Lung Sounds: Wheezes, Crackles, Rhonchi and Stridor for EMS

Lung sounds, also called breath sounds, are what you hear through a stethoscope as air moves in and out of the lungs. Listening to them is part of every breathing assessment. They tell you whether air is reaching both lungs, whether the airways are narrowed, and whether there is fluid or secretions where air should be. They are one finding among several, and they mean the most when you compare one side with the other and one reassessment with the last.

How to listen to lung sounds in the field

• Quiet the scene first. Turn down the radio and the television, pause the suction and the oxygen hiss if you can, and ask people in the room to stop talking for a moment. Good technique cannot overcome a loud room.
• Listen on skin, not through clothing. Fabric rubbing on the stethoscope makes sounds that can be mistaken for crackles. Use the diaphragm of the stethoscope and hold it firmly against the chest.
• Position the patient sitting up and, for the back, leaning slightly forward with the arms crossed in front, which moves the shoulder blades out of the way. A patient who cannot sit up can be rolled to listen to the back, within any spinal precautions your protocol calls for.
• Ask the patient to breathe a little deeper than normal through an open mouth. Listen to at least one full breath, in and out, at each site.
• Compare side to side at the same level, moving down the chest like a ladder: right then left, right then left. A difference between the two sides is often more important than the sound at any one spot.
• Listen front, side and back. Most of the lower lobes are heard from the back, and the right middle lobe is heard from the front and side on the right, so a patient examined only from the front can have findings you never reach.
• Do not over-breathe the patient. A patient asked for many deep breaths in a row can become lightheaded; let them rest if they need to.

Normal breath sounds

Normal lung sounds change depending on where you listen, because you are hearing air moving through airways of different sizes. Knowing what is normal at each site is what lets you notice something abnormal.

Bronchial sounds heard over the outer lung fields, where you would expect soft vesicular sounds, are abnormal. Solid or fluid-filled lung, such as the consolidation of pneumonia, carries the sound of the large airways out to the chest wall.

Lung sounds chart: the adventitious sounds

Adventitious sounds are added sounds that are not part of normal breathing. The terms below are the ones most EMS texts use. The names vary between programs: rales and crackles are two names for the same sound, and the standard nomenclature many references follow prefers crackles. Some texts no longer use rhonchi and describe the same sound as coarse crackles or a low-pitched wheeze. Describe what you hear, where you hear it and when in the breath, and the name matters less.

A pleural friction rub that stops when the patient holds their breath is coming from the lungs. A rub that keeps going while the breath is held follows the heartbeat and suggests the pericardium instead.

Wheezes: not all that wheezes is asthma

A wheeze means air is moving through a narrowed airway. Asthma and COPD are the common causes, but anaphylaxis, a foreign body and heart failure can all produce it. Fluid in the lungs from a failing left ventricle can narrow the small airways and make a patient wheeze, sometimes alongside crackles. The history, the age, the onset, the skin and the rest of the exam tell you which one you are looking at, and that matters because the treatments are different. Our Asthma vs COPD guide compares the two most common causes.

The silent chest

A silent chest in a patient struggling to breathe is one of the most dangerous findings in a breathing assessment. Wheezing needs moving air. When the airways are narrowed so far that almost no air moves, the wheeze fades or disappears. A patient with severe asthma who was wheezing loudly and now has a quiet chest, with exhaustion, an inability to speak, a falling respiratory rate or a change in mental status, is getting worse, not better. The reverse is also true: a wheeze that becomes louder after treatment can mean more air is moving. Read the lung sounds alongside the work of breathing, the ability to speak and the mental status, never on their own.

Stridor: an upper airway problem

Stridor comes from narrowing above the lungs, in the larynx or the trachea, so you usually hear it best over the neck and often without a stethoscope at all. It means a patient's main airway is partly blocked. In a child, croup and epiglottitis are classic causes, and a foreign body is always on the list. In an adult, think of anaphylaxis and angioedema, a foreign body, swelling from burns or smoke, and trauma to the neck.

• Keep the patient calm and in the position they choose. A child with stridor is often most comfortable on a parent's lap.
• In a child with suspected epiglottitis, do not look in the throat or do anything that upsets them. Agitation can turn a partial obstruction into a complete one.
• As with wheezing, stridor that gets quieter in a patient who is tiring can mean less air is moving, not that the obstruction is better.
• Stridor with hives, swelling or low blood pressure points to anaphylaxis, which our Perfusion and Shock guide covers.

