Chapter 6 – Airway Management and Mechanical Ventilation in the Neurocritical Care Unit




Abstract




The airway management and mechanical ventilation of patients with neurological disease requires continuous attention to the effects of respiration on neurophysiology. Brain-injured patients frequently lack compensatory reserves and are therefore vulnerable to “minor” physiologic changes to which we may pay little attention – an intubation during which the bed is left flat, ventilation interrupted, light analgosedation administered, and prolonged direct laryngoscopy performed may precipitate brain herniation in a patient with a mass lesion or elevated intracranial pressure (ICP). Yet it takes little effort to minimize the time the head is down, to see that ventilation is not interrupted, and to provide adequate analgosedation – possibly leading to a very different outcome.





Chapter 6 Airway Management and Mechanical Ventilation in the Neurocritical Care Unit


David B. Seder and Julian Bösel



Introduction


The airway management and mechanical ventilation of patients with neurological disease requires continuous attention to the effects of respiration on neurophysiology. Brain-injured patients frequently lack compensatory reserves and are therefore vulnerable to “minor” physiologic changes to which we may pay little attention – an intubation during which the bed is left flat, ventilation interrupted, light analgosedation administered, and prolonged direct laryngoscopy performed may precipitate brain herniation in a patient with a mass lesion or elevated intracranial pressure (ICP). Yet it takes little effort to minimize the time the head is down, to see that ventilation is not interrupted, and to provide adequate analgosedation – possibly leading to a very different outcome.


Airway and ventilation concerns in neurocritical care can be considered in terms of those general to all patients with critical illness, and those specific to patients with neurological diseases. This chapter will describe fundamental concerns related to airway management and mechanical ventilation in patients with acute neurological disease.



General Airway and Ventilation Management Concerns


Airway management is conceived in terms of indications for intubation, extubation, or a surgical airway, prediction of difficult bag-mask ventilation or intubation, preparation for intubation, the intubation procedure itself, including use of specialized airway adjunct devices, peri-intubation patient management, and general criteria for extubation.


Ventilation concerns include maintenance of acid–base status and systemic oxygenation, lung-protective ventilation in patients at risk of ventilator-associated lung injury, and ventilatory management of respiratory pathophysiology, such as obstructive airway disease, severe hypoxemia, or pneumothorax.



Airway Management


Airway management issues specific to neurocritical care include intubation of patients with known or suspected elevated ICP, an unstable cervical spine, threatened cerebral perfusion, and management of neuromuscular respiratory failure. The extubation or tracheostomy of patients with neurological injury is increasingly acknowledged as an area of wide variability in practice, and will be discussed in detail.


Ventilation concerns specific to neurocritical care include the effects of ventilation on cerebral blood flow, including intentional hyperventilation for elevated ICP, the effects of airway pressure on ICP and cerebral perfusion pressure (CPP), and effects of oxygen and pH on reperfusion injury.



Indications for Intubation


Common indications for intubation of patients with neurological diseases are failure to oxygenate, failure to ventilate, failure to protect the airway, anticipated neurological or cardiopulmonary decline, and prevention of ischemia or secondary neurological injury related to anxiety, pain, work of breathing, or aspiration.


Because of the potential for respiratory arrest, large-volume aspiration, or unsafe hemodynamic fluctuations, intubation and the initiation of mechanical ventilation are critical to protect patients in a period of neurological decline. In particular, patients that will require transport, neuroimaging, and medical or surgical procedures to maintain clinical stability should be intubated to ensure a stable airway and adequate oxygenation and ventilation. It should be noted that “failure to protect the airway” is a grossly subjective measure but involves two primary components – adequate airway clearance involving oropharyngeal coordination, cough reflexes, and respiratory muscle strength, and the ability to maintain a patent upper airway.



