Respiratory Volume

Respiratory Volume

Objectives:

A. Define and compare the various volumes and capacities

B. Define dead space

C. Indicate types of information that can be gained from pulmonary function tests

Respiratory Volumes

Tidal Volume

Inspired reserve volume

Expiratory reserve volume

Residual volume

Respiratory Volumes

• During normal quiet breathing, about 500 ml of air moves into and then out of the lungs with each breath. This respiratory volume is the tidal volume (TV). 

• The amount of air that can be inspired forcibly beyond the tidal volume (2100 to 3200 ml) is the inspiratory reserve volume (IRV). 

• The expiratory reserve volume (ERV) is the amount of air— normally 1000 to 1200 ml—that can be expelled from the lungs after a normal tidal volume expiration.

• Even after the most strenuous expiration, about 1200 ml of air remains in the lungs; this is the residual volume (RV), which helps to keep the alveoli patent (open) and prevent lung collapse.

Male 20 years of Age, 70 kg. weight

Volumes and Capacities

Dead Space

DEAD SPACE: It is the volume of the respiratory tract that does not participate in gas exchange. It is approximately 300 ml in normal lungs.

Pulmonary Function Test

A. Forced vital capacity (FVC) measures the amount of gas expelled when a subject takes a deep breath and then forcefully exhales maximally and as rapidly as possible.

 B. Forced expiratory volume (FEV) determines the amount of air expelled during specific time intervals of the FVC test.