A pulmonary embolus can be a life-threatening condition. Its recognition is of vital importance as it is a potentially treatable condition. Which of the following is NOT consistent with a diagnosis of a pulmonary embolus?

b. Acute pulmonary emboli is normally present with type I respiratory failure, e.g. low PaO2 and normal or low PCO2. This option represents type II respiratory failure which is seen in the context of chronic pulmonary emboli. The diagnosis of a pulmonary embolus should be considered in patients with hypoxia and tachypnoea in the absence of any clinical signs, e.g. pneumonia. Occasionally on chest X-ray a pulmonary embolus can cause a wedge-shaped infarct (due to loss of blood supply to an area of lung), more commonly the chest X-ray is clear. In cases of large pulmonary embolus the characteristic SIQIII TIII pattern may be seen on ECG, more commonly a tachycardia and right axis deviation are seen. Calf swelling unilaterally virtually confirms the diagnosis in a patient who has become acutely short of breath – in fact, guidelines state that in patients with a confirmed deep vein thrombosis with acute onset shortness of breath the diagnosis of a pulmonary embolism should be assumed and treatment continued for the appropriate length of time, usually 6 months.