Drug Targeting Organ-Specific Strategies

56 3 Pulmonary Drug Delivery: Delivery To and Through the Lung
volume (l)
7
0
inspiratory
reserve
volume
tidal
volume
expiratory
reserve
volume
residual
volume
vital
capacity
inspiratory
capacity
functional
residual
capacity
total
lung
capacity
Figure 3.2. Schematic diagram of the different volumes describing pulmonary ventilation.
volume (V T) of approximately 0.7 l, and inhale with a frequency of about 12 times a minute
at rest [8].The amount of air processed under these conditions is 12 m 3 per day (with a range
of 10–20 m 3 per day). During heavy work, the tidal volume may be increased by a factor 3. A
residual volume (RV) of 1 to 1.5 l is not exhaled during normal breathing: this volume is increased
when a patient suffers from an obstruction e.g. in the case of asthma. Total lung capacities
(TLCs) of adults are estimated to be 5 to 7 l [1], maximal inspired volumes (vital capacities:
VCs) were found to be dependent on the external resistance and vary from less than
Table 3.1. Definitions of the different parameters describing pulmonary ventilation.
Parameter Definition
Total lung capacity The volume of air in the lung after a maximal inspiratory effort
Inspiratory capacity The volume of air maximally inspired after a normal tidal expiration
Functional residual capacity The volume of air remaining in the lung at the end of normal tidal expiration
Vital capacity The maximum volume of air expired after a maximal forced inspiration
Inspiratory reserve volume The maximum volume of air inspired after a normal tidal inspiration
Tidal volume The volume of air entering or leaving the lung at each normal breath
Expiratory reserve volume The maximum volume of air expired after normal tidal expiration
Residual volume The volume of air left in the lung after a maximal forced expiratory effort