CHICAGO -- CPR quality is worse during in-hospital cardiac arrests occurring overnight than those that happen during the day, according to a new University of Pennsylvania School of Medicine study that will be presented at the American Heart Association's annual Scientific Sessions on November 14. The researchers found that chest compression rates varied more at night - often dipping well below the rate per minute that's necessary to properly circulate blood - than during resuscitation efforts during the day, and rescuers paused for longer when switching between chest compressions and defibrillator shocks at night.

"Our study reveals an important factor to explain why, as previous studies have shown, patients who have cardiac arrests in hospitals during daytime hours are more likely to survive,” says senior author Benjamin Abella, MD, MPhil, an assistant professor of Emergency Medicine and clinical research director in Penn's Center for Resuscitation Science. “These findings suggest that more attention to clinical emergency training and staffing at night may be an important way to improve hospital safety and patient outcomes.”

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