Dear Doctor: A woman in the mall near our home collapsed and wasn't breathing. A shopper performed CPR until the paramedics showed up. Later, my friends and I realized that none of us could have helped her. Should we get trained in CPR?

Dear Reader: Only a small percentage of the population in the United States knows how to perform CPR, so the woman you and your friends saw was lucky. As you can probably guess, our answer is yes; learning proper CPR technique is a very good idea.

More than 350,000 people per year in the U.S. suffer from sudden cardiac arrest, which is when the heart abruptly stops beating. Although heart arrhythmias and heart disease are the major causes of sudden cardiac arrest, heart function may also stop due to near drowning, smoke inhalation, asthma attack, poisoning or even a severe allergic reaction.

Cardiopulmonary resuscitation, or CPR, really does make a difference. It consists of two separate components -- chest compression and mouth-to-mouth rescue breathing. (According to the latest American Heart Association guidelines, only individuals who are trained in CPR should attempt rescue breathing.)

When someone goes into cardiac arrest and stops breathing, the first few minutes are critical. Studies show that the survival rate of someone in cardiac arrest can double or triple when prompt and high-quality CPR is performed.

So what happens when you perform CPR?

Your body needs oxygen to survive. When your heart suddenly stops beating, the biological chain of events that provides you with oxygen also stops. Without that oxygen, cells begin to die. Brain damage can occur in just 4 or 5 minutes, and death in 8 to 10 minutes.

The purpose of CPR is to keep oxygenated blood flowing to the victim's brain and other vital organs. This is done by chest compressions, in which you're essentially providing an artificial heartbeat. Although by itself CPR will not restart someone's heart, it can help the person survive until medical aid arrives.

When shown on TV or in films, CPR may look easy. However, where and how you place your hands on a victim's chest to perform compressions is very important. So is the rate and depth at which you press on the chest, as well as exactly how and for how long you release.

That's why it's critical to get certified training. Classes, which are offered throughout the nation, are interesting and easy. The American Red Cross offers classes, and the American Heart Association (AHA) has a list of other training centers.

You'll learn proper CPR technique and may also get trained in the use of an automated external defibrillator, or A.E.D.

Although attending in-person class with fellow students and a mannequin to practice on is optimal, a video on the AHA's updated method of hands-only CPR is available online.

A final thought: Between 70 and 80 percent of sudden cardiac arrests occur in or near the home. Why not make CPR certification a family, neighborhood or even community project? Everyone will be just that much safer.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: I have been taking fish oil capsules daily over the last five years. Is there any benefit in doing this?

Dear Reader: The short answer is "maybe." Scientists have shown that societies with higher fish intake have lower rates of heart disease. The belief is that this benefit comes from fish oil. Fish oil contains substances known as long-chain fatty acids (omega-3 fatty acids), specifically DHA, DPA and EPA, with many health benefits. These fatty acids help lower blood triglyceride levels; lower blood pressure (by 1.5 to 4 points); and have an ability to help the heart relax so that blood flows more easily into its chambers. Furthermore, the omega-3 fatty acids in fish oil have also been linked to a slightly slower heart rate and to a decrease in inflammation.

Small studies have shown that fish oil may be linked to a slight reduction in the formation of plaque in the arteries that supply the heart, but evidence of its ability to reduce the rates of heart attack hasn't been as robust or as statistically significant.

One fish oil finding that was indeed statistically significant was from a large study published in the Journal of the American Medical Association in 2006. That study linked fish oil intake of 250 milligrams per day to a 36 percent reduction in rates of sudden cardiac death. That amount -- 250 mg of fish oil -- equals 1 to 2 servings of fish per week.

One other property that fish oil may have is an ability to reduce electrical excitability of the heart. That reduced excitability may decrease the heart's chances of going into an abnormal rhythm, which can lead to death. Furthermore, among people who have had a heart attack, 1 gram of fish oil per day has been linked to a significant decrease in death rates. The benefits of fish oil have been seen as early as four months after a heart attack and even as late as 36 months after a heart attack. Again, this appears to be related to fish oil's potential protective effect against abnormal heart rhythms after a heart attack.

Fish oil hasn't been shown to decrease the chance of a stroke. Nor has it been shown to decrease the risk or incidence of cancer. In fact, some studies have shown a correlation between fish oil and prostate cancer, but other studies have failed to support that connection.

In summary, fish oil does appear to decrease the chance of sudden cardiac death, but you don't need to take capsules to see this benefit. Eating fish twice a week can do that.

Before you turn to eating tuna fish from a can, keep in mind that tuna has much less omega-3 fatty acids than Atlantic salmon, mackerel or herring. If you don't care for fish, taking 1 gram of a fish oil supplement twice a week will likely yield a benefit. If you've had a heart attack, consider taking 1 gram of fish oil a day.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: Our young son fell off his skateboard recently, and the items my wife and I needed to tend to his cuts and scrapes were scattered throughout the house. Now we want to assemble a home first-aid kit. What should it contain?

Dear Reader: Great idea! A well-stocked first-aid kit is an important safety feature for every home. And while first-aid kits are available for purchase, you can easily put one together yourself.

Take an afternoon to evaluate your family needs, make a list, then hit your local drugstore. With just a little bit of planning, you'll be ready to handle the minor bumps and mishaps of everyday life at a moment's notice.

With a home first-aid kit, you're preparing to deal with three basic types of medical issues -- injury, infection and allergy.

Everyday injuries include scrapes, cuts, splinters, burns, sprains and stings. Infections may range from an inflamed wound to fever, a sore throat or the flu. You'll also want to be prepared for common allergic reactions such as the rash from poison oak and poison ivy, and itching and swelling from insect stings.

It's important that if anyone in your family has severe food allergies or a respiratory condition such as asthma, you stock a backup of the appropriate medication. Mark each item with its expiration date and replace as needed. It's a good idea to keep a separate checklist, which will make it easy to know when it's time to replace that inhaler or EpiPen.

So how do you build a first-aid kit?

Start with a container such as a plastic storage tub, a tackle box or a tote bag with separate compartments. It should be easy to open, easy to carry, and have enough room for everything to be organized and recognizable at a glance.

Delegate one compartment for personal items -- those allergy medications we talked about or backup doses of any other vital medications your family members may need. You'll also want to include a list of emergency phone numbers.

For a family of four to deal with common emergencies, you should have:

-- 2 absorbent compress dressings

-- 25 adhesive bandages of assorted sizes

-- 1 adhesive cloth tape

-- Antibiotic ointment and antiseptic wipes

-- Ibuprofen

-- Acetaminophen

-- An instant cold compress

-- Non-latex gloves to be worn when dealing with blood or bodily fluids

-- Hydrocortisone ointment

-- A pair of scissors and a set of tweezers

-- A 3-inch and a 4-inch roller bandage

-- 10 sterile gauze pads (3 by 3 inches and 4 by 4 inches)

-- An oral thermometer that is not glass and does not contain mercury

-- 2 triangular bandages

-- A good first-aid instruction booklet

Rather than in the bathroom, where humidity may affect the contents, keep your first-aid kit in the kitchen. It's also wise to consider a version of this kit for your car.

Finally, read through the first-aid instruction booklet on a regular basis. You don't want to be holding a page open while you're trying to bandage a sprained ankle!

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)