Opening the Airway

The first concern in the management of a critically ill patient is patency of the airway. Upper airway obstruction most commonly occurs when patients are unconscious or sedated. It can also be due to injury to the mandible or muscles that support the hypopharynx. In these situations, the tongue moves posteriorly into the upper airway when the patient is in a supine position (Fig. 3-1A). Upper airway obstruction caused by the tongue can be relieved by positioning maneuvers of the head, neck, and jaw; the use of nasopharyngeal or oropharyngeal airways; or the application of continuous positive airway pressure (CPAP).

Manual Airway Maneuvers

Airway obstruction in unconscious patients may be due to posterior displacement of the tongue, but research in patients with obstructive sleep apnea using CPAP supports the concept that the airway collapses like a flexible tube.3,15 Upper airway obstruction may cause obvious snoring or stridor, but it may be difficult to appreciate in some patients. All unconscious patients are at high risk for upper airway obstruction.

More than 35 years ago, Guildner¹⁶ compared different techniques for opening obstructed upper airways and found that the head-tilt/chin-lift and jaw-thrust techniques were both effective (Fig. 3-1B and C). Modern airway textbooks still describe the head-tilt/chin-lift and jaw-thrust maneuvers but also use the term “triple airway maneuver,” which is a combination of head tilt, jaw thrust, and mouth opening.^3,17 Many airway experts believe that the jaw-thrust maneuver (anterior mandibular translation to bring the lower incisors anterior to the upper incisors) is the most important technique for opening the upper airway (Fig. 3-1C).^3,18,19

It is widely accepted that the jaw-thrust-only (without head tilt) maneuver should be performed in patients with suspected cervical spine injury,¹⁷ but there is no evidence that it is safer than the head-tilt/chin-lift maneuver.²⁰ In 2005, the American Heart Association (AHA)²¹ concluded that airway maneuvers are safe during manual in-line stabilization of the cervical spine but highlighted evidence that all airway maneuvers cause some spinal movement. Both the chin-lift and the jaw-thrust maneuvers have been shown to cause similar substantial movement of the cervical vertebrae.^22–26 The AHA recommended that “in a victim with a suspected spinal injury and an obstructed airway, the head-tilt/chin-lift or jaw-thrust (with head-tilt) techniques are feasible and may be effective for clearing the airway” and emphasized that “maintaining an airway and adequate ventilation is the over-riding priority in managing a patient with a suspected spinal injury.”²¹

Importantly, the addition of CPAP may relieve airway obstruction when simple manual positioning maneuvers fail. Meier and colleagues¹⁵ showed that adding CPAP to the chin-lift and jaw-thrust maneuvers decreased stridor and improved the nasal fiberoptic view of the glottic opening in anesthetized children.

Patient Positioning

The best way to position a patient’s head and neck for opening the upper airway is to mimic how patients position themselves when they are short of breath, with the neck flexed relative to the torso and with atlanto-occipital extension.² This is known as the “sniffing position” and was described by Magill almost 100 years ago.²⁷ In normal-sized supine adults, this is accomplished by elevating the head about 10 cm while tilting the head back so that the plane of the patient’s face tilts slightly toward the provider at the head of the bed (see Chapter 4, Fig. 4-8).^2,3,28–30 Morbidly obese patients require much more head elevation to achieve the proper sniffing position. This can be accomplished by building a ramp of towels and pillows under the upper torso, head, and neck or by using a Troop Elevation Pillow (Mercury Medical, Clearwater, FL) or similar device (Fig. 3-2).^31–34 Horizontal alignment of the external auditory meatus with the sternum is the best position for opening the upper airway in morbidly obese patients.^33–36

The sniffing position is contraindicated in patients with cervical spine injuries. The best technique for opening the airway in this situation is a simple jaw-thrust maneuver with anterior mandibular translation to bring the lower incisors anterior to the upper incisors (Fig. 3-1C).^3,18,19

In young children, this position is often achieved without lifting the head because the occiput of a child is relatively large, so the lower cervical spine is normally flexed when the child is lying supine on a flat surface.

Airway management is usually easiest when patients are in the supine position, but the lateral position may be best for patients who are actively vomiting and those with excessive upper airway bleeding or secretions. Some evidence suggests that rotating patients to the lateral position may not prevent aspiration.³⁷ Patients with suspected cervical spine injury should have their head immobilized with in-line stabilization if they need to be rolled to the lateral position. Airway management maneuvers may be limited or difficult when patients are in the lateral position.

Foreign Body Airway Obstruction

Awake patients with partial airway obstruction can usually clear a foreign body on their own. Intervention is required when the patient is not moving air or has altered mental status. Some patients with upper airway obstruction can be ventilated and oxygenated with aggressive high-pressure BMV, so always try this if standard BMV fails. Massive aspiration of vomitus, however, is often a fatal event because of inability of the patient and clinician to adequately clear the airway.

