Ventilation Bags and Masks (Excerpt)
Ventilation with a bag-mask device requires more skill than mouth-to-mouth or mouth-to-mask ventilation. A bag mask device should be used only by personnel with proper training. Training should focus on selecting an appropriately sized mask and bag, opening the airway and securing the mask to the face, delivering adequate ventilation, and assessing the effectiveness of ventilation. We recommend periodic demonstration of proficiency.
Types of Ventilation Bags (Manual Resuscitators)
There are two types of manual resuscitators: self-inflating and flow-inflating. Ventilation bags used for resuscitation should be self-inflating and should be available in child and adult sizes, suitable for the entire pediatric age range.
Neonatal-size (250 mL) ventilation bags may be inadequate to support effective tidal volume and the longer inspiratory times required by full-term neonates and infants.1 For that reason, resuscitation bags used for ventilation of full-term newborns, infants, and children should have a minimum volume of 450 mL to 500 mL. Studies using infant manikins showed that effective infant ventilation can be accomplished using pediatric (and larger) resuscitation bags.2 Regardless of the size of the manual resuscitator, take care to use only that force and tidal volume necessary to cause the chest to visibly rise. Excessive ventilation volumes and airway pressures may compromise cardiac output by raising the intrathoracic pressure and by distending alveoli, increasing afterload on the right heart. In addition, excessive volumes may distend the stomach, impeding ventilation and increasing the risk of regurgitation and aspiration. In patients with small-airway obstruction (e.g., asthma and bronchiolitis), excessive tidal volumes and rate can result in air trapping, barotraumas, air leak, and severe compromise to cardiac output. In head-injured and post-arrest patients, excessive ventilation volumes and rate may result in hyperventilation, with potentially adverse effects on neurological outcome. Therefore, the routine target in postarrest and head-injured patients should be physiological oxygenation and ventilation.
Ideally, manual resuscitators used for resuscitation should have either no pressure-relief valve or a pressure relief valve with an override feature to permit use of high pressures to achieve visible chest expansion if necessary.3 High pressures may be required during bag-mask ventilation of patients with upper or lower airway obstruction or poor lung compliance. In those patient, a pressure-relief valve may prevent delivery of sufficient tidal volume.4
Self-Inflating Bags
The self-inflating bag delivers only room air (21% oxygen) unless supplemental oxygen is provided. At an oxygen inflow of 10 L/min, pediatric manual resuscitator devices without oxygen reservoirs deliver from 30% to 80% oxygen to the patient. The actual concentration of oxygen delivered is unpredictable because entrainment of variable quantities of room air occurs, depending on the tidal volume and peak inspiratory flow rate used. To deliver consistently higher oxygen concentrations (60% to 95%), all manual resuscitators used for resuscitation should be equipped with an oxygen reservoir. An oxygen flow of at least 10 L to 15 L/min is necessary to maintain an adequate oxygen volume in the reservoir of a pediatric manual resuscitator; this should be considered the minimum flow rate.4 The larger adult manual resusicitators require at least 15 L/min of oxygen to deliver high oxygen concentrations reliably.
To provide bag-mask ventilation, open the airway, seal the mask to the face, and deliver an adequate tidal volume. To open the airway and seal the mask to the face in the absence of suspected neck trauma, tilt the head back while two or three fingers are positioned under the angle of the mandible to lift it up and forward, moving the tongue off the posterior pharynx. Place the thumb and forefinger in a "C" shape over the mask and exert downward pressure on the mask while the other fingers maintain the jaw thrust to create a tight seal. This technique of opening the airway and sealing the mask to the face is called the "E-C clamp" technique. The third, fourth, and fifth fingers (forming an E) are positioned under the jaw to lift it forward; then the thumb and index finger (forming a C) hold the mask on the child’s face.
Determine appropriate mask size by the ability to seal it around the mouth and nose without covering the eyes or overlapping the chin. Once the mask is properly sealed, the other hand compresses the ventilation bag until the chest visibly rises.
Self-inflating bag-mask systems that contain a fish-mouth or leaf-flap outlet valve cannot be used to provide continuous supplemental oxygen to the child with spontaneous respirations. The valve in the self-inflating bag opens only if the bag is squeezed or the child’s inspiratory effort is significant. If the bag is not squeezed, the valve usually remains closed, so the child receives only a negligible amount of escaped oxygen and rebreathes the exhaled gases contained within the mask itself.
Flow-Inflating Bags
Flow-inflating bags (also called "anesthesia bags") refill only with oxygen inflow, and the inflow must be individually regulated. Since flow-inflating manual resuscitators are more difficult to use, they should be used by trained personnel only.5 Flow-inflating bags permit the delivery of supplemental oxygen to a spontaneously breathing victim.
Two-person Bag-Mask Ventilation
Superior bag-mask ventilation can be achieved with two persons, and this technique may be necessary when there is significant airway obstruction or poor lung compliance.6 One rescuer uses both hands to open the airway and maintain a tight mask-to-face seal while the other rescuer compresses the ventilation bag. Both rescuers should observe the chest to ensure chest rise with each breath.
References
1. Field D, Milner AD, Hopkin IE. Efficiency of manual resuscitators at birth. Arch Dis Child 1986; 61:300-302.
2. Terndrup TE, Kanter RK, Cherry RA. A comparison of infant ventilation methods performed by prehospital personnel. Ann Emerg Med 1989; 18:607-611.
3. Hirschman AM, Kravath RE. Venting vs. ventilating: A danger of manual resuscitation bags. Chest 1982; 82:369-370.
4. Finer NN, Barrington KJ, Al-Fadley F, et al. Limitations of self-inflating resuscitators. Pediatrics 1986; 77:417-420.
5. Mondolfi AA, Grenier BM, Thompson GE, et al. Comparison of self-inflating bags with anesthesia bags for bag-mask ventilation in the pediatric emergency department. Pediatr Emerg Care 1997; 13:312-316.
6. Jesudian MC, Harrison RR, Keenan RL, et al. Bag-valve-mask ventilation: Two rescuers are better than one: Preliminary report. Crit Care Med 1985; 13:122-123.
Source
Reproduced with permission. American Heart Association in collaboration with the International Liaison Committee on Resuscitation. Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science, Part 10: Pediatric Advanced Life Support. Circulation 2000; (suppl I):I-291-I-342. ©American Heart Association.
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