Contraindications to (Elective) Intubation


Except for a “Do Not Intubate” order, there are no absolute contraindications to intubation – that is to say contraindications must be weighed against the benefits of intubation for patients in a period of rapid decompensation. Relative contraindications include the need to preserve the neurological examination without the interfering effects of sedative and analgesic agents, the presence of critical brain ischemia, such as in an acute cerebrovascular flow-failure event, in which a large ischemic penumbra is perfused by maximally dilated collateral vasculature, significant cervical spine instability, and an anticipated difficult airway (such as mechanical upper airway obstruction) with inadequate resources present. Each of these relative contraindications will be discussed further in this chapter, but clinicians must recognize these circumstances require special attention, and should not be attempted without a risk–benefit assessment and maximal preparation.



Alternatives to Intubation


Intubation and postintubation management often require analgesia and sedation, at times muscle relaxants, and vasoconstrictor agents and/or intravascular fluids to counteract the effects of those vasodilators. Intubation is extremely uncomfortable, activates the sympathetic nervous system, and requires frequent analysis of the adequacy of ventilation by arterial blood gas or end-tidal carbon dioxide measurement. Alternatively, high-flow oxygen delivery by a standard or high-flow nasal cannula or face mask device can provide close to 100% inspired oxygen, provide a small amount of positive end expiratory pressure (PEEP), and may be better tolerated than noninvasive positive pressure ventilation (NPPV) with a pressure mask.


Technology to provide NPPV has dramatically improved in recent years – including the development of portable ventilators specifically designed for noninvasive ventilation that can compensate for mask leaks and typically provide excellent patient–ventilator synchrony [Reference Scala and Naldi1,Reference Hess2]. Hundreds of different pressure masks, including full hoods, face masks, oronasal masks, nasal masks, and tight-fitting nasal cannulas make patient comfort during mask ventilation less of an issue than ever before. Using modern equipment, the practical limitations to NPPV are that it provides partial, not complete, ventilatory support, and it offers no lower airway protection or maintenance of an open upper airway.


Finally, tracheostomy should be viewed as an alternative to intubation. Many patients with neurological disease and especially those with brain injury lack adequate airway protective reflexes, but ventilate and oxygenate perfectly well. In such cases, early tracheostomy can provide a reliable and patent upper airway, facilitate suctioning of the lower airways, allow patients to breathe spontaneously, therefore preserving respiratory muscle function, and eliminate the need for analgesia and sedation that may slow neurological recovery by interfering with the return of consciousness [Reference Bösel, Schiller and Hook3,Reference Seder, Lee and Rahman4]. Tracheostomy will be discussed later in this chapter.




Table 6.1 ATS/ERS guidelines to contraindications of NPPV [Reference Celli and MacNee5]




  • Cardiac or respiratory arrest



  • Non-respiratory organ failure



  • Hemodynamic instability or unstable cardiac arrhythmia



  • Severe encephalopathy (GCS <10)



  • Severe upper gastrointestinal bleeding



  • Facial trauma, surgery or deformity



  • Upper airway obstruction



  • Inability to cooperate or protect airway



  • Inability to clear respiratory secretions



  • High risk for aspiration



Preparation for Intubation


Preparation for intubation of the neurological patient should include a presedation neurological assessment, assessment of factors associated with difficult bag-mask ventilation and difficult intubation, and selection of induction agents, as well as fluids and vasopressors to maintain hemodynamic stability. Anticipatory of intubation, clinicians should assess and consider five categories of risk:




  • Is this a difficult airway or difficult mask-ventilation scenario?



  • What medications or maneuvers should be avoided?



  • Is this intubation high risk due to elevated intracranial pressure?



  • Is this intubation high risk due to threatened cerebral perfusion?



  • Is the cervical spine unstable?



