V/Q Scan

Sudden dyspnea, pleuritic chest pain, tachycardia, or unexplained hypoxemia can raise concern for pulmonary embolism (PE). The imaging question is not simply whether the lungs look abnormal; it is whether air is reaching a region that has lost its blood supply. A V/Q scan compares those two distributions. V/Q scanning is the preferred first-line imaging option for suspected PE when iodinated contrast is contraindicated, such as severe renal insufficiency or a contrast allergy. It is also preferred in pregnancy and may be selected in younger patients when reducing radiation exposure is a concern. A standard study exposes the client to approximately 1–2 mSv, compared with about 5–7 mSv for CTPA; the lower dose does not remove the need to justify the study or individualize the choice. The RPN’s immediate task is to recognize whether the client is stable enough for imaging, preserve oxygenation during the process, and communicate deterioration. The scan’s probability category must be interpreted with the pre-test clinical picture by the authorized provider or radiology team.