When to Use the Diaphragm of a Stethoscope? And Everything You Should Know

When to Use the Diaphragm of a Stethoscope And Everything You Should KnowStethoscopes are pretty confusing to some people who are just learning how to use them. They don’t know what part of the stethoscope should go on the patient’s chest. Considering this, do you know when to use the diaphragm of the stethoscope?

Using the diaphragm, you can hear sounds such as S1, S2, the murmur of aortic and mitral contractions, and a pericardial friction rub. The diaphragm picks up high-pitched or high-frequency sounds. On the other hand, the bell is suited for low-pitched sounds.  

The following sections of the blog contain all the information you need to know to use the diaphragm properly.

When to Use the Diaphragm of a Stethoscope?

The problem is that many newbies don’t know the difference between the bell and diaphragm and how to use them properly. You must know that they are utilized to detect differing pitches in sounds. 

The diaphragm is designed as a big rounded part or, as said, the plastic disc of a stethoscope used to detect sounds like heart murmurs, lung sounds, bowel sounds, and check blood pressure

All of these sounds are high-frequency sounds that are comparatively easier to auscultate. So let’s dig deeper into examples of these high-pitched sounds made by the body.

What are the High-Frequency Sounds?

Normal heartbeat sounds:

The normal heartbeats are high-pitched sounds. Moreover, the sound of wheezes provided by the lungs when the patient has asthma or any other inflammation is easily detected using a diaphragm. 

Murmurs and bowels:

With the use of a diaphragm, one can better hear high-pitched murmurs such as those associated with aortic insufficiency and mitral insufficiency. Bowel sounds are another example of high-pitched sounds. 

Sound of crackling and harshness in the lungs:

Moreover, the crackling in the lungs is like the sound of firecrackers, which produces high frequencies and is better heard with the diaphragm. 

In addition, it also filters out distracting heart sounds with low frequencies. Therefore, the frequency spectrum of audible high-frequency sounds varies with the pressure applied to the diaphragm.

When to Use the Two-Sided Chest Piece?

The diaphragm (plastic disc) filters out low-pitched sounds and highlights high-pitched sounds like breathing sounds and normal heart sounds. 

In other words, to evaluate the heart (cardiac exam), you should listen using the diaphragm and repeat with the bell, as it is suitable for low-pitched sounds like some bowel sounds or some heart murmurs. 

Additionally, the diaphragm is a large size often used for adults, while young or skinny patients should use the smaller bell in diameter. 

How Can the Diaphragm Be Used for Cardiac Auscultation?

Step 1: (Aortic listening post)

On the chest structure, the doctor has to start with an aortic listening post at the second intercostal space to the right of the sternum. You have to place the diaphragm there for a few seconds to listen to any high-frequency sounds.

Step 2: (Pulmonic listening post)

 Once you have oscillated for murmurs, thrills, and gallops, you then have to move your diaphragm to a pulmonic listening post. It is at the third intercostal space to the fourth intercostal space on the left side of the sternum for listening for any murmurs or rubs. 

Step 3: (Tricuspid listening post)

You then have to move and place your diaphragm to the tricuspid listening post, which is at the fifth intercostal space to the left of the sternum.

Step 4: (Mitral valve listening post)

Lastly, finish your diaphragm examination with the mitral valve listening post at the fifth intercostal space mid-clavicular line. Again, if you are examining a female patient, you have to ask them to lift their left breast slightly to place the diaphragm on the mid-clavicular line.  

With that said, do you know what the features of a tunable diaphragm are? Don’t worry; we’ve got you covered!

What Are Tunable Diaphragms?Tunable Diaphragm stethoscope

Littmann’s stethoscopes have tunable diaphragms that can be adjusted to listening to both high and low-pitched sounds by adjusting the pressure on the chest piece. 

You could also say that pressing the chest piece gently on a patient allows you to hear low-pitched sounds. The high pitches can also be heard by pressing firmly. 

Thus, this tunable technology has made the auscultation process more manageable and effective. 

As we move on to the later parts of the blog, let’s discuss a few important ways to handle the diaphragms appropriately. 

How to Turn on Your Diaphragm? 

Step 1: A little tap on the diaphragm:

When you are using and putting your stethoscope for the first time, you have to give a little tap on the diaphragm, and that’s how your diaphragm is on if you hear a gentle tap inside your ear.

Step 2: Flip the Tubing to Hear:

However, if it doesn’t transmit the sound, flip over the tubing from where it’s connected to the diaphragm. Then click it again, and you will hear that it’s transmitting the sound to your ears, which means it is working. 

This is how your stethoscope is set up for diaphragm listening.

Step 3: Rotate the Chest Piece to Open on Any Side:

In addition, when the diaphragm is on, the bell is automatically off, which helps in preventing sound from entering through the diaphragm and vice versa. To open it, rotate it and tap it. 

How to Hold and Place the Chest Piece?3m Littman EKO CORE Digital Stethoscope

Place it directly against the skin:

The chest piece is designed with two sides, a diaphragm and a bell. Place any of these sides and hold the chest piece directly against the patient’s skin. 

It produces the best and most precise sound transmission without any distractions. However, when placing it on the cloth, it generally rubs on the chest piece and creates extra sounds. And we don’t want it.

Placing It Over a Layer of Clothing May Also Work

However, if you are in a hurry or your patient is uncomfortable, you can place the chest piece over one layer of clothing like a Tee shirt. Nevertheless, performing this is not recommended because it might result in missing essential sounds, which may be critical. 

Use the index and middle finger to hold:

Many of us do not know an essential tip regarding holding a chest piece: holding it between your index finger and middle finger. 