Suctioning

Patient positioning and airway-opening maneuvers are often inadequate to achieve complete airway patency. Ongoing hemorrhage, vomitus, and particulate debris frequently require suctioning. Several types of suctioning tips are available. A large-bore dental-type suction tip is the most effective in clearing vomitus from the upper airway because it is less likely to become obstructed by particulate matter. The tonsil tip (Yankauer) suction device can be used to clear hemorrhage and secretions. Its rounded tip is less traumatic to soft tissues, but the tonsil tip device is not large enough to effectively suction vomitus.

A large-bore dental-type tip device, such as the HI-D Big Stick suction tip, should be readily available at the bedside during all emergency airway management (Fig. 3-4). The large-bore tip allows rapid clearing of vomitus, blood, and secretions.

A limiting feature of many suction catheters is the diameter of the tubing. Vomitus may obstruct the standard -inch-diameter catheter.⁵² A – or -inch-diameter suction tube (Kuriyama Tubing, -inch inner diameter, 0.44-inch outer diameter, clear; www.grainger.com) has been shown to significantly decrease suction time for viscous and particulate material (see Fig. 3-4).⁵³

Keep suctioning equipment connected and ready to operate. Everyone participating in emergency airway management should know how to use it. Interposition of a suction trap close to the suction device prevents clogging of the tubing with particulate debris. A trap that fits directly onto a tracheal tube has been described, and use of this device allows effective suctioning during intubation.⁵⁴

No specific contraindications to airway suctioning exist. Complications of suctioning may be avoided by anticipating problems and providing appropriate care before and during suctioning maneuvers. Nasal suction is seldom required, except in infants, because most adult airway obstruction occurs in the mouth and oropharynx.

Avoid prolonged suctioning because it may lead to significant hypoxia, especially in children. Do not exceed 15 seconds for suctioning intervals and administer supplemental O₂ before and after suctioning. Naigow and Powasner⁵⁵ found that suctioning consistently induced hypoxia in dogs and that it was best avoided by hyperventilation with high-concentration O₂ before and after suctioning.

When feasible, perform suctioning under direct vision or with the aid of the laryngoscope. Forcing a suction tip blindly into the posterior pharynx can injure tissue or convert a partial obstruction to a complete obstruction.

Oropharyngeal and Nasopharyngeal Artificial Airways

Indications and Contraindications

Resuscitate all patients in cardiac or respiratory arrest with 100% O₂. The most certain indication for supplemental O₂ is the presence of arterial hypoxemia, defined as a Pao₂ lower than 60 mm Hg or arterial oxygen saturation (Sao₂) less than 90%.⁵⁶ Normal subjects will begin to experience memory loss at an arterial oxygen partial pressure (Pao₂) of 45 mm Hg, and loss of consciousness occurs at a Pao₂ of 30 mm Hg.^57–59 Chronically hypoxemic patients can adapt and function with a Pao₂ of 50 mm Hg or lower.⁶⁰

When tissue hypoxia is present or suspected, give O₂ therapy.56,61 Shock states resulting from hemorrhage, vasodilatory states, low cardiac output, and obstructive lesions can all lead to tissue hypoxia and benefit from supplemental O₂. Whatever the cause of the shock state, administration of O₂ is indicated until the situation can be thoroughly evaluated and cause-specific therapy instituted.

Respiratory distress without documented arterial hypoxemia is a common indication for O₂ administration, although no evidence exists to support this practice.⁶² Oxygen therapy is often recommended for acute myocardial infarction, but there is no difference in outcomes between patients receiving O₂ and those receiving room air after myocardial infarction. The AHA has given a class I recommendation for O₂ only in patients with hypoxemia, cyanosis, or respiratory distress.^{56,61,63–65}

Although O₂ is routinely administered to acute stroke patients, there is no convincing evidence that this practice is beneficial without documented hypoxia, and it is not recommended by current guidelines.66–68 It is reasonable to administer O₂ to hypotensive patients and those with severe trauma until tissue hypoxia can definitively be excluded.⁶²

Administer 100% O₂ to patients with carbon monoxide poisoning. The half-life of carboxyhemoglobin is 4 to 5 hours in a subject breathing room air but can be decreased to approximately 1 hour by the administration of 100% O₂ by non-rebreather face mask at atmospheric pressure.⁶⁹

There are no contraindications to O₂ therapy when a definite indication exists. The risks associated with hypoxemia are grave and undeniable. Never withhold oxygen therapy from a hypoxemic patient for fear of complications or clinical deterioration. Carbon dioxide retention is not a contraindication to O₂ therapy. Rather, it demands that the clinician administer O₂ carefully and recognize the potential for respiratory acidosis and clinical deterioration. Although the mechanism for the development of respiratory acidosis in patients with chronic obstructive pulmonary disease (COPD) who are administered O₂ is debated, its occurrence is not.70,71 Use caution when administering supplemental O₂ to hypoxic patients with arterial carbon dioxide pressure (Paco₂) higher than 40 mm Hg, but do not withhold it.

