词条 | Respiratory minute volume |
释义 |
Respiratory minute volume (or minute ventilation or minute volume) is the volume of gas inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs per minute. It is an important parameter in respiratory medicine due to its relationship with blood carbon dioxide levels. It can be measured with devices such as a Wright respirometer or can be calculated from other known respiratory parameters. Although minute volume can be viewed as a unit of volume, it is usually treated in practice as a flow rate (given that it represents a volume change over time). Typical units involved are (in metric) 0.5 L × 12 breaths/min = 6 L/min. Several symbols can be used to represent minute volume. They include (V̇ or V-dot) or Q (which are general symbols for flow rate), MV, and VE. Determination of minute volumeMinute volume can either be measured directly or calculated from other known parameters. Measurement of minute volumeMinute volume is the amount of gas inhaled or exhaled from a person's lungs in one minute. It can be measured by a Wright respirometer or other device capable of cumulatively measuring gas flow, such as mechanical ventilators. Calculation of minute volumeIf both tidal volume (VT) and respiratory rate (ƒ or RR) are known, minute volume can be calculated by multiplying the two values. One must also take care to consider the effect of dead space on alveolar ventilation, as seen below in "Relationship to other physiological rates". Physiological significance of minute volumeBlood carbon dioxide (PaCO2) levels generally vary inversely with minute volume.{{Citation needed|date=November 2011}} For example, a person with increased minute volume (e.g. due to hyperventilation) should demonstrate a lower blood carbon dioxide level. The healthy human body will alter minute volume in an attempt to maintain physiologic homeostasis. A normal minute volume while resting is about 5–8 liters per minute in humans.{{Citation needed|date=November 2011}} Minute volume generally decreases when at rest, and increases with exercise. For example, during light activities minute volume may be around 12 litres. Riding a bicycle increases minute ventilation by a factor of 2 to 4 depending on the level of exercise involved. Minute ventilation during moderate exercise may be between 40 and 60 litres per minute.[1] [2] Hyperventilation is the term for having a minute ventilation higher than physiologically appropriate. Hypoventilation describes a minute volume less than physiologically appropriate. Relationship to other physiological ratesMinute volume comprises the sum of alveolar ventilation and dead space ventilation. That is: where is alveolar ventilation, and represents dead space ventilation. References1. ^{{cite journal | last = Zuurbier, M., Hoek, G., van den Hazel, P., Brunekreef, B. | first = | title = Minute ventilation of cyclists, car and bus passengers: an experimental study.| journal = Environmental Health | volume = 8 | issue = 48 | pages = | year = 2009 | url = http://www.ehjournal.net/content/8/1/48 | doi = 10.1186/1476-069x-8-48 | pmid = | month =}} 2. ^{{cite journal | last = Int Panis | first = L | title = Exposure to particulate matter in traffic: A comparison of cyclists and car passengers | journal = Atmospheric Environment | volume = 44 | issue = | pages = 2263–2270 | year = 2010 | url = | doi = 10.1016/j.atmosenv.2010.04.028 | pmid = | month =}} External links
1 : Respiratory physiology |
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