Dear Doctor: My hearing loss is related to my Eustachian tubes: They stay closed. I can open them and improve my hearing by holding my nose and blowing, but the effect lasts only a short time. Hearing aids don't help. What can I do?

Dear Reader: First, let's consider the size and location of the Eustachian tubes, one on each side of your head. Only half a centimeter wide, each one starts behind the nose and travels through cartilage and bone toward the middle ear, an air-filled chamber bordered on one side by the eardrum. The pressure within the middle ear should be equal to the air pressure outside, and the Eustachian tube is the only way for the body to equalize these pressures. This gas pressure homeostasis is necessary for optimal hearing.

The most common reason that the Eustachian tube closes is from inflammation within the tube and secretions that can block it from opening. With the tube closed, the middle ear has no way for the air to go in or out. When that happens, the air in the middle ear gets absorbed by the surrounding structures, creating a negative pressure in the middle ear. The sensation is similar to how your ears feel at the bottom of a pool. This negative pressure makes it even more difficult for the Eustachian tube to open, increasing to the point where fluid starts to fill the middle ear. In severe cases, blockage of the Eustachian tube can lead to vertigo and balance problems.

Now let's look at the possible causes for a closed Eustachian tube. In my experience, the most common cause is chronic nasal congestion, either from allergies or environmental irritants. Infection of the adenoids, sinus or nose also are likely causes; to determine this, an ear, nose and throat doctor would visualize the adenoids to assess their condition.

Chronic nasal swelling is another potential culprit. If that's the case, medications such as nasal steroids, leukotriene inhibitors and antihistamines could decrease the swelling, opening your Eustachian tubes and thus improving your hearing.

Note that one study, however, did not show significant change in Eustachian tube dysfunction with the use of a common steroid delivered via nasal spray, Nasacort. In addition, an over-the-counter expectorant, guaifenesin, could thin secretions sufficiently in the Eustachian tube to help clear it.

Essentially, the treatment depends on the cause. For inflammation and closure of the Eustachian tube caused by infection, antibiotics can help. For inflammation caused by acid reflux, which can lead to inflammation in the nasopharynx, look for ways to decrease acid reflux. If adenoids are blocking the Eustachian tube, the adenoids can be surgically removed.

As for medications, if those are ineffective, either balloon dilation of the Eustachian tube or laser therapy can be used to clear the opening in the nasopharynx.

Talk to your doctor about your symptoms. Eustachian tube dysfunction can be treated and, because symptoms can worsen, it should not be ignored.

Also, a note to my readers: A recent column on the potential link between proton pump inhibitors and heart disease referred to a study involving both clopidogrel and Plavix. In fact, they're the same drug. The reference should have said that researchers found an increase in the rate of heart events among those taking a proton pump inhibitor and clopidogrel/Plavix after angioplasty, but no difference in death rates. Thanks to those readers who pointed this out.

(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. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have heard several stories on the news recently about carbon monoxide-related deaths, and they have me concerned. Where does carbon monoxide come from, and how do I protect my family?

Dear Reader: Carbon monoxide, also referred to as CO, is a colorless and odorless gas that is impossible to detect without specialized equipment. Because of that, it has been called the "invisible killer." About 400 people die each year from CO poisoning, and another 20,000 seek medical treatment.

In the home, carbon monoxide can be produced by fuel-powered devices like stoves, furnaces, water heaters, dryers, boilers and lanterns. It is emitted by wood-burning fireplaces, charcoal grills and generators. Virtually any substance that contains carbon and can burn will produce carbon monoxide as a byproduct.

The reason carbon monoxide is so toxic is that, when we breathe it in, it takes the place of oxygen in our red blood cells. In fact, the chemical structure of CO is such that it binds far more readily to the hemoglobin in our blood than does oxygen.

When you're breathing in an enclosed space where CO is present, your body will become starved for oxygen in a very short time. Cells and tissues that are denied oxygen quickly begin to die. Brain cells, for example, begin to die after just three minutes without oxygen. Beyond that, permanent brain damage begins.

