Cardiopulmonary resuscitation


Cardiopulmonary resuscitation is an emergency procedure used during cardiac or respiratory arrest that involves chest compressions, often combined with artificial ventilation, to preserve brain function and maintain circulation until spontaneous breathing and heartbeat can be restored. It is recommended for those who are unresponsive with no breathing or abnormal breathing, for example, agonal respirations.
CPR involves chest compressions for adults between and deep and at a rate of at least 100 to 120 per minute. The rescuer may also provide artificial ventilation by either exhaling air into the subject's mouth or nose or using a device that pushes air into the subject's lungs. Current recommendations emphasize early and high-quality chest compressions over artificial ventilation; a simplified CPR method involving only chest compressions is recommended for untrained rescuers. With children, however, 2015 American Heart Association guidelines indicate that doing only compressions may result in worse outcomes, because such problems in children normally arise from respiratory issues rather than from cardiac ones, given their young age. Chest compression to breathing ratios are set at 30 to 2 in adults.
CPR alone is unlikely to restart the heart. Its main purpose is to restore the partial flow of oxygenated blood to the brain and heart. The objective is to delay tissue death and to extend the brief window of opportunity for a successful resuscitation without permanent brain damage. Administration of an electric shock to the subject's heart, termed defibrillation, is usually needed to restore a viable, or "perfusing", heart rhythm. Defibrillation is effective only for certain heart rhythms, namely ventricular fibrillation or pulseless ventricular tachycardia, rather than asystole or pulseless electrical activity, which usually requires the treatment of underlying conditions to restore cardiac function. Early shock, when appropriate, is recommended. CPR may succeed in inducing a heart rhythm that may be shockable. In general, CPR is continued until the person has a return of spontaneous circulation or is declared dead.

Medical uses

CPR is indicated for any person unresponsive with no breathing or breathing only in occasional agonal gasps, as it is most likely that they are in cardiac arrest. If a person still has a pulse but is not breathing, artificial ventilations may be more appropriate, but due to the difficulty people have in accurately assessing the presence or absence of a pulse, CPR guidelines recommend that lay persons should not be instructed to check the pulse while giving healthcare professionals the option to check a pulse. In those with cardiac arrest due to trauma, CPR is considered futile but still recommended. Correcting the underlying cause such as a tension pneumothorax or pericardial tamponade may help.

Pathophysiology

CPR is used on people in cardiac arrest to oxygenate the blood and maintain a cardiac output to keep vital organs alive. Blood circulation and oxygenation are required to transport oxygen to the tissues. The physiology of CPR involves generating a pressure gradient between the arterial and venous vascular beds; CPR achieves this via multiple mechanisms.
The brain may sustain damage after blood flow has been stopped for about four minutes and irreversible damage after about seven minutes. Typically if blood flow ceases for one to two hours, then body cells die. Therefore, in general, CPR is effective only if performed within seven minutes of the stoppage of blood flow. The heart also rapidly loses the ability to maintain a normal rhythm. Low body temperatures, as sometimes seen in near-drownings, prolong the time the brain survives.
Following cardiac arrest, effective CPR enables enough oxygen to reach the brain to delay brain stem death and allows the heart to remain responsive to defibrillation attempts. If an incorrect compression rate is used during CPR, going against standing American Heart Association guidelines of 100–120 compressions per minute, this can cause a net decrease in venous return of blood, for what is required, to fill the heart. For example, if a compression rate of above 120 compressions per minute is used consistently throughout the entire CPR process, this error could adversely affect survival rates and outcomes for the victim.

Order of CPR in a first aid sequence

The best position for CPR maneuvers in the sequence of first aid reactions to a cardiac arrest is a question that has been long studied.
As a general reference, the recommended order is:
  1. Asking for help from bystanders in case any of them have received first aid training or can perform additional tasks.
  2. * Variation: when the rescuer is alone and no phone is nearby, the rescuer would go first for a phone to call for emergency medical services.
  3. Calling by phone for emergency medical services. Also, go for an automated defibrillator, but only if the AED is available within a few minutes.
  4. Attempting defibrillation with the automated external defibrillator, because it is easy to use if it has been found. If not, or until it has arrived, attempting CPR maneuvers as the latest step of those possible ones.
If there are multiple rescuers, these tasks can be distributed and performed simultaneously to save time.

