VentilationVentilation is the mechanical process by which air is drawn in and out of the lungs. Situations in which a patient may require ventilatory support range from apnea to patients with depressed respiratory function. If the patient's respiratory rate decreases significantly, this can lead to hypercapnia, hypoxia, lowered pH level, and decreased respiratory minute volume. If not corrected, this can result in cardiac or respiratory arrest. Exhaled air ventilation has been accepted as the technique of choice since the late 1950s. It has been proven to be an effective practice for both professionals and laypeople, including children over the age of 5. Ventilation using the rescuer's exhaled air can be applied to the mouth or nose of the adult victim and to the mouth and nose of the infant. Mouth-to-mouth ventilation and mouth-to-nose ventilation can provide effective ventilatory support to the patient. One of the main advantages of these ventilation methods is that no equipment is required to offer effective ventilatory support to the patient. However, the disadvantage of these methods of ventilatory support is that both methods offer only a limited oxygen supply as the oxygen exhaled by the rescuer will only contain 17% oxygen. Mouth-to-mask ventilation or pocket mask ventilation A clear plastic, molded face mask similar to that used in anesthesia can be used to provide mouth-to-mask ventilation. A one-way valve diverts the patient's exhaled air away from the rescuer and traps any macroscopic particles that emerge from the patient. This valve improves aesthetics and reduces the risk of cross infection. The mouth-mask method involves intermittent two-hour use of paper, restoring controlled mechanical ventilation in patients who are not breathing. Some contain a "pop-off" valve that prevents pressure-related injuries. A "pop-off" valve may prove harmful in situations where the patient is suffering from pulmonary contusion, bronchospasm, cardiogenic pulmonary edema, adult respiratory distress syndrome, or disorders where high levels of pressure in the airways must be overcome. In closing, there are several effective methods for providing respiratory support to patients. Although the mechanical ventilator has many advantages, as mentioned above, the bag valve method proves to have the most advantages. However, it should be noted that the bag valve technique has also proven problematic when attempting to offer respiratory support to non-intubated patients.