BLS — Basic Life Support — All Questions
22 questions
At what rate should chest compressions be delivered to an adult in cardiac arrest?
- a.60 to 80 compressions per minute
- b.At least 140 compressions per minute
- c.80 to 100 compressions per minute
- d.100 to 120 compressions per minute✓
Current AHA guidelines specify a compression rate of 100 to 120 per minute for all ages. Slower than 100 does not generate adequate perfusion, while faster than 120 shortens the recoil phase so the heart cannot refill, which paradoxically lowers the blood delivered per compression.
What is the correct compression depth for an adult victim?
- a.At least 5 cm, not over 6 cm✓
- b.At least 7.5 cm (3 inches)
- c.About 2.5 cm (1 inch)
- d.As deep as possible
Evidence behind the 2025 AHA Guidelines links survival with depths of at least 5 cm (about 2 inches) and reduced survival with depths over 6 cm (about 2.4 inches).
What is the correct compression depth for an infant (under 1 year)?
- a.About 1 inch (2.5 cm)
- b.One-third of chest depth, about 4 cm✓
- c.About 0.5 inch (1 cm)
- d.At least 2.4 inches (6 cm)
The pediatric chest can be compressed to one-third of its front-to-back depth without organ damage; for an infant that is about 1½ inches (4 cm).
To maximize blood flow during CPR, rescuers should allow complete chest recoil and aim for a chest compression fraction of at least:
- a.30%
- b.60%✓
- c.40%
- d.50%
Chest compression fraction — the proportion of arrest time spent actively compressing — should be at least 60%. Allowing full recoil between compressions lets the heart refill, and minimizing pauses (keeping any interruption under 10 seconds) preserves the coronary and cerebral perfusion that compressions build up.
A rescuer's compressions on an adult measure 3.5 cm deep on a feedback device. What does the evidence behind the 2025 Guidelines say about this depth?
- a.Too shallow; aim for 5 cm or more✓
- b.It is too deep and risks injury
- c.Depth matters only in children
- d.It is ideal for most adults
Survival was better with compression depths of at least 5 cm than with depths under 4 cm, so 3.5 cm is too shallow. Depth also matters in children, where the target is one-third of the chest's depth.
Which pairing correctly lists the adult compression rate and the maximum sensible depth?
- a.60–80 per minute; no more than about 8 cm
- b.100–120 per minute; no more than about 6 cm✓
- c.80–100 per minute; no more than about 4 cm
- d.120–150 per minute; as deep as possible
Adult compressions are given at 100 to 120 per minute, at least 5 cm deep, and excessive depth above 6 cm has been linked with reduced survival. Faster or deeper is not better.
A team's compression fraction in a 15-minute code was 85%. How should this be interpreted?
- a.It means too few breaths were given
- b.It is below the recommended minimum
- c.It shows the compressor pressed too hard
- d.It is above the 60% minimum target✓
The Guidelines describe a 60% chest compression fraction as a minimum target and note that high-performing teams can exceed 80%. A high fraction means pauses were kept short.
During CPR, a rescuer lifts his hands slightly off the chest after each compression. Which component is he protecting?
- a.Rescuer rotation
- b.Compression rate
- c.Breath volume
- d.Full chest recoil✓
Letting the chest re-expand completely increases the blood returning to the heart and the blood flow CPR can produce; leaning on the chest reduces coronary perfusion.
Why do pauses in chest compressions matter so much during CPR?
- a.Pauses cause rib fractures
- b.Coronary perfusion drops at once✓
- c.They make breaths less effective
- d.The AED loses its charge during pauses
The Guidelines note that pauses cause an almost immediate drop in coronary perfusion pressure, which is associated with a lower chance of return of spontaneous circulation.
A patient in cardiac arrest is on a hospital bed with an air mattress. What does the 2025 guidance suggest to improve compression depth?
- a.Use CPR mode or deflate the mattress✓
- b.Compress faster to make up for the softness
- c.Inflate the mattress further
- d.Move the patient to a chair
Compressions on a deflated dynamic mattress, or using the bed manufacturer's CPR mode, can improve compression depth; CPR should be performed on a firm surface whenever possible.
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A rescuer kneels on the floor beside an adult in cardiac arrest. Which 2025 positioning principle does this meet?
