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      4 Which of the following is the minimum chest compression fraction (defined as amount of time spent delivering chest compressions during CPR) shown to be associated with improved survival?0–20%21–40%41–60%61–80%81–100%Optimal outcomes have been demonstrated with minimal pauses between compressions for pulse checks and breaths given during high‐quality CPR. A compression fraction of at least 60% has been shown to be necessary for best outcomes. Animal studies previously conducted have demonstrated decreased coronary and cerebral perfusion when chest compressions are not being conducted resulting in worsened outcomes. Multiple retrospective analyses and cohort studies have resulted in many emergency agencies targeting a compression fraction of between 60 and 80% as a quality metric. This involves delivery of high‐quality compressions of appropriate depth, 2 inches, and rate, at least 100/min.Answer: DChristenson J, Andrusiek D, Everson‐Stewart S et al. Chest compression fraction determines survival in patients with out of hospital ventricular fibrillation. Circulation. 2009; 120: 1241–1247.Panchal AR, Bartos JA, Cabanas JG et al. Part 3: Adult basic and advanced cardiac life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020; 142 (suppl 2): S366–S468.

      5 Which of the following is considered the highest predictor of survival for in‐ and out‐of‐hospital CPR?Age.Shockable rhythm.Arrest at home.Arrest at night vs during the day.Delayed EMS response time.On the whole, survivability is dependent on patient, system, event, and therapeutic factors. With increasing comorbidity and age, survivability decreases. System factors include time to arrival of EMS, time to initiation of CPR, and time to defibrillation. Event factors include preceding symptoms. Finally, therapeutic factors include availability of medications to treat suspected cause, time to ER, time to cath lab should it be required, etc. The greatest mortality risk with out of hospital cardiac arrest stems from unwitnessed arrests without bystander CPR often occurring at night in the elderly. Highest survivability stems from witnessed arrests with rapid initiation of bystander CPR and initial shockable rhythm, such as ventricular fibrillation.Answer: BMyat A, Song K‐J, Rea T . Out of hospital cardiac arrest: current concepts. Lancet. 2018; 391: 970–79.Navab E, Esmaelli M, Poorkhorshidi N et al. Predictors of out of hospital cardiac arrest outcomes in pre‐hospital settings; a retrospective cross‐sectional study. Arch Am Emerg Med. 2019; 7 (1): e36.

      6 A 70‐year‐old man is 2 weeks status‐post laparoscopic sleeve gastrectomy and he undergoes witnessed cardiac arrest at home after complaint of new onset chest pain. Bystander CPR achieves ROSC after 10 minutes. He is now in the ICU, intubated, and on vasopressors for associated hypotension. Which of the following interventions has the strongest associated survival benefit in post‐arrest care according to current resuscitation guidelines?Maintain 100% FiO2.Pursuit of cardiac intervention when STEMI identified.Use of corticosteroids.Targeted temperature management to prevent fever.Seizure prophylaxis.If a cardiac cause is suspected, pursuit of cardiac intervention such as with percutaneous coronary intervention (PCI) is strongly recommended. Hyperoxygenation therapy, the use of corticosteroids, and seizure prophylaxis have thus far shown no survival benefit (choices A, C, and E). Finally, targeted temperature management is currently recommended for post‐arrest care with target of 32–36°C. This is based on several studies showing potential neurologic benefit. Preventing fever has not yet been proven to improve outcome though the 2020 AHA guideline (choice D). Ischemic heart disease is a major cause of out of hospital cardiac arrest. Among patients who had been successfully resuscitated after out of hospital cardiac arrest and had no signs of STEMI, immediate angiography was not found to be better than a strategy of delayed angiography with respect to overall survival at 90 days.Answer: BPanchal AR, Bartos JA, Cabanas JG et al. Part 3: Adult basic and advanced cardiac life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020; 142 (suppl 2): S366–S468.Yannapoulos D, Bartos JA, Aufderheide TP et al. The evolving role of the cardiac catherization laboratory in the management of patients with out of hospital cardiac arrest: a scientific statement from the American Heart Association. Circulation. 2019; 139 (12): e530–e552.Lemkes JS, Janssens GN, van der Hoeven NW et al. Coronary angiography after cardiac arrest without ST‐Segment elevation. April 11, 2019. N Engl J Med. 2019; 380: 1397–1407. DOI: https://doi.org/10.1056/NEJMoa1816897

