastinal air is often missed on posterior " anterior view - Aids in excluding pneumothorax, pneumopericardium - Identification of a pleural effusion or parenchymal infiltrate may suggest an esophageal rupture. - Negative in up to 30 " 35% of cases - Spinnaker sail sign or "angel wing " sign (produced by air lifting the thymus off the heart and major vessels) - Continuous diaphragm sign (air collecting between the diaphragm and the pericardium) - SC or superior mediastinal emphysema

- Spontaneous pneumomediastinum: - Usually a benign, self-limiting condition - Does not require specific treatment - Efforts should focus on pain relief and reassurance once diagnosis is confirmed. - High-flow oxygen may facilitate the reabsorption of nitrogen and provide comfort. - Withhold PO intake if suspected esophageal source (pending diagnostic studies) - Condition is self-limiting and may be expected to resolve over 2 " 5 days.

- Treat underlying cause aggressively (e.g., asthma exacerbation or DKA). - Oxygen 15 L via nonrebreather mask - Analgesia (non-narcotic and narcotic as necessary) - Antibiotics have limited use, but in the setting of concern for mediastinitis use broad-spectrum coverage to include GI flora, resistant organisms, and Pseudomonas: - Vancomycin 10 " 15 mg/kg IV q12h and - Piperacillin/tazobactam 3.375 " 4.5 g IV q6h and - Clindamycin 600 " 900 mg IV q8h or Metronidazole 500 mg IV q8h

  • Presence of free air or gas within the mediastinum (mediastinal emphysema)
  • May originate from esophagus, lungs, or bronchial tree (aerodigestive process)
  • May occur spontaneously (primary pneumomediastinum) or as result of trauma, surgery, or other pathologic processes (secondary pneumomediastinum)
  • Spontaneous pneumomediastinum:Caused by extrapleural tracheobronchial injury:Increased intra-alveolar pressure, low perivascular pressures, or bothTerminal alveolar rupture into the lung interstitium and bronchovascular tissue sheathDissection of air into the hilum and subsequently the mediastinum along a pressure gradientMediastinal air then dissects into the fascial planes, most commonly into the tissues of the neck.Often in setting of a Valsalva maneuver, forceful vomiting, in association with bronchospasm or inhalational drug useMen > women (2:1 in some series)Young > old (most common in 2nd/3rd decades of life in most series)Pediatric patients have a bimodal age distribution of peak incidence (<7 and 13 " 17 yr)
  • Relatively rare, 1/30,000 " 50,000 hospital admissions

Etiology

  • Primary or spontaneous pneumomediastinum:Associated with forced Valsalva maneuvers:Forceful vomitingForceful straining during exerciseStraining during defecationCoughing/sneezingIntense screamingLabor and deliveryPlaying wind instrumentsPulmonary function testingAnorexia nervosaObesityPre-existing lung disorders (interstitial lung disease, pulmonary fibrosis, pneumonitis)Illicit inhalation drug use (marijuana, cocaine, methamphetamine)Tobacco abuseA majority of cases will have no identified precipitating event/causeHas been rarely described after dental extraction/procedures.
  • Secondary pneumomediastinum:Secondary to thoracic barotraumaCommon traumatic mechanisms:Motor vehicle collisionFallBlows to chest or neckRecent esophageal/tracheobronchial instrumentationPositive-pressure ventilationEsophageal rupture (Boerhaave syndrome)In association with mediastinal infection caused by gas-forming organisms
  • Tension pneumomediastinum:Rare but life-threatening eventUsually in patients on positive-pressure ventilation
  • May be associated with pneumopericardium and/or extension of a pneumothorax/tension pneumothorax

Diagnosis

Signs and Symptoms

  • Chest pain (most common symptom in multiple series):SharpPleuriticRetrosternalRadiating to back and armsOften positional
  • Dyspnea
  • Neck pain:Occurs in association with dissection of air into soft tissues of neckOften described as "neck swelling, " "neck pain, " "throat pain, " or "difficulty swallowing "
  • SC emphysema:Most commonly located at the supraclavicular area and anterior neck
  • Dysphagia/odynophagia
  • Dysphonia/hoarseness
  • Hamman crunch: Presence of a precordial crinkling or crepitance during systole:Uncommon but pathognomonicBest heard with patient in left lateral decubitus position
  • Meckler triad (esophageal rupture): Vomiting, lower chest pain, and cervical SC emphysema following overindulgence of food or alcohol

History

  • Inhalational drug use
  • Asthma exacerbation
  • Pre-existing lung disorders
  • Forceful vomiting (such as in diabetic ketoacidosis [DKA], or hyperemesis)
  • Preceding strenuous athletic activity

Physical Exam

  • SC emphysema
  • Hamman crunch

Essential Workup

  • Exclude secondary causes, notably esophageal rupture.
  • Chest radiography
  • Chest CT (if high index of suspicion)

Diagnosis Tests & Interpretation

Lab

CBC if there is suspicion of mediastinitis (the most concerning consequence of esophageal rupture, with high morbidity and mortality)

Imaging

  • CXR:Most valuable initial testImportant to include lateral view because mediastinal air is often missed on posterior " anterior viewAids in excluding pneumothorax, pneumopericardiumIdentification of a pleural effusion or parenchymal infiltrate may suggest an esophageal rupture.Negative in up to 30 " 35% of casesSpinnaker sail sign or "angel wing " sign (produced by air lifting the thymus off the heart and major vessels)Continuous diaphragm sign (air collecting between the diaphragm and the pericardium)SC or superior mediastinal emphysema
  • Chest CT:Imaging test of choice if suspicion is high but CXR is negative (CXR has high false-negative rate)
  • Esophagram with water-soluble contrast material:Study of choice to exclude diagnosis of esophageal rupture

