Posterior auscultation, which involves placing the stethoscope at the back during a physical examination, is always done to provide data for comparison with anterior readings. It is set to determine if an individual has normal, abnormal, decreased, or absent breath sounds.
Comparing Anterior and Posterior Sounds with a Stethoscope
Listening to the anterior surface primarily focuses on the heart and parts of the lungs, while the posterior surface allows for better evaluation of the lungs, as well as certain aspects of the heart.
The diaphragm (larger) side is ideal for detecting breathing, as well as normal heart rhythms. The bell (smaller) side is better for detecting abnormal heart sounds and bruits, as well as bowel sounds.
The small pinhole size hole in the centre of the diaphragm is perfectly normal and will not affect the performance of your stethoscope, and has been placed there specially by the 3M Littmann designers.
The diaphragm of the stethoscope is the larger flat side and is typically used to hear normal high pitched sounds, and the bell of the stethoscope is the cone shaped side of the stethoscope, which is usually used to hear low pitched sounds.
Rotate to the correct side. When using a double-sided Littmann stethoscope, you need to open (or index) the side you want to use—bell or diaphragm—by rotating the chestpiece. If the diaphragm is open, the bell will be closed, preventing sound from coming in through the bell, and vice versa.
Place the diaphragm of your stethoscope lightly over the right lower quadrant and listen for bowel sounds. If you don't hear any, continue listening for 5 minutes within that quadrant. Then, listen to the right upper quadrant, the left upper quadrant, and the left lower quadrant.
Conclusions: Both sides of the acoustic stethoscope give similar results in the measurement of office blood pressure and either side can be used in the reliable measurement of blood pressure.
Stethoscope Basics
There are two sides of the chestpiece. On one side is the diaphragm, a flat, metal disc that in turn contains a flat, plastic disc. The diaphragm is the larger component of the chestpiece. On the other side is the bell, a hollow, bell-shaped piece of metal with a tiny hole on top.
The intestines are hollow, so bowel sounds echo through the abdomen much like the sounds heard from water pipes. Most bowel sounds are normal. They simply mean that the gastrointestinal tract is working. A health care provider can check abdominal sounds by listening to the abdomen with a stethoscope (auscultation).
But what about when your doctor moves it to the back of your body? This helps doctors hear your lungs—especially the two lower lobes, which you can't hear at all from the front of your body, explains Robin Maier, M.D., an assistant professor of family medicine at the University of Pittsburgh School of Medicine.
The aorta is the main blood vessel coming from the heart. Your provider may listen to the blood flow in the carotids with a stethoscope. This can tell them if you may be in danger of suffering a stroke. A clear carotid makes a "thump, THUMP" noise like a heartbeat.
Fluid in the lungs: Doctors listen for absent or decreased breath sounds to determine if you have fluid blocking your breathing, which can be caused by pneumonia, heart failure, and pleural effusion. Rhonchi, a snoring-like sound: This sound occurs when air is blocked or inhibited through your large airways.
Physical exam
Your doctor will listen to your lungs with a stethoscope. If you have pneumonia, your lungs may make crackling, bubbling, and rumbling sounds when you inhale.
Your doctor may also use the stethoscope to listen for sounds that your intestines make. These sounds can show problems including: Constipation or slow movement of waste through the intestines. Diarrhea or other intestinal distress.
The diaphragm is best for detecting high-pitched sounds such as bowel sounds. Bowel sounds are sometimes loud enough to hear without a stethoscope.
Wearing the headset improperly, (eartips pointing backwards, for example, as in Figure C) can result in a poor acoustic seal and, in some cases, complete sound blockage.
The stethoscope is placed gently over the artery at the point of maximal pulsation. It must not be pressed too firmly or touch the cuff, or the diastolic pressure may be underestimated.