Now, some good news. The presence of carbon monoxide in the home is easily detected by special alarms. Just like a smoke alarm, the CO alarm contains specialized sensors that will activate when the gas approaches unsafe levels. These alarms, which can plug into electric outlets and also have backup batteries, are sensitive, accurate and affordable. In many states, they are required by law.

It is recommended that a CO alarm with a backup battery be installed on every level of the family residence, including the basement, attic and garage. There should also be a CO alarm outside of each sleeping area.

There are several other steps that you can take to keep your family safe.

-- Perform a monthly test of each CO alarm to be sure it is working.

-- Keep a supply of extra batteries on hand, so they can be replaced right away.

-- When you use your fireplace, be sure the damper is wide open. Leave it open until the ashes have completely cooled.

-- Never use your gas stove or oven to heat a room in your home.

-- Never use a portable generator in the house or in any enclosed space. Generators should be kept at least 20 feet from the home when in use.

-- Don't use a gas or charcoal grill inside the home. Be sure to operate grills far away from any open windows.

-- Know the symptoms of carbon monoxide poisoning: weakness, dizziness, sleepiness, headache, weak pulse, nausea, vomiting and confusion.

If you suspect that you or a family member has CO poisoning, immediately go outside to the fresh air, and then call 911.

(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. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I've been seeing advertisements for glutathione, saying the supplement enhances the body's cells. The ads also say the claims haven't been evaluated by the Food and Drug Administration. What can you tell me about it?

Dear Reader: Glutathione is an antioxidant produced in the body through enzymatic reactions, using the amino acids cysteine, L-glutamic acid and glycine. It helps repair cells damaged by pollution, stress and other harmful influences, and it is undeniably important.

Mice unable to form glutathione will die before birth. Mice that have been genetically altered to not produce glutathione in the liver will die after one month. People with mutations in the enzymes that form glutathione are more susceptible to oxidative stress. The deficiency in the production of glutathione leads to the breakdown of red blood cells, enlargement of the spleen, gall stones, and after many years can lead to mental deterioration. Also, these patients are more prone to severe anemia when exposed to certain chemicals or drugs.

Less is known about glutathione's use as a general supplement, although it has been evaluated by the FDA for AIDS-related weight loss. People with AIDS have reduced production of glutathione in the intestine, and supplementation with glutathione could help in the ability to digest food.

Glutathione has also been studied in cystic fibrosis patients. Decreased glutathione in their intestines can lead to inflammation of the intestine, pain, decreased absorption of food, weight loss and growth failure. A 2015 study published in the Journal of Pediatric Gastroenterology and Nutrition found that supplementation with glutathione three times per day with meals has been shown to decrease intestinal inflammation and improve growth in children with cystic fibrosis.

Other research assessed glutathione's effect on people with vascular disease of the arteries that go to the legs. Decreased blood flow can lead to calf pain when walking, but the study found that glutathione given intravenously twice a day helped ease patient symptoms.

Because you're presumably healthy, you're unlikely to have any deficiency in the production of glutathione. If you're interested in improving your body's ability to recover from exercise by enhancing your muscles' ability to heal, that's a different question. People who exercise vigorously create oxidative free radicals, which can lead to muscle fatigue and decrease muscle performance -- suggesting that an antioxidant may be helpful.

However, people who exercise regularly naturally produce more antioxidants in the muscles to prevent damage, possibly in response to the regular formation of oxidative free radicals. Regardless, the body takes care of itself without the need of a supplement.

As of yet, there is no good study of the use of glutathione in healthy people. Some nutritionists recommend increasing the intake of the amino acids cysteine and glutamate, which make glutathione, but this hasn't been studied either.

In short, the supplement has shown benefit among cystic fibrosis and AIDS patients who have decreased glutathione in the intestine, and it may show benefit in inflammatory conditions of the intestine, such as ulcerative colitis and Crohn's disease, but this needs to be studied as well.

At this point, I would not recommend taking glutathione. If you're healthy, your body should produce an adequate amount of this important antioxidant.

(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. Owing to the volume of mail, personal replies cannot be provided.)