Seeing, smelling, swallowing, walking and even digesting are activities that we don’t think much about until a cataract, cold, strep throat, arthritic knee or heartburn intervenes. Then, what was taken for granted suddenly becomes a focus of attention.
Breathing is one such unconscious activity. Most of us do it automatically at least 20,000 times a day. Its purpose is to supply the body with oxygen and rid it of carbon dioxide. If anything interferes with that exchange of gases, causing a deficit of oxygen or a surplus of carbon dioxide, the breathing rate will automatically increase to compensate. You perceive that as shortness of breath or, in medicalese, dyspnea.
The mechanics of normal breathing involve not only the heart and lungs but also the muscles of the chest wall and the nervous system, so the causes of dyspnea are many. Nevertheless, with proper evaluation, the diagnosis is apparent about two-thirds of the time. Risk factors such as smoking, chronic exposure to irritating chemicals or the use of certain medications, notably beta blockers (such as atenolol or metoprolol), can be important clues. Signs and symptoms such as cough, bloody or colored sputum, wheezing, chills, fever, chest pain, ankle swelling and heartburn are giveaways for diagnoses such as pneumonia, asthma, pulmonary embolism, heart failure and acid reflux. Anemia, a deficiency of oxygen-carrying red blood cells, also commonly produces dyspnea on exertion.
But not all shortness of breath is caused by disease. When we exercise, our muscles require more oxygen than they do when we are at rest. Therefore, our breathing rate increases and our heart beats faster to satisfy that need. Visitors to high altitudes, where the oxygen content of the air is lower than what they’re used to, often find breathing difficult. People who live in such regions become acclimated when their red-blood-cell count increases, thereby improving their body’s oxygen content.
And what pregnant woman hasn’t complained of shortness of breath from respiratory stress caused by her swollen belly and increased weight? Chronic anxiety can produce a type of air hunger characterized by “sighing respirations,” often described as being “unable to get on top of a breath.” This differs from the hyperventilation episodes that are more likely to be associated with acute anxiety and that result in intense tingling of the extremities, faintness and, occasionally, loss of consciousness.
Lipman’s friend’s shortness of breath on exertion was a puzzle — until he asked her to walk around his office building and checked her oxygen level and pulse rate before and after that mild exercise. Imagine his surprise when her pulse rate dropped instead of increasing, as expected. An electrocardiogram showed that with exercise, each electrical impulse, initiated in an upper heart chamber, had an increasingly difficult time activating the lower heart chambers to cause a heartbeat. This condition is called heart block and sometimes, as in her case, occurs only upon physical exertion. It prevented the increase in heart rate required to supply her tissues with oxygen, which in turn caused her breathing to speed up in an effort to make up the deficit.
A cardiologist colleague suggested implanting a permanent cardiac pacemaker, which was done a few days later and solved the problem immediately. She has resumed her usual activities and continues to do well. Attempts at finding a cause for the heart block came up empty.
Copyright 2012. Consumers Union of United States Inc.