Cardiopulmonary Resuscitation (CPR) is a life-saving sequence of actions designed to manually circulate blood and oxygen when the heart has stopped beating. The goal is to maintain a minimal flow of oxygenated blood to the brain and heart until advanced medical help arrives. CPR guidelines are highly specific and change depending on the environment, the number of rescuers, and the availability of specialized equipment. The most significant modification occurs when a protected, or “advanced,” airway is secured during the resuscitation effort.
Standard CPR without an Advanced Airway
When CPR is performed without a secured airway, the technique requires a specific rhythm of alternating compressions and ventilations. The standard approach for adult two-rescuer CPR mandates a compression-to-ventilation ratio of 30 compressions followed by 2 breaths. This ratio ensures oxygen is provided while limiting interruptions to the blood-pumping action of chest compressions.
The compressions must be momentarily paused to allow the rescuer to deliver the two rescue breaths. Pausing is necessary because, without a protected airway, air delivered has a potential route to the stomach, which can cause complications like gastric inflation. This stop-and-start approach is the baseline until a more sophisticated airway management strategy can be implemented.
Understanding Advanced Airway Devices
An “advanced airway” refers to a device healthcare professionals insert to secure a sealed pathway directly into the trachea, or windpipe. Examples include an endotracheal tube (ETT) or supraglottic devices like laryngeal mask airways (LMAs). Placement creates a tight seal, isolating the lungs from the esophagus and the upper airway.
This sealed connection allows positive-pressure ventilation to be delivered directly to the lungs, minimizing the risk of air leakage or aspiration. The primary benefit is that it removes the necessity of pausing chest compressions to deliver breaths. This secured pathway allows rescuers to separate the actions of ventilation and circulation during the resuscitation effort.
The Asynchronous Compression and Ventilation Rates
The placement of an advanced airway triggers a fundamental shift in the CPR technique, moving from a cyclical ratio to an asynchronous, continuous process. The chest compression rate remains the same as in standard CPR, but compressions are delivered without interruption for breaths. The recommended compression rate is a continuous 100 to 120 compressions per minute.
The ventilation rate is delivered completely independently of the compressions, in an asynchronous manner. Rescuers deliver one breath every 6 seconds, resulting in a consistent rate of 10 breaths per minute. This asynchronous technique means the compression rescuer no longer counts or pauses for the breathing rescuer.
The controlled ventilation rate of 10 breaths per minute is specifically designed to prevent hyperventilation. Excessive or rapid ventilation can inadvertently increase intrathoracic pressure within the chest cavity. This increased pressure can impede the return of blood to the heart, undermining the effectiveness of the chest compressions.
Maintaining Perfusion Pressure During Resuscitation
The primary physiological reason for adopting continuous compressions with an advanced airway is to maximize Coronary Perfusion Pressure (CPP). CPP is the pressure difference that drives blood flow to the heart muscle itself, and it is a strong predictor of whether a person will achieve a return of spontaneous circulation (ROSC). This pressure is generated primarily during the relaxation phase of a chest compression.
Studies show that every time chest compressions are paused, even briefly to deliver a breath, the CPP drops precipitously. It takes several subsequent compressions for this pressure to “rebuild” to an effective level. Interruptions cause a significant loss of blood flow to the heart.
Therefore, the main goal of securing the airway is not simply to provide oxygen more efficiently, but to allow for uninterrupted, high-quality chest compressions that sustain this perfusion pressure. By eliminating the pauses required for ventilation, the continuous compression technique ensures a more consistent and higher average CPP. Maintaining this blood flow to the heart muscle is considered a more important factor for survival than the brief oxygenation provided by the breaths.