5 Management of Ventilation During Resuscitation

Chapter 5 / Management of Ventilation 95 5 Management of Ventilation During Resuscitation

Marsh Cuttino, MD

CONTENTS INTRODUCTION VENTILATION INDICATIONS FOR ASSISTED VENTILATION TECHNIQUE VENTILATION VOLUME INTERMEDIATE AIRWAY TECHNIQUES AND DEVICES ADVANCED AIRWAYS CONCLUSION REFERENCES

INTRODUCTION The decision to control a patient’s airway during cardiopulmonary resuscitation (CPR) is straightforward. Patients in cardiopulmonary arrest generally are totally unresponsive, and airway techniques can be used without the need for pharmacological adjuncts. Much of the decision making relates to timing and the type of ventilation method to use. These decisions are influenced by the patient’s oxygenation status, duration of arrest, expected difficulties with airway control, and operator experience and training.

VENTILATION Establishing a secure patent airway is one of the primary tasks of the emergency care provider during resuscitation. Adequate ventilation can reduce hypoxia and hypercapnea. The airway should be obtained as soon as possible during resuscitation. Failure to control the airway can have ominous consequences. Endotracheal intubation is considered the optimal method for securing the airway currently because it allows adequate ventilation, oxygenation, and airway protection. The Combitube (Kendall Healthcare Products, Mansfield, MA) and laryngeal mask airway (LMA North America, San Diego, CA) are acceptable and possibly helpful alternative airway devices. The main advantages of alternative airway devices is that they (a) are generally easier to insert than an endotracheal tube (ETT); (b) may provide ventilation results similar to

From: Contemporary Cardiology: Cardiopulmonary Resuscitation Edited by: J. P. Ornato and M. A. Peberdy © Humana Press Inc., Totowa, NJ 95 96 Cardiopulmonary Resuscitation that provided by endotracheal intubation and superior to bag-valve-mask ventilation; and (c) have similar complication rates to endotracheal intubation. Additionally, alternative airway devices can sometimes be used when tracheal intubation is not possible (1). The amount of ventilation required during resuscitation is not well established. Although the minute ventilation requirements may be decreased by a low cardiac output, the excess load of carbon dioxide returning from ischemic tissue beds must be cleared by ventilation. Chest compressions alone do not generate adequate or consistent ventilation in humans, even after intubation (2). In the resuscitation patient, 100% oxygen should be started immediately using a bag-valve-mask. This should be followed rapidly by endotracheal intubation once skilled individuals arrive on scene. If intubation is unsuccessful, then an alternative airway should be employed. When a nonintubated patient is ventilated, the distribution of gas between the lungs and stomach depends on the patient’s lower esophageal sphincter pressure, respiratory mechanics (the respiratory system compliance and degree of airway obstruction), and the technique of the rescuer performing basic life support (BLS; inspiratory flow rate, peak airway pressure, and tidal volume). Accidental stomach inflation during CPR can elevate intragastric pressure and lead to the cascade of regurgitation, aspiration, pneumonia, and death even in the successfully resuscitated patient (3). Ventilation has an impact on blood gases even at very low cardiac output states (4). Hypoxia and hypercarbia have an independent adverse effect on resuscitation, and can be corrected with appropriate ventilation. Adequate ventilation is important for return of spontaneous circulation (5). Successful ventilation with rapid and uninterrupted chest compressions significantly improves coronary perfusion during CPR (6) and this makes successful defibrillation more likely (7). In cardiac arrest (CA) there is generally sufficient oxygenation in the blood that a reasonable oxygen saturation persists for approx 5 minutes when there is adequate chest compression (8). Bystander CPR for the first 5 minutes has equivalent outcomes with or without mouth-to-mouth ventilation (9). This suggests that airway control is most useful when achieved in the first 5–6 minutes of CA.

