And how to know if you need one! While it gets lost easily in the noise of the WIC, the truth is that the wedding is the ceremony, and the reception is the party that happens after the wedding. In a similar way, the rehearsal dinner has become a big deal in the American Wedding Machine, and the rehearsal itself is often an afterthought.
Residual volume (RV) is a lung volume representing the amount of air left in the lungs after a forced exhalation; this volume cannot be measured, only calculated.
Now, everybody has some air in their lungs even after they breathe out as much as they can. This prevents the alveoli, the little air sacks, from collapsing, flat as an old balloon. But patients with COPD may have a 200% or even larger increase in air trapping or residual volume.