Rescue breaths during cardiopulmonary resuscitation (CPR)

Rescue breaths during cardiopulmonary resuscitation (CPR)

Rescue breaths during cardiopulmonary resuscitation (CPR): Rescue breaths are not as important as chest compressions in the initial few minutes of cardiac arrest due to ventricular fibrillation. This is because the oxygen level in the blood is high in the initial few minutes while the myocardial and cerebral oxygen delivery is hampered by the lack of blood flow. But in asphyxial arrest as in children or drowning, hypoxemia is present at the time of cardiac arrest. These victims need rescue breaths before chest compressions. Since the blood flow to the lungs is limited during cardiopulmonary resuscitation, lower tidal volumes and respiratory rates may be enough to maintain an adequate ventilation perfusion ratio (during CPR, cardiac output is only one fourth to one third of normal). Overventilation may be harmful as it can increase intrathoracic pressure, decrease venous return to the heart and consequently cardiac output and survival. Large and too forceful breaths may also cause gastric dilatation. Each rescue breath should be delivered over one second and be of sufficient tidal volume to produce a visible chest rise. The ratio of compressions to breaths is 30:2 when an advanced airway is not present. When an advanced airway like an endotracheal tube has been in place, 8-10 breaths per minutes may be given without interrupting chest compressions.
When rescue breaths are given without an advanced airway, gastric inflation can develop. This can lead to regurgitation of gastric contents into the esophagus and aspiration into the tracheobronchial tree as well as elevation of the diaphragm, restrict lung movement. High pressure breaths are more likely to enter the stomach as the pressure in the esophagus exceeds the lower esophageal sphincter opening pressure. Pressure can be increased by short inspiratory time, large tidal volume, high peak inspiratory pressure, incomplete opening of the airway and decreased lung compliance. That is why there is a recommendation to deliver the rescue breath over one second, and with just enough force to cause a visible chest rise.