Every year, more than 300,000 people die of sudden cardiac arrest. Cardiopulmonary resuscitation, or CPR, can improve survivability rates when performed immediately by lay rescuers. This life-saving skill works by mimicking the normal function of the heart and lungs when they are no longer able to function on their own. Learning CPR is the best way to prepare for a sudden cardiac arrest encounter.
The Normal Heart
Every living cell in the body relies on blood for a systematic exchange of oxygen and nutrients and for the elimination of waste products. The heart performs this function by beating approximately 100,000 times each day, pumping enough blood to fill 40 55-gallon drums. The right side of the heart begins the circulation process by gathering blood returning from the body and pumping it to the lungs for oxygenation. From there, the blood returns to the left side of the heart to be pumped to the body tissues. This process repeats unending until the end of a person's life. Age, drugs and disease processes may change the efficiency in the heart's ability to pump blood.
Sudden Cardiac Arrest
Sudden cardiac arrest, or SCA, results from the complete cessation of blood flow, usually due to a lethal chaotic rhythm of the heart that stops blood flow to the brain and other vital organs. SCA is the leading cause of death in the United States and Canada, accounting for approximately 250,000 out-of-hospital deaths annually. CPR has been linked with higher survival rates. When performed immediately after the heart stops, it may supply the brain and heart with enough blood to survive until emergency responders can assume care and initiate more aggressive measures.
Chest Compressions
Under normal circumstances, heart contractions force blood through blood vessels out to the body tissues. When the heart stops, or is in a chaotic rhythm, this flow is interrupted and must be resumed. For the lay rescuer, the single act of chest compressions is the best way to simulate the normal action of the heart if it stops. There is enough oxygen in the blood immediately following the heart stopping to make rescue breathing unnecessary. Compressing the chest at least two-thirds of the diameter of the chest squeezes the heart, causing blood to flow out to the brain. Fully releasing the chest after a compression allows the heart to relax; its refill passively with more blood, which can be forced out again on the next compression. This cycle of compression and release is the mechanism that provides necessary blood flow to and from the brain and the heart until normal heart function resumes.
More advanced rescuers are trained to deliver chest compressions along with respirations at a ratio of 30:2 for more prolonged resuscitation attempts and to simulate the lack of breathing that occurs when the heart stops.
Pump Hard, Pump Fast
The act of chest compressions is only 25 percent to 30 percent effective as the heart to circulate blood. This concept explains why the slogan "pump hard, and pump fast" has been given for performing CPR. This theory is like a manual liquid pump: after a few pumps to prime, the liquid flows efficiently until stopped and the liquid drains out again. Each chest compression builds on the next until it is stopped or slowed. Delayed, lost, or ineffective compressions will result in a decrease amount of blood flow.
Becoming Certified
Becoming certified in CPR is the best way to prepare for encountering someone in SCA. Check with the hospitals, emergency medical services or fire departments in the community. They are required to maintain current CPR certification and may conduct public classes. The American Heart Association and the American Red Cross have on-line resources that list available local courses.
References
- "Anatomy & Physiology for Emergency Care"; Frederic Martini, Ph.D., Edwin Bartholomew, M.S. and Bryan Bledsoe, D.O.; 2002
- American Heart Association: Overview of CPR
- EMS1.com: CPR---Hard, Fast, and Don't Stop
