Lung Sounds for EMT-B: Crackles, Wheezes, Stridor, and What Each Means

Lung sounds are an EMT-B assessment finding. They are not a reason to invent ALS-level treatment or make a hospital diagnosis in the field. Your job is to hear what is happening, connect it to breathing and perfusion, treat within scope, request ALS when appropriate, and reassess.

That framing matters. Lung sounds are useful because they change priority and treatment decisions. They help you decide whether oxygen, positioning, suction, bag-valve-mask ventilation, albuterol assistance, epinephrine auto-injector, CPAP where authorized, ALS intercept, or rapid transport is needed.

How to actually listen

Most missed lung sounds are technique failures, not knowledge failures.

• Use the diaphragm of the stethoscope, placed on skin. Clothing generates noise that sounds like crackles.
• Listen for a full inspiration and expiration at each site. One quick breath tells you almost nothing.
• Compare side to side at the same level. You are looking for symmetry as much as for a specific sound.
• Cover the standard fields: anterior apices near the second intercostal space at the midclavicular line, the mid-axillary lines at roughly the fifth intercostal space, and the posterior bases when the patient's position allows it.
• Listen to the bases when you suspect fluid and the upper fields when you suspect bronchospasm. Early crackles collect at the bases in a seated patient.
• In a moving ambulance, road noise wins. Get your baseline before you move if the patient is stable enough.

Note where the sound is, when in the respiratory cycle it happens, and whether it is one side or both. Location, timing, and symmetry carry most of the information.

Quick reference: sound to likely cause

Each entry gives the sound, where it originates, the classic timing, and the conditions students should associate with it.

• Wheezes: lower airway narrowing, usually expiratory and high-pitched, sometimes both phases. Think asthma, COPD, bronchiolitis, allergic reaction, and fluid-related narrowing in heart failure.
• Crackles, also called rales: fluid or collapsed alveoli reopening, usually end-inspiratory, often at the bases. Think pulmonary edema, heart failure, pneumonia, and atelectasis.
• Rhonchi: secretions in the larger airways, low-pitched and coarse, often changing after a cough. Think bronchitis, pneumonia, COPD exacerbation, and aspiration.
• Stridor: upper airway obstruction, classically inspiratory and high-pitched, often audible without a stethoscope. Think anaphylaxis, croup, epiglottitis, foreign body, and airway burns or swelling.
• Pleural friction rub: inflamed pleural surfaces, a grating sound during both phases, often painful with breathing. Think pleurisy or pleural inflammation.
• Diminished or absent sounds: air is not moving in that region. Think pneumothorax, hemothorax, severe bronchospasm, obstruction, or shallow ineffective breathing.

The classic timing is a starting point, not a rule. Severe bronchospasm can produce inspiratory and expiratory wheezing, and severe upper airway obstruction can produce stridor in both phases.

Wheezes

Wheezes come from air moving through narrowed lower airways. Students usually associate them with asthma, but wheezing also appears in COPD, bronchiolitis, allergic reactions, and heart failure. At EMT-B level the action set is the same regardless of the label.

• Assess severity by speech. Full sentences, phrases, single words, or no words is a fast severity scale.
• Check SpO2 and work of breathing. Target saturation for most adults is at least 94%. Many protocols accept a lower target for known COPD patients, commonly 88-92%, because of the risk of blunting respiratory drive. Follow your local protocol.
• Provide oxygen when hypoxic or in significant distress.
• Assist with the patient's prescribed albuterol metered-dose inhaler if your protocol allows it. Expect a tachycardic side effect. That is not a reason to withhold it from a bronchospastic patient.
• Request ALS for severe distress, poor response, or a deteriorating mental status.

Do not let wheezing distract from work of breathing. A patient who is tiring, altered, cyanotic, or unable to speak needs escalation now.

The silent chest

A severely asthmatic patient who stops wheezing has not necessarily improved. If wheezing disappears while effort increases, saturation falls, and mental status declines, air movement has stopped. That is a pre-arrest finding. Ventilate, request ALS, and transport.

Cardiac wheeze

Wheezing can occur in heart failure when fluid narrows small airways. Bronchodilators do less for it than positioning and pressure support. This is one reason to build your impression from history, edema, onset, and skin signs rather than the sound alone.

Crackles

Fine crackles at the bases suggest fluid in the alveoli or alveoli popping open. They are strongly associated with pulmonary edema and heart failure, and also occur in pneumonia.

• Sit the patient upright unless something prevents it. Position is a real intervention here.
• Provide oxygen titrated to the patient's saturation and effort.
• Apply CPAP if your state and local protocol authorize EMT-level CPAP and the patient meets criteria. Where it is not authorized, this is an ALS or hospital intervention.
• Trend vital signs closely. Rising work of breathing with falling saturation is a deterioration curve.
• Request ALS for severe distress. Transport without delay.

Combine crackles with the rest of the picture. Gradual onset with fever and a productive cough points a different direction than sudden nocturnal breathlessness with leg edema and a history of heart failure. You are not diagnosing either one in the field. You are deciding urgency and destination.