Preparation for Difficult Mask Ventilation and Difficult Airway Scenarios


Difficult bag-mask ventilation is usually a more dangerous situation than difficult intubation – a sedated or paralyzed patient may arrest if they cannot be oxygenated or ventilated, while a difficult intubation can typically be bag-mask ventilated indefinitely – long enough for neuromuscular blockade to wear off or help to arrive. The “MOANS” pneumonic can be used to predict difficulty of bag-mask ventilation:




  • M = Mask seal (beard, unusual anatomy)



  • O = Obesity/obstruction



  • A = Age >55



  • N = No teeth



  • S = Stiff lungs


The “LEMON” pneumonic helps to predict a difficult airway:




  • L = Look (at the face, mouth, and neck)



  • E = Evaluate the mouth opening and airway position



  • M = Mallampati score



  • O = Obstruction



  • N = Neck mobility


The airways of patients with risk factors for either difficult mask ventilation or difficult intubation should be approached with caution. The urgency of the intubation, as well as the skill level of the intubating clinician must be considered. Because not every difficult intubation can be predicted, clinicians should enter into every intubation situation with a “backup” plan. Patients anticipated to be difficult to ventilate or intubate should prompt preparation with appropriate back-up in terms of skilled individuals (e.g. anesthesiology assistance) and special equipment. Adjunct airway devices such as laryngeal mask airways, special blades, video scopes, intubating stylets, fiberoptic intubating equipment, and surgical airway equipment should be immediately available. In modern airway management, the availability of basic airway adjunct devices such as laryngeal mask airways (LMAs), videoscopes, and intubating stylets should be considered mandatory.



Induction Medication Issues to Consider in the Neurocritically Ill


As a neuromuscular blockade agent, succinylcholine should be withheld in patients with hyperkalemia, as well as those with normal potassium levels, but at risk for a surge in serum potassium due to prolonged immobility. Examples of such patients in the neurological population include those with upper motor neuron lesions resulting from stroke, brain or spinal cord tumors, other intracerebral or spinal cord masses, closed head injury, spinal cord injury, or encephalitis. Ketamine, a dissociative agent that maintains blood pressure was suspected to increase ICP by older reports, but according to more recent studies is safe if coadministered with a sedative. Especially in a dehydrated patient, propofol and opioids may cause excessive vasodilation and blood pressure drop unless counteracted with vasopressors or fluids.



Intubation in the Setting of Elevated Intracranial Pressure


Patients with intracranial hypertension are at risk for ICP or inadequate cerebral perfusion during intubation. Clinicians should pay special attention to the adequacy of sedation and analgesia during laryngoscopy, to head-of-the-bed up positioning, and to the adequacy of blood pressure and ventilation. Direct laryngoscopy causes sympathetic stimulation, potentially triggering tachycardia, hypertension, bronchospasm, and increased ICP. When preparing for intubation, leave the head of the bed up at 30° to 45°, briefly bring the bed flat during the procedure, then return the bed to its original position. If necessary, the patient can be maintained in reverse Trendelenburg positioning throughout the intubation. Medications that blunt the ICP rise associated with laryngoscopy include intravenous lidocaine, analgesics such as fentanyl, and sympatholytics like esmolol. Hypotension, hypoxemia, and hypercarbia cause vasodilation and an increase in cerebral blood volume, leading to a rise in ICP. Preoxygenation is vital as it washes out nitrogen in the lungs and prolongs the time to oxyhemoglobin desaturation. The patient’s minute ventilation should be maintained throughout the procedure to avoid CO2 retention – a matter of urgency in patients with central nervous system mass lesions and elevated ICP. Adequate intravenous access is critically important to manage hemodynamic changes during intubation, and we suggest routine infusion of isotonic crystalloid during the procedure. Vasopressors should be readily available in the event of hypotension to maintain adequate CPP.



Intubation in the Setting of Impaired Cerebral Perfusion


In suspected or proven ischemic stroke, one should proceed with intubation as with elevated ICP by avoiding hypotension during induction and postintubation, and taking special precautions to avoid hypotension-inducing drugs, especially in hypotensive patients. When an ischemic stroke is suspected or known to be occurring, or a state of inadequate cerebral blood flow (CBF) exists for other reasons, brain ischemia should be presumed to be present.


