DEAR DR. DONOHUE: I haven’t read anything about chronic obstructive pulmonary disease, COPD, in your column. Will you do something on cause and treatments? – V.F.

ANSWER: And I thought I had overdone chronic obstructive pulmonary disease.

COPD is worth repeating. It the fourth leading cause of death in Canada and the U.S., and it affects more than 16 million Americans. Emphysema and chronic bronchitis are the two COPD illnesses. Emphysema is destruction of air sacs, the millions of delicate little bulges clustered on the ends of the breathing tubes. Oxygen passes through those air sacs into the blood. The main symptom of emphysema is breathlessness upon even slight activity. Chronic bronchitis is irritation and inflammation of the breathing tubes (the airways, the bronchi). A cough and the production of thick, yellow sputum are the major signs of chronic bronchitis.

Emphysema and chronic bronchitis are conjoined twins. If people have one, they usually have the other. Cigarette smoking is the principal cause of both.

Breathing tests – spirometry – assess the severity of COPD. Measuring the oxygen content of blood is another way to determine the extent of this illness.

Pulmonary rehabilitation classes, often sponsored by local hospitals, teach people what exercises are beneficial and safe, and they instruct people on breathing techniques. Pursed-mouth breathing is one. The person breathes out through lips held in the whistling position. Bending slightly forward at the waist increases the chest’s space and allows the lungs to expand more and hold more air.

The number of medicines for COPD is large. Bronchodilators expand breathing tubes, and these medicines come in both inhaler and oral forms. Medicines that soothe inflamed airways and decrease mucus production also come in oral and inhaler forms. Oxygen is essential for those with severe symptoms.

The booklet on COPD gives more details and explains the medicines used for it. To order a copy, write: Dr. Donohue – No 601, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: Is there a period in the normal menstrual cycle in which a girl cannot get pregnant? If so, how long is it? – S.C.

ANSWER: This is one of many questions from the students of Mr. S.’s anatomy and physiology class in California’s San Jacinto High School. I apologize for the time it has taken me to answer these questions. I will answer more of them in the coming weeks. They were all great.

Ovulation is a requisite for pregnancy. It occurs around day 14 of a 28-day menstrual cycle. An ovum (egg) has a 24-hour period in which it can be fertilized. The “fertile window” is considered to extend from day eight to day 19 for a woman who has a menstrual period of 26 to 32 days. Those are the days most likely for fertilization to take place.

All of this is not as exact as it sounds. The human body doesn’t work like a robot, so rough approximations are the best that can be given. A woman can determine when she has ovulated by testing for luteinizing hormone. Egg release occurs after a surge of that hormone. Commercial kits are available for this testing. Basal body temperature is another way to ascertain the timing of the release of an egg. Body temperature rises by 0.58 F after ovulation. Basal body thermometers are also commercially available.

DEAR DR. DONOHUE: Why are people shy? – E.B.

ANSWER: Genes and the early family and social environment work together to produce shyness. In the extreme, shyness is called social anxiety disorder, a condition in which people dread social contact and become sweaty, frightened, tremulous and dizzy when forced to engage in such contact.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.