A. Airway Management. The techniques used for airway maintenance during anesthesia are also applicable to cardiac arrest victims (Table 58-2).

1. Foreign body airway obstruction must be considered in any person who suddenly stops breathing and becomes cyanotic and unconscious. (This occurs most commonly during eating and is usually caused by food, especially meat, impacting in the laryngeal inlet, at the epiglottis, or in the vallecula).

2. The signs of total airway obstruction are the lack of air movement despite respiratory efforts and the inability of the victim to speak or cough.

3. Treatment is the abdominal thrust maneuver (chest thrusts are an alternative for parturients and massively obese individuals) and the finger sweep.

4. In an awake victim, the rescuer reaches around the victim from behind, placing the fist of one hand in the epigastrium between the xiphoid and umbilicus. The fist is grasped with the other hand and pressed into the victim’s epigastrium with a quick upward thrust. If the first attempt is unsuccessful, repeated attempts should be made because hypoxia-related muscular relaxation may eventually allow success.

B. Ventilation. When ventilation is provided in the rescue setting, mouth-to-mouth or mouth-to-nose ventilation is the most effective immediately available method. Although inspired gas with this method contains only about 17% oxygen and nearly 4% carbon dioxide (composition of exhaled air), it is sufficient to maintain viability.

1. Physiology of Ventilation During Cardiopulmonary Resuscitation

a. Avoiding gastric insufflation requires that peak inspiratory airway pressures remain below esophageal opening pressure (∼20 cm H₂O). Partial airway obstruction by the tongue and pharyngeal tissues is a major cause of increased airway pressure contributing to gastric insufflation during CPR. Properly applied pressure to the anterior arch of the cricoid (Sellick maneuver) causes the cricoid lamina to seal the esophagus and can prevent air from entering the stomach at airway pressures up to 100 cm H₂O.

b. Achievement of an acceptable tidal volume during low inspiratory pressures characteristic of rescue breathing requires a slow inspiratory flow rate and long inspiratory time (breaths over 1.5–2.0 seconds during a pause in chest compressions).

2. Techniques of Rescue Breathing (Table 58-3)

C. Circulation

1. Physiology of Circulation During Closed Chest Compression. Two theories of the mechanism of blood flow during closed chest compression have been suggested. The mechanism that predominates varies from victim to victim and even during the resuscitation of the same victim.

a. The cardiac pump mechanism proposes that pressure on the chest compresses the heart between the sternum and spine. Compressions increase the pressure in the ventricular chambers (closing the atrioventricular valves) and eject blood into the lungs and aorta. During the relaxation phase of closed chest compression, expansion of the thoracic cage causes a subatmospheric intrathoracic pressure, facilitating blood return.

b. The thoracic pump mechanism proposes that the increase in intrathoracic pressure caused by sternal compressions forces blood out of the chest (backward flow into veins is prevented by valves) with the heart acting as a passive conduit.

2. Distribution of Blood Flow During Cardiopulmonary Resuscitation. Cardiac output is decreased between 10% and 33% of normal during CPR, and nearly all the blood flow is directed to organs above the diaphragm. (Abdominal viscera and lower extremity blood flow are decreased to <5% of normal.)

a. Myocardial perfusion is 20% to 50% of normal, and cerebral perfusion is maintained at 50% to 90% of normal.

b. Total flow tends to decrease with time during CPR, but the relative distribution is not altered. Epinephrine may help sustain cardiac output over time during CPR.

3. Gas Transport During Cardiopulmonary Resuscitation

a. During the low-flow state of CPR, excretion of carbon dioxide is decreased to the same extent that cardiac output is reduced.

b. Exhaled carbon dioxide concentrations reflect only the metabolism of the part of the body that is being perfused.

c. When normal circulation is restored, carbon dioxide that has accumulated in nonperfused tissues is washed out, and a temporary increase in carbon dioxide excretion is seen.

d. Although carbon dioxide excretion is decreased during CPR, measurement of blood gases reveals an arterial respiratory alkalosis and a venous respiratory acidosis, reflecting the severely reduced cardiac output.

4. Technique of Closed Chest Compression

a. Some circulation may be present in a “pulseless” patient (systolic blood pressure of about 50 mm Hg is necessary to palpate a peripheral pulse) with primary respiratory arrest. In such a patient, opening the airway and ventilation of the lungs may be sufficient for resuscitation. For this reason, a further search for a pulse should be made after artificial ventilation before beginning sternal compressions.

b. Important considerations in performing closed chest compressions are the position of the rescuer relative to the victim, the position of the rescuer’s hands, and the rate and force of compression (Table 58-4).

5. Alternative Methods of Circulatory Support. Standard CPR can sustain most patients for only 15 to 30 minutes. If return of spontaneous circulation has not been achieved in that time, the outcome is dismal.

a. Alternatives to standard techniques for CPR are based on the thoracic pump mechanism with the goal of improving hemodynamics. Unfortunately, none of these alternatives has proven reliably superior to the standard technique.

b. Invasive Techniques. Open chest cardiac massage or cardiopulmonary bypass must be instituted early to improve survival. If open chest massage is begun after 30 minutes of ineffective closed chest compressions, there is no better survival even though hemodynamics are improved.

6. Assessing the Adequacy of Circulation During Cardiopulmonary Resuscitation (Table 58-5)

a. The adequacy of closed chest compressions is usually judged by palpation of a pulse in the carotid or femoral artery. (A palpable pulse primarily reflects systolic blood pressure.)

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