INDICATIONS FOR ASSISTED VENTILATION Rapid assessment of the patient allows for appropriate decision on airway management. Important considerations include adequacy of ventilation, airway patency, need for neuromuscular blockade, cervical spine stability, safety of the technique, and the skill of the operator (10). Some patients are intubated for airway protection and others are intubated specifically for failure of ventilation or oxygenation. Objective indicators of ventilatory status include arterial blood gas, pulse oximetry, capnography, chest radiography, and spirometry. Meth- ods to maintain an open airway range from BLS measures (e.g., head tilt–chin lift) to advanced airway techniques (e.g., endotracheal intubation). Medical providers should be proficient in several techniques at each level of airway control. This allows the operator to be flexible in the management of the airway as the situation demands. Once a patient has been found to be unresponsive, and the emergency response system has been activated, the airway needs to be assessed. First, the patient should be placed in the supine position. If trauma is suspected, the cervical spine must be protected, and the patient should be log rolled. The rescuer should open the airway and assess breathing by looking for a chest rise, listening for exhaled breath, and feeling for air exchange at the Chapter 5 / Management of Ventilation 97 nose and mouth. If the airway and breathing are inadequate, the airway should be opened. In the unresponsive patient, the tongue and epiglottis may be obstructing the pharynx. There are two techniques for opening an airway manually: the head tilt–chin lift and the jaw thrust maneuver. In some patients, spontaneous breathing returns after the airway becomes patent. These patients should then be placed in a recovery position to reduce the risk of aspiration. The American Heart Association (AHA) Guidelines released in 2000 for the recovery position include the following (11): • Use a lateral position, with the head dependent to allow free fluid drainage. • Make sure position is stable. • Avoid pressure on the chest that impairs breathing. • Good observation and access to the airway should be possible. • The position should not give rise to injury to the patient. • It should be possible to return the patient to the supine position quickly and easily, and maintain cervical stability. • Repositioning should occur to prevent prolonged time in one position. • Patient should be monitored until airway is definitively secured.

Head Tilt–Chin Lift Placing one hand on the patient’s forehead and the index and middle finger of the other hand on the bony part of the chin performs the head tilt–chin lift. The patient’s head is rotated as the chin is lifted. This lifts the jaw and elevates the tongue off the back of the pharynx, opening the airway. Jaw Thrust Grasping the angles of the jaw with the index and middle fingers and lifting with both hands performs the jaw thrust. The head is maintained in the neutral position without any flexion or extension. As the jaw is lifted, the patient’s mouth is opened with the thumbs. This is the preferred method when there is a possibility of cervical spine injury.

Basic Life Support Techniques The first step is to open the airway, then look, listen, and feel for breathing. If the patient is not breathing adequately, rescue breathing must be performed. The AHA rec- ommends that lay rescuers check for “signs of circulation” (e.g., normal breathing, cough- ing, or normal movement in response to stimulation) rather than perform a pulse check to determine if chest compression’s should be administered. Trained health care providers are encouraged to check for a pulse. Rescue breathing for both single rescuer CPR and multiple rescuer CPR with an unprotected airway is at a 15:2 ratio of chest compression to breathing with a rate of 100 compressions per minute (11).

Mouth-to-Mouth Ventilation and Variants Rescue breathing through mouth-to-mouth ventilation has been an important part of CPR for more than 30 years. Concern about transmission of infectious disease has made both professional medical providers and lay people reluctant to provide mouth-to-mouth ventilation to adult strangers (12). This has led to consideration of removing mouth-to- mouth ventilation guidelines from CPR (9). Current guidelines still recommend mouth- to-mouth ventilation in out-of-hospital arrest, but recognize that basic CPR with chest 98 Cardiopulmonary Resuscitation compression alone is still better than no CPR (13). All out of hospital pediatric arrest victims should receive mouth-to-mouth ventilation, since most pediatric CA have a large respiratory component (14).

TECHNIQUE Mouth-to-mouth ventilation is the most basic form of positive pressure ventilation. The rescuer positions him or herself at the patient’s side. After opening the airway, the rescuer takes a deep breath, pinches the patient’s nose, and seals his or her mouth around the patient’s mouth. Slow deep breaths are delivered, and after each breath the mouth is removed to allow passive exhalation. Using slow breaths helps prevent gastric inflation and aspiration from reflux and regurgitation. Mouth-to-Nose Rescue Breathing Mouth-to-nose rescue breathing can be used when there are contraindications to mouth- to-mouth breathing. Conditions such as anatomic abnormalities, trismus, or severe trauma could prevent formation of an appropriate seal. The rescuer positions the patient’s head in extension. One hand is placed on the forehead and the other lifts the mandible and closes the mouth. The rescuer’s mouth is placed over the patient’s nose and a seal is formed with the lips. The appropriate breaths are delivered, and the mouth is removed from the patient’s nose to allow passive exhalation. It may be necessary to open the mouth intermittently to allow complete exhalation. Mouth-to-Shield Ventilation Face shields are small, disposable, plastic barrier devices that can be used during mouth-to-mouth ventilation. This removes any concern over infectious disease transmission. Shields may have enhancements such as one-way valves. The rescuer positions the shield on the patient, pinches the nose and seals his or her mouth around the center opening of the face shield. After the appropriate breaths are delivered, the rescuer lifts his or her mouth from the shield and allows the patient to exhale. Figure 1 shows an example of a pocket shield device. There are numerous other examples available on the market with similar function. Mouth-to-Mask Method Another technique designed to isolate the rescuer from the patient is the mouth-to- mask method. A standard face mask is used and fitted over the mouth using the same position as used for the bag-valve-mask (Fig. 2). The rescuer can provide rescue breaths either into the mask directly or indirectly using a one-way valve adapter. When the adapter is used the face mask must be released to allow exhalation.

