During CPR, the bag-mask is used to give two breaths after every 30 compressions. On arrival of trained rescuers, bag-mask ventilation with supplemental oxygen is the most common initial approach and can be aided with an oropharyngeal or nasopharyngeal airway. Studies in late cardiac arrest (40–50 minutes) show that the tidal volumes generated are less than the patient’s estimated deadspace. Whether chest compressions generate a sufficient tidal volume for gas exchange is uncertain and likely to vary over time. Observational studies show improved survival to discharge for all adult OHCAs, and improved survival with good neurological outcome for witnessed cardiac arrest or if the initial rhythm is shockable. Some EMS services deliver continuous high-quality chest compressions with passive oxygenation with an oropharyngeal airway and simple oxygen mask (minimally interrupted cardiac resuscitation) and an advanced airway is delayed until after 600 chest compressions for witnessed OHCA with a shockable rhythm. Additional benefits of CPR with compressions and ventilations are most likely when delivered by rescuers trained in ventilation, when emergency medical service (EMS) response times are long or after an asphyxial cardiac arrest. In addition, dispatch-assisted compression-only CPR appears to give similar or improved outcomes compared with dispatcher CPR instructions for both compressions and ventilations. This could be because of an increased likelihood of bystanders performing compression-only CPR rather than no CPR, or CPR with long pauses for probably ineffective ventilation attempts. Observational data suggest that early lay-bystander compression-only CPR can improve survival after sudden cardiac arrest. Patients often have severe brain injury associated with hypoxaemia and low blood flow preceding cardiac arrest, a period of no or low flow during CPR and reperfusion injury following ROSC.Īs VF/pVT has a better response to treatment, CPR interventions prioritise treatment for VF/pVT at the expense of those that may be helpful for PEA or asystole. Survival after a non-cardiac cause of cardiac arrest, such as asphyxial cardiac arrest and which more commonly lead to an initial non-shockable cardiac arrest rhythm (pulseless electrical activity (PEA) or asystole), is relatively poor even if there is ROSC. Sudden cardiac arrest, with an initial shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia ) has good outcomes with early CPR and early defibrillation. Studies show that lay rescuer compression-only CPR is better than no CPR. When cardiac arrest follows airway and/or breathing problems (asphyxial cardiac arrest), earlier interventions to restore adequate oxygenation to the vital organs may be preferable.Ĭurrent guidelines for CPR emphasise chest compressions for all cardiac arrests because:Ĭhest compressions are easy to learn and do for most rescuers and do not require special equipment. The premise is that there is an adequate oxygen reservoir at the time of cardiac arrest and further oxygen is only required after about 4 minutes. After ROSC, rescuers should titrate inspired oxygen and ventilation to achieve normal oxygen and carbon dioxide targets.Ĭurrent guidelines recommend that, after a primary cardiac arrest, restoring a circulation with chest compressions and, if appropriate, attempted defibrillation to restart the heart take priority over airway and ventilation interventions. During CPR, rescuers should provide the maximum feasible inspired oxygen and use waveform capnography once an advanced airway is in place. Current evidence supports a stepwise approach to airway management based on patient factors, rescuer skills and the stage of resuscitation. This narrative review describes the current evidence, including the relative roles of basic and advanced (supraglottic airways and tracheal intubation) airways, oxygenation and ventilation targets during CPR and after ROSC in adults. Current guidelines are based predominantly on evidence from observational studies and expert consensus recent and ongoing randomised controlled trials should provide further information. The optimal combination of airway techniques, oxygenation and ventilation is uncertain. After cardiac arrest a combination of basic and advanced airway and ventilation techniques are used during cardiopulmonary resuscitation (CPR) and after a return of spontaneous circulation (ROSC).
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