Pneumomediastinum & PC

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radiology

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PNEUMOMEDIASTINUMDef: free air/gas within the mediastinumGas origin:IntrathoracicTrachea, bronchiEsophagusLungsPleural spaceExtrathoracicHead & neck injuryRetroperitoneumCan lead to pneumothorax, pnemopericardium, pneumoperitoneum

RADIOLOGICAL FEATURESSubcutaneous emphysemaHyperlucent lines enhancing mediastinal viscera & outline lateral heart bordersContinuous diaphragm signRing-around-pulmonary-artery signThymic/spinnaker sail signNaclerios V signTubular artery signpneumopericardiumExtrapleural sign1) ring-aroundpulmonary-artery sign (air surrounding the extrapericardial segment of the right main pulmonary artery and appearing as a lucent ring around the right pulmonary artery)2) thymic/spinnaker sail sign (outlining of the thymus due to large pneumomediastinum elevating the thymic lobes)3) V sign (confluence of innominate veins outlined in a frontal view)4) Naclerio's V sign (air outlining the lateral border of the descending aorta and extending laterally between the parietal pleura and medial left hemidiaphragm)3Subcutaneous emphysemaLucencies overlying the shoulder and upper chest (blue circle)Red arrow: supraclavicular emphysemaWhite arrow: air in mediastinum

Enhancement of heart borders

Enhancement on mediastinal structuresAir outlining ascending aorta

Continuous diaphragm sign

Ring around pulmonary artery signLucent ring around pulmonary artery

Thymic/Spinnaker sail signthymus separated from mediastinal structures

Naclerios V signAir outlining the descending aorta intersects with air outlining the left hemidiaphragm

Tubular artery signAir outlining left subclavian artery & left carotid artery

PneumopericardiumAir between sternum & heart

Extrapleural signAir outlining the left hemidiaphragm

CT ScanAir in supra-aortic, sub-aortic & para-cardiac mediastinum

Air within mediastinum (white arrows)Subcutaneous emphysema (black arrows)

PULMONARY CONTUSIONDef: injury to the lung parenchyma without laceration (blunt trauma)often occur in small children in the absence of fractures due to the high compliance of the chest wall.a/w bruising, ribs #, flail chestPathology:Hemorrhage into the lung parenchyma produces airspace disease

The diagram depicts the onset of selected aspects of acute inflammation and permeability injury associated with blunt trauma-induced LC. Direct traumatic insult to the lungs generates an innate inflammatory response that includes the recruitment and activation of blood leukocytes, the activation of lung tissue macrophages, and the production of multiple mediators such as cytokines and chemokines. Neutrophils contribute significantly to the severity of inflammatory LC injury, and are activated at least in part via Toll-like receptors (TLRs) such as TLR 2 and 4 in the epithelium. Inflammatory mediators in LC are also released by alveolar type II cells and other resident pulmonary cells. This inflammatory response, in conjunction with direct LC-induced tissue injury, damages the barrier integrity of the alveolocapillary membrane and increases epithelial cell apoptosis/necrosis. Plasma proteins and other substances in permeability edema enter the alveoli and inactivate (inhibit) lung surfactant, exacerbating respiratory deficits. LC injury can also induce fibroblast activation and proliferation, although the mechanistic contributions of these cells to the progression of acute inflammatory injury are unclear17Plain radiographFeatures seen within 6 hours after traumaNot sensitive, low clinical valueFaint patchy consolidative regions following history of blunt trauma.Usually shows rapid improvement with time, signs of contusion have often resolved within 48 hoursIf consolidation > 72 hours, consider:AspirationARDSPneumoniaBlue: alveolar opacitiesRed: associated ribs #

CT ScanRed: evidence of pulmonary contusionBlue: rib #

Most sensitive

Typically seen as focal, non segmental (typically crescentic) areas of parenchymal opacification