Part 4: Adult Basic Life Support IV-2 CPR training should emphasize how to recognize synchronize breaths between compressions. There should nal gasps and should instruct rescuers to give rescue be no pause in chest compressions for delivery of ventila- and proceed with the steps of CPR when the unre- tions(Class Ila). victim demonstrates occasional gasps(Class Ila). Studies in anesthetized adults (with normal perfusion Give 2 rescue breaths, each over 1 second, with enough normal oxygenation and elimination of CO2. During CPR volume to produce visible chest rise. This recommended cardiac output is 25% to 33% of normal, 8 so oxygen 1-second duration to make the chest rise applies to all forms uptake from the lungs and cO2 delivery to the lungs are also of ventilation during CPR, including mouth-to-mouth and reduced. 9 As a result, low minute ventilation (lower than bag-mask ventilation and ventilation through an advanced normal tidal volume and respiratory rate)can maintain airway, with and without supplementary oxygen( Class Ila) effective oxygenation and ventilation during CPR. 20-123 During CPR the purpose of ventilation is to maintain During adult CPR tidal volumes of approximately 500 to 600 mL adequate oxygenation, but the optimal tidal volume, respira- (6 to 7 mL/kg)should suffice( Class IIa). Although a rescuer tory rate, and inspired oxygen concentration to achieve this cannot estimate tidal volume, this guide may be useful for are not known. The following general recommendations can setting automatic transport ventilators and as a reference for be made manikin manufacturers If you are delivering ventilation with a bag and mask, use I. During the first minutes of VF SCA, rescue breaths are an adult ventilating bag(volume of I to 2 L); a pediatric bag probably not as important as chest compressions 13 be- delivers inadequate tidal volume for an adult.124,125 cause the oxygen level in the blood remains high for the first several minutes after cardiac arrest. In early cardiac When giving rescue breaths, give sufficient volume to arrest, myocardial and cerebral oxygen delivery is limited cause visible chest rise (LOE 6, 7; Class Ila). In I observa- nore by the diminished blood flow(cardiac output) than tional study trained BLS providers were able to detect lack of oxygen in the blood. During CPR blood flow is "adequate"chest rise in anesthetized, intubated, and para provided by chest compressions. Rescuers must be sure to lyzed adult patients when a tidal volume of approximately provide effective chest compressions (see below) and 400 mL was delivered. 114 It is likely, however, that a larger minimize any interruption of chest compressions 2. Both ventilations and compressions are important for volume is required to produce chest rise in a victim with no victims of prolonged VF SCA, when oxygen in the blood advanced airway (eg, endotracheal tube, Combitube, LMA) is utilized. Ventilations and compressions are also imp in place. We therefore recommend a tidal volume of 500 to tant for victims of asphyxial arrest, such as children and 600 mL but emphasize that the volume delivered should drowning victims who are hypoxemic at the time of proa produce visible chest rise(Class Ila). It is reasonable to use cardiac arrest the same tidal volume in patients with asphyxial and arrhyth 3. During CPR blood flow to the lungs is substantially mic cardiac arrest(Class IIb) reduced, so an adequate ventilation-perfusion ratio can be Currently manikins show visible chest rise when tidal maintained with lower tidal volumes and respiratory rates volumes reach about 700 to 1000 mL. To provide a realistic than normal. 4 Rescuers should not provide hyperventi- tion(too many breaths or too large a volume). Excessive practice experience, manikins should be designed to achieve ventilation is unnecessary and is harmful because it a visible chest rise at a tidal volume of 500 to 600 mL 114 increases intrathoracic pressure, decreases venous return Automated and mechanical ventilators are discussed briefly to the heart, and diminishes cardiac output and survival. I5 at the end of this chapter and in Part 6: " CPR Techniques and 4. Avoid delivering breaths that are too large or too forceful. Devices. Such breaths are not needed and may cause gastric Gastric inflation often develops when ventilation is pro- inflation and its resultant complications. 6 vided without an advanced airway. It can cause regurgitation and aspiration, and by elevating the diaphragm, it can restrict The ECC Guidelines 2000117 recommended a variety of lung movement and decrease respiratory compliance. 7 Air tidal volumes, respiratory rates, and breath delivery intervals. But it is unrealistic to expect the rescuer to distinguish delivered with each rescue breath can enter the stomach when half-second differences in inspiratory times or to judge tidal ssure in the esophagus exceeds the lower esophageal lumes delivered by mouth-to-mouth or bag-mask ventila- phincter opening pressure. Risk of gastric inflation is in- on. So these guidelines provide simple recommendations for creased by high proximal airway pressurell4 and the reduced delivery of rescue breaths during cardiac arrest as follows: opening pressure of the lower esophageal sphincter. 26 High pressure can be created by a short inspiratory time, large tidal Deliver each rescue breath over I second(Class Ila) olume, high peak inspiratory pressure, incomplete airway nd decreased lung compliance. 