Friday, December 12, 2008

Changes in Total Lung Capacity

Why is it that some people can blow up a balloon easily while others struggle? How can some people hole their breaths and swim the length of a pool, while others are gasping for air? What affects lung volume? And how can we improve lung volume?

Why are the lungs important?
About 23,000 breaths are taken everyday; that is almost 10,000 quarts of air. This air contains (among other things) oxygen which is vital for cell function and survival. The lungs bring oxygen into the body. The blood then carries the oxygen to all the cells of the body. If a cell is deprived of oxygen for even a few seconds, the cell can die


Anatomy of the lung
Humans physiologically have two lungs. The right lung is
slightly larger than the left lung. Air is inhaled through the nose and mouth. It then travels down the trachea and into the lungs. In each lung there is a complex system of branching tubes. The largest is the bronchi. This then branches into smaller bronchioles. The bronchioles continue to branch until the terminal ends where there are alveoli.
The alveoli are air filled sacs almost completely surrounded by blood vessels. This is where gas exchange occurs. The oxygen in the air gets transported into the blood to fuel the cells. Simultaneously carbon-dioxide (a cell byproduct) is transported from the blood into the alveoli where it is eventually exhaled.

Lung Capacities
- Residual volume (RV) is the volume of air in the lungs after maximum expiration.
- Tidal volume (TV) is the volume of air inspired and expired during normal (not forced) breathing.
- Inspiratory reserve volume (IRV) is the additional air that can be inhaled after a normal inhalation takes place.
- Expiratory reserve volume (ERV) is the additional air that can be exhaled after a normal exhalation takes place.
- Total lung volume (TLV) is the amount of air in the lungs after a maximal inspiration.

TLV = RV + TV + IRV + ERV

Factors affecting lung volumes:
- Sex: males have larger lung volumes then females because their thoracic cavity size is bigger.
- Height: taller people have larger lung volumes because the thoracic cavity size is bigger.
- Obesity: individuals with increased body mass index (BMI) have smaller lung volumes because the increased fat decreases the space in the thoracic cavity and decreases lung elasticity (the ability of the lung to recoil after being expanded).
- Age: older individuals have smaller lung volumes because they have less lung elasticity.

Sources:
1. "Lungs." Mama's Health. 5 December 2008. http://www.mamashealth.com/organs/lungs.asp.
2. Nelson, Steve, ed. "Lung - Anatomy." NLHEP. August 2006. National Lung Health Education Program. 5 Demeber 2008. http://www.nlhep.org/lung_anat.html.
3. Jones, Richard, and Mary Nzekwu. "The effects of body mass index on lung volumes." Chest. 130 (2006): 827-833.
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