When ventilating during CPR how long should each inspiration last?

• A. 1 second
• B. 0.5 second
• C. 2 seconds
• D. 3 seconds

Answer: (A)

During CPR, ventilation and chest compressions must be balanced. Breathing for too long holds the thorax in a positive-pressure state, which raises intrathoracic pressure and reduces venous return to the heart, decreasing the effectiveness of chest compressions. Breathing for too short a time may not deliver enough air to fully inflate the lungs and oxygenate the bloodstream.

Delivering each inspiration over about one second achieves a practical compromise: it provides a tidal volume that inflates the lungs with a visible chest rise, while keeping intrathoracic pressure low enough to allow good venous return and maintain CPR effectiveness. This timing also fits common CPR protocols that call for rapid, repeated breaths without long interruptions.

Breaths lasting around 0.5 second are usually too short to achieve adequate lung inflation. Breaths lasting 2–3 seconds are too long, increasing chest pressure, risking gastric inflation, and interrupting the compression/ventilation cycle. So, one second per inspiration is the most appropriate duration.