27 To minimize the bag mask with or without supplementary oxygen)to potential for gastric inflation and its complications, deliver produce visible chest rise( Class Ila) each breath to patients with or without an advanced airway Avoid rapid or forceful breaths over I second and deliver a tidal volume that is sufficient to When an advanced airway (ie, endotracheal tube Comb produce a visible chest rise(Class Ia). But do not deliver tube, or LMA)is in place during 2-person CPR, ventilate at more volume or use more force than is needed to produce a rate of 8 to 10 breaths per minute without attempting to visible chest rise.breaths. CPR training should emphasize how to recognize occasional gasps and should instruct rescuers to give rescue breaths and proceed with the steps of CPR when the unre￾sponsive victim demonstrates occasional gasps (Class IIa). Give Rescue Breaths (Boxes 4 and 5A) Give 2 rescue breaths, each over 1 second, with enough volume to produce visible chest rise. This recommended 1-second duration to make the chest rise applies to all forms of ventilation during CPR, including mouth-to-mouth and bag-mask ventilation and ventilation through an advanced airway, with and without supplementary oxygen (Class IIa). During CPR the purpose of ventilation is to maintain adequate oxygenation, but the optimal tidal volume, respira￾tory rate, and inspired oxygen concentration to achieve this are not known. The following general recommendations can be made: 1. During the first minutes of VF SCA, rescue breaths are probably not as important as chest compressions113 be￾cause the oxygen level in the blood remains high for the first several minutes after cardiac arrest. In early cardiac arrest, myocardial and cerebral oxygen delivery is limited more by the diminished blood flow (cardiac output) than a lack of oxygen in the blood. During CPR blood flow is provided by chest compressions. Rescuers must be sure to provide effective chest compressions (see below) and minimize any interruption of chest compressions. 2. Both ventilations and compressions are important for victims of prolonged VF SCA, when oxygen in the blood is utilized. Ventilations and compressions are also impor￾tant for victims of asphyxial arrest, such as children and drowning victims who are hypoxemic at the time of cardiac arrest. 3. During CPR blood flow to the lungs is substantially reduced, so an adequate ventilation-perfusion ratio can be maintained with lower tidal volumes and respiratory rates than normal.114 Rescuers should not provide hyperventi￾lation (too many breaths or too large a volume). Excessive ventilation is unnecessary and is harmful because it increases intrathoracic pressure, decreases venous return to the heart, and diminishes cardiac output and survival.115 4. Avoid delivering breaths that are too large or too forceful. Such breaths are not needed and may cause gastric inflation and its resultant complications.116 The ECC Guidelines 2000117 recommended a variety of tidal volumes, respiratory rates, and breath delivery intervals. But it is unrealistic to expect the rescuer to distinguish half-second differences in inspiratory times or to judge tidal volumes delivered by mouth-to-mouth or bag-mask ventila￾tion. So these guidelines provide simple recommendations for delivery of rescue breaths during cardiac arrest as follows: ● Deliver each rescue breath over 1 second (Class IIa). ● Give a sufficient tidal volume (by mouth-to-mouth/mask or bag mask with or without supplementary oxygen) to produce visible chest rise (Class IIa). ● Avoid rapid or forceful breaths. ● When an advanced airway (ie, endotracheal tube, Combi￾tube, or LMA) is in place during 2-person CPR, ventilate at a rate of 8 to 10 breaths per minute without attempting to synchronize breaths between compressions. There should be no pause in chest compressions for delivery of ventila￾tions (Class IIa). Studies in anesthetized adults (with normal perfusion) suggest that a tidal volume of 8 to 10 mL/kg maintains normal oxygenation and elimination of CO2. During CPR cardiac output is 25% to 33% of normal,118 so oxygen uptake from the lungs and CO2 delivery to the lungs are also reduced.119 As a result, low minute ventilation (lower than normal tidal volume and respiratory rate) can maintain effective oxygenation and ventilation during CPR.120–123 During adult CPR tidal volumes of approximately 500 to 600 mL (6 to 7 mL/kg) should suffice (Class IIa). Although a rescuer cannot estimate tidal volume, this guide may be useful for setting automatic transport ventilators and as a reference for manikin manufacturers. If you are delivering ventilation with a bag and mask, use an adult ventilating bag (volume of 1 to 2 L); a pediatric bag delivers inadequate tidal volume for an adult.124,125 When giving rescue breaths, give sufficient volume to cause visible chest rise (LOE 6, 7; Class IIa). In 1 observa￾tional study trained BLS providers were able to detect “adequate” chest rise in anesthetized, intubated, and para￾lyzed adult patients when a tidal volume of approximately 400 mL was delivered.114 It is likely, however, that a larger volume is required to produce chest rise in a victim with no advanced airway (eg, endotracheal tube, Combitube, LMA) in place. We therefore recommend a tidal volume of 500 to 600 mL but emphasize that the volume delivered should produce visible chest rise (Class IIa). It is reasonable to use the same tidal volume in patients with asphyxial and arrhyth￾mic cardiac arrest (Class IIb). Currently manikins show visible chest rise when tidal volumes reach about 700 to 1000 mL. To provide a realistic practice experience, manikins should be designed to achieve a visible chest rise at a tidal volume of 500 to 600 mL.114 Automated and mechanical ventilators are discussed briefly at the end of this chapter and in Part 6: “CPR Techniques and Devices.” Gastric inflation often develops when ventilation is pro￾vided without an advanced airway. It can cause regurgitation and aspiration, and by elevating the diaphragm, it can restrict lung movement and decrease respiratory compliance.117 Air delivered with each rescue breath can enter the stomach when pressure in the esophagus exceeds the lower esophageal sphincter opening pressure. Risk of gastric inflation is in￾creased by high proximal airway pressure114 and the reduced opening pressure of the lower esophageal sphincter.126 High pressure can be created by a short inspiratory time, large tidal volume, high peak inspiratory pressure, incomplete airway opening, and decreased lung compliance.127 To minimize the potential for gastric inflation and its complications, deliver each breath to patients with or without an advanced airway over 1 second and deliver a tidal volume that is sufficient to produce a visible chest rise (Class IIa). But do not deliver more volume or use more force than is needed to produce visible chest rise. Part 4: Adult Basic Life Support IV-23