Advanced Cardiovascular Life Support (ACLS) protocols are used by healthcare professionals to manage life-threatening emergencies, primarily cardiac arrest. The goal of ACLS is to restore spontaneous circulation and breathing, ensuring oxygenated blood reaches the brain and heart. While chest compressions are widely recognized as the most important element of CPR, providing the correct amount of ventilation is equally important. The frequency of rescue breaths changes depending on whether a standard or advanced airway device is used. Striking the precise balance is paramount, as providing too many breaths can be as detrimental as providing too few.
Ventilation Rates During Standard CPR
When a patient is receiving CPR without a definitive airway, such as with a pocket mask or a bag-mask device, the ventilation rate is linked to the compression rate. The American Heart Association (AHA) guidelines recommend a synchronized approach using the compression-to-ventilation ratio. For adults, this ratio is set at 30 compressions followed by 2 breaths.
Chest compressions must be temporarily paused to deliver these two rescue breaths. Each breath should be delivered over approximately one second, providing just enough volume to cause a visible chest rise. This interruption is necessary because a non-advanced airway does not create a sealed system, making effective ventilation difficult during continuous chest compressions. This ratio applies whether a single rescuer or multiple rescuers are present.
Ventilation Rates With an Advanced Airway
The ventilation strategy changes significantly once a definitive or advanced airway is secured in the patient’s trachea, such as an endotracheal tube or a supraglottic device. With an advanced airway in place, chest compressions no longer need to be paused for breaths. This allows the team to perform continuous, uninterrupted chest compressions at the recommended rate of 100 to 120 per minute.
Ventilation delivered through the advanced airway becomes asynchronous with compressions. The chest compressor can continue their work while the ventilation provider gives breaths independently. The recommended rate for this continuous ventilation is one breath every 6 seconds, translating to 10 breaths per minute. This precise, low rate ensures adequate oxygenation while strictly avoiding the detrimental effects of excessive ventilation.
The Physiological Impact of Controlled Breathing
Strict control over the ventilation rate, particularly the transition to a low rate with an advanced airway, is based on the physiology of the circulatory system during cardiac arrest. Excessive or overly frequent ventilation (hyperventilation) creates a significant problem by increasing intrathoracic pressure. This increased pressure is counterproductive to the goal of CPR, which is to circulate blood.
Positive pressure ventilation at a high rate impedes the flow of blood back to the heart from the body, a process known as venous return. When venous return is decreased, cardiac output is also reduced. This effect directly lowers the coronary perfusion pressure, which drives blood flow to the heart muscle. Lowering this pressure severely reduces the chances of achieving a return of spontaneous circulation (ROSC).
Hyperventilation can lead to respiratory alkalosis, where excessive carbon dioxide is exhaled, making the blood more alkaline. This imbalance can cause blood vessels in the brain to constrict, reducing cerebral blood flow at a time when the brain is already vulnerable due to lack of oxygen. Studies show that patients who receive excessive ventilation during CPR have lower survival rates and worse neurological outcomes. The precise guideline of 10 breaths per minute reflects the understanding that “less is more” to protect the heart’s blood supply and brain perfusion.