      7 A 35‐year‐old, 26 week pregnant woman has cardiac arrest with CPR ongoing in the ED. CPR has been ongoing for 5 minutes. Which of the following has been shown to provide greatest benefit for achieving ROSC?Corticosteroids.Targeted temperature management.Left lateral uterine displacement.Fetal monitoring.C‐section.In conditions of cardiac arrest after pregnancy, rapid delivery of the fetus, typically by C‐section, termed perimortem cesarean delivery (PMCD), has been shown to be associated with improved outcomes when CPR does not achieve ROSC. However, the decision must be made quickly as a review article states that if done within 10 minutes of arrest, it was associated with better maternal outcomes. It was also thought that it was beneficial to the mother in 31% of cases and was not harmful in any case. The review of the cases resulted in only 94 cases supporting that PMCD is rare. Corticosteroids have shown no benefit and targeted temperature management may be used after achievement of ROSC (choices A and B).The left lateral uterine displacement alleviates aortocaval compression in patients with hypotension, but delivery achieves this much more effectively (choice C). Fetal monitoring during maternal CPR is a distraction and may hinder care (choice D).Answer: EEinav S, Kaufman N, Sela HY . Maternal cardiac arrest and perimortem caesarean delivery: evidence or expert based? Resuscitation. 2012; 83 (10): 1191–1200.Panchal AR, Bartos JA, Cabanas JG et al. Part 3: Adult basic and advanced cardiac life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020; 142 (suppl 2): S366–S468.

      8 Which of the following scenarios causes a shift of the oxygen dissociation curve to the left?A patient found unconscious in a basement apartment with malfunctioning heater.Patient with pneumonia and fever of 102°C.Patient with lactic acidosis from mesenteric ischemia.Patient with depressed mental status taking slow, shallow breaths.Patient returning from climbing Mt Everest where he had to stop and be treated for hypoxia after leaving base camp.Everest where he had to stop and be treated for hypoxia after leaving base camp. The oxygen–hemoglobin dissociation curve is sigmoidal in shape based on allosteric interactions of each globin monomer binding oxygen. A shift to the right indicates decreased affinity favoring unloading of oxygen while a shift to the left achieves the opposite effect. The strength by which oxygen binds to hemoglobin is affected by several factors and can be represented as a shift to the left or right in the oxygen dissociation curve. A rightward shift of the curve indicates that hemoglobin has a decreased affinity for oxygen, thus, oxygen actively unloads. A shift to the left indicates increased hemoglobin affinity for oxygen and an increased reluctance to release oxygen. Several physiologic factors are responsible for shifting the curve left or right, such as pH, carbon dioxide (CO2), temperature, and 2,3‐Disphosphoglycerate. Carbon monoxide exposure, as can be seen in enclosed spaces with a malfunctioning heater, can result in a leftward shift. If the patient was hypothermic or alkalotic, these conditions would also shift it toward the left.Answer: AWoodson, RD . Physiologic significance of oxygen dissociation curve shifts. Crit Care Med. 1979; 7 (9): 368–373.

      9 You are caring for a patient in the SICU, currently intubated after undergoing left upper lobectomy for tumor. Patient’s current hemoglobin is 10 g/dL, oxygen saturation 95%, and PaO2 of 92 mmHg. What is the expected oxygen content (CaO2)?0.9 mL/dL9 mL/dL13 mL/dL21 mL/dL140 mL/dLBlood oxygen content is based on the following formula influenced by oxygen saturation, partial pressure of arterial oxygen, and patient’s hemoglobin: The single biggest factor for oxygen content is hemoglobin. Doubling of hemoglobin would double the oxygen content. Increasing the partial pressure of oxygen from 60 mmHg to 100 would increase saturation from 90 to 100% and would not be a large change in content. The doubling of partial pressure of oxygen from 60 mmHg to 120 mmHg would still only increase the content by 10% as the dissolved amount of oxygen in plasma is negated by the factor of 0.003. The constant of 1.34 is the amount of oxygen that one gram of hemoglobin carries at 1 atmosphere of pressure.Answer: CCrocetti J, Diaz‐Abad M, Krachman SL . Oxygen content, delivery, and uptake. In GJ Criner, RE Barnette, GE D’Alonzo (Eds), Critical Care Study Guide. New York: Springer, 2010.

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