Pneumonia is an infection occurring within the aveolar sacs of the lungs. Pneumonia is caused by a variety of micro-organisms, including bacteria, viruses, fungi, and mycoplasma.

The most predominant symptom of pneumonia is a deep cough, which can produce mucous that is yellow or green in color and may be tinged with blood.

Other symptoms include difficulty breathing, chest pain, fever, chills, muscle aches, headaches, and sometimes delirium or mental confusion. In most cases, pneumonia is highly treatable.

However, people with pneumonia-like symptoms should seek medical care, as untreated pneumonia can develop into a serious medical condition.

In order to diagnose pneumonia, a medical practitioner will perform a series of tests to assess overall lung function, examine the efficiency of oxygen delivery to the body, and try to determine the infectious agent in order to guide treatment decisions.

Assessment of Lung Function

A visit to the doctor will always begin with a complete physical exam and medical history.  During the exam, the doctor will perform an initial assessment of breathing quality using a stethoscope.

A patient with pneumonia, who oftentimes has difficulty breathing, may exhibit breathing sounds that include wheezing, bubbling, or crackling noises—these sounds are formed as air tries to pass through and over lung secretions.

If the breathing quality, as detected by the stethoscope, indicates an infection, a doctor will typically order one or more imaging tests to visualize the interior of the lung in order to identify areas of infection and assess the overall severity of disease.

Most patients begin with a chest x-ray for this purpose; however, in severe cases, or in patients where initial treatment methods are not producing positive results, a computerized tomography (CT) scan may be performed, which generates images in greater detail.

An alternative imaging technique is bronchoscopy; this procedure involves the insertion of a tube containing a camera down the airway and into the lung in order to visualize the inflamed lung tissue.

The purpose of the lungs is for air exchange so that oxygen can be delivered throughout the body and waste products (i.e, carbon dioxide) can be removed.

Pneumonia infection can negatively impact this exchange process, as the buildup of mucous secretions can prevent the proper amount of oxygen from crossing the lung lining and entering the bloodstream.

To assess if the lungs are operating at optimal levels, doctors can test arterial blood gases to measure blood oxygen levels or perform a pulse oximetry test, which is a non-invasive method to measure blood oxygen levels using a small finger clip attached to a reader machine.

Determination of the Infectious Agent

Given that pneumonia can be caused by one of over 30 different micro-organisms, it is important to identify the underlying cause of each patient’s pneumonia, if possible.

Distinguishing the causative agent is important for guiding subsequent treatment decisions. For example, a bacterial-induced pneumonia can be treated with antibiotics, while fungal-induced pneumonia must be treated with an anti-fungal agent.

Testing can be done in a number of ways, including a sputum (mucous-based secretion brought up from a deep cough) test, a blood test, or a pleural fluid (liquid around the lining of the lungs and within the chest cavity) test.

In each test, the substance or fluid is examined by microscope and/or cultured to identify causative organisms.