- a.Patient raised to the rescuer's waist
- b.Rescuer compressing from the patient's feet
- c.Torso at about the rescuer's knee level✓
- d.Rescuer standing above the patient's head
The 2025 Adult BLS top-ten list says compressions should be done with the patient's torso at approximately the level of the rescuer's knees, by kneeling alongside or using a step stool.
A nurse notices depth dropping on the feedback screen after about 2 minutes of compressions. Why is this expected?
- a.The chest becomes stiffer during CPR
- b.Depth declines after 90–120 seconds✓
- c.Rates always rise after 2 minutes
- d.Feedback devices drift after 2 minutes
Compression depth begins to decrease after 90 to 120 seconds of CPR, which is why rotating the compressor about every 2 minutes, at a planned pause, maintains quality.
What is the recommended compression depth for an infant in cardiac arrest?
- a.About 6 cm
- b.Half of the chest depth
- c.About 1 cm
- d.One-third of chest depth, about 4 cm✓
The pediatric chest can be compressed to one-third of its front-to-back diameter without organ damage; for an infant, that is about 1½ inches (4 cm).
Which infant compression technique did the 2025 Guidelines eliminate?
- a.One hand on the lower sternum
- b.The heel of one hand
- c.Two thumbs encircling the chest
- d.Two fingers on the sternum✓
The 2025 Pediatric BLS Guidelines recommend the one-hand or two thumb–encircling hands technique and eliminated two-finger compressions because they failed to reach proper depth.
For children 1 to 8 years old, which compression technique produced greater depth in a registry study?
- a.Two hands✓
- b.Two thumbs
- c.Two fingers
- d.One hand
The 2-hand technique resulted in greater compression depth than the 1-hand technique in children aged 1 to 8, although the 1-hand technique matched target rates better.
An adult in cardiac arrest has severe obesity. What does the 2025 guidance say about technique?
- a.Use standard technique, with more force if needed✓
- b.Use two fingers to avoid injury
- c.Compress only half as deep
- d.Compress more slowly to save energy
CPR for adults with obesity uses the same technique as for other adults; rescuers may need more force to achieve adequate depth and may tire faster.
A hospital is choosing between buying CPR feedback devices and mechanical CPR devices for routine use. Which is recommended for routine use?
- a.Neither device
- b.Mechanical CPR devices
- c.Real-time feedback devices✓
- d.Both equally for every arrest
Real-time feedback devices are recommended to improve manual CPR performance, while routine use of mechanical CPR devices is not recommended because they have not improved survival.
A rescuer's hands have slipped down onto the xiphoid during compressions. What should she do?
- a.Keep going; the xiphoid is ideal
- b.Switch to one-finger compressions
- c.Move up to the lower half of the sternum✓
- d.Move to the upper chest near the neck
Compressions over the lower part of the sternum gave better physiological measures, while hands placed too low may compress over the xiphoid, which may be less effective.
What is the target compression rate for a child in cardiac arrest?
- a.60 to 80 per minute
- b.80 to 100 per minute
- c.140 to 160 per minute
- d.100 to 120 per minute✓
Pediatric data found higher blood pressures with rates of 100 to 120 per minute than with faster rates, and lay teaching uses 100 to 120 for children and infants.
A patient arrests while lying face down after spine surgery, and turning him would badly delay CPR. What is acceptable?
- a.Giving breaths only until turned
- b.Starting CPR in the prone position✓
- c.Starting CPR only after an AED arrives
- d.Waiting until the patient can be turned
Supine CPR is preferred, but rescuers can consider prone CPR if the supine position is not possible or would significantly delay compressions.
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Which statement best describes why compression-only CPR by an untrained bystander is still valuable?
- a.It is far better than no CPR at all✓
- b.It replaces the need for an AED
- c.It is required for all children
- d.It is always better than CPR with breaths
A compression-only approach is appropriate for untrained or unwilling lay rescuers, and in children it is superior to no bystander CPR, although CPR with breaths gives better outcomes in children.
A tall 12-year-old boy without signs of puberty collapses. Which compression guidance applies?
- a.Adult guidance: at least 5 cm by age
- b.No compressions until EMS arrives
- c.Child guidance: one-third depth✓
- d.Infant guidance: two thumbs
Child guidelines apply from about 1 year of age until puberty, and signs of puberty — not age alone — move a patient to adult BLS; child compressions are one-third of chest depth.