VENTILATION VOLUME Mouth-to-mouth ventilation with a tidal volume of 1000 mL contains about 17% oxygen and about 4% carbon dioxide (15). The gas composition can be improved to about 19% oxygen and 2–3% carbon dioxide by taking a deep breath and exhaling only about 500 mL (16). With normal cardiac output, tidal volumes of 800–1000 mL are required to maintain adequate oxygenation (17,18). Some authors have suggested that because Chapter 5 / Management of Ventilation 99

Fig. 1. Example of a pocket shield device.

Fig. 2. Ventilation masks. cardiac output is reduced to at best 20–30% of normal during CPR there is a reduced requirement for ventilation (19,20). It appears that a tidal volume of 500 mL may be adequate during CPR when supplemental oxygen is added (21). Current guidelines recommend a tidal volume of 10 mL/kg or 700 to 1000 mL over 2 seconds (13). 100 Cardiopulmonary Resuscitation

Fig. 3. Example of a typical bag-valve-mask assembly.

INTERMEDIATE AIRWAY TECHNIQUES AND DEVICES Bag-Valve-Mask Device The bag-valve-mask is a common device for delivering positive pressure ventilation in the initial stages of resuscitation (Fig. 3). The key to proper use of the bag-valve-mask is to maintain a tight seal. There are different techniques depending on whether there is a single operator or two operators. Techniques SINGLE OPERATOR The rescuer stands at the head of the patient. The mask is applied to the patient’s face with one hand. The thumb and index fingers secure the mask, and the remaining fingers are placed over the bony portion of the mandible. As the rescuer ventilates the patient, the fingers on the mandible maintain the head tilt and jaw thrust to keep the airway patent and the mask snug against the face.

DUAL OPERATORS The first rescuer stands at the head of the patient. The mask is applied to the patient’s face, and the thumb and index fingers of both hands secure the mask and maintain a good seal. The remaining fingers are used on the bony portion of the mandible to maintain the head tilt and jaw thrust. The second rescuer stands to the right of the patient, and provides two-handed compression of the bag to ventilate the patient (Fig. 4). Oropharyngeal Airway Device An oropharyngeal airway is a plastic or rubber device that can be inserted into a victim’s mouth to elevate the tongue and create a path between the tongue and palate (Fig. 5). This device should not be used on a patient who has an intact gag reflex. It is indicated in the unresponsive or obtunded patient and can be used in conjunction with a bag-valve-mask device. To size an oropharyngeal airway, choose one that fits from the middle of the mouth to the angle of the jaw. The airway is inserted by turning it 90° and inserting it halfway into the mouth. Then rotate back 90° so that the bottom wraps around the back of the tongue. Chapter 5 / Management of Ventilation 101

Fig. 4. Two-person bag-valve-mask technique. Note the set of hands on the bottom left maintain- ing in-line cervical stabilization.

Fig. 5. Oropharyngeal airways.

The distal portion of the airway should remain outside of the mouth to ensure that it does not become an airway obstruction. If the patient begins to gag, the oropharyngeal airway should be pulled out. The oropharyngeal airway may be contraindicated in facial or mandibular trauma patients. This airway will not maintain a patent airway if the patient has incorrect head placement. 102 Cardiopulmonary Resuscitation

Fig. 6. Nasopharyngeal airways.

Nasopharyngeal Airway Device A flexible tube designed to be inserted into the nares and extend to the base of the tongue (Fig. 6). A nasopharyngeal airway can help maintain airway patency in an uncon- scious or obtunded patient but does not ensure patency without good head positioning. This airway adjunct can be used in conjunction with a bag-valve-mask to facilitate ventilation. Nasopharyngeal airways can be used with patients that still have an intact gag reflex. To size a nasopharyngeal airway, choose a tube that extends from the tip of the nose to the angle of the patient’s mandible. The diameter of the tube should approximate the diameter of the nares. The tube is lubricated and inserted into the nares so that the beveled tip is midline, and the curve of the tube follows the curvature of the patient’s airway.