Absent breath sounds on one side

Breath sounds that are clear on one side and diminished or absent on the other tell you air is not reaching one lung. The common field causes are air in the chest (a pneumothorax) and blood in the chest (a hemothorax). A large pleural effusion, a collapsed lung and a mucus plug can do the same thing more slowly.

• Pneumothorax: diminished or absent sounds on the affected side, often with sudden chest pain and shortness of breath. It can follow trauma or happen on its own, classically in a tall, thin young adult or a patient with lung disease.
• Tension pneumothorax: air builds up under pressure and blocks blood returning to the heart. Look for absent sounds on one side with worsening distress, difficulty ventilating, low blood pressure and distended neck veins, which is the obstructive shock picture our Perfusion and Shock guide describes. Tracheal deviation away from the affected side is a late sign and is often hard to see in the field; do not wait for it. Decompression is within paramedic scope in many systems under protocol.
• Hemothorax: diminished sounds on the affected side with the signs of blood loss, because each side of the chest can hold a large share of the circulating volume. Neck veins may be flat rather than distended.
• After an advanced airway: breath sounds heard on the right but not the left can mean the tube has passed too far into the right mainstem bronchus. How placement is confirmed and corrected, including capnography, is your protocol's.

Crackles and fluid in the lungs

Crackles are the sound of small airways and air sacs popping open against fluid or collapse. When the left ventricle fails, blood backs up into the lungs and fluid leaks into the air sacs, and the patient becomes short of breath with crackles that usually start at the bases and climb higher as it worsens. That is the fluid backing up that our Heart Anatomy and Blood Flow and Perfusion and Shock guides describe in left-sided failure and cardiogenic shock. Not every patient with crackles is in shock, and the absence of crackles does not rule out a heart problem: a patient in shock from a right ventricular infarct can have clear lungs.

Crackles have other causes too. Pneumonia tends to produce crackles in one area, often with fever, cough and bronchial sounds over the same spot. Patients with long-standing lung fibrosis may have crackles at their baseline. Fine crackles at the bases in a patient who has been lying still can clear after a few deep breaths or a cough. Ask what is new, and compare one side with the other.

The limits of auscultation in a moving ambulance

Road noise, the engine, the siren and the vibration of a moving ambulance make subtle lung sounds very hard to hear and can create sounds that are not there. Listen carefully before the wheels move, so you have a baseline, and recheck at a stop where you can. While moving, lean on the findings you can still trust.

• Work of breathing: the rate, the depth, the use of accessory muscles, retractions in a child, and the position the patient chooses.
• How many words the patient can say between breaths.
• Skin color and mental status, including new confusion or drowsiness.
• The pulse oximeter, remembering it can read poorly when perfusion is poor.
• The capnography waveform, if your service uses it on a patient who is not intubated. A sloping shark-fin shape suggests narrowed airways, as our Capnography guide describes.

Documenting and reporting lung sounds

Write down what you heard, where and when, and on which side, and how it changed: "expiratory wheezes in all fields on arrival, decreasing after treatment" tells the receiving team far more than "wheezes". Say whether you listened to the back. If you could not hear well, say so rather than recording clear and equal breath sounds you did not truly hear.

The short version

• Quiet the scene, listen on skin, sit the patient up, and compare side to side at the same level, front, side and back.
• Vesicular sounds are normal over most of the lungs; bronchial sounds belong over the trachea, and heard elsewhere they suggest consolidation.
• Wheezes are lower airway narrowing; crackles are fluid or collapse in the small airways; rhonchi are secretions in the large airways; stridor is upper airway narrowing; a friction rub is inflamed pleura.
• A silent chest in a struggling patient means almost no air is moving. It is a sign of a life-threatening attack, not improvement.
• Absent sounds on one side suggest a pneumothorax or hemothorax; with low blood pressure, distended neck veins and difficulty ventilating, think tension pneumothorax.
• Crackles from fluid often start at the bases, and a patient in shock can still have clear lungs.
• In a moving ambulance, listen before you leave and rely on work of breathing, speech, skin, mental status and your monitors en route.