TheoryBLS Practice Questions
Free BLS practice questions with answers and plain-English explanations. Browse the PDF, video and online mock test.
BLS Questions
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Q1You arrive at a scene where a person is lying motionless on the floor. What is the FIRST action you should take before approaching?
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✓ Correct answer: Ensure the scene is safe for you to approach
Scene safety is the first priority in any emergency response — a rescuer who becomes a victim cannot help anyone, so you must ensure the environment is safe before approaching.
Q2When performing adult CPR as a lone rescuer, what is the correct compression-to-ventilation ratio?
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✓ Correct answer: 30:2
The AHA BLS standard for a lone rescuer performing adult CPR is 30 compressions followed by 2 ventilations, regardless of whether an advanced airway is in place.
Q3A colleague collapses at work. After confirming the scene is safe, you tap the person's shoulders firmly and shout. There is no response. What should you do NEXT?
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✓ Correct answer: Simultaneously check for breathing and a carotid pulse for no more than 10 seconds
After confirming unresponsiveness, the AHA BLS protocol directs you to simultaneously check for breathing and a carotid pulse for no more than 10 seconds before deciding on the next action.
Q4During adult CPR, your partner notes that the patient's chest is not fully returning to its resting position between compressions. What is the MOST likely consequence of this finding?
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✓ Correct answer: Venous return to the heart will be reduced, lowering cardiac output
Incomplete chest recoil (leaning on the chest) elevates intrathoracic pressure and impairs venous return, which decreases cardiac output and reduces the effectiveness of CPR.
Q5You are performing solo CPR on an adult. After your first set of 30 compressions, you deliver 2 rescue breaths, each taking about 1 second. Approximately how long should both rescue breaths take in total before you resume compressions?
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✓ Correct answer: About 2 seconds combined
Each breath should be delivered over 1 second with visible chest rise, meaning both breaths together take approximately 2 seconds, minimizing interruptions to compressions.
Q6A bystander CPR team has been performing compressions for nearly 2 minutes. According to AHA BLS guidelines, what should they do at this point regarding the compressor role?
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✓ Correct answer: Switch compressors every 2 minutes or 5 cycles to prevent fatigue-related quality decline
The AHA recommends switching compressors approximately every 2 minutes (or every 5 cycles of 30:2) because rescuer fatigue quickly degrades compression depth and rate, reducing CPR quality.
Q7While checking a collapsed adult, you observe slow, irregular, gasping breaths occurring about every 8 seconds. How should you interpret this finding?
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✓ Correct answer: This is agonal breathing and should be treated as absent breathing — begin CPR
Agonal respirations are ineffective, irregular gasps that occur shortly after cardiac arrest and should not be mistaken for normal breathing; the AHA treats agonal breathing as absent breathing, requiring immediate CPR.
Q8During adult CPR you are pressing down approximately 1.5 inches (3.8 cm) on each compression. Why is this a concern?
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✓ Correct answer: Compressions that are too shallow generate insufficient blood flow to vital organs
AHA BLS guidelines require adult compression depth of at least 2 inches (5 cm) because shallower compressions are associated with inadequate perfusion pressure and reduced survival rates.
Q9At which point in the adult in-hospital Chain of Survival does CPR fit MOST directly?
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✓ Correct answer: High-quality CPR
The in-hospital adult Chain of Survival includes surveillance and prevention, recognition and activation of the emergency response system, high-quality CPR, defibrillation, and post-cardiac-arrest care — CPR is the third link.
Q10You are performing compressions on an adult at a rate you estimate to be around 110/min. A metronome app reads 125/min. Which statement about your actual rate is correct?
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✓ Correct answer: 125/min exceeds the maximum of 120/min and should be slowed
The AHA BLS target compression rate is 100–120/min; exceeding 120/min is associated with inadequate compression depth and reduced diastolic filling time, so the rate should be corrected downward.
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