Oxygen Administration during Cardiac Arrest and Neonatal Resuscitation

The 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care⁴ address the potential harm of oxygen therapy and hyperoxemia following cardiac arrest and during neonatal resuscitation. Excerpts from this document are shown in Box 3-1. Although it is still prudent to administer oxygen in the prehospital and ED setting as discussed earlier, additional research may alter current recommendations. See also “Complications of Oxygen Therapy” in this chapter. As a general guideline, fear of oxygen toxicity should not prevent the use of O₂ when there is an indication but should encourage the clinician to use the minimum concentration of O₂ necessary to achieve the therapeutic goals.

Oxygen Delivery Devices

High-flow delivery systems provide an Fio₂ that is relatively constant despite changes in the patient’s respiratory pattern. The Venturi mask is the high-flow delivery device that is most widely available (Fig. 3-6). Room air is entrained into the system through entrainment ports and mixes with the O₂ provided from the O₂ source. The proportion of entrained air—and therefore Fio₂—is constant and determined by the velocity of the O₂ jet and the size of the entrainment ports. Because the total gas flow (O₂ plus air through the entrainment ports) meets or exceeds the patient’s inspiratory flow rate, no additional entrainment of air occurs around the mask, thereby minimizing changes in Fio₂ as the patient’s respiratory pattern changes.^72,73 The mask is continuously flushed by the high flow of gas, which prevents the accumulation of exhaled gas in the mask. Venturi masks are packaged with multiple inserts, each with a different size orifice for O₂ inflow. Fio₂ is determined by selecting the appropriate colored insert and O₂ flow rate according to the manufacturer’s instructions. The inspiratory flow rate for a resting adult is about 30 L/min, a rate matched by the total gas flow provided by the Venturi mask at all settings. A patient in respiratory distress may have an inspiratory flow rate of 50 to 100 L/min.⁷³ If the inspiratory flow rate exceeds the total gas flow delivered by the mask, additional air will be entrained around the mask, and Fio₂ will decrease. Masks with higher Fio₂ ratings entrain less outside air and therefore provide less total flow. Caution should be used with masks rated above 35% in patients with respiratory distress because Fio₂ may be significantly reduced with high inspiratory flow rates.

Low-flow delivery devices provide gas flow that is less than the patient’s inspiratory flow rate. The difference between the patient’s inspiratory flow and the flow delivered by the device is met by a variable amount of room air being drawn into the system. Patients with normal respiratory rates and tidal volumes will require less outside air than those in respiratory distress, who typically receive a higher Fio₂. As a patient’s inspiratory flow changes, so will the Fio₂ that they receive from a low-flow device.72,73

The prongs of a nasal cannula deliver a constant flow of O₂ that accumulates in the nasopharynx and provides a reservoir of oxygen-enriched air for inspiration. The Fio₂ delivered by nasal cannulas is determined by many factors, including the respiratory rate, tidal volume, pharyngeal geometry, and O₂ flow. Most importantly, at a constant O₂ flow rate, Fio₂ varies inversely with the respiratory rate. Despite this limitation, nasal cannulas are very comfortable for patients and are the most common low-flow O₂ delivery device. Although it may seem intuitive, patients using a nasal cannula should be reminded that they should not smoke while oxygen is being delivered (Fig. 3-7).

Simple masks receive a constant flow of O₂ from the O₂ source and have multiple vent holes. During inspiration, the oxygen-enriched air that has accumulated in the mask, along with room air entrained through the vent holes, is inhaled. During expiration, 200 mL (the approximate volume of the mask) of exhaled gas is deposited in the mask with the rest exiting through the vent holes. The continuous flow of O₂ then partially washes out the mask before the next inspiration. The mask itself provides the reservoir of oxygen-rich gas for inhalation. A complex interplay between mask volume, tidal volume, respiratory rate, and O₂ flow determines the Fio₂ delivered to the patient.

A partial rebreathing mask incorporates a bag-type reservoir to increase the amount of O₂ available during inspiration, thereby requiring less outside air to be entrained. Non-rebreathing masks are similar to partial rebreathing masks but have a series of one-way valves. One valve lies between the mask and the reservoir and prevents exhaled gas from entering the reservoir. Two valves in the side of the mask permit exhalation while preventing the entry of outside air. In practice, one of these valves is often removed to permit inhalation in the event of interruption of flow of O₂ to the mask. A variable amount of air can still leak around the mask. This outside air and the exhaled gas remaining in the mask dilute the O₂ from the reservoir and prevent the mask from providing 100% O₂. Oxygen flow to the mask should be sufficient to prevent collapse of the bag during inspiration. As with all low-flow devices, the Fio₂ delivered varies with the patient’s respiratory pattern. Many clinicians have the misconception that a non-rebreathing mask can provide an Fio₂ near 100%. In practice, a non-rebreathing mask usually delivers an Fio₂ of about 70%.

