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.
Mouth-to-mouth ventilation has its own costs. Exhaled air contains 17 percent oxygen, less than 21 percent of fresh air, and 4 percent carbon-dioxide, which can inhibit cardiac contraction. Studies have found that from 10 to 35 percent of patients who receive CPR inhale stomach contents, emitted after air is blown into the stomach rather than to the lungs. And time allocated to ventilation, especially if only one rescuer is involved, is subtracted from the efforts to provide chest compressions.