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 unresponsive 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, respiratory 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 because 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 important 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 hyperventilation (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 ventilation. 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, Combitube, 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 ventilations (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 observational study trained BLS providers were able to detect “adequate” chest rise in anesthetized, intubated, and paralyzed 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 arrhythmic 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 provided 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 increased 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
ⅣV2 Circulation December 13. 2005 Mouth-to- Mouth Rescue breathing period of I second and provide sufficient tidal volume to Mouth-to-mouth rescue breathing provides oxygen and ven- cause visible chest rise on to the victim. 28 To provide mouth-to-mouth rescue aths, open the victims airway, pinch the victims nose, The Bag-Mask Device create an airtight mouth-to-mouth seal. Give I breath A bag-mask device should have the following140 overI seco take a"regular"(not a deep)breath, and give inlet valve; either no pressure relief valve or a pressure relief a second rescue breath over I second(Class IIb). Taking valve that can be bypassed; standard 15-mm/22-mm fittings regular rather than a deep breath prevents you from getting an oxygen reservoir to allow delivery of high oxygen con dizzy or lightheaded. The most common cause of ventilation alve that cannot be difficulty is an improperly opened airway, 12 so if the obstructed by foreign material and will not jam with an victims chest does not rise with the first rescue breath, oxygen flow of 30 L/min; and the capability to function perform the head tilt-chin lift and give the second rescue satisfactorily under common environmental conditions and extremes of temperature Masks should be made of transparent material to allow Mouth-to-Barrier Device Breathing detection of regurgitation. They should be capable of creatin Despite its safety, 29 some healthcare providers30-132 and lay a tight seal on the face, covering both mouth and nose. Masks rescuers may hesitate to give mouth-to-mouth rescue breath should be fitted with an oxygen(insufflation) inlet, have a ing and prefer to use a barrier device Barrier devices may not standard 15-mm/22-mm connector, 141 and should be avail- reduce the risk of infection transmission, 29 and some may able in one adult and several pediatric sizes. increase resistance to air flow. 33. 134 If you use a barrier device, do not delay rescue breathing Bag-Mask ventilation Barrier devices are available in 2 types: face shields and Bag-mask ventilation is a challenging skill that requires face masks. Face shields are clear plastic or silicone sheets considerable practice for competency. 142 143 The lone rescuer that reduce direct contact between the victim and rescuer but using a bag-mask device should be able to simultaneously do not prevent contamination of the rescuer's side of the open the airway with a jaw lift, hold the mask tightly against shield 35-13 the patients face, and squeeze the bag. The rescuer must also A rescuer with a duty to respond should use a face shield watch to be sure the chest rises with each breath only as a substitute for mouth-to-mouth breathing. These Bag-mask ventilation is most effective when provided by 2 responders should switch to face mask or bag-mask ventila trained and experienced rescuers. One rescuer opens the tion as soon as possible. 137 Masks used for mouth-to-mask airway and seals the mask to the face while the other squeezes breathing should contain a 1-way valve that directs the the bag. Both rescuers watch for visible chest rise. 143-144 The rescuer should use an adult(I to 2 L) bag to deliver a exhaled air away from the rescuer, diverting the patient's tidal volume sufficient to achieve visible chest rise(Class Some masks include an oxygen inlet for administration of a). If the airway is open and there are no leaks(ie, there supplementary oxygen. When oxygen is available, healthcare a good seal between face and mask), this volume can be providers should provide it at a minimum flow rate of 10 to delivered by squee l-L adult bag about one half to two 12 L/min thirds of its volume or a 2-L adult bag about one-third its volume. As long as the patient does not have an advanced Mouth-to-Nose and Mouth-to. Stoma Ventilation airway in place, the rescuer(s) should deliver cycles of 30 Mouth-to-nose ventilation is recommended if it is impossible compressions and 2 breaths. The rescuer delivers the breaths to ventilate through the victims mouth(eg, the mouth is during pauses in compressions and delivers each breath over seriously injured, the mouth cannot be opened, the victim is I second( Class Ila) in water mouth-to-mouth seal is difficult to achieve The healthcare provider should use supplementary ( Class IIa). A case series suggests that mouth-to-nose venti-(02>40%, a minimum flow rate of 10 to 12 L/mi lation in adults is feasible, safe, and effective(LOE 5). 138 available. Ideally the bag should be attached to an Give mouth-to-stoma rescue breaths to a victim with reservoir to enable delivery of 100% oxygen tracheal stoma who requires rescue breathing. A reasonable Advanced airway devices such as the LMA45, 146 and the alternative is to create a tight seal over the stoma with a round sophageal-tracheal combitubel47-149 are currently within the pediatric face mask ( Class IIb). There is no published scope of BLS practice in a number of regions(with specific idence on the safety, effectiveness, or feasibility of mouth- authorization from medical control). These devices may to-stoma ventilation. One study of patients with laryngecto- provide acceptable alternatives to bag-mask devices for mies showed that a pediatric face mask created a better healthcare providers who are well trained and have sufficient peristomal seal than a standard ventilation bag(LOE 4). 139 experience to use them(Class IIb). It is not clear that these Ventilation With Bag and Mask devices are any more or less complicated to use than a bag Rescuers can provide bag-mask ventilation with room air or and mask: training is needed for safe and effective use of both oxygen. a bag-mask device provides positive-pressure ven- the bag-mask device and each of the advanced airways tilation without an advanced airway and therefore may Ventilation With an Advanced Airway produce gastric inflation and its complications (see above). When the victim has an advanced airway in place during When using a bag-mask device, deliver each breath over a CPR, 2 rescuers no longer deliver cycles of CPr (ie
