I. Lung Volumes.

     A. Tidal volume (V_T)  =  Volume of air entering or leaving the lungs during a single breath.

     B. Inspiratory reserve volume (IRV)  =  Volume of air which can be inspired over and
          above the resting tidal volume

     C. Expiratory reserve volume (ERV)  =  Volume of air which can be expired after a normal
          expiration.

     D. Residual volume (RV)  =  Volume of air remaining in the lungs after a maximal expiration.
          Can be estimated as 25% of the vital capacity.
 

II. Lung Capacities.

     A. Inspiratory capacity (IC)  =  Maximum volume which can be inspired after a normal
          expiration.  IC  =  V_T + IRV.

     B. Vital capacity (VC)  =  Maximum volume that can be expired after a maximal inspiration.
          VC  =  V_T + IRV + ERV.

     C. Functional residual capacity (FRC)  =  Volume of air left in the lungs after a normal
          expiration.  FRC  =  ERV + RV.

     D. Total lung capacity (TLC)  =  Volume of the lungs when fully inflated.
          TLC  =  VC + RV  (or 1.25  x  VC).
 

III. Other.

     A. Respiratory rate (f)  =  Number of breaths per minute.

     B. Minute ventilation (V_E)  =  Total volume of air expired per minute.  V_E  =  V_T  x  f.

     C. Dead space (V_D)  =  Volume of inspired air which is not available for gas exchange.

     D. Alveolar ventilation (V_A)  =  Volume of air which reaches the alveoli per minute.
          V_A  =  (V_T - V_D)  x  f.