Letters to the Editor: Letter to the Editor
To the Editor
Lurie et al1 have written an impressive review on the physiology of cardiopulmonary resuscitation (CPR). We are, therefore, surprised at an apparent misstatement on chest compression-only CPR (CO-CPR). These authors stated that there are no prospective randomized studies in support of CO-CPR. In fact, there are 3 studies.2–4 Only 1 study2 is cited but not as a randomized controlled trial (RCT). All 3 RCTs involved adult out-of-hospital witnessed cardiac arrest, and the rescuer(s) were untrained bystanders receiving basic life support instructions over the phone. Patients either received conventional CPR (2 rescue mouth-to-mouth breaths followed by cycles of 15 chest compressions alternating with 2 breaths) or CO-CPR. All 3 studies showed a trend toward improved outcomes with the latter2–4 culminating into a significant survival advantage when meta-analyzed.5
Based in part on these studies,1–4 the International Liaison Committee on Resuscitation recommends CO-CPR for out-of-hospital witnessed cardiac arrest when performed by bystanders who are untrained/unwilling to perform conventional CPR. Trained rescuers should continue to incorporate rescue breathing in all CPRs. Mouth-to-mouth respiration by the lay public has been removed because it delays and interrupts chest compressions; is difficult to perform; may lead to hyperventilation, reduced venous return and coronary perfusion, and raised intracranial pressure; and may deter some people from performing CPR. However, rescue breathing consists of 2 components: (1) head-tilt-chin-lift; and (2) mouth-to-mouth ventilation. The objectionable aspects of rescue breathing as mentioned previously come from mouth-to-mouth ventilation. Maintaining a patent airway allows passive ventilation. In intubated humans, sustained levels of Etco2 akin to high-frequency ventilation are observed in most patients during chest compression. Furthermore, passive ventilation through an oropharyngeal airway during chest compression among patients with witnessed ventricular fibrillation results in significant survival advantage over positive-pressure ventilation using a bag-mask technique. Head-tilt–chin-lift produces adequate airway patency in 91% of anesthetized patients.
Our point is when the International Liaison Committee on Resuscitation eliminated rescue breathing by lay rescuers, they threw the baby out with the bath water. Ventilation is vital in all resuscitations. This is even more so in cardiac arrests because of noncardiac primary causes and in rural areas, where ambulance response time to provide defibrillation is long. We are of the opinion that if a second bystander is present, he or she should pull back the chin (no different from what anesthesiologists routinely do when transporting patients to the postanesthesia care unit) such that passive ventilation is possible during chest compression.
In a recent international cardiology conference, 1 of us raised that point after a lecture on CPR. The speaker responded by saying that there is no RCT on the subject, shutting down further discussion. Although we fully agree that there is a need to conduct RCTs, which could take years, common sense suggests that we should incorporate chin lift, whenever possible, into untrained bystander-performed CPR for witnessed and nonwitnessed arrests until proven otherwise. All in all, as stated by Lurie et al,1 “some would argue that current approaches to cardiac arrest are fatally flawed.” We think that the underappreciation of passive ventilation for out-of-hospital resuscitation by untrained bystanders for witnessed arrest fits this assertion.
Anthony M.-H. Ho, MD, FRCPC, FCCPDavid C. Chung, MD, FRCPCGlenio B. Mizubuti, MD, MScSong Wan, MD, PhD, FRCSDepartment of Anesthesiology and Perioperative MedicineQueen’s University, KingstonOntario, CanadaDepartment of Anaesthesia and Intensive CareDepartment of SurgeryThe Chinese University of Hong KongHong Kong SARhoamh@hotmail.com
1. Lurie KG, Nemergut EC, Yannopoulos D, Sweeney M. The physiology of cardiopulmonary resuscitation. Anesth Analg. 2016;122:767783.
2. Rea TD, Fahrenbruch C, Culley L, et al. CPR with chest compression alone or with rescue breathing. N Engl J Med. 2010;363:423433.
3. Svensson L, Bohm K, Castrèn M, et al. Compression-only CPR or standard CPR in out-of-hospital cardiac arrest. N Engl J Med. 2010;363:434442.
4. Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. N Engl J Med. 2000;342:15461553.
5. Hüpfl M, Selig HF, Nagele P. Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis. Lancet. 2010;376:15521557.