ADVANCED AIRWAYS Orotracheal Intubation The most common technique of advanced airway control is orotracheal intubation with direct visualization laryngoscopy. Laryngoscopes are used to provide a direct view of the vocal cords and facilitate placement of the ETT. Most intubations during CPR are “crash” airways and do not require pharmacologic adjuncts such as rapid sequence induction. Chapter 5 / Management of Ventilation 103

Fig. 7. Examples of laryngoscope handles and blades.

Fig. 8. Miller and MacIntosh laryngoscope blades.

The laryngoscope is an apparatus designed to permit direct visualization of the larynx and facilitate endotracheal intubation through direct laryngoscopy (Figs. 7 and 8). There are two basic blade designs. The first is the curved blade, typified by the MacIntosh blade. The second type is the straight blade such as the Miller or Wisconsin blades (Welch Allyn, Skaneateles Falls, NY). Various sizes are available for adult and pediatric use. The main 104 Cardiopulmonary Resuscitation

Fig. 9. Endotracheal tubes.

difference in the usage of the blades regards the epiglottis. A straight blade lifts the epiglottis directly, but the curved blade tip fits in the vallecula and indirectly lifts the epiglottis. The choice of which blade to use should be based on the patient’s clinical history. Straight blades are better for pediatric patients, patients with an anterior larynx, patients with a long floppy epiglottis, or patients with a scarred epiglottis. Straight blades allow for more control of the airway in trauma patients, and may offer some advantages when there is debris in the airway. There are several disadvantages with straight blades. They are hard to use with large teeth, and may be more likely to break teeth than their curved counterparts. Straight blades can stimulate the superior laryngeal nerve and lead to laryngospasm. These blades can be inserted inadvertently into the esophagus and lead to esophageal intubation. Curved blades offer better control of the tongue can allow more room in the hypopharynx to pass the endotracheal tube. Curved blades possibly require less forearm strength to use. Medical providers with less experience frequently prefer curved blades as they can provide a superior view with less provider effort. Endotracheal Tubes The standard endotracheal tube is plastic and about 30 cm in length (Fig. 9). The tube size is measured based on the internal diameter in millimeters. An adult male usually requires a 7.5–9.0 mm ETT, however women can usually be intubated with a 7.0–8.0 mm tube. The best time to intubate a patient during resuscitation is often described as “as soon as physically possible.” Animal models of out-of-hospital arrest suggest that the defini- Chapter 5 / Management of Ventilation 105 tive airway can be delayed for 5–6 minutes without decreasing the likelihood of spontaneous return of circulation (5). Technique PREPARE EQUIPMENT 1. Check suctioning equipment. 2. Inflate and deflate the endotracheal tube balloon to check for leaks. 3. Connect laryngoscope blade to the handle to check bulb function.

POSITION 1. Place the patient’s head in the sniffing position if no evidence of trauma. 2. If trauma is suspected, maintain in-line cervical stabilization in the neutral position. 3. Preoxygenate. 4. Maximize oxygen saturation by administering 100% O2 preferably by face mask or bag- valve-mask. 5. Pass the tube. 6. Holding the laryngoscope in the left hand, insert the laryngoscope into the right side of the mouth and sweep the tongue to the left. Advance the blade and visualize the epiglottis and vocal cords. Insert the endotracheal tube through the vocal cords. Inflate the balloon.

PLACEMENT Check for tube placement by auscultating over the chest and abdomen. If capnometry or capnography is available, it can be used to confirm placement. Capnometry (colori- metric, analog, or digital) can yield false negative results during low-flow states such as during resuscitation. Capnography remains accurate in determining endotracheal tube placement even in the presence of a low-flow state. An alternate method to confirm ETT placement is to use an esophageal detector suction device. When time allows, obtain a chest x-ray to confirm endotracheal tube location.

DEVICES FOR CONFIRMATION OF ENDOTRACHEAL TUBE PLACEMENT There are numerous devices that can be utilized to confirm the proper placement of an ETT. A detailed examination of placement confirmation devices is beyond the scope of this chapter. Capnography uses a chemical paper to rapidly determine the presence of carbon dioxide in exhaled air. This is a qualitative, not quantitative device. A change in color suggests tracheal intubation (Fig. 10). To use the bulb suction device, first deflate the bulb with the thumb and then place the device securely on the ETT connector (Fig. 11). The bulb is released, and if the endotracheal tube is inserted in the esophagus the suction of the bulb collapses the flexible tissue of the esophagus and the bulb does not inflate. With proper placement the rigid structures of the trachea do not collapse and the bulb rapidly inflates. Rapid bulb inflation confirms tracheal intubation. A similar technique is used with the syringe aspiration test (Fig. 12). Instead of bulb inflation, the syringe is attached and the plunger rapidly drawn back by the provider. Increased resistance suggests esophageal intubation. These confirmation techniques have the advantage that they can be utilized in high noise environments or in situations in which stethoscopes are unavailable or unusable, such as during a disaster. 106 Cardiopulmonary Resuscitation

Fig. 10. Example of a capnograph.

