allow the body to achieve airway control by itself. However, if the bag-valve-mask is left on for more than five minutes, air may be introduced into the stomach. At that point, a nasogastric tube should be inserted to take the accumulated air out. During this process, practitioners must carefully position and maneuver the bag-valve-mask in order to keep airways open. To ensure an adequate seal when using the bag valve mask to ventilate, specific hand positioning is typically used. The provider places his or her thumb and index finger in a 'C' shape on top of the mask and grips the jaw under the mask with the other three fingers, creating an 'E' shape. The thumb and index finger provide downward pressure on the mask while the remaining fingers maintain head tilt and jaw thrust. The free hand can then be used to provide ventilation via the bag. For children, pediatric bags can be used. Pediatric bags have a valve that limits peak airway pressures to around 35–40 cm of water. Practitioners must tweak valve settings to accurately determine each of their patients to avoid hypoventilation or hyperventilation. When applying ventilation with the bag valve mask, the provider should apply just enough pressure to bag to see a chest rise. Providing excessive bag pressure can actually impair the blood flow to the heart and brain, so during CPR extra caution should be taken to limit size of tidal volume. The rate of manual ventilation should not exceed 12 times per minute, or one ventilation every 5 seconds as to avoid hyperventilation. Airway patency devices An oropharyngeal or nasopharyngeal airway is used during bag-valve-mask ventilation to prevent soft tissues from blocking the airway. An oropharyngeal airway may cause gagging and vomiting. Therefore, an oropharyngeal airway must be sized appropriately. An airway that is incorrectly sized can worsen the airway obstruction. The distance measured should be from the corner of the patient's mouth to the angle of the jaw or earlobe. Laryngeal mask airways The laryngeal mask airway (LMA) is a tube with an inflatable cuff. A laryngeal mask airway can be positioned in the lower oropharynx to prevent airway obstruction by soft tissues and to create a safe channel for ventilation. The laryngeal mask airway is the standard rescue ventilation when endotracheal intubation cannot be accomplished. To insert the laryngeal mask airway into the patient, the deflated mask should be pressed