DEAR DR. ROACH: I am a 78-year-old man with severe COPD who is on oxygen 24/7. I use a portable oxygen generator when I need to go to the store or for medical appointments. Does the oxygen protect me from getting virus or flu germs, or is it more likely I will inhale them with the air and deliver it to me in my oxygen? I go out seldom and try to practice social distancing when I do. I wear latex gloves but can’t wear a mask because of the cannula. — J.T.D.

ANSWER: Oxygen concentrators work by utilizing the unique characteristics of a mineral called zeolite. Under pressure from a compressor, the nitrogen in the atmosphere is adsorbed onto the zeolite pellets in the concentrator. The resultant gas is highly concentrated oxygen, and is delivered to the patient at the prescribed concentration, while the nitrogen is vented to the atmosphere when the pressure in the compressor is released.

If there are virus particles in the air, they are associated with liquid, ranging from large droplets to very small ones. Very small droplets can remain in the air for long periods of time (hours). Some viruses, such as measles, are able to remain infectious in the air for many hours, while others are more associated with larger droplets and are infectious for a much shorter time in the air. If the infectious particles are in the air, they can theoretically be passed to you through the concentrator or directly through the air that is also inhaled through the mouth and nose.

Thus, with or without an oxygen concentrator, it is possible to be infected by someone close by, especially one who is coughing, which expels large amounts of infectious particles on both large and small droplets. That’s why the distancing of 6 feet or more is helpful in reducing infection rates.

However, severe COPD is a major risk factor for bad outcomes in respiratory infections, such as influenza or coronavirus, which is why staying away from potentially infectious people is so important.

DEAR DR. ROACH: My husband has an enlarged prostate. Our daughter suggested he eat avocados every day (at least 1/2 of one every day). He has been doing this for quite some time now, and has had no problem at all. We believe it has helped and would like your opinion as to whether the avocados have anything to do with helping him. He also takes one tamsulosin HCL 0.4 mg every night. — C.R.

ANSWER: Avocados naturally contain a substance called beta-sitosterol. In a review, using beta-sitosterol improved urine flow rates and prostate symptoms. So, there is some evidence that there may be benefit from avocados.

Avocados are generally healthy, and a half an avocado a day is unlikely to cause any overall health problems. Given his success — along with tamsulosin, a standard medication therapy — I see no reason to stop.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.