| Lung Volumes |
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| CATEGORIES ABOUT LUNG VOLUMES | |
| respiratory system | |
| pulmonology | |
FACTORS AFFECTING LUNG VOLUME The breathing mechanisms in mammals is called Tidal Breathing. Tidal breathing means that air goes into the lungs the same way that it comes out. The total lung capacity depends on the person's age, weight, sex and the degree of physical activity. For example, females tend to have a 20–25% lower capacity than males. Tall people tend to have a larger total lung capacity than shorter people. Heavy Smokers have a drastically lower capacity than nonsmokers. Lung capacity is also affected by altitude. A person who is born and lives at Sea Level will have a smaller lung capacity than a person who spends their life at a high Altitude . This is because there is less Oxygen in the air at altitude, so the lungs gradually expand to process more air. When someone from sea level travels up to the higher parts of the earth (eg. the Andes , Mexico City , Tibet and the Himalayas ) they will often develop a condition called Altitude Sickness because their lungs cannot process enough oxygen for their body's needs. MEASUREMENT The ''tidal volume'', ''vital capacity'', ''inspiratory capacity'' and ''expiratory reserve volume'' can be measured directly with a Spirometer . Determination of the ''residual volume'' can be done by radiographic planemetry, Body Plethysmography , closed circuit dilution and nitrogen washout. These are the basic elements of a ventilatory '' Pulmonary Function Test ''. The results can be used to divide pulmonary diseasese into restrictive diseases, in which the volumes are decreased, and obstructive disease, where volumes are essentially normal but flow rates are impeded. There are four basic measured lung volumes:
From these volumes, several important capacities are also calculated:
Respiratory quotient = RQ = rate of CO2 production/rate of O2 consumption. RQ can vary with diet and exercise, but under typical conditions, RQ = 0.8. Following is a list of average Partial Pressure s of Oxygen gas (torr) for a human at rest:
Only ~ 7.5% of lung air is changed over on one breath at rest. |
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