Acute Severe Asthma Asthma can be unpredictable, but it is important to recognize the difference between a minor flare-up and an attack that could be life-threatening. Peak Flow Meter A peak flow meter for asthma is like a thermometer for a fever—it helps you monitor what's going on inside your lungs by measuring airflow out of the lungs. Emergency Care: When Is It the Right Choice? You may think of the ER as a source of the most immediate medical attention, but if your situation is not a real emergency, this isn't true.