Procedure

In selecting the proper delivery device, consider the clinical condition of the patient and the amount of O₂ needed. High-flow systems should generally be used for patients who need precise control of Fio₂, such as COPD patients with chronic respiratory acidosis. Low-flow masks are appropriate for patients who need supplemental O₂ but do not require precise control of Fio₂. Nasal cannulas are traditionally used in patients who do not require a high Fio₂ and will not be harmed by the lack of precise control. An oxygen flow rate of 1 to 3 L/min by nasal cannula will result in an Fio₂ of 23% to 35%. Patients with significant hypoxemia, end-organ dysfunction, or respiratory distress require a higher Fio₂ delivery system.

An initial Fio₂ of 24% to 28% delivered by Venturi mask is indicated for patients with hypoxemia and chronic respiratory acidosis.62,70

Frequent clinical assessment and Spo₂ monitoring are needed in all patients receiving O₂ therapy. Periodic blood gas analysis or capnography is imperative for those at risk for respiratory acidosis.74–76 Equilibration of Sao₂ after changes in supplemental O₂ occurs within 5 minutes.⁷⁷

Fio₂ should be titrated to achieve therapeutic goals while minimizing the risk for complications. An Sao₂ of 90% to 95% (Pao₂ ≈ 60 to 80 mm Hg) is an appropriate target for most patients receiving supplemental O₂.⁶² Increases above these levels do not add appreciably to the O₂ content of blood and are unlikely to confer an additional benefit. One may exceed these parameters in patients with shock and end-organ dysfunction, but the added risk and small potential benefit should be considered on an individual basis. In patients with COPD-associated hypercapnia, an Sao₂ of 90% (Pao₂ ≈ 60 mm Hg) should be the goal of O₂ therapy.^74–76 Mechanical ventilation should be considered when oxygenation goals cannot be achieved without progressive respiratory acidosis.

Preoxygenation for Rapid-Sequence Intubation

Preoxygenation is one of the most important aspects of emergency airway management. Preoxygenation before rapid-sequence intubation (RSI) provides much more time for intubation before desaturation occurs and thus significantly increases the chance of successful intubation on the first attempt. Failure to preoxygenate before RSI is often a critical factor when a straightforward emergency airway becomes an airway disaster. Preoxygenation is usually accomplished by providing the maximal Fio₂ with a non-rebreather mask for 3 to 5 minutes before intubation. Alternatively, eight vital capacity breaths from a maximal Fio₂ system, such as a non-rebreather mask or a bag-valve-mask device, is acceptable when there is no time for standard preoxygenation.⁷⁸ When using a bag-valve-mask device for preoxygenation, it is important that the exhalation port have a one-way valve so that room air is not drawn into the mask when the patient inhales.

The purpose of preoxygenation is not just to maximize oxygen saturation but to wash out nitrogen from the patient’s lungs and replace it with oxygen. This provides the maximum safe apneic time during RSI. Those at greatest risk for rapid desaturation include obese, pregnant, critically ill, and pediatric patients, and they will benefit the most from good preoxygenation. Most studies addressing preoxygenation have been conducted under ideal conditions in relatively healthy individuals. It is far more challenging to effectively preoxygenate critically ill patients.⁷⁹

Morbidly obese patients are best preoxygenated in a 25-degree head-up position because significantly higher oxygen tension can be achieved in this position.⁸⁰ Patients who are hypoxic despite maximal oxygen delivery have been shown to benefit from 3 minutes of NPPV (with 100% O₂) just before intubation.^81,82

Sometimes patients who need preoxygenation the most are uncooperative with a face mask because of delirium from hypoxia, hypercapnia, or other factors. These patients may benefit from delayed-sequence intubation—careful sedation without blunting of respirations to allow oxygenation with a face mask or NPPV for 2 to 3 minutes before administering a paralytic agent.⁸² Ketamine (1 to 1.5 mg/kg by slow intravenous push) has been suggested for this technique. Delayed-sequence intubation is a practical way to deal with a difficult problem, but it has not been well studied, and providers using this method should be prepared for clinical deterioration, hypoventilation, or apnea.

Oxygen Therapy during Apnea

Another method to delay desaturation during RSI is nasopharyngeal oxygen insufflation during apnea. Many studies have shown that providing oxygen therapy during apnea is much more beneficial than one might imagine.83–86 During apnea, oxygen continues to be absorbed through the alveoli, and air with a low oxygen concentration is left in the lower airways. Supplying oxygen to the nasopharynx during apnea allows air with a higher oxygen concentration to passively replenish oxygen in the alveoli. Multiple studies, in normal and morbidly obese patients, have shown that nasopharyngeal oxygen insufflation results in a significant delay in desaturation after the onset of apnea.^83,86,87 In these studies, nasopharyngeal oxygen insufflation was accomplished by inserting a 10-Fr catheter into the nasopharynx to a distance equal to the distance from the mouth to the tragus of the ear and delivering oxygen at a flow rate of 5 L/min when apnea occurred.⁸³ Using a standard nasal cannula with a nasopharyngeal airway is simpler and would probably provide the same benefit. Also, it is important to keep the upper airway open by using a jaw thrust or artificial airway for this technique to be most beneficial.