Mouth-to-Mouth Rescue Breathing Mouth-to-mouth rescue breathing provides oxygen and ventilation to the victim.128 To provide mouth-to-mouth rescue breaths, open the victim’s airway, pinch the victim’s nose, and create an airtight mouth-to-mouth seal. Give 1 breath over 1 second, take a “regular” (not a deep) breath, and give a second rescue breath over 1 second (Class IIb). Taking a regular rather than a deep breath prevents you from getting dizzy or lightheaded. The most common cause of ventilation difficulty is an improperly opened airway,112 so if the victim’s chest does not rise with the first rescue breath, perform the head tilt–chin lift and give the second rescue breath.120,121 Mouth-to–Barrier Device Breathing Despite its safety,129 some healthcare providers130–132 and lay rescuers may hesitate to give mouth-to-mouth rescue breathing and prefer to use a barrier device. Barrier devices may not reduce the risk of infection transmission,129 and some may increase resistance to air flow.133,134 If you use a barrier device, do not delay rescue breathing. Barrier devices are available in 2 types: face shields and face masks. Face shields are clear plastic or silicone sheets that reduce direct contact between the victim and rescuer but do not prevent contamination of the rescuer’s side of the shield.135–137 A rescuer with a duty to respond should use a face shield only as a substitute for mouth-to-mouth breathing. These responders should switch to face mask or bag-mask ventilation as soon as possible.137 Masks used for mouth-to-mask breathing should contain a 1-way valve that directs the rescuer’s breath into the patient while diverting the patient’s exhaled air away from the rescuer.137 Some masks include an oxygen inlet for administration of supplementary oxygen. When oxygen is available, healthcare providers should provide it at a minimum flow rate of 10 to 12 L/min. Mouth-to-Nose and Mouth-to-Stoma Ventilation Mouth-to-nose ventilation is recommended if it is impossible to ventilate through the victim’s mouth (eg, the mouth is seriously injured), the mouth cannot be opened, the victim is in water, or a mouth-to-mouth seal is difficult to achieve (Class IIa). A case series suggests that mouth-to-nose ventilation in adults is feasible, safe, and effective (LOE 5).138 Give mouth-to-stoma rescue breaths to a victim with a tracheal stoma who requires rescue breathing. A reasonable alternative is to create a tight seal over the stoma with a round pediatric face mask (Class IIb). There is no published evidence on the safety, effectiveness, or feasibility of mouthto-stoma ventilation. One study of patients with laryngectomies showed that a pediatric face mask created a better peristomal seal than a standard ventilation bag (LOE 4).139 Ventilation With Bag and Mask Rescuers can provide bag-mask ventilation with room air or oxygen. A bag-mask device provides positive-pressure ventilation without an advanced airway and therefore may produce gastric inflation and its complications (see above). When using a bag-mask device, deliver each breath over a period of 1 second and provide sufficient tidal volume to cause visible chest rise. The Bag-Mask Device A bag-mask device should have the following140: a nonjam inlet valve; either no pressure relief valve or a pressure relief valve that can be bypassed; standard 15-mm/22-mm fittings; an oxygen reservoir to allow delivery of high oxygen concentrations; a nonrebreathing outlet valve that cannot be obstructed by foreign material and will not jam with an oxygen flow of 30 L/min; and the capability to function satisfactorily under common environmental conditions and extremes of temperature. Masks should be made of transparent material to allow detection of regurgitation. They should be capable of creating a tight seal on the face, covering both mouth and nose. Masks should be fitted with an oxygen (insufflation) inlet, have a standard 15-mm/22-mm connector,141 and should be available in one adult and several pediatric sizes. Bag-Mask Ventilation Bag-mask ventilation is a challenging skill that requires considerable practice for competency.142,143 The lone rescuer using a bag-mask device should be able to simultaneously open the airway with a jaw lift, hold the mask tightly against the patient’s face, and squeeze the bag. The rescuer must also watch to be sure the chest rises with each breath. Bag-mask ventilation is most effective when provided by 2 trained and experienced rescuers. One rescuer opens the airway and seals the mask to the face while the other squeezes the bag. Both rescuers watch for visible chest rise.142–144 The rescuer should use an adult (1 to 2 L) bag to deliver a tidal volume sufficient to achieve visible chest rise (Class IIa). If the airway is open and there are no leaks (ie, there is a good seal between face and mask), this volume can be delivered by squeezing a 1-L adult bag about one half to two thirds of its volume or a 2-L adult bag about one-third its volume. As long as the patient does not have an advanced airway in place, the rescuer(s) should deliver cycles of 30 compressions and 2 breaths. The rescuer delivers the breaths during pauses in compressions and delivers each breath over 1 second (Class IIa). The healthcare provider should use supplementary oxygen (O2 40%, a minimum flow rate of 10 to 12 L/min) when available. Ideally the bag should be attached to an oxygen reservoir to enable delivery of 100% oxygen. Advanced airway devices such as the LMA145,146 and the esophageal-tracheal combitube147–149 are currently within the scope of BLS practice in a number of regions (with specific authorization from medical control). These devices may provide acceptable alternatives to bag-mask devices for healthcare providers who are well trained and have sufficient experience to use them (Class IIb). It is not clear that these devices are any more or less complicated to use than a bag and mask; training is needed for safe and effective use of both the bag-mask device and each of the advanced airways. Ventilation With an Advanced Airway When the victim has an advanced airway in place during CPR, 2 rescuers no longer deliver cycles of CPR (ie, IV-24 Circulation December 13, 2005