Chapter 52, Problem 2.2A

Why is the predicted vital capacity dependent upon the height of the subject?

Summary Introduction

To analyze:

The relation between vital capacity and height of a person.

Introduction:

The volumes of air that moves into and out of the lungs during various phases of breathing are called respiratory volumes and capacities.A volume is a single measurement, whereas capacity represents two or more combined volumes. Vital capacity is the maximum volume of air getting exhaledafter taking the deepest breath. Vital capacity differs from individual to individual depending on the gender, height, weight, age and exercise history.

Explanation of Solution

A normal adult has the vital capacity of 3-5L. Height of the individual plays a major role in determining the vital capacity. The lung volume of an individual is proportional to the cube of his height. With increasing height, lung volume and the surface area increases which results in increased vital capacity. Among the several factors which determine the vital capacity of an individual, vital capacity can be estimated fairly accurately based on gender, height (H) in cm and age (A) in years, using the following equation,

  Male: Vital capacity = 0.052 H − 0.022 A − 3.60

  Female: Vital capacity = 0.041 H − 0.018 A − 2.69

Conclusion

Predicted vital capacity is directly dependent on the height of the person, because lung volume and surface area increases with increasing height which results in increased vital capacity.