BAG-VALVE-MASK VENTILATION

Indications and Contraindications
Correctly performed, the BVM method of ventilation appears to be simple and effective. Still, it is fraught with difficulty and therefore deserves special mention. Bag-valve-mask ventilation should be used by experienced individuals who are able to ensure a tight mask seal in situations requiring positive-pressure ventilation. The BVM is often used with an oropharyngeal or nasopharyngeal airway in place.
Inexperience is a relative contraindication to the use of a BVM. A rescuer who is not skilled with the BVM will achieve much better ventilation with mouth-to-mouth or mouth-to-mask breathing than with a BVM. However, concern regarding transmission of infectious diseases has reduced the willingness of the lay public and health professionals to perform mouth-to-mouth ventilations. Although BVM ventilation may provide excellent respiratory support in the anesthetized, paralyzed patient in the operating room, the device frequently is of marginal value during cardiopulmonary resuscitation (CPR), during an ambulance run, or in the combative patient. A tight mask seal is mandatory to prevent loss of air volume during ventilation. Another hazard of BVM ventilation occurs when vomitus, blood, or other debris is present in the mouth or pharynx. The foreign material may be insufflated down the trachea if it is not cleared before ventilation. The three major problems encountered with BVM ventilation are inadequate tidal volumes, inadequate oxygen delivery, and gastric distention.

Ventilation Technique
Achieving adequate tidal volume with BVM ventilation requires a tight mask seal and adequate compression of the bag. Even trained paramedics practicing on manikins have difficulty delivering tidal volumes above 650 mL, which is well below the 10-15 mL/kg recommended by the American Heart Association. A variety of mask configurations are available to facilitate a tight seal, but none substitutes for the practiced skill of the rescuer. For the single rescuer, only one hand can be used to achieve the seal because the other must squeeze the bag. The rescuer's hand must be large enough
to apply pressure anteriorly while simultaneously lifting the jaw forward. The thumb and index finger provide anterior pressure while the fifth and fourth fingers lift the jaw. Care must be exercised to deliver an adequate tidal volume by full compression of the bag. Dentures generally should be left in place to help ensure a better seal with the mask.
It has been suggested that effective BVM ventilation during CPR requires two hands and, therefore, two rescuers. We suggest using the two-rescuer technique whenever it is practical. The presence on the BVM device of a pop-off valve may further frustrate ventilation efforts in the patient with reduced compliance.
All BVM devices should be attached to a supplemental oxygen source (with a flow rate of 15 L/min) to avoid hypoxia. A significant problem with the BVM method is the low oxygen saturation achieved with various reservoirs. The amount of delivered oxygen is dependent on the ventilatory rate, the volumes delivered during each breath, the oxygen flow rate into the ventilating bag, the filling time for reservoir bags, and the type of reservoir used. The commonly used corrugated tube reservoir is the least effective of those examined by Campbell and colleagues. [14] It is too sensitive to ventilatory technique and does not alert the clinician to changes in oxygen flow. A 2.5-L bag reservoir and a demand valve are the preferred supplementation technique during BVM ventilation.
Pediatric BVM devices should have a minimum volume of 450 mL. Pediatric and larger bags may be used for ventilation of infants with the proper mask size, but care should be taken to administer only the volume necessary to effectively ventilate the infant. Pop-off valves should be avoided because airway pressure under emergency conditions may often exceed the pressure of the valve.

Complications
Hypoventilation often occurs because of the difficulty of carrying out the technique properly. Three mechanisms can result in complications: poor mask seal, failure to achieve airway patency, and low tidal volume. Practiced skill development is necessary to avoid these errors. Gastric distention can also result from poor airway patency. Air is insufflated down the esophagus, which inflates the stomach. Consequently, the risk of regurgitation and aspiration increases. When assistance is available, the application of firm posterior pressure on the cricoid ring helps reduce gastric inflation during BVM ventilation. [15] [16] The technique must be used carefully in infants, whose airway is more pliable and subject to obstruction with excessive cricoid pressure. Even with proper BVM technique, aspiration can occur. The rescuer must be vigilant to recognize complications early and take corrective action.