Nasal High-Flow Oxygen

High-flow nasal oxygen is a relatively new concept that may have some utility for optimizing oxygenation in critically ill children and adults.⁸⁸ At lower flow rates, Fio₂ is somewhat dependent on the patient’s respiratory rate, but at very high flow rates, Fio₂ is consistently very high. In one study, the Fio₂ delivered by nasal cannula ranged from about 25% at 1 L/min to 70% to 80% at 15 L/min.⁸⁹ Commercially available humidified high-flow nasal cannula (HHFNC) systems use flow rates of 5 to 40 L/min and deliver an Fio₂ of close to 100%. High-flow oxygen by nasal cannula is not well tolerated unless it is humidified, so commercially available systems (Vapotherm 2000i, Fisher and Paykel Nasal High Flow, AquinOx) deliver oxygen with nearly 100% humidity. HHFNC devices are popular in neonatal and pediatric intensive care units and are commonly used for respiratory support after extubation and for management of respiratory disease.^90,91 Some evidence suggests that high-flow nasal oxygen may provide low-grade CPAP.^92,93 Several adult studies have shown that high-flow nasal oxygen systems are well tolerated and deliver a higher Fio₂ than a high-flow mask in patients with respiratory failure or simulated respiratory failure.^94–96

Complications of Oxygen Therapy

Worsening of CO₂ retention leading to progressive respiratory acidosis and obtundation in patients with COPD is the complication most likely to be seen in the ED. This phenomenon is well documented and was first described by Barach in 1937.⁹⁷ It has been attributed to several mechanisms, including loss of hypoxic respiratory drive, ventilation-perfusion () mismatch, and decreased hemoglobin affinity for CO₂ (Haldane effect). This avoidable complication is best prevented by administering O₂ to chronic CO₂ retainers only when there is an indication, administering it at the smallest effective dose, and carefully monitoring clinical, capnographic, and arterial blood gas parameters.

Exposing the brain and lung to excessive concentrations of O₂ can lead to toxicity and, in severe cases, can cause acute respiratory distress syndrome. Injury to the pulmonary parenchyma occurs as a result of the formation of reactive oxygen species. Oxygen toxicity is of special concern in premature neonates, in whom prolonged hyperoxemia can lead to retinopathy. No data describe what concentration or duration of exposure to O₂ leads to toxicity, but presumably both these factors and individual patient characteristics determine the likelihood of toxicity. The benefits of O₂ therapy in the ED usually outweigh the risk for O₂ toxicity. Fear of toxicity should not prevent the use of O₂ when there is an indication but should encourage the clinician to use the minimum concentration of O₂ necessary to achieve therapeutic goals. High concentrations of O₂ are well tolerated over short periods and may be lifesaving.

In patients receiving high concentrations of supplemental O₂, nitrogen in the alveoli is largely replaced by O₂. If this O₂ is then absorbed into the blood faster than it can be replaced, the volume of the alveoli will decrease and absorptive atelectasis can occur. Airway obstruction potentiates this problem by preventing the rapid replacement of absorbed gas.

Indications and Contraindications

BMV is the most common initial technique for ventilation of apneic patients and for rescue ventilation after failed intubation.1,2 Many authors note that BMV is relatively contraindicated in patients with a full stomach, those in cardiac arrest, and those undergoing RSI.^2,3 These patients have a high risk for stomach inflation and subsequent aspiration. Unfortunately, these are the patients for whom ED providers most commonly use BMV. In ED situations, the need for ventilation and oxygenation always takes priority over potential aspiration.²

The only contraindication to attempting BMV is when application of a face mask is impossible. It is often impossible to achieve an effective face mask seal on patients with significant deforming facial trauma and those with thick beards. An intermediate ventilation device, such as an LMA, is a better choice for initial ventilation in such patients.

Bag-Mask Ventilation Technique

Achieving adequate ventilation with a bag-mask device requires an open upper airway and a good mask seal. Overly aggressive BMV causes stomach inflation and increases the risk for aspiration. The goal is to achieve adequate gas exchange while keeping peak airway pressure low. Squeezing the bag forcefully creates high peak airway pressure and is more likely to inflate the stomach. Several studies have shown that increased tidal volume is associated with higher peak airway pressure and increased gastric inflation.66,98–101 Data also show that decreased inspiratory time increases peak airway pressure and gastric inflation.^102,103 Therefore, the best method of BMV is to provide a tidal volume of about 500 mL delivered over a period of 1 to 1.5 seconds.¹⁰³ Using a ventilator (instead of a resuscitation bag) to provide the proper tidal volume and inspiratory time is a novel alternative to using a bag-valve device.⁸² Effective ventilation and oxygenation should be judged by chest rise, breath sounds, Spo₂, and capnography.

A variety of mask configurations are available to facilitate a tight seal. The most common mask used in ED situations is a transparent disposable plastic mask with a high-volume, low-pressure cuff. This type of mask eliminates the need for an anatomically formed mask and can be used for a wide variety of patients with different facial features. Various mask sizes are available.

