Mechanical Ventilation of the Lungs

If the human body cannot spontaneously breathe, it will die in four to five minutes. If breathing is interrupted for any reason —trauma; drugs, legal or recreational; or problems with the nervous system — mechanical methods of ventilation must be established.

Each lung contains three lobes or sections. Problems are most common in the lower lobe where particulate matter often accumulates over the years from the workplace: mining, cotton, construction dust or smoking are common contributing agents. These contaminates will reduce the capacity of the lungs and potentially lead to other diseases. As a person breathes, the diaphragm and muscles in the rib cage work together by contracting, inhaling and relaxing, exhaling, to allow air to enter the lungs via the bronchi into the millions of alveoli within the lungs. The alveoli are moist membranes that allow oxygen to pass into the blood stream and carbon dioxide and other gases to pass from the blood stream to be exhaled. A healthy person breathes between 15 times and 20 times per minute. The respiration rate will increase with fear or pain and decrease with sleep, drugs and removal of the fear or pain.

The normal breath volume for a person is called the tidal volume; this varies with the physical size of the person, pathology and levels of effort (work). An average-size adult at rest may have a tidal volume of 500 cc, but if he or she is exercising or working that volume could be as high as 1,000 cc’s. Persons with pulmonary problems often do not have the ability to expand their tidal volume, which limits the amount of oxygen that crosses into the blood and so contributes to other medical problems.

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