Exception to the main sequence

  • If a rescuer is completely alone with a victim of drowning, or with a child who was already unconscious when the rescuer arrived, the rescuer should:
  1. First perform two minutes of CPR maneuvers.
  2. * Variation: when the lone rescuer does not have a phone, it is recommended to perform about two minutes of CPR maneuvers, and then go for a phone to call for emergency medical services .
  3. Call by phone for emergency medical services. Also, go for an automated defibrillator, but only if the AED is available within a few minutes.
  4. Attempt defibrillation with the automated external defibrillator, because it is easy to use if it has been found. If not, or until it has arrived, attempt CPR maneuvers as the latest step of those possible ones.
The reason is that CPR ventilation is considered the most important action for those victims. Cardiac arrest in drowning victims originates from a lack of oxygen, and a child would probably not suffer from cardiac diseases.

Methods

In 2010, the AHA and International Liaison Committee on Resuscitation updated their CPR guidelines. The importance of high quality CPR was emphasized. The order of interventions was changed for all age groups except newborns from airway, breathing, chest compressions to chest compressions, airway, breathing. An exception to this recommendation is for those believed to be in a respiratory arrest.
The most important aspects of CPR are: few interruptions of chest compressions, sufficient speed and depth of compressions, completely relaxing pressure between compressions, and not ventilating too much. It is unclear if a few minutes of CPR before defibrillation results in different outcomes than immediate defibrillation.

Compressions with rescue breaths

A normal CPR procedure uses chest compressions and ventilations for any victim of cardiac arrest, who would be unresponsive, not breathing, or only gasping because of the lack of heartbeats. But the ventilations could be omitted for untrained rescuers aiding adults who suffer a cardiac arrest. There has been evidence of increased effectiveness of CPR when the time between bouts of 30 compressions is limited.The patient's head is commonly tilted back for improving the airflow if ventilations can be used. However, when a patient seems to have a possible serious injury in the spinal cord, the head must not be moved except if that is completely necessary, and always very carefully, which avoids further damages for the patient's mobility in the future. And, in the case of babies, the head is left straight, looking forward, which is necessary for the ventilations, because of the size of the baby's neck.In CPR, the chest compressions push on the lower half of the sternum —the bone that is along the middle of the chest from the neck to the belly— and leave it to rise up until recovering its normal position. The rescue breaths are made by pinching the victim's nose and blowing air mouth-to-mouth. This fills the lungs, which makes the chest rise up, and increases the pressure into the thoracic cavity. If the victim is a baby, the rescuer would compress the chest with only 2 fingers and would make the ventilations using their own mouth to cover the baby's mouth and nose at the same time. The recommended compression-to-ventilation ratio, for all victims of any age, is 30:2. Victims of drowning receive an initial series of 2 rescue breaths before that cycle begins.
As an exception for the normal compression-to-ventilation ratio of 30:2, if at least two trained rescuers are present and the victim is a child, the preferred ratio is 15:2. Equally, in newborns, the ratio is 30:2 if one rescuer is present, and 15:2 if two rescuers are present. In an advanced airway treatment, such as an endotracheal tube or laryngeal mask airway, the artificial ventilation should occur without pauses in compressions at a rate of 1 breath every 6 to 8 seconds.
In all victims, the compression speed is at least 100 compressions per minute. Recommended compression depth in adults and children is of 5 cm, and in infants it is 4 cm. In adults, rescuers should use two hands for the chest compressions, while in children one hand could be enough, and with babies the rescuer must use only two fingers.
There exist some plastic shields and respirators that can be used in the rescue breaths between the mouths of the rescuer and the victim, with the purposes of sealing a better vacuum and avoiding infections.
In some cases, the problem is one of the failures in the rhythm of the heart that can be corrected with the electric shock of a defibrillator. So, if a victim is suffering a cardiac arrest, it is important that someone asks for a defibrillator nearby, to try with it a defibrillation process when the victim is already unconscious. The common model of a defibrillator is an automatic portable machine that guides the user with recorded voice instructions along the process, analyzes the victim, and applies the correct shocks if they are needed.
The time in which a cardiopulmonary resuscitation can still work is unclear, and it depends on many factors. Many official guides recommend continuing cardiopulmonary resuscitation until emergency medical services arrive. The same guides also indicate asking for any emergency defibrillator near, to try an automatic defibrillation as soon as possible before considering that the patient has died.
A normal cardiopulmonary resuscitation has a recommended order named 'CAB': first 'Chest', followed by 'Airway', and 'Breathing'. As of 2010, the Resuscitation Council was still recommending an 'ABC' order, with the 'C' standing for 'Circulation', if the victim is a child. It can be difficult to determine the presence or absence of a pulse, so the pulse check has been removed for common providers and should not be performed for more than 10 seconds by healthcare providers.