Egophony is a condition characterized by a shift in vowel sound that is heard through a patient's lungs. A positive egophony test indicates that fluid has accumulated in or around the lungs or that scar tissue has formed inside the lungs. This test is one of a number of voice transmission tests that require the patient to speak softly while the doctor listens to the lungs with a stethoscope. In patients with egophony, the sound of the letter E will take on the qualities of the letter A when heard through the lungs.
The term egophony, which may also be spelled aegophony, comes from two Greek terms that mean "goat" and "sound." This name was given to the disorder because the shift in sound from E to A makes a patient's voice sound vaguely goat-like when heard through a stethoscope. This condition is only noticeable when listening directly to a patient's lungs as the vowels will not sound distorted when a patient is heard through the air.
A non-invasive diagnostic tool, an egophony test is conducted in a doctor's office or hospital. The patient will be asked to speak, often repeating a word with a strong E sound, while the doctor listens to the lungs in a number of different places. It is possible for some parts of the lungs to indicate egophony while other parts sound normal.
The shift in vowel sound when heard through the lungs is usually caused by the presence of additional fluid in or around the lungs. This fluid transmits high frequency sounds more easily than it does low frequency sounds. In patients with healthy lungs, listening to the lungs while a patient speaks will sound the same as listening to a patient speak through the air.
An egophony test may be used by doctors as a preliminary diagnostic tool and can indicate pneumonia, pleural effusion, or idiopathic pulmonary fibrosis. In pneumonia, fluid builds up in a patient's lungs, making some areas of the lungs unsuitable for oxygen-carbon dioxide exchange with red blood cells. Patients with pleural effusion may have a build-up of fluid around the lungs, a condition that makes it harder for the lungs to expand to their full capacity. Idiopathic pulmonary fibrosis is a build-up of scar tissue or a swelling of lung tissue that can also make the lungs less efficient. If egophony is found in a patient, further tests to determine whether one of these conditions is the cause need to be performed.