For a single rescuer, only one hand can be used to achieve the seal because the other must squeeze the bag. The rescuer must apply pressure anteriorly while simultaneously lifting the jaw forward. The thumb and index finger provide anterior pressure while the fifth and fourth fingers lift the jaw. The C-E clamp technique is often the most effective: the thumb and index finger form a “C” to provide anterior pressure over the mask, whereas the third, fourth, and fifth fingers form an “E” to lift the jaw (Fig. 3-8, steps 1 and 2). Generally, well-fitting intact dentures should be left in place to help ensure a better seal with the mask.

In the ED setting it is best to hold the face mask with two hands and have an assistant squeeze the bag. If face mask ventilation is difficult, the most experienced provider should hold the face mask while the less experienced provider squeezes the bag.

There are two different methods for two-handed face mask control. The traditional technique is the double C-E method, where the thumb and index finger of both hands encircle the top of the mask (Fig. 3-8, step 3) and the third, fourth, and fifth fingers of both hands form an “E” to lift both sides of the mandible to meet the mask (Fig. 3-8, step 4). The problem with the double C-E technique is that it is difficult to perform a good jaw lift with the hands in this position. Having an assistant lend a third or fourth hand to help lift the jaw is an option, but this can be awkward unless the assistant is a very experienced provider. A better two-handed method is to hold the mask in place with the thenar eminence of both hands (Fig. 3-8, step 5) and use the long fingers under the angle of the mandible to perform a jaw lift while also pressing the mask firmly against the face (Fig. 3-8, step 6). This technique allows the operator to perform a good jaw lift (create mandibular protrusion or an “underbite”) and create a good mask seal with the strongest muscles of the hands.^104,105 This method is best for patients with difficult mask ventilation, and it also allows inexperienced providers and those with small hands to do a better job with face mask ventilation.¹⁰⁵ In addition, it is important to remember to use oropharyngeal or nasopharyngeal airways (or both) whenever face mask ventilation is difficult.

All bag-mask devices should be attached to a supplemental O₂ source (with a flow rate of 15 L/min) to avoid hypoxia. A significant problem with the bag-mask method is the low percentage of O₂ achieved with some reservoirs. The amount of O₂ delivered is dependent on the ventilatory rate, the volumes delivered during each breath, the O₂ flow rate into the ventilating bag, the filling time for reservoir bags, and the type of reservoir used. A 2500-mL bag reservoir and a demand valve are preferred for O₂ supplementation during BMV.¹⁰⁶

Pediatric bag-mask devices should have a minimum volume of 450 mL. Pediatric and larger bags may be used to ventilate infants with the proper mask size, but care must be maintained to administer only the volume necessary to effectively ventilate the infant. Avoid pop-off valves because airway pressure under emergency conditions may often exceed the pressure of the valve.¹⁰⁷

BMV may be the best method of prehospital airway support in trauma patients and children. Murray and coworkers¹⁰⁸ performed a large retrospective study suggesting that patients with severe head injury had a higher risk for mortality if they were intubated in the prehospital setting. In the same year, Gausche and associates¹⁰⁹ reported that neurologic outcomes and ultimate survival rates after prehospital pediatric resuscitation with BMV by emergency medical service (EMS) providers were as good as those with tracheal intubation.

Complications

The main complications of the bag-mask technique are an inability to ventilate and gastric inflation. Langeron and colleagues¹¹⁰ performed a large prospective study of adults undergoing general anesthesia and reported a 5% incidence of difficult mask ventilation. The incidence is obviously much higher in the emergency setting. Risk factors for difficult BMV include presence of a beard, obesity, lack of teeth, age older than 55 years, history of snoring, short thyromental distance, and limited mandibular protrusion (Box 3-2).^110–113 Patients who are not spontaneously breathing but awake enough to interfere with the procedure can also be difficult to bag-mask ventilate. A recent study showed that most patients with difficult BMV became easier to ventilate after paralytic agents were administered and none were more difficult to ventilate after paralytics.¹¹⁴

When mask ventilation is technically difficult, higher peak airway pressure is often required to provide adequate tidal volume. In these situations, gastric inflation is more likely and aspiration may occur. Be vigilant to recognize complications early and take corrective action. Even when BMV is easy and good technique is used, some gastric dilation will generally occur. Minor gastric distention should not be considered substandard in the setting of prolonged BMV.

Cricoid Pressure: Sellick’s Maneuver

In 1961, B.A. Sellick described the use of cricoid pressure to prevent regurgitation during anesthesia, and this technique has since become known as Sellick’s maneuver.¹¹⁵ The purpose of this technique is to apply external force to the anterior cricoid ring to push the trachea posteriorly and compress the esophagus against the cervical vertebrae. In theory, cricoid pressure compresses the distensible upper esophagus but not the airway because the cricoid ring is fairly rigid.

