대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Postobstructive pulmonary edema & hemorrhage

Radiologic Findings

Immediately postoperative anteriorposterior chest radiograph shows diffuse bilateral pulmonary consolidation. Chest CT scans (lung window images) reveal diffuse pulmonary consolidation and ground-glass attenuation in both lungs, predominantly in dependent lung. Also noted are poorly-defined ground-glass attenuation nodules. This was caused by Postobstructive pulmonary edema & hemorrhage (Negative pressure pulmonary edema & hemorrhage) due to upper airway obstruction caused by aspiration & packing for hemostasis at the site of tonsillectomy.
Follow-up chest radiograph 2 days later shows marked improvement of pulmonary consolidation.

Brief Review

Postobstructive pulmonary edema (negative pressure pulmonary edema, NPPE) is noncardiogenic pulmonary edema caused by upper airway obstruction. In children, it has been observed after intubation secondary to croup and epiglottitis. In both children and adults, it has been reported as a complication of postanesthetic laryngospasm, strangulation, hanging, foreign body airway obstruction, upper airway tumors, and obstructive sleep apnea.
Postobstructive pulmonary edema is the result of a marked decrease in intrathoracic pressure caused by forced inspiration against a closed upper airway resulting in a disruption of the normal intravascular Starling mechanism, ultimately leading to the transudation of intravascular proteins and fluid into the pulmonary interstitium. An obstruction that prevents both inspiration and expiration may create a high positive intrathoracic pressure that impairs the development of edema initially. Later, edema develops as the obstruction is relieved and the intrathoracic pressure suddenly drops. The onset of postobstructive pulmonary edema is usually rapid, and without prompt recognition and intervention, the outcome can be fatal.
Diffuse alveolar hemorrhage may develop following an acute upper airway obstruction. The mechanism underlying negative pressure pulmonary hemorrhage (NPPH) is stress failure of the alveolar-capillary membrane caused by the marked elevation of pulmonary capillary wall tension. Decreases in pericapillary interstitial pressure might contribute significantly to the development of stress failure in NPPH.
At chest radiography and CT, postobstructive pulmonary edema typically manifests as septal lines, peribronchial cuffing, and, in more severe cases, central alveolar edema. Cardiac size is usually normal, indicating a pressure edema that is not related to overhydration.
It is characterized by a rapid onset (within minutes) and resolution, with a significant clinical and radiographic improvement in 12 to 24 h. Most patients require temporary intubation and positive end-expiratory pressure. Diuresis and/or fluid restriction are often utilized. Hemodynamic measurements, including pulmonary capillary wedge pressure, pulmonary arterial pressure, and central venous pressure taken following the development of edema, are normal.

References

1. Thomas CL, Palmer TJ, Shipley P. Negative pressure pulmonary edema after a tonsillectomy and adenoidectomy in a pediatric patient: case report and review. AANA J. 1999;67:425-430.
2. Gluecker T, Capasso P, Schnyder P, et al. Clinical and radiologic features of pulmonary edema. Radiographics 1999;19:1507-1531
3. Schwartz DR, Maroo A, Malhotra A, Kesselman H. Negative pressure pulmonary hemorrhage. Chest. 1999;115:1194-1197.

Keywords

Lung, Iatrogenic lung disease,