Rhonchi

Rhonchi are coarse and low-pitched, and usually mean secretions in the larger airways. They often shift or clear after a cough, which is a useful bedside distinction from crackles.

• Position for airway protection and drainage.
• Suction when secretions are audible, visible, or interfering with ventilation.
• Provide oxygen as indicated and reassess after suctioning.
• Escalate if the patient cannot protect their own airway.

A patient who cannot clear their own secretions is an airway patient, not a lung sound patient. Treat the airway.

Stridor

Stridor is an upper airway warning sound. It means the obstruction is at or above the larynx, and it can deteriorate faster than any other finding on this page.

• In allergic reactions, stridor with swelling, hives, respiratory distress, or hypotension should make you think anaphylaxis. Administer the epinephrine auto-injector per protocol, 0.3 mg intramuscularly for adults and 0.15 mg for pediatric patients under 30 kg, in the lateral thigh.
• Provide high-flow oxygen and keep airway and suction equipment immediately available.
• Do not force a position change on a child who has found a position that works. Agitation worsens upper airway obstruction.
• Do not attempt blind finger sweeps for a suspected foreign body.
• Request ALS and transport. Airway swelling that is progressing is a time-critical problem.

Stridor in a child raises specific concerns that are managed the same way at EMT-B level: keep the child calm, give oxygen in whatever form is tolerated, avoid instrumenting the airway, and move.

Absent, diminished, or unequal breath sounds

Unequal or absent sounds are structural findings until proven otherwise.

• Absent unilateral breath sounds after trauma is a high-risk finding. EMT-Bs do not perform needle decompression in the national scope. Your actions are rapid recognition, oxygen or assisted ventilation, rapid transport, early hospital notification, and ALS intercept.
• Diminished sounds everywhere with poor chest rise means inadequate ventilation. Bag-valve-mask ventilation with supplemental oxygen is the treatment, not a nonrebreather.
• Sounds absent on one side after an airway intervention or a choking episode may indicate obstruction. Reassess the airway before assuming a chest problem.

Watch for the associated findings that raise urgency: tracheal deviation, distended neck veins, hypotension, subcutaneous emphysema, and progressive difficulty ventilating. Those belong in your radio report.

Fitting lung sounds into the assessment

Lung sounds are one input. The decision hierarchy at EMT-B level does not change.

• Is the airway patent and protected? If not, fix that first.
• Is ventilation adequate in rate and depth? If not, assist with a bag-valve mask.
• Is oxygenation adequate? If not, apply oxygen appropriate to severity.
• Is perfusion adequate? Skin, pulse, mental status, and blood pressure.
• Does this patient need ALS, and how early can that intercept happen?
• Reassess after every intervention. Unstable patients every 5 minutes, stable patients every 15.

How to document lung sounds

Document what you heard, where you heard it, and what changed. "Wheezes bilateral upper fields, SpO2 89%, improved to 94% after oxygen and prescribed MDI assistance" is stronger than "asthma." The first sentence is an assessment trail. The second is a label.

Record a set before intervention and a set after. A documented response to treatment is the most useful thing you hand off, and it is also what a chart review will look for.

Common NREMT traps

• Treating the sound instead of the patient. The scenario says wheezing, so students reach for albuterol while ignoring an altered mental status and a falling saturation. The failing patient needs ventilation first.
• Reading a silent chest as improvement. Decreasing wheeze with increasing effort and falling saturation is deterioration, not resolution.
• Choosing needle decompression for absent unilateral breath sounds. That is outside the EMT-B national scope. The answer set for a Basic is oxygenate, ventilate, transport rapidly, and get ALS.
• Assuming crackles always mean heart failure. Pneumonia produces crackles too, and the field treatment differences at EMT-B level are position, oxygen, and urgency rather than a diagnostic label.
• Withholding oxygen from a COPD patient in severe distress out of fear of hypoxic drive. Hypoxia kills faster than the theoretical risk. Titrate to your protocol's target, commonly 88-92% for known COPD, and never leave a severely hypoxic patient untreated.
• Confusing stridor with wheezing. Stridor is upper airway and usually inspiratory. That distinction changes whether you are thinking bronchodilator or epinephrine and rapid transport.
• Applying a nonrebreather to a patient whose problem is inadequate ventilation. Supplemental oxygen does not correct a rate and depth failure.
• Delaying epinephrine in anaphylaxis while gathering more history. Stridor plus hives plus distress after an exposure is enough.
• Forgetting to reassess lung sounds after treatment. A missing post-intervention reassessment is a frequent scored miss.

Practice this next

Turn this into reps rather than rereading it.

• Respiratory Emergencies — work of breathing, oxygen versus ventilation, and escalation triggers.
• Pharmacology — albuterol, epinephrine auto-injector, and contraindication checks.
• Primary Assessment — first-minute sequencing when breathing is the threat.
• Free NREMT practice test — full mixed-domain set.