The cerebrovascular circulation is ordinarily well collateralized, and many patients presenting with stroke symptoms can be seen to have an infarct core and an ischemic penumbra on perfusion computed tomography (CT) or magnetic resonance imaging (MRI). Under these circumstances, the ischemic penumbra may be conceptualized as a region of maximally vasodilated vessels, receiving maximal shunting of the cerebrovascular circulation, yet CBF is severely compromised and maximally compensated. Hypertension and tachycardia in such patients may reflect a physiologic, not pathophysiologic, response to this ischemia and may be necessary to maintain perfusion of the ischemic territory [Reference Talke, Sharma and Heyer6,Reference Seder, Riker, Jagoda, Smith and Weingart7].


Further, even vasoactive agents that do not perceptibly drop the systemic blood pressure or alter CPP may reverse physiological regional shunting of blood to the region of ischemia, and should be avoided in conditions of active ischemia. An episode of relative or actual hypotension, such as would be precipitated by the administration of a vasodilator sedative medication like propofol to a volume-depleted patient, can dramatically worsen infarction size by “stealing” blood flow from maximally dilated watershed territories between vascular distributions.


Brain ischemia is not limited to ischemic stroke, but can also be variably present in patients with cerebral vasospasm, traumatic brain injury (TBI), intracranial and extracranial cerebrovascular stenosis, intracerebral hemorrhage, and hypoxic-ischemic encephalopathy following resuscitation from cardiac arrest. Strong associations between episodic hypotension in the critical hours following resuscitation and poor neurological outcome have been noted in TBI and hypoxic-ischemic encephalopathy after cardiac arrest [Reference Chesnut, Marshall and Piek8,Reference Trzeciak, Jones and Kilgannon9] The intubating clinician should be aware of the risks of even a transient decrease in cerebral blood flow, and strive to maintain both cerebral and systemic vascular tone during airway management.


Brain ischemia is also worsened by hyperventilation – an association clearly demonstrated in TBI [Reference Davis, Idris and Sise10] and explained in the laboratory by a dramatic and immediate decrease in CBF and increase in the volume of ischemic brain tissue when hyperventilation is performed [Reference Coles, Fryer and Coleman11]. Clinicians should attempt to maintain normocapnea during this period, and early correlation of an arterial CO2 sample with end-tidal CO2 (ETCO2) is suggested, so that continuous capnography can be used to verify normocarbia.



Intubation of a Patient with an Unstable Cervical Spine


When spinal column or ligamentous injury to the neck is suspected due to the mechanism of injury – such as any blunt head trauma resulting in loss of consciousness – all measures must be taken to protect the spinal cord during any movements or procedures. Preintubation airway maneuvers, including jaw tilt, bag-mask ventilation, cricoid pressure, and direct laryngoscopy can all injure the spinal cord when cervical instability is present.


Any patient with a confirmed or suspected unstable cervical spine should be immediately placed in a rigid cervical collar or other stabilization device. During intubation, manual in-line axial stabilization and gentle traction of the head and neck by an assistant are mandatory if the patient requires any manipulation of the head or neck. During airway management, cervical subluxation occurs during chin lift, jaw thrust, bag-mask ventilation, and tracheal intubation, as well as maneuvers such as cricoid pressure and head turning. Mask ventilation was found in one study to cause more cervical spine displacement than any other method used for tracheal intubation [Reference Hauswald, Sklar, Tandberg and Garcia12]. These maneuvers must not be used.


The basic principles of cervical spine stabilization have been developed and refined over decades, though no modifications to the algorithm mapped out by the American College of Surgeons’ Advanced Trauma Life Support (ATLS) course are recommended. In urgent circumstances in the field, endotracheal intubation is preferred to bag-mask ventilation or cricothyrotomy and should be performed with in-line spinal stabilization. Although cricoid pressure is no longer recommended during intubation, it definitely should not be used in patients with cervical spine injury, since it may cause posterior displacement of the cervical spine.