Fig. 11. Bulb esophageal detector.

Endotrol Endotracheal Tube Nasotracheal intubation is an alternative technique in which the ETT or Endotrol tube (Mallinckrodt Critical Care Inc., St. Louis, MO) is inserted through the nares down into the trachea. The Endotrol tube is an ETT with a loop attached that increases the curvature of the tip when pulled. The Endotrol is used during nasogastric intubation. Usually the tube size chosen is slightly smaller (by 0.5–1.0 mm) than would be used for endotracheal intubation. As nasotracheal intubation requires that the patient be spontaneously breathing, it will not be considered further in this chapter. Chapter 5 / Management of Ventilation 107

Fig. 12. Syringe aspirator.

Fig. 13. Combitubes.

Combitube The Combitube is a double lumen tube with two balloons (Fig. 13). It is designed for blind insertion during emergency situations and difficult airways. The esophageal obtu- rator tube is sealed at the distal end, and has perforations at the pharyngeal level. The tracheal tube has a clear distal opening. The large upper oropharyngeal balloon serves to seal off the mouth and nose. The distal cuff balloon seals off either the trachea or the esophagus. One advantage of the Combitube is that insertion requires less skill than direct laryngoscopy. Because it can be inserted blindly, it can be used under difficult lighting and space restrictions. It is very useful when visualization of the vocal cords is impossible. 108 Cardiopulmonary Resuscitation

Contraindications include patients with intact gag reflexes, patient height less than 4 feet, a history of known esophageal pathology, a recent history of ingestion of caustic sub- stances, or central airway obstruction.

TECHNIQUE To insert a Combitube, grasp the back of the tongue and jaw between the thumb and index finger and lift. Insert the Combitube in a curved downward motion. Insertion should not require any force by the operator. Inflate the oropharyngeal balloon first with between 85 and 100 cc of air (depending on the size of the Combitube) then inflate the distal balloon with 5–15 cc of air. The most likely result of a blind intubation is esophageal intubation. Attempt ventilation through the longer blue tube. If breath sounds are present then the tip of the Combitube is in the esophagus. If breath sounds are absent, then the tip of the tube is in the trachea. If the tube has entered the trachea, ventilation is performed using the distal lumen just like a standard endotracheal tube. Tracheal intubation can be achieved by using a laryngoscope in conjunction with a Combitube. Laryngeal Mask Airway The LMA was introduced into clinical practice in 1988. The LMA is a triangular shaped inflatable pink silicon laryngeal mask (Fig. 14). The mask has an opening in the middle that prevents accidental obstruction of the tube by the tip of the epiglottis. Gastric distention is minimized because excess pressure is vented upward around the LMA instead of into the esophagus. The LMA can be used when the patient is unresponsive or the protective reflexes have been sufficiently depressed. The mask is deflated to form a flat wedge that will pass behind the tongue and behind the epiglottis. The LMA is blindly inserted into the pharynx with the point of the triangle in the esophagus and the mask over the laryngeal inlet. The mask is then inflated and seals off the laryngeal inlet. The LMA is not a definitive airway, and provides almost no prevention of aspiration of stomach contents from below or blood and secretions from above. The LMA is best for providers not trained in endotracheal intubation. It can be used as an adjunct in the difficult airway when primary endotracheal intubation has been attempted unsuccessfully.

TECHNIQUE Completely deflate the LMA until the cuff forms a smooth spoon shape without any wrinkles. Hold the LMA like a pen, with the mask facing forward and the black line on the tube oriented toward the upper lip. Insert the mask with the tip of the cuff up toward the hard palate. The index finger can be used to assist in guiding the LMA behind the tongue. Advance the LMA into the hypopharynx until resistance is felt. Inflate the cuff with enough air to obtain a seal. Normal intracuff pressures are around 60 cm H2O. CONCLUSION Providers should be familiar with BLS techniques in addition to advanced airway techniques. The patient’s airway should be secured definitively within the first 5–6 minutes of CPR. This allows for adequate ventilation, and increases the possibility of return of spontaneous circulation. Endotracheal intubation is the method most commonly used to secure the airway. Alternative methods include the Combitube and LMA. The position of an advanced airway should be confirmed with capnography or an esophageal detector device. Chapter 5 / Management of Ventilation 109

Fig. 14. Laryngeal mask airway.

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