Auscultation in High Noise Environments

Some reports I get from first responders at emergency scenes always peg the skepticism meter. Whenever I hear those things, I nod inscrutably, thank the EMT for his help, and make a mental note to verify what he told me, because the information cannot be trusted.

And nothing is more untrustworthy than a perfect set of blood pressure readings.

Whenever an EMT reports a blood pressure reading of 110/70, or 120/80, or I notice a pattern where that EMT always reports systolic and diastolic readings that end in zero, I begin to suspect his readings. Real patients are rarely that perfect, even when their blood pressures are within normal ranges.

Likewise, a reading with odd numbers also invites skepticism. Take a look at the gauge on your manual BP cuff; all the increments are in even numbers. Whenever I hear blood pressure readings like 133/75, I know that EMT is guessing.

Honestly, you’ll be more credible if you simply say, “I’m having a hard time hearing a blood pressure, but I palpated one at 144 systolic.”

See, that one is believable. Every experienced EMT has been in a situation where, for whatever reason, it was difficult to auscultate a blood pressure or hear breath sounds. We can believe you when you admit fallibility. What we can’t believe is an EMT who gets a too-precise reading, every single time. Sometimes, you have to resort to less accurate methods, like palpating a blood pressure.

By the way, unless your name is Liz Hyde, if you give me anything other than a systolic reading when you palpate a blood pressure, I won’t believe you either. Liz was my boss when I first became an EMT oh-so-many years ago, and she is the only person I have met or even heard of in the years since, who could consistently obtain an accurate systolic and diastolic blood pressure by palpation.

And even Liz can’t explain how she does it.

In Ron’s last post, he noted his improving skill at auscultating a blood pressure. One of the most difficult things for a newbie is learning to interpret what your ears are picking up. Is the patient making that noise, or is it artifact? If it is the patient making that noise, are the sounds normal or abnormal?

As it is with so many things, there is no substitute for practice. Check blood pressures on enough patients, eventually you’ll learn to discern the difference between Korotkoff sounds and ambient noise. Not only that, but you should assess breath sounds on every patient you encounter, especially the ones who have no respiratory complaints. Only when you understand what normal sounds like, will you be able to recognize abnormal sounds.

While you’re learning to recognize what normal sounds like, you can educate yourself on abnormal breath sounds over at the Rale Repository.

However, you will soon discover that obtaining blood pressures and listening to lung sounds is far easier in a quiet classroom than at a chaotic, noisy scene or in the back of a moving ambulance. Ambient noise and motion artifact tend to drown out everything we want to hear.

There are, however, a few things you can do to limit the amount of ambient noise you hear. First, and foremost, is a quality stethoscope with properly fitting ear tips.

If your stethoscope has hard plastic ear tips, ditch them and get some quality Gelseal ear tips that conform to your ear canal. Replace your old, hard plastic diaphragm with a disposable Safeseal diaphragm. This diaphragm will result in significantly louder and clearer sounds than your stock diaphragm, but you will have to use a lighter touch to notice the difference.

Next, make sure your stethoscope fits properly. For the best results, make sure the binaurals (those are the metal ear pieces) are angled forward slightly. If your soft ear tips fit properly, you should notice a substantial reduction on ambient noise when you fit them in your ears.

For an even better seal, close your mouth, pinch your nostrils shut, and try to breathe in. The resulting negative pressure will suck the soft ear tips deeper into your ear canals.

The next step is to isolate yourself and the patient (actually, whatever part of the patient you’re auscultating) from the surrounding environment. When you’re in a moving ambulance, the tires on the road, vibration from the suspension and body of the rig, and vibration from the stretcher all combine to form a distinct, low-frequency roar that often makes it impossible to hear those equally low-frequency breath sounds and Korotkoff sounds.

So, to minimize that low-frequency roar, you must minimize contact with the ambulance itself. Now you may ask, “How do I minimize contact with the ambulance if both of us are in the ambulance?”

Simple – you remove the patient’s arm from anything that vibrates. Don’t allow it to lay on the stretcher rail, or even your leg. If you hold their arm in yours, don’t rest your arm on your leg. Don’t place your feet flat on the floor. Instead, rise to your tiptoes, minimizing contact with that vibrating, moving floor.

You can avoid artifact noise from BP cuff tubing by placing the cuff on your patient’s arm upside-down, with the tubing nearer to the shoulder than the wrist. It won’t make a difference in accuracy as long as you have the artery marker correctly aligned, and it will keep those tubes out of your way. Position the cuff high enough that it doesn’t rub against the bell of your stethoscope.

This, incidentally, is the same technique you’ll use to start IVs in a moving ambulance, should you ever choose to become a paramedic. It’s just your hand, the needle, and the patient’s arm – just a fixed point in space – while everything else is moving around you.

When you’re listening to breath sounds, try to have the patient sit up, if possible. With their back pressed against the stretcher mattress, much more ambient noise is transmitted through their chest via vibration. Move clothing out of the way so that it does not brush against the tubing or bell of your stethoscope. Avoid listening through clothing if you can.

Using these tips should make it substantially easier for you to hear in the back of a moving ambulance, but if not, sometimes you must resort to less accurate, but still effective means. Palpate your blood pressures if you must. If you can’t hear breath sounds, try assessing for tactile fremitus instead. It takes practice, and it isn’t nearly as accurate as actually listening, but it’s better than nothing.

Good luck!



Korotkoff sounds: arterial sounds heard through a stethoscope applied to the brachial artery distal to the cuff of a sphygmomanometer that change with varying cuff pressure and that are used to determine systolic and diastolic blood pressure.

Artifact: noise or interference not naturally present in the matter being observed, but formed by artificial means.

Tactile fremitus: The vibrations felt by a hand placed on a chest during vocal fremitus. Place your hands on either side of the patient’s chest, and have them say, “Ninety-nine.” You should feel equal vibration on both sides of the chest.

5 thoughts on “Auscultation in High Noise Environments”

  1. Ok, next up: Tips for not falling on your face while standing on tip-toes in the back of a moving ambulance? 😀

  2. Having difficulty finding the correct spot to auscultate? Feel around with 3 fingers for the brachial pulse, and put your stethoscope bell right over to that spot, and BAM! Bob’s your uncle!

  3. I had an instructor once who would get bent about BP readings that DIDN’T end in nice even numbers, on the theory that it wasn’t possible to call it that closely. I remember taking my time, and calling it as closely as I could, and being told “that number isn’t on the dial. The dial goes ‘100, 110, 120’, so where are you getting this ‘106’ from?” Real pet peeve there, along with OB nurses who talk about cervical dilation and pronounce centimeters as ‘sawndeemeeder’. Downside of getting a hard science degree first, then going back for nursing.

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