Diagnostic Procedures/Surgery

  • Esophagoscopy:Limited usefulness (overutilized)May be used to further delineate injuries identified with CT and/or esophagram
  • Laryngoscopy/bronchoscopy:Limited usefulness (overutilized)May be used to exclude diagnosis of laryngeal/tracheobronchial injury
  • Pericardiocentesis:Only in the setting of tension pneumopericardium in the crashing patient
  • Tube thoracostomy:Only in the setting of concomitant pneumothorax of sufficient size, or one that is rapidly progressing

Differential Diagnosis

  • Aortic dissection
  • Coronary ischemia
  • Esophageal diverticula
  • Esophageal webs
  • Mediastinitis
  • Myocarditis
  • Pericarditis
  • Pneumonia
  • Pneumopericardium
  • Pneumothorax/tension pneumothorax
  • Pulmonary embolus
  • Schatzki rings

Treatment

Pre-Hospital

  • Resuscitation of the acutely ill patient (as in the patient with septic mediastinitis)
  • In the appropriate setting, standard care of the trauma patient
  • Withhold PO intake
  • Rapid patient evolution and transport to an appropriate facility

Initial Stabilization/Therapy

  • IV access
  • Oxygen
  • Cardiac monitoring
  • Pulse oximetry

Ed Treatment/Procedures

  • Spontaneous pneumomediastinum:Usually a benign, self-limiting conditionDoes not require specific treatmentEfforts should focus on pain relief and reassurance once diagnosis is confirmed.High-flow oxygen may facilitate the reabsorption of nitrogen and provide comfort.Withhold PO intake if suspected esophageal source (pending diagnostic studies)Condition is self-limiting and may be expected to resolve over 2 " 5 days.
  • Secondary pneumomediastinum:Once diagnosis is made, direct invasive diagnostic modalities toward the most likely underlying cause (esophagoscopy, laryngoscopy, bronchoscopy).Direct therapy toward underlying cause.

Medication

  • Treat underlying cause aggressively (e.g., asthma exacerbation or DKA).
  • Oxygen 15 L via nonrebreather mask
  • Analgesia (non-narcotic and narcotic as necessary)
  • Antibiotics have limited use, but in the setting of concern for mediastinitis use broad-spectrum coverage to include GI flora, resistant organisms, and Pseudomonas:Vancomycin 10 " 15 mg/kg IV q12h andPiperacillin/tazobactam 3.375 " 4.5 g IV q6h andClindamycin 600 " 900 mg IV q8h or Metronidazole 500 mg IV q8h

Follow-Up

Disposition

Admission Criteria

  • Secondary pneumomediastinum
  • Associated pneumothorax
  • Possibility of esophageal rupture has not been excluded
  • Abnormal vital signs
  • Ill/toxic-appearing patient
  • Intractable pain
  • Underlying disorder requires admission (asthma exacerbation, exacerbation of lung disorder, DKA).
  • Social situation prevents compliance or follow-up
  • Extremes of age (pediatric and elderly)
  • Immunosuppression
  • Failure of outpatient management

Discharge Criteria

  • Spontaneous pneumomediastinum
  • Normal vital signs
  • No pneumothorax
  • No significant comorbidities
  • Period of observation in the ED with resolution of symptoms
  • Close outpatient follow-up

Follow-Up Recommendations

  • Patients should be followed up for re-evaluation of clinical symptoms and imaging for resolution of the process.
  • Recurrent spontaneous pneumomediastinum may warrant cardiothoracic consultation for further diagnostic evaluation (invasive studies).

Pearls and Pitfalls

  • Ensure that underlying causes are excluded.
  • Be aware of typical presenting features (chest pain, dyspnea, and neck swelling), pre-existing conditions, and precipitating factors associated with pneumomediastinum.
  • Hamman crunch is pathognomonic but not commonly seen.
  • Remember Meckler triad:VomitingLower chest painCervical SC emphysema

Additional Reading

  • Al-Mufarrej F, Badar J, Gharagozloo F, et al. Spontaneous pneumomediastinum: Diagnostic and therapeutic interventions. J Cardiothorac Surg. 2008;3:59.
  • Caceres M, Ali SZ, Braud R, et al. Spontaneous pneumomediastinum: A comparative study and review of the literature. Ann Thorac Surg. 2008;86:962 " 966.
  • Dissanaike S, Shalhub S, Jurkovich GJ. The evaluation of pneumomediastinum in blunt trauma patients. J Trauma. 2008;65(6):1340 " 1345.
  • Houn LK, Chang YL, Wang PC, et al. Head and neck manifestations of spontaneous pneumomediastinum. Otolaryngol Head Neck Surg. 2012;146(1):53 " 57.
  • Iyer VN, Joshi AY, Ryu JH. Spontaneous pneumomediastinum: Analysis of 62 consecutive adult patients. Mayo Clinic Proc. 2009;84(5):417 " 421.

See Also (Topic, Algorithm, Electronic Media Element)

  • Pneumothorax
  • Vomiting, Adult

Acknowledgment

The author gratefully acknowledges the contributions of Jennifer De la Pena and Leon D. Sanchez for previouseditions of this chapter.

Codes

ICD9

518.1 Interstitial emphysema

ICD10

J98.2 Interstitial emphysema

SNOMED

  • 16838000 Mediastinal emphysema (disorder)
  • 427445002 Tension pneumomediastinum (disorder)