A 56 yo lady comes to GP with SOB. Has 2 pack a day smokeing history for 37 years. Pulmonary function tests show: Function residual capacity = 4.5 Inspiratory reserve volume = 1.5 Inspiratory capacity = 2.0 Vital capacity = 3.0 1. What is the residual volume?

The main function of the respiratory system is gas exchange (O2 and CO2). Ventilation is the movement of air through the respiratory tract into (inspiration) and out of (expiration) the respiratory zone (lungs).