Steven A. Godwin
Description
Blind intubation techniques are those methods of airway management that do not provide direct visualization of the larynx during the intubation process. Both blind nasotracheal intubation (NTI) and digital tracheal intubation (DTI) use indirect indicators of airway identification in lieu of direct vision laryngoscopy. NTI relies on listening to and feeling air movement, whereas DTI depends on the provider's ability to use tactile senses to distinguish airway anatomy as the tube is inserted. Other methods of airway management that do not require direct visualization of the glottis, but that do require specialized equipment, such as lighted stylets and gum elastic bougies, are discussed in other chapters.
I. Blind Nasal Intubation
Although NTI was widely used in emergency departments (EDs) in the past, it is rapidly being supplanted by superior techniques of oral intubation with neuromuscular blockade, even in the prehospital setting. In general, NTI has a number of serious drawbacks, and few advantages when compared to the other techniques that are now commonly used for emergency airway management. NTI has largely fallen out of favor in the ED because it takes longer, has a higher failure rate, has a higher complication rate, and requires smaller tube sizes than oral rapid sequence intubation (RSI). However, despite these inherent problems, NTI is still considered an important skill because it may be useful in certain difficult airway situations, particularly in departments without fiberoptic capability.
A. Indications and contraindications
As clinicians become more facile and comfortable with neuromuscular blockade and a variety of other approaches, the one remaining indication for NTI may be the spontaneously breathing patient with an identified difficult airway, for whom RSI is judged to be inadvisable (see Chapters 2 and 7). NTI is achieved by listening to the patient's spontaneous respirations through the tube and, therefore, should not be attempted in the apneic patient. It is relatively contraindicated in combative patients; in those with anatomically disrupted or distorted airways (e.g., neck hematoma, upper airway tumor); in cases of increased intracranial pressure; in the context of severe facial trauma with suspected basal skull fracture; in upper airway infection, obstruction, or abscess; and in the presence of coagulopathy. NTI should be performed with great reservation on any patient who needs rapid intubation because, despite optimistic claims to the contrary, intubation usually requires several minutes to complete using this technique, and significant oxygen desaturation can occur. Therefore, it is a poor choice for patients with respiratory failure, such as the asthmatic patient in extremis, who cannot be oxygenated during the protracted intubation attempt. In addition, one of the primary indications for NTI in the past, the multiply injured patient with potential cervical spine injury, has been discarded, and oral RSI with inline stabilization is now the recommended route (see Chapter 27).
B. Technique
1. Preoxygenate the patient with 100% oxygen as for RSI (see Chapter 3), if possible. Try to avoid bagging with positive pressure if spontaneous ventilation is adequate.
2. Choose the nostril to be used. Inspect the interior of the naris, with particular reference to the septum and turbinates. It may help to occlude each nostril in turn and listen to the flow of air through the orifices. If there appears to be no clear favorite, the right naris should be selected because it better facilitates passage of the tube with the leading edge of the bevel laterally placed.
3. Instill two or three drops of Neo-Synephrine or oxymetazoline nasal solution into each nostril. This will vasoconstrict the nasal mucosa and makes tube passage easier. The incidence of epistaxis may also be reduced. It may also be helpful to soak two or three cotton-tipped applicators in the vasoconstrictor solution and place them gently and fully into the naris until the tip touches the nasopharynx. This provides vasoconstriction at the area that is often most difficult to negotiate blindly with the endotracheal tube (ETT). Nasal topical anesthesia may then be placed as time permits. Insertion of a 4% cocaine pack or instillation of 2% lidocaine jelly will provide anesthesia for the nose. The oral cavity can be sprayed with 4% lidocaine or a similar spray, and, if desired, the pharynx may be anesthetized similarly. An alternative is to nebulize a solution of 4 mL of 4% lidocaine with 1 mL of 0.5% Neo-Synephrine in a gas-powered nebulizer, as one would do with albuterol. This takes approximately 5 to 10 minutes but provides excellent anesthesia and is well tolerated. Still another suggested method involves insertion of an absorbent nasal tampon (as is used for epistaxis) and application of several milliliters of 2% lidocaine with 1:100,000 epinephrine. Cricothyroid puncture with instillation of 5 to 10 mL of 1% to 2% lidocaine is often advocated. This technique is reasonably simple and effective but usually produces coughing, perhaps an undesirable result. Importantly, complete anesthesia of the glottis may not be desirable in all cases. Advancing the tube during the inspiratory phase of a cough sometimes allows immediate intubation of an otherwise elusive trachea. If the patient is awake, explain the procedure. This is a crucial step that is often neglected. If the patient becomes combative during intubation, the attempt must cease because epistaxis, turbinate damage, or even pharyngeal perforation may ensue. A brief, reassuring explanation of the procedure, its necessity, and anticipated discomfort may avert this undesirable situation.