It makes gripping easier.

Using your two fingertips to grip the bell or diaphragm is a better choice than using your entire hand. Thus, you can use the tap to gently apply pressure to the patient’s skin without rubbing it with your fingers not to create any unwanted sounds. Likewise, auscultation should be performed with a gentle touch. 

How does the diaphragm work?

Diaphragms are closed membranes that vibrate as eardrums do. Vibrating causes the air column inside the stethoscope tube to rise and fall. The movement of air in and out of your ear canal is what causes you to hear.

The diaphragm has a much larger surface area than the column of air in the tube, so the air in the tube travels a greater distance than the diaphragm, causing increased pressure waves that leave the ear tip. 

We hear louder sounds due to larger pressure waves in our ears. The sounds are amplified in this way by stethoscopes. 

The diaphragm or the bell: Which is the most suitable to check BP? 

Well, the bell is the most suitable part if you want to check the BP of a patient. However, there is another side to the story. Let’sLet’s explore by evaluating different studies.

As a result of BP differences, it can be determined that the use of the bell and diaphragm of the stethoscope has very little, but still significant, impact on clinical BP measurements. 

What does the Research say About this Issue?

Studies involving stethoscopes with different characteristics showed somewhat different blood pressure measurements. However, comparing the bell to a diaphragm, the use of the bell results in an increased DBP of 0.66

With the short tube, the SBP is significantly higher at 0.77 mmHg compared to the standard tube. 

Comparison between bell and diaphragm:

  1. Researchers have reported conflicting results on studies comparing blood pressure between diaphragm and bell measurements in stethoscopes. For example, one of the studies found that SBP was higher and DBP was lower with a stethoscope bell than the diaphragm. 
  2. Another study measured acoustic blood pressure with both stethoscope sides, with similar results. However, significant differences were found when the Korotkoff sound was amplified with a low or high frequency
  3. Jacob, a clinician, reported significantly higher values to be obtained when the stethoscope bell was positioned over the brachial artery than utilizing the diaphragm.

Wrap Up

We have quantified the effects of stethoscope sides on BP measurements, showing that stethoscope sides have only a small effect on clinical BP measurements.

However, the diaphragm side may be more receptive to the high-frequency component of Korotkoff sounds. Therefore, clinicians mostly recommend using the bell to measure blood pressure. 

Common mistakes while using the diaphragm:

The common mistakes that people often make while using the diaphragm for the first time are:

Ignoring the Cleaning Aspect

They don’t clean their diaphragm or stethoscope after examining each patient. By not keeping it clean, your diaphragm can be infected with germs and bacteria. 

Improper Holding of the diaphragm:

Another common mistake everyone makes is they do not hold the diaphragm properly as it is recommended. Instead, they hold the chest piece with all their fingertips with the pressure that creates extra noise. 

This can be a problem when a trainer or nurse examines his patient and looks for critical sounds. 

Placement of the chest piece:

Most doctors in a hurry forget to place the chest piece directly against the patient’s skin. Unfortunately, they make this mistake again and again and fail to listen to crucial noises. 

As the cloth rubs against the chest piece, it creates unwanted noise, which most nurses and physicians ignore. 

Using the bell instead of the diaphragm:

Some who are new to the medical world don’t know the proper use of the diaphragm. For example, they don’t know which areas are detected by the diaphragm and what sounds are easy to hear by it. 

So they are confused and start using the bell side of the chest piece in areas where they may use the diaphragm. 

Does cleaning the stethoscope affect its performance?

Regular cleaning of your device creates a new and shiny look and prolongs the life of your device. 

Moreover, it is essential to buy stethoscopes from reputable manufacturers and good quality as they are more durable and reliable. The best acoustic performance is assured by routine cleaning. 

There are some general cleaning tips below that will help you keep your stethoscope in good condition. 

Cleaning your diaphragm:

If you are using a tunable diaphragm, you must keep it clean as well for better functioning. As the tunable diaphragms are removable, you can remove them from your chest piece and wipe them with alcohol and cloth. 

Besides, after the check-up of every patient, a nurse or anyone using the stethoscope may try to clean their diaphragm so that it may not be infected with germs. 

Tips to consider for Using the Diaphragm

Avoid getting your tool wet or cold:

The stethoscope should never be submerged in liquids or undergo any form of sterilization. This could be dangerous for your tool. 

Moreover, keep your tool away from skin oils, chemicals, or hot and cold liquids, they may damage the tubing, and it may eventually stop functioning. 

Rotate the diaphragm to check in case of responsiveness: 

If you suddenly can’t hear any sound from your stethoscope, make sure to rotate or check your chest piece if it’s headed correctly. Also, make sure the diaphragm is not cracked, and its rings are fixed and not loose. 

Keep your tool away from oils:

Further, check your tool’s condition to ensure the tubing is not damaged or overly tight. Also, keep your tubing away from your neck, as it produces oils that easily damage your tubing. 

Take care of your earpieces:

Over time, your stethoscope ear tips may be filled with dirt and earwax, which may not help the sound reach your ears properly. In this case, you can remove the ear tips from the ear tubes to clean them. Also, ensure that the ear tips are securely attached to the ribbed sections of the ear tubes. 

In addition, hand sanitizer should not be used to clean the stethoscope, as it contains food additives and other sensory qualities that could damage the parts of your tool.


Photo of author

Muhammad Bilal Qayyum

MBBS from Taishan Medical University and currently working in Bahawal Victoria Hospital. The blog is a great resource for both novices and experienced users when it comes to stethoscopes. As I studied and practiced, I evaluated various models on the market, which led me to become an expert in stethoscopes.

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