There are no good data that Sellick’s maneuver prevents regurgitation,116,117 but there are data that cricoid pressure prevents gastric inflation during BMV,^{115,116,118–121} thereby reducing the risk for subsequent regurgitation and vomiting. Several studies have confirmed that Sellick’s maneuver reduces tidal volumes, increases peak inspiratory pressure, and prevents good air exchange when applied during BMV.^{118,120–129} Sellick’s maneuver also decreases successful insertion of and intubation through LMAs.^130–137

BMV can produce gastric inflation, especially if high volume and high pressure are used. To avoid gastric inflation it is best to ventilate with a small volume (500 mL or 6 to 8 mL/kg) and avoid high peak pressure by using a long inspiratory time (1 second). Applying Sellick’s maneuver during BMV may further decrease the risk for gastric inflation and is still recommended by most airway experts.138,139 It should be noted that the routine use of cricoid pressure during BMV of patients in cardiac arrest is not recommended in the 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.⁶ It is recommended that cricoid pressure be released immediately if there is any difficulty ventilating with a face mask in an emergency setting.¹¹⁷ In addition, it is reasonable to release or relax cricoid pressure during insertion of an LMA and if ventilation with the LMA is difficult.^116,117,136 It may be reasonable to release cricoid pressure during laryngoscopy and tracheal intubation, and this is discussed in Chapter 4.

Some authors believe that improper technique is to blame for the many reported failures of Sellick’s maneuver.¹¹⁶ The proper technique for applying Sellick’s maneuver is to place the thumb and middle finger on either side of the cricoid cartilage with the index finger in the center anteriorly.¹¹⁵ Apply 30 N (6.7 lb) of force to the cricoid cartilage in the posterior direction.^116,139 As a reference, about 40 N of digital force on the bridge of the nose will usually cause pain.¹¹⁶

LMAs

The first LMA, the LMA Classic (Laryngeal Mask Company, Singapore; www.lmaco.com) became available in 1988. Since then it has been used more than 200 million times and has been described in more than 2500 academic papers.^136,140 LMAs are widely considered to be essential adjuncts for rescue ventilation and difficult intubation.^141,142 LMAs are primary rescue adjuncts in the difficult airway guidelines put forth by the American Society of Anesthesiologists¹⁴¹ and the Difficult Airway Society in Europe.¹⁴² Advanced Cardiac Life Support guidelines suggest that the LMA provides a more secure and reliable means of ventilation than a face mask does.^4,6 Pediatric Advanced Life Support guidelines acknowledge the LMA as a potential backup device for difficult pediatric airways.^143,144 Several manufacturers now make LMAs since the patent on the LMA Classic expired in 2003. It is important to recognize that all LMAs are not the same and that some of the newer devices have not been well studied.

Either an intubating LMA (ILMA) or a nonintubating LMA can be used in the “cannot-intubate/cannot-ventilate” scenario when face mask ventilation is difficult because of a beard, massive facial trauma, or obesity. Both devices can be inserted in less than 30 seconds and provide effective ventilation in more than 98% of patients.¹³⁶ In the emergency setting, where obtaining a definitive airway (i.e., tracheal intubation) is the eventual goal, it is more practical to use an ILMA. In addition, the LMA Fastrach (Laryngeal Mask Company, Singapore; www.lmaco.com), the most widely used and well-studied ILMA, is easier to insert than the LMA Classic.^145–149 Finally, when the head is in the neutral position, the LMA Fastrach is more likely to allow successful ventilation than the LMA Classic during in-line stabilization of the cervical spine.^150–152

The LMA Supreme (Laryngeal Mask Company, Singapore; www.lmaco.com) is the latest offering from the Laryngeal Mask Company; it has a new mask shape that may allow a better mask seal and a gastric evacuation tube. It features a firm curved shape and a bite block handle, so ease of insertion may be similar to that of the Fastrach, and it is available in all sizes from neonate to large adult.^153–162 Drawbacks are that it has not been extensively studied and does not facilitate tracheal intubation.

The Cookgas air-Q (Mercury Medical, Clearwater, FL), i-gel (Intersurgical, Berkshire, UK), and Ambu Aura-I (Ambu, Glen Burnie, MD) are promising new LMAs that can facilitate tracheal intubation and are available in pediatric sizes. The air-Q features a large-bore flexible airway tube and an inflatable mask that is stiffer than other LMAs. A few studies in adults and children show that it provides adequate ventilation in nearly all patients, but it has not been extensively tested.163–170 i-gel features a thermoplastic elastomer cuff that does not need inflation, so it may be easier to insert than other LMAs, but it has not been extensively tested.^{160,171–177} The Ambu Aura-I has some attractive features, but it is very new and almost completely untested.

This chapter describes how to insert the LMA Fastrach and use it for rescue ventilation. Details about intubation with the Fastrach are described in Chapter 4. Use of the LMA Unique (the disposable version of the LMA Classic) and LMA Supreme will also be described because they are cheap, disposable, well tested, and widely available.

