Pneumomediastinum

* More Common Among Children and Neonates

• First Described By Laennec 1819 as a consequence of Traumatic Injury• Then Spontaneous Pneumomediastinum was described by Hamman in 1939

* Rare Condition

It is defined as free air or gas contained within the mediastinum, which almost invariably originates from the alveolar space or the conducting airways.

Pneumomediastinum

Spontaneous

Traumatic

Spontaneous

• Rupture of Marginally Situated Alveoli (high intraalveolar pressure)

• Erosion of a Tracheal Or Esophageal Tumor

•Pneumoperitoneum, Pneumoretroperitoneum

Traumatic

• pulmonary interstitial emphysema (positive pressure ventilation)

• ruptured bronchus (commonly associated with pneumothorax)

• ruptured esophagus (diabetic acidosis, alcoholic, Boerhaave)  

Pathophysiology

The Macklin Effect 1944

o alveolar rupture

o air dissection along the bronchovascular sheath

o free air reaching the mediastinum

ComplicationsRarely leads to significant complications by it self

Significant Illness Comorbid Disease

Trauma

Tension Pneumomediastinum• Rare• Elevated Mediastinal pressure leads to

diminished cardiac output, either by:

• When extensive subcutaneous and mediastinal gas is present, airway compression may also occur.

direct cardiac compression

reduced venous return

Statistics• SPM from 1 per 800 to 1 per 42,000 pediatric

patients presenting to ER. from 1 per 12,000 to 1 per 30,000

admission to the hospital. 0.3% incidence of PM in association with

asthma over a 10-year period.

• TPM 10% of blunt chest injury patients will

develop PM.

Mortality & Morbidity

SPM is a self limited condition

are generally attributable to underlying disease states.

as high as 50-70% as seen in Boerhaave syndrome

is not associated with an increased mortality rate in patients with sepsis-induced ARDS

Gender

29 cases of SPM over a 10-year period, 69% were males

Is a body habitus favoring a tall thin build is an additional risk factor for the development of SPM?

TPM is more common in males, reflecting the male predominance among those who experience trauma and accidents.

AgeThe peak prevalence of SPM is seen in the second to fourth decades of life.

reflects involvement in activities that increase the risk of developing SPM

the force of an individual's cough, vomit, and Valsalva maneuvers (all of which may lead to PM) attenuates with age

The age distribution for PM occurring in conjunction with specific disease processes reflects the age profile of the particular disease.

Clinically• Chest pain• Dyspnea• Fever• Dysphonia• Throat pain• Jaw pain• Miscellaneous : Dysphagia, neck swelling, and torticollis

Chest pain

IN SPM said to be a feature in 50-90% of cases

• retrosternal in location• worsened by inspiratory maneuvers• may radiate to the shoulders or back thus suggesting MI or pericarditis

in 27% of persons with asthma with PM

Dyspnea

may reflect associated illnesses such as asthma, a coexistent pneumothorax, or a tension PM.

FeverLow-grade fever may be present

following cytokine release that is associated with air leak.

mediastinitis or infectious/inflammatory disorders should be included in the differential diagnosis

Dysphonia

Signs• Subcutaneous air

•The Hamman sign

•Associated pneumothorax

•Other diseases

•Oxygen saturation

• not pathognomic of PM

•subcutaneous emphysema in 73% of patients presenting with asthma subsequently found to have PM.

•The positive predictive value of this sign for PM in the previous series was 100%.

Subcutaneous air

The Hamman sign• pathognomic of PM

• precordial systolic crepitations and diminution of heart sounds

• prevalence of 10% to 50% PM patients

Oxygen saturation

• Pulse oximetry is mandatory in all patients with suspected PM

•In a series of children with asthma presenting to an emergency department, those with PM had a significant difference in oxyhemoglobin saturation (90% vs 94% of those without PM, p = 0.03).

Work Up

Chest X-Rayusually reveals a pneumomediastinum.

• thymic sail sign

•"ring around the artery" sign

•double bronchial wall sign

•continuous diaphragm sign

•the extrapleural sign

spinnaker sail sign

Subcutaneous air

continuous diaphragm sign

CT-Scan• provide additional diagnostic information regarding the presence of coexisting illness•in diagnosing small pneumomediastinum not visible on chest radiography.

chest radiography alone may result in a missed diagnosis in 10% of patients presenting with pneumomediastinum.

Contrast radiography

suspected esophageal perforation

ABG

ECG

Spirometry

?should not be undertaken in patients with pneumomediastinum

because the increased alveolar pressures may further exacerbate the air leak.

TreatmentMedical Care

• Most are AsymptomaticSpontaneously resolve

• Adequate analgesia

• Some Points mechanical ventilation & PM? high-frequency oscillatory ventilation Children with ARDS and PM? Nitrogen washout with inhalation of

100% oxygen

• The use of the lowest pressures or tidal volumes necessary to achieve satisfactory carbon dioxide removal and oxygenation.

Mechanical Ventilation & PM?

• Permissive hypercapnia, a ventilatory strategy that is based on maintaining adequate oxygenation and blood pH while allowing high partial pressure of carbon dioxide, allows for ventilatory support while minimizing barotrauma.

TreatmentSurgical Care

Mediastinoscopy

Mediastinal drainage

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