|Subcutaneous emphysema occurs when air gets into tissues under the skin. This usually occurs in the skin covering the chest wall or neck, but can also occur in other parts of the body. Subcutaneous emphysema is characterized by painless swelling of the tissues because of air tracking along tissue planes. It is commonly seen over the chest wall around drain sites, in the head and neck. Palpation elicits a characteristic tissue paper feeling beneath the fingers. Air may track deeper into the mediastinum, retroperitoneum, scrotum, and down into the limbs. It is rarely a problem clinically but may herald the presence of a pneumothorax or other visceral damage.
High-impact journals are those considered to be highly influential in their respective fields. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.