Hypoxia, hypoventilation, and large-volume aspiration are larger risks to trauma patients than complications of endotracheal intubation; in-line spinal stabilization helps ensure safe intubating conditions when direct laryngoscopy is performed [Reference Grande, Barton and Stene13], and is the standard of care. The minimum amount of anterior–posterior displacement of the cervical spine occurs with flexible fiberoptic intubation, however [Reference Brimacombe, Keller and Kunzel14], and is preferred when time and circumstances allow, and when severe instability is present.



Reducing Peri-Intubation Risk


Backup plans for oxygenation and ventilation, and for securing the airway under difficult circumstances, should include airway adjuncts and special equipment, and routine “ramping up” of obese patients prior to administration of muscle relaxants. Clinicians should use medications best suited to an individual patient’s pathophysiology, including intravascular volume expansion, prevention of episodic hypotension with vasopressors and hemodynamically neutral intubating agents, blunting of the ICP response to direct laryngoscopy with analgesics, and minimizing time with the head of the bed flat.



Neuromuscular Respiratory Failure


Respiratory failure in patients with neuromuscular disease is often associated with a weak cough and failure to clear secretions, leading to atelectasis, shunting, pneumonia, and the inability to meet ventilatory demands. Alternatively, some rapidly progressive forms of neuromuscular respiratory failure cause severe bulbar dysfunction and loss of cough reflexes. When bulbar dysfunction is predominant, intubation is typically required. But when respiratory muscle weakness is the dominant problem, patients with preserved bulbar function and dyspnea or increased work of breathing should undergo a trial of noninvasive ventilation combined with airway clearance by the frequent use of chest physiotherapy and a cough-assist device. Such interventions can prevent the need for intubation and improve outcomes, particularly in patients with myasthenia gravis [Reference Seneviratne, Mandrekar, Wijdicks and Rabinstein15].





Figure 6.1Ramping up” an obese patient. In panel A, the usual supine alignment in obesity is shown. In panel B, the patient is “ramped up” with blankets, bringing the external auditory meatus to the level of the sternal notch.


Any patient with neuromuscular weakness and dyspnea should undergo an assessment of respiratory function that includes:




  • Arterial blood gas measurement



  • Serial pulmonary function testing to include negative inspiratory force (NIF) and vital capacity (FVC)



  • Assessment of bulbar function, neck strength, and cough.


Patients with a rapidly progressive course and those who do not rapidly stabilize gas exchange and work of breathing with noninvasive ventilation should be intubated [Reference Seneviratne, Mandrekar, Wijdicks and Rabinstein15]. Because of the potential for exacerbating weakness and prolonged effects of the medications, the administration of corticosteroids, muscle relaxants, or neuromuscular blocking agents is discouraged.


In myasthenia gravis, succinylcholine may require approximately 2.5 times the dose to produce the same effects, and the action may be prolonged. Nondepolarizing agents such as rocuronium are also safe, but will have a prolonged duration [Reference Abel and Eisenkraft16]. In conditions such as Guillain–Barré, succinylcholine can precipitate life-threatening hyperkalemia, and only nondepolarizing agents should be used. Rocuronium, a short-acting nondepolarizing agent is a safe and almost identically effective induction agent in cases of neuromuscular weakness, often administered at a dose of 0.6–1.2 mg/kg.



Preintubation Neurological Evaluation


Urgent management of the airway should coincide with a rapid, but detailed, neurological assessment [Reference Seder, Riker, Jagoda, Smith and Weingart7]. The presedation/preintubation neurologic exam is crucial to subsequent triage decisions, and can typically be conducted in a few minutes. It establishes a baseline that is used to assess therapeutic interventions or may identify injuries that are at risk of progressing (e.g. unstable cervical spine fractures). The assessment identifies the most appropriate testing and helps to avoid unnecessary, uncomfortable interventions, such as cervical spine immobilization. The preintubation neurological assessment is the responsibility of the team leader who is coordinating resuscitation efforts; findings should be documented and communicated directly to the treatment team that assumes care of the patient.


