A person's ventilation rate refers to the number of breaths he takes during a specific amount of time, usually the space of a minute. This will affect the amount of time that is required for oxygen to replace carbon dioxide in red blood cells. Respirations, or breaths, can be measured by counting the upward movement of the chest and abdomen when the lungs fill with air. The ventilation rate is divided into three categories, minute ventilation, alveolar ventilation, and dead space ventilation.
Minute ventilation is the total amount of air drawn into the lungs and exhaled over the space of 60 seconds. It is calculated by counting the amount of respirations per minute and multiplying it against the tidal volume of each breath. The minute ventilation rate is usually displayed automatically on an artificial ventilation machine. A high minute ventilation count is also known as hyperventilation.
Alveolar ventilation describes the amount of oxygen that is drawn into the alveoli of the lungs per unit of time measurement. During respiration, carbon dioxide and oxygen molecules are diffused in the alveoli before circulating throughout the body. The alveolar ventilation rate is determined by subtracting the volume of air that does not become oxygenated in the alveoli from the total amount of oxygenated air and multiplying it by the respiration rate.
Dead space ventilation is the term used to describe the amount of air that is drawn into the lungs during respiration but is not oxygenated in the alveoli. The total volume of the un-oxygenated air is multiplied by the respiration rate to reveal the dead space ventilation rate. An increase in the dead space ventilation rate may be an indicator of an inefficient respiration process.
Ventilation speed may be affected by the levels of different gases in the bloodstream. The pace of ventilation may be increased when high concentrations of carbon dioxide are found in the body. Similarly, elevated oxygen levels may prompt a decrease in the rate of ventilation. Exercise and other physical activities may also cause the ventilation rate to increase.
The overall health of the lungs can be evaluated with a device called a spirometer. There are many different types of spirometers used in respiratory medicine. The peak-flow spirometer is used to measure the amount of air exhaled in one forceful breath. A pneumotachometer is a type of spirometer that can analyze the concentration of the different gases in the air inhaled and exhaled. When precise results are important, a whole body plethysmography is obtained.