Flash pulmonary oedema. Coloured chest X-ray of a patient with flash pulmonary oedema (grainy white areas), the sudden onset of fluid accumulation in the lungs. This is most often caused by an acute heart attack but may also be caused by failure of the kidneys. The presence of fluid in the lungs interferes with gaseous exchange, where oxygen enters the blood from the lungs, and carbon dioxide enters the lungs from the blood to be exhaled. This causes shortness of breath, wheezing, anxiety and can lead very quickly to respiratory arrest and death. Immediate treatment is with ventilation and vasodilatory drugs, but the underlying cause needs to be treated to prevent reoccurrence.