This normal vital capacity calculator estimates vital capacity based on gender, age and height when inspiratory, tidal and expiratory volumes are not available. Below the form, there are instructions on how to compute VC by this method and information on the factors taken into account.
How does the normal vital capacity calculator work?
This health tool estimates vital capacity based on subject gender, age and height in centimeters. It is based on a formula which aims to facilitate the calculation of VC when physical measurement testing is not possible.
These are the three factors accounted in the estimation:
■ Age is used as factor in the calculation as VC increases during the 20s and 30s and then follows a steady decrease towards the 50s.
■ Gender is taken in consideration as men usually have higher pulmonary volumes than women.
■ Height is also a factor as taller individuals tend to have higher vital capacities compared to individuals of normal or subnormal height.
The formulas used in this normal vital capacity calculator are gender specific:
Male Vital Capacity in L = ((27.63 – 0.112 x Age in years) x Height in cm)/1000
Female Vital Capacity in L = ((21.78 – 0.101 x Age in years) x Height in cm)/1000
Vital capacity can be defined as the sum of three air volumes: the quantity of air inhaled and exhaled during normal respiration, the quantity of air possible to be inhaled during forced inhalation and the quantity of air possible to be exhaled during forced exhalation.
It is one of the four respiratory capacities calculated while performing functional lung testing, along inspiratory capacity, functional residual capacity and total lung capacity. Similar to VC, functional residual capacity depends on the residual volume which is estimated through a set of formulas, more often than it is measured directly.
The usual method of determining vital capacity involves the three measurements taken during lung spirometry:
■ Inspiratory reserve volume – which is the additional volume of air possible to be inhaled forcefully after a normal inspiration.
■ Tidal volume – represents the volume of air inhaled and exhaled during one normal breathing: inhalation and exhalation.
■ Expiratory reserve volume – which is the volume of air that can be extracted forcefully during exhalation, after the expiration of the normal volume.
The above parameters have the following average values:
| Lung volume | Males (L) | Females (L) |
| Inspiratory reserve volume | 3.1 | 1.9 |
| Tidal volume | 0.5 | 0.5 |
| Expiratory reserve volume | 1.2 | 0.7 |
Example calculation
Taking the case of a male patient aged 30 with a height of 175 cm. The estimated vital capacity based on the formula ((27.63 – 0.112 x Age) x Height)/1000 is:
Vital Capacity = ((27.63 – 0.112 x 30) x 175)/1000 = 4.247 Litres.
Similar, a female patient aged 26 with a height of 168 cm, would have the estimated VC after the formula: ((21.78 – 0.101 x Age) x Height)/1000:
Vital Capacity = ((21.78 – 0.101 x 26) x 168)/1000 = 3.218 Litres.
References
1) Godfrey MS, Jankowich MD. (2016) The Vital Capacity Is Vital: Epidemiology and Clinical Significance of the Restrictive Spirometry Pattern. Chest; 149(1):238-51.
2) Steltner H, Vogel M, Sprung E, Timmer J, Guttmann J, Sorichter S. (2004) Incomplete forced expiration - estimating vital capacity by a mathematical method. Respiration; 71(4):353-9.
3) Marini JJ, Rodriguez RM, Lamb VJ. (1986) Involuntary breath-stacking. An alternative method for vital capacity estimation in poorly cooperative subjects. Am Rev Respir Dis; 134(4):694-8.
21 Sep, 2016