The preintubation neurological examination should routinely include assessment of:




  • Level of arousal, interaction, and orientation, as well as an assessment of simple cortical functions such as vision, attention, and speech comprehension and fluency



  • Cranial nerve function



  • Motor function of each individual extremity



  • Tone and reflexes



  • Comment on subtle or gross seizure activity



  • Cervical spine tenderness, when appropriate



  • Sensory level in patients with suspected spinal cord injury.



Intubation


Rapid sequence intubation may provide protection against the reflex responses to laryngoscopy and rises in ICP [Reference Sakles, Laurin, Rantapaa and Panacek17]. The presence of coma should not be interpreted as an indication to proceed without appropriate analgesia and sedation. Although the patient may seem unresponsive, laryngoscopy and intubation trigger elevates ICP unless appropriate pretreatment and induction agents are used.


Outcomes in patients with intracranial catastrophes are related to the maintenance of brain perfusion and oxygenation; consequently, tight control of these two parameters is critical. Cerebral perfusion pressure (CPP) is the physiologic correlate for blood flow to the brain and is calculated as the difference between the mean arterial pressure (MAP) and ICP. It is generally recommended that the ICP be maintained below 20 mmHg, MAP at 80–110 mmHg, and CPP at a minimum of 60 mmHg. Because the intracranial pressure may not be known at the time of urgent intubation, clinicians should anticipate elevated ICP in patients with a mass lesion such as hematoma, hydrocephalus, tumor, or cerebral edema, and choose an appropriate BP target accordingly. Although some authors have postulated that ICP may be unimportant in the setting of a preserved CPP [Reference Young, Blow, Turrentine, Claridge and Schulman18], there are data suggesting ICP >30 is independently associated with injury [Reference Ziai, Melnychuk and Thompson19], and a CPP-only ICP management strategy is not recommended.


Many neurologically impaired patients have compromised CBF, even with a normal ICP. For example, patients with ischemic stroke, vasospasm, and hypoxic-ischemic brain injury often have impaired cerebrovascular autoregulation and are each critically sensitive to decreases in blood pressure and CBF. In these patients, the goal is to maintain MAP and CPP, as for the patients with known or suspected elevation of ICP. Vasodilators, which reverse physiological shunting, should be avoided. Common induction agents are described in Table 6.2.




Table 6.2 Induction agents
























































































Drug Dose Onset of action Duration of effect Indications Precautions
Fentanyl 1–3 μ/kg IV push

over 1–2 min
Within 2–3 min 30–60 min Pre-induction, blunts ICP rise Respiratory depression, hypotension, rare muscle rigidity
Lidocaine 1.5 mg/kg IV 2–3 min

before intubation
45–90 s 10–20 min Pre-induction, blunts ICP rise Avoid if allergic or high grade heart block if no pacemaker
Esmolol 2 mg/kg IV 2–10 min 10–30 min Pre-induction, blunts ICP rise Bradycardia, hypotension, increased airway reactivity
Etomidate 0.3–0.5 mg/kg IV push 30–60 s 3–5 min Induction, sedation; does not cause hypotension. Decreases CBF, ICP, preserves CPP Decreases seizure threshold, fasciculations mimicking seizures, decreases cortisol synthesis
Propofol 1–2 mg/kg IV push 9–50 s 3–10 min Induction, sedation, reduces ICP and airway resistance, anticonvulsive effects Hypotension, myocardial depression
Ketamine 2 mg/kg IV push 1–2 min 5–15 min Induction, analgesia, sedation, amnesia, bronchodilatory effects; good in hypotension Catecholamine surge, tachycardia, hypertension
Thiopental 3 mg/kg IV push 30–60 s 5–30 min Good for normotensive, normovolemic pts with status epilepticus or ↑ICP Hypotension, bronchospasm
Succinylcholine 1.5–2 mg/kg IV 30–60 s 5–15 min Preferred paralytic unless contraindicated Caution in hyperkalemia, myopathy, neuropathy/denervation; avoid if history of malignant hyperthermia
Rocuronium 1 mg/kg 45–60 s 30–50 min Paralysis when succinylcholine contraindicated Long acting, avoid in renal failure
Vecuronium 0.1 mg/kg Within 3 min 25–40 min Long acting, avoid in renal failure, slower onset than rocuronium