Retroglottic Airway Devices

• Adequacy of current ventilation

• Potential for hypoxia

• Airway patency

• Need for neuromuscular blockade (uncooperative, full stomach, teeth clenching)

• Cervical spine stability

• Safety of the technique and skill of the operator

Rapid-Sequence Intubation

RSI in anesthesia has evolved since the introduction of succinylcholine in 1951. RSI was initially used as an abbreviation for rapid-sequence induction but is now synonymous with rapid-sequence intubation. Initially, the main purpose of RSI was to decrease the risk for aspiration in patients with full stomachs who needed emergency intubation. RSI has now become the most common method of emergency airway management because it provides optimal conditions for direct laryngoscopy.14,239–243 Providers using RSI must appreciate the importance of basic skills such as preoxygenation, patient positioning, and BMV.

Emergency providers should be very careful to not use RSI in a cavalier manner. When giving a paralytic agent, the provider takes complete responsibility for airway maintenance, ventilation, and oxygenation of the patient. Consider awake intubation in patients with known difficult airways. RSI is contraindicated in patients who cannot be orally intubated. It should be avoided in patients with laryngotracheal abnormalities caused by tumors, infection, edema, or a history of cervical radiation therapy.

One of the most important concepts to appreciate when using RSI is that of optimal laryngoscopy to maximize first-pass success.244–246 Preparation, preoxygenation, proper patient positioning, anterior neck maneuvers, and good laryngoscopy skills are all important components of optimal laryngoscopy (see Chapter 4). Just as important as optimal laryngoscopy is the ability to recognize when laryngoscopy (or any technique) has failed and it is time to move to a different approach. It is easier to take a different approach when you follow a simple preconceived algorithm. Patient safety during RSI depends on the provider’s ability to maintain ventilation and oxygenation if the first attempt at intubation fails.²⁴⁶ In this situation, BMV restores oxygenation and keeps the patient stable enough for further intubation attempts. Therefore, the importance of BMV skills cannot be overstated, and mastery of this skill alleviates much of the anxiety associated with difficult emergency airways and improves the chance for successful RSI.³ Also, it is critical to have an EGA device immediately available during every RSI in the event that BMV is difficult or impossible. Finally, all providers who perform RSI should be prepared to perform a surgical airway when all other procedures and devices fail.

Difficult Airways, Failed Intubation, and When to Avoid Rapid-Sequence Intubation

The term difficult airway is popular, but there is no standard definition of this term. It is most commonly used to describe patients who are difficult to intubate with direct laryngoscopy. Subsequently, there has been a significant amount of literature dedicated to predicting difficult direct laryngoscopy. However, even in the best circumstances only about half the instances of difficult laryngoscopy can be predicted.²⁴⁷ Many factors such as Mallampati scoring and measurement of thyromental distance have not been found to accurately predict difficult laryngoscopy, especially in the emergency setting.^247–250 Only obvious anatomic and pathologic abnormalities and a history of difficult intubation are accurate predictors of difficult laryngoscopy (see Chapter 4).²⁴⁸

In the emergency setting it is more useful to think of difficult airways as situations in which our usual methods of ventilation and intubation fail. Our goal should be to avoid RSI in patients who cannot be ventilated with a bag-mask device and cannot be intubated by direct or video laryngoscopy. Risk factors for difficult or impossible BMV have been well studied and include the presence of a beard, obesity, lack of teeth, age older than 55 years, a history of snoring, short thyromental distance, and limited mandibular protrusion (see Box 3-2).^110–113 Interestingly, one recent study showed that patients who were difficult to ventilate with a face mask usually became easier to ventilate when paralytic agents were administered and that none had worsened ventilation quality when paralyzed.¹¹⁴ Regardless, the realization that we cannot predict all cases of failed BMV and failed laryngoscopy mandates the need for a simple preconceived algorithm that uses proven rescue techniques that are applicable to a broad range of clinical scenarios, such as the bougie and the LMA Fastrach. The value of the bougie is indisputable, and it is clear that use of the LMA Fastrach after failed RSI has decreased the frequency of failed airways and the need for surgical airways (Fig. 3-14).* Finally, if RSI is our usual method of intubation, we must be prepared to perform a surgical airway when laryngoscopy, BMV, and backup devices fail.^2,5

Emergency Airway Management Algorithm

The algorithm presented here summarizes the general approach used in the Department of Emergency Medicine at Hennepin County Medical Center (Fig. 3-15, Box 3-3). This algorithm is presented as an example. Individual providers and institutions should determine their own algorithms based on the availability of skills and resources. There are many similarities between this algorithm and those put forth by the American Society of Anesthesiologists and the Difficult Airway Society.^141,142 However, this algorithm is simpler and more applicable to emergency airway management. Most published airway algorithms are not ideal for emergency airway management because they do not account for the conditions that are commonly encountered: patients with full stomachs who are critically ill and often uncooperative, and intubations that cannot be canceled if the airway is too difficult. Also, many algorithms resemble wish lists of equipment and skills that are simply not available to many emergency airway providers. Our algorithm is based on the concept that oxygenation, not intubation, is the key.²⁵⁵ It stresses well-proven concepts, procedures, and devices, and it is modeled after a simple algorithm developed by Combes and colleagues that was validated in a large prospective study.^5,180,254

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