Assessment of spontaneous breathing should imme-diately follow the opening or the establishment of the airway. Chest compressions and ventila-tion should not be delayed for intubation if apatent airway is established by a jaw-thrust maneu-ver. Apnea is confirmed by lack of chest movement, absence of breath sounds, and lack of airflow. Regardless of the airway and breathing methods employed, a specific regimen of ventilation has been proposed for the apneic patient. Initially, two breaths are slowly administered (2 s per breath in adults, 1–1½ s in infants and children). If these breaths can-not be delivered, either the airway is still obstructed and the head and neck need repositioning or a for-eign body is present that must be removed.
Mouth-to-mouth or mouth-to-mask (mouth-to-barrier-device) rescue breathing should be insti-tuted in the apneic patient, even in the hospital setting when the crash cart is on its way. Pinching the nose allows formation of an airtight seal between the rescuer’s lips and the outside of the victim’s mouth. Successful rescue breathing (700–1000 mL Vt, 8–10 times per minute in an adult with a secured air-way and a ratio of 30 compressions to 2 ventilations if the airway is unsecured) is confirmed by observ-ing the chest rising and falling with each breath and hearing and feeling the escape of air during expira-tion. The most common cause of inadequate mouth-to-mouth ventilation is insufficient airway control. Mouth-to-mouth-and-nose breathing is more effec-tive in infants and small children than in adults.
A rescuer’s exhaled air has an oxygen concen-tration of only 16–17% and contains significant CO2
Supplemental oxygen, preferably 100%, should always be used if available. If supplemental oxygen is used, a smaller VT of 400–700 mL is recommended. Mouth-to-mask or barrier device breathing hashygienic advantage over mouth-to-mouth breath-ing as the rescuer’s lips form a seal with an inter-vening device. Devices that avoid mouth-to-mouth contact should be immediately available everywhere in the hospital. Ventilation with a mask may be per-formed more easily in some patients because the rescuer may be able to adjust the airway or make an airtight seal more effectively. Furthermore, some mouth-to-mask devices allow the delivery of supple-mental oxygen.
These devices can be less effective than mouth-to-mask or bag-valve-TT venti-lation because of the difficulty inexperienced person-nel may have in maintaining an airway and seal with one hand and simultaneously delivering an adequate Vt with the other. Use of cricoid pressure to prevent regurgitation during cardiac arrest resuscitation may be considered; however, there are no data to support its efficacy in this circumstance and its routine use is not recommended in the new guidelines.
Tracheal intubation should be attempted as soonas practical. Attempts at intubation should not interrupt ventilation for more than 10 s. Afterintubation, the patient can be ventilated with a self-inflating bag capable of delivering high oxygen con-centrations. Because two hands are now available to squeeze the bag, ventilation should be satisfactory.
A ratio of 8–10 breaths/min in a secure airway should be maintained, as high respiratory rates can impede cardiac output in a cardiac arrest situation.
The ratio of physiological dead space to tidal volume (Vd/Vt) reflects the efficiency of CO2 elimi-nation. Vd/Vt increases during CPR as a result of low pulmonary blood flow and high alveolar pres-sures. Thus, minute ventilation may need to be increased by 50–100% once circulation is restored as CO2 from the periphery is brought back to the lungs.
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