Approach to the Difficult Airway


A stylet is a smooth malleable plastic or metal rod that is placed through the endotracheal tube to facilitate intubation – a “J” or “hockey stick” shape allowing the tube to be directed anterior towards the vocal cords is preferred. Another common technique is bimanual laryngoscopy. The laryngoscopist uses his or her right hand to apply either cricoid pressure or the “BURP” maneuver (backward, upward, rightward pressure on thyroid cartilage) to attempt to obtain a better view of the airway. An assistant then holds this position as the laryngoscopist intubates.


Airway adjuncts can facilitate intubation. The gum-elastic bougie is a common choice. It is a 60 cm malleable intubating stylet with a 40° angled tip that is placed through the visualized vocal cords. Alternatively, a bougie can be placed blindly through the vocal cords by “feeling” the tracheal rings upon appropriate placement. The endotracheal tube is then advanced and the bougie removed.


A lighted stylet, or light wand, is placed blindly. When the lighted tip enters the glottis, the anterior neck displays a bright red light, and when it enters the esophagus, there is a diffuse dull glow. The endotracheal tube is then advanced over the stylet into the trachea.


Video intubation has revolutionized airway management, in part because there does not need to be a direct line of vision between the eye and the vocal cords – a video camera at the curved tip of an intubating blade allows for an intubating stylet or endotracheal tube to be passed between the vocal cords without a direct line of vision – making difficult anterior airways accessible. Flexible bronchoscopy facilitates nasal or oral intubation, though oral intubation is preferred unless absolute spinal neutrality is demanded. Except in unusual circumstances, the video laryngoscope is preferred over the fiberoptic bronchoscope due to its ease of use and utility in anterior displacement of the tongue, improving laryngeal visualization.


The most commonly used superglottic device is the laryngeal mask airway (LMA). The LMA is a small, inflatable latex mask mounted on the end of a hollow tube. The deflated device is placed blindly into the hypopharynx with the opening of the mask projected anteriorly. Once positioned, the mask is inflated, the opening positioned over the glottis, and the device is secured by tape like an endotracheal tube. The intubating LMA (ILMA) has a more rigid and wider tube with a handle for insertion. This device allows for blind placement of a modified endotracheal tube through the ILMA. The Combitube® is an esophageal-tracheal double-lumen airway that is also placed blindly. If the tracheal lumen is placed into the trachea, ventilation is achieved through the distal lumen. If it is placed into the esophagus (more common), ventilation is achieved through the proximal apertures above the distal cuff.


A true emergency arises when a patient cannot be intubated or ventilated. In this situation, a surgical airway is necessary. A needle, wire-guided, or surgical cricothyroidotomy should be performed; tracheostomy is a more complex and time-consuming procedure and should be reserved for nonemergent situations. In a needle cricothyroidotomy, a small catheter over a needle is passed percutaneously in a caudad direction through the cricothyroid membrane. When air bubbles are seen in the syringe, the catheter is advanced over the needle and the syringe and needle are removed. The catheter is then connected to high-pressure oxygen tubing and transtracheal jet ventilation is performed. The guide-wire technique is performed similarly, with the exception that a guide-wire is placed through the needle and the needle and syringe are removed with only the guide-wire left behind. A dilator-airway catheter is passed over the guide-wire, the guide-wire is removed, and the catheter cuff is inflated. A surgical airway using a scalpel can be performed quickly and successfully by nonsurgeons.

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