A patient who arrives at an emergency room or other healthcare facility and complains of an asthma attack will undergo a quick examination during which a nurse or physician will:

• Listen for breath sounds, particularly wheezing (a whistling or high-pitched sound that results when breathing tubes are narrowed or obstructed). The absence of wheezing may indicate severe bronchoconstriction, a condition known as “silent chest” that can be extremely dangerous.
  
  
• Note the patient’s rate of breathing and other physical signs. These include observing whether or not the patient is using additional muscles to help with breathing.
  
  
• Perform a pulse oximetry test. This is a painless procedure during which a probe is attached to the patient’s fingertip or earlobe to measure the amount of oxygen in the blood.
  
  
• Take readings of the patient’s blood pressure and pulse.

A physical examination and brief medical history will follow. Medications will not be given until a physician is absolutely sure the patient has no other conditions that might cause administration of a drug to harm the patient. The patient may receive oxygen, and an asthma medication designed to quickly open airways and ease breathing.  

Other tests that may be performed include:

• Chest x-ray. A physician may request this to check for coexisting medical conditions, such as an upper respiratory infection or pneumonia.
  
  
• Arterial blood gas test. A blood sample is taken from an artery, usually in the wrist. This sample is then used to measure the levels of both oxygen and carbon dioxide in the blood. As an asthma attack progresses, oxygen levels in the blood drop while carbon dioxide increases. Too much carbon dioxide buildup in the blood can be dangerous, and requires immediate treatment.