You're asked to review a patient with dyspnoea and a wheeze.
Does he have pulmonary odema or an exacerbation of COPD? Is there a pneumonia? Could he have a pneumothroax?
Right, lets get an ECG and a CXR, some troponins and, for completeness (Oh how I dislike that as a reason), throw in a BNP for what it's worth. Now while we're waiting for all that to happen, we'll start him on some salbutamol nebs, give him a bolus of frusemide and get some antibiotics into him to cover for community acquired pneumonia. Is the CXR guy on his way yet? Damn, what if he has a PE? Better get a CTPA too.
Or, we could do a bedside lung ultrasound, decide what the patient actually has in the next 2 or 3 minutes and tailor the therapy to the problem.