To catch a cold

Our respiratory system is designed primarily to exchange gases.  Each time we inhale, oxygen is brought into the lungs to be absorbed into our blood stream and distributed throughout the body for energy production.  When we exhale, carbon dioxide, a byproduct of normal metabolism, is eliminated.  The components of this system, the nose, pharynx, larynx, bronchi, bronchioles, and alveoli of the lungs, are all lined with specialized cells that aid in this important process.  

The lining of the upper respiratory system is intended to provide a moist and protective surface for normal breathing.  There are cells that make mucus to moisten and trap debris; cells that have tiny hairs to brush debris up and out of the airway; and cells that fight off invaders that enter the airway.         

A healthy individual will inhale and exhale between 18,000 and 26,000 times a day.       Agents such as viruses take advantage of this constant flow of air to gain entry into the body through the respiratory lining.  Their sole purpose is to use our cells as factories to replicate and propagate their species, a process we call infection.

Though viral infections can occur at any time of the year, the low humidity and cold air of winter time can make the respiratory system more susceptible to infection.  It may adversely affect the body’s overall immune system as well.  

In order to “catch a cold”, one has to be exposed to a virus.  Viruses are passed from person to person through coughing or direct contact.  Certain viruses can infect specific areas of the respiratory system; for example, the rhinovirus infects the nasal passages and sinuses around the nose causing symptoms we commonly call a “head cold”.  

Infections in the bronchial tubes are referred to as acute bronchitis.  This simply means that the infection has caused inflammation of the bronchial lining.  Acute bronchitis can also be caused by inhaled irritants such as chemicals or smoke.
Viruses have been around for a long, long time and they have developed ways to skirt the defenses of the human body.  If they are not trapped by the mucus, swept out by the hair cells, or simply coughed back out, the virus sets up its replicating shop in the respiratory cells.  
Since a virus is an unwanted guest, the respiratory and immune systems must alert the rest of the body that an intruder is present and must be eliminated.  This is when all the symptoms begin.  The respiratory and immune cells are programmed to release chemicals both to fight the infection and to recruit other “soldiers” from other parts of the body.  These chemicals result in more mucus production, congestion, cough, and fever.  So, though symptoms of a respiratory infection are annoying, they are a result of your body’s attempt to fight the infection.  

We can help the fight by resting and getting proper sleep, drinking plenty of fluids, and maintaining adequate nutrition.  A virus will usually be eliminated within seven to ten days.  At times, some symptoms, particularly the cough, can last for several days longer.  If symptoms persist for longer than this time period, you should see your doctor.

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices Family Medicine in Chesterfield.

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