4. Lubricate the tube and the nostril. The use of 2% lidocaine jelly has been advocated, but it is not in contact with the nasal mucosa long enough to result in anesthesia. However, the jelly is an adequate lubricant and is not harmful, so it is a reasonable choice.
5. Select the appropriate size of ETT. In general, the tube should be the largest one that will fit through the nostril without inducing significant trauma. In most patients, a tube with an ID of 6.0 to 7.5 cm will suffice. A smaller tube will fit through a difficult or tight space better than a larger tube. Test the ETT cuff for leaks.
6. Because the patient is often seated, it is probably easiest for a right-handed person to intubate from the patient's left side. This allows the right hand to be used for the intubation, while the left hand manipulates the location of the larynx and provides feedback to the right hand. By leaning slightly forward between the two hands, the operator can listen to the breath sounds and guide the tube into place. If the patient is supine, the operator will position him- or herself immediately above the patient's head. Positioning the head as for oral intubation is worthwhile, however. The so-called sniffing position, with the neck flexed on the body and the head extended on the neck, optimizes the alignment of the mouth and pharynx with the vocal cords and trachea. Care must be taken to avoid overextending the neck, which causes the tube to pass anteriorly to the epiglottis. A small towel may be placed behind the patient's occiput to help maintain this relationship.
7. Some advise gently inserting a gloved and lubricated little finger into the chosen nostril as deeply as possible to check for patency and to dilate the nostril to accept the tube as atraumatically as possible. The intubation sequence begins by gently inserting the ETT into the nostril with the leading edge carefully avoiding the rich vascular area of the anterior septum. For consistency, the remainder if this discussion assumes a right naris intubation by a right-handed operator. The tube should be turned so that the leading edge of the bevel is “out” (i.e., away from the septum). This will minimize the chances of septum injury and epistaxis. This also orients the natural curve of the ETT tube with the natural curve of the airway. The major nasal airway is located below the inferior turbinate and placement of the ETT should follow the floor of the nose backward. The tip of the tube should be directed caudad at an approximately 10-degree angle to follow the gently downsloping floor of the nose (see Chapter 4). This entire process should be done slowly and with meticulous care. Once the nasal portion of the airway is navigated, inciting epistaxis is unlikely. When the tip of the tube approaches the posterior pharynx, resistance will often be felt, particularly if the leading edge of the ETT enters the depression in the nasopharynx where the eustachian tube enters. At this point, it is possible to penetrate the nasopharyngeal mucosa with the ETT and dissect submucosally if care is not taken (see Chapter 4). If this occurs, the ETT should be removed and the alternate nostril attempted. In the event that this anatomical structure cannot be navigated, the insertion of a stylet into the ETT with a gentle C-shaped curve and reinserting the curve will keep the ETT off the post nasopharynx and is usually successful. Often, rotating the proximal end of the ETT 90 degrees toward the left nostril once this resistance is felt will facilitate “turning the corner” by orienting the leading edge of the ETT away from the depression. Once the oropharynx is successfully entered, restore the tube to the original orientation and proceed.
8. The tube should now be advanced until the breath sounds are best heard through it (usually approximately 3–5 cm). At this point, the distal tip of the tube is positioned immediately above the vocal cords. This process may be facilitated by occluding the opposite naris and closing the mouth.
9. Simultaneous with an inspiratory effort by the patient, advance the tube gently but firmly 3 to 4 cm while applying laryngeal pressure with the left hand. The vocal cords abduct during inspiration and are most widely separated at this time.
10. When the tube is advanced, one of three things will occur. If the trachea is entered, a series of long, wheezy coughs will usually emanate from the patient. Inflation of the cuff and a few ventilations with an end-tidal carbon dioxide (CO2) detector will confirm intratracheal placement. If the trachea is not entered, the tube either will slide easily down the esophagus or will come to an abrupt halt as it tries to pass anterior to the vocal cords or abuts against the anterior wall of the larynx. In the former case, the patient will not cough, and ventilation through the tube will be better heard over the stomach than over the lungs. End-tidal CO2 will not be detected. If the tube has passed down the esophagus, it is necessary to bring the distal tip of the tube further anteriorly. Withdraw the tube until the breath sounds are well heard again. Then extend the patient's head slightly and try again. If the intubation is being performed on a patient with possible cervical spine trauma, movement is impossible, and the intubation should be reattempted without any change in patient position. In the event the ETT repeatedly passes anterior to the larynx, flex the head on the neck.
11. Inflate the cuff and confirm position with an end-tidal CO2 detection device. Do not administer neuromuscular blocking agents to a patient who has undergone NTI unless tracheal tube placement has been confirmed by end-tidal CO2 detection. Breath sounds are never reliable as an indicator of tracheal placement, but this is particularly true in the spontaneously breathing patient who has undergone nasoesophageal intubation, whose own breath sounds will continue to be heard over the lungs, even when the ETT is being bag ventilated. A chest radiograph should also be obtained. If the presence of the tube or inflation of the cuff leads to prolonged coughing by the patient, administer 2 mL of 2% lidocaine solution through the ETT during an inspiration. This will often dramatically improve tube tolerance in seconds.
12. Only 60% to 70% of intubations will succeed on the first attempt. The “blind” nature of the procedure requires adjustment and attention to feedback. If the intubation is proving extremely difficult, consider the various options in Box 9-1.
II. Digital Tracheal Intubation
DTI is a tactile intubation technique in which the intubator uses his or her fingers to direct an ETT into the larynx. The technique has gained limited utility in clinical practice. It is not easy to perform, especially if the intubator has small hands or short fingers, nor is it aesthetically pleasing. However, in certain failed airway circumstances in an austere environment, DTI may be an option.
A. Indications and contraindications
DTI may be indicated:
1. In situations with poor lighting, difficult patient position, disrupted airway anatomy, or potential C-spine instability. Many of these situations are more likely in the prehospital setting (e.g., a patient trapped in a automobile).
2. If laryngoscopy equipment is unavailable or not working.
3. When visualization of the larynx is impossible (e.g., blood secretions) and no alternative devices or techniques are possible.
4. In failed intubation in an austere environment without rescue airway devices.
The patient must be sufficiently obtunded to prevent a biting injury to the intubator. Generally, this technique should only be considered in a patient who is frankly comatose and unresponsive or who has arrested.
B. The technique of tactile digital intubation is as follows:
1. Have an assistant use a gauze sponge to gently but firmly retract the tongue.
2. Insert a stylet in the ETT and bend the ETT/stylet at a 90-degree angle just proximal to the cuff, as for a lighted stylet intubation (see Chapter 11), and place the ETT/stylet into the mouth.
3. Slide the index and long fingers of the nondominant hand palm down along the tongue positioning the ETT/stylet on the palmar surface of the hand.
4. Identify the tip of the epiglottis with the tip of the long finger and direct it anteriorly.
5. Use the index finger to gently direct the ETT/stylet into the glottic opening.
C. Success rates and complications
Perhaps the most substantial limitation in performing this technique successfully is the length of the intubator's fingers relative to the patient's oropharyngeal dimensions. Biting injuries or unintentional dental injuries to the hand with the risk of infectious disease transmission may occur. The technique has only infrequently been used in the ED and most authors agree that some degree of experience is needed to perform this skill in an efficient and effective manner.
The two major tips for performing this technique are to have an assistant retract the tongue, thereby allowing the intubator the best access to the epiglottis and to ensure that the patient is sufficiently obtunded to tolerate airway manipulation.
BOX 9-1 Nasotracheal Intubation: Techniques
· The “Endotrol” tube, which has a ringlike apparatus connected to the distal end to allow anterior deflection of the tip of the tube, may be extremely helpful in such cases.
· If the tube has met with a “dead end,” it is anterior to the cords or abutted against the anterior wall of the trachea. It may be possible to ascertain by palpation with the left hand whether the tube is off to the left, off to the right, or anterior in the midline. If the tube is truly anterior, slight withdrawal of the tube until breath sounds are well heard followed by slight flexion of the head should facilitate passage. This is a common pitfall. When a first attempt fails, the operator often continues to further extend the neck in an attempt to succeed, each extension making the situation anatomically more impossible. If it is believed that the tube is off to the left or right in addition to being anterior, withdraw the tube, flex the head slightly (if possible), and turn the head slightly in the direction to which the distal tip of the tube was off the midline. For example, if the distal end of the tube was off to the right, turning the head to the right will cause the distal end of the tube to swing to the left (i.e., toward the midline), which is the desired corrective direction. Alternatively, if it is desirable to keep the patient's head in the midline, the proximal end of the endotracheal tube (ETT) may be rotated to the side where the distal end was detected to achieve this effect.
· Inflation of the cuff as the tube lies in the oropharynx may aid in alignment of the ETT with the glottic opening. The tube is then advanced until it meets resistance at the cords, and then the cuff is deflated prior to being pushed through the cords during inspiration. Inflation of the cuff is felt to lift the end of the tube away from the esophagus and into alignment with the vocal cords.
· Use of a guide such as a nasogastric tube or ETT changer in combination with the previously described inflated cuff technique may improve success rates. With this method, after the ETT has been advanced with the cuff inflated to meet resistance at the laryngeal opening, the nasogastric tube is inserted through the ETT. The inflated cuff allows for alignment of the outlet of the ETT with the vocal cords, and the nasogastric tube will slide through the outlet, through the glottis, and into the trachea. As the nasogastric tube slides through the glottis, coughing may occur, suggesting proper placement. The cuff can then be deflated and guided into the trachea over the nasogastric tube, which is then withdrawn from the ETT.
· Pass a fiberoptic laryngoscope or bronchoscope through the tube into the trachea (see Chapter 12).
· Pass a lighted stylet through the tube to assist in locating the glottis (see Chapter 11).
· Change to a new tube, perhaps one that is 0.5 to 1.0 mm ID smaller. The tube often becomes warm and soft during the intubation attempt and is no longer capable of being appropriately manipulated.
· Use a laryngoscope and Magill forceps. This may require conditions that are not present (i.e., the ability to insert a laryngoscope into the mouth and visualize the vocal cords).
· Grasp the tongue with a piece of gauze and pull it forward, or sit the patient up (if possible). This may improve the angle at the back of the tongue.
· Abandon the attempt. Prolonged attempts are associated with hypoxemia and glottic edema caused by local trauma. Either situation can worsen the situation substantially. Repeated attempts are not significantly more successful than the first. In 10% to 20% of cases, nasotracheal intubation will simply not be possible.
· In an unconscious patient, the nasal passage may be dilated with a nasopharyngeal airway or a gloved small finger if problems are encountered trying to get the tube through the naris. Again, a smaller tube may be advisable.
Evidence
1. Although historically recommended as the primary method for difficult airway management, NTI is an infrequently performed procedure for patients requiring emergent airway management and is now less commonly selected as a rescue method: Because RSI has become the method of choice for intubation of emergency patients, fewer physicians routinely perform NTI. In a recent review, of 610 intubations performed in a large ED with a Level I trauma center, Sakles et al. (1) reported only 8 (1.3%) NTIs. Of these patients, two attempts were unsuccessful. A review of ED intubations from 30 hospitals as part of the National Emergency Airway Registry (NEAR) databank project, identified 207/7,712 (2.7%) patients that required the use of rescue techniques and/or additional personnel. Rescue RSI was performed after failure of an alternative technique in 102/207 (49%) patients, whereas NTI was used as a rescue in 36/207 (17%) of patients. Although there were a greater number of rescue intubations with NTI than fiberoptic devices, 10/207 (4.8%), Bair et al. (2) emphasized the rapid growth in the use of fiberoptics over other methods for both primary and rescue airway management. Although still an important backup skill to maintain, NTI has a diminished role in emergency airway management.
2. When no other alternatives are available, NTI may be performed safely in facial trauma, but clinicians should be aware of rare, yet devastating, possible complications: Historically, facial trauma was believed to be an absolute contraindication for NTI due to the perceived associated risk of intracranial placement in the presence of cribriform plate disruption. There have been two reported cases of intracranial placement of a nasotracheal tube after facial trauma (3,4). These case reports have been criticized for demonstrating the outcome of poor technique rather than the presence of facial trauma as the cause of these injuries (5). At least one study has been published evaluating the risk of NTI in the presence of facial trauma. This retrospective review of 311 patients with intubation in the presence of facial fractures found that 82 patients underwent NTI (6). The authors found no episodes of intracranial placement, significant epistaxis requiring nasal packing, esophageal intubation, or osteomyelitis. Although there is no evidence that facial trauma is not a contraindication for NTI, in the modern era of RSI and the availability of multiple alternative airway devices, the indications for NTI in the ED setting are limited.
3. Cuff inflation, neutral head position, and use of ETTs with directional tip control provide added benefit to increase success rates for NTI in both normal and difficult airways: A number of improvements to the technique for passage of the nasotracheal tube through oropharynx and into the glottis have been suggested over the years. The most studied and successful aid to NTI appears to be the addition of cuff inflation during passage of the tube through the oropharynx until the outlet abuts the glottic opening. A prospective randomized trial evaluating successful NTI with the cuff inflated versus deflated technique demonstrated the inflated cuff technique to be superior. The results showed that 19/20 (95%) patients were intubated with the cuff inflated. In contrast, only 9/20 (45%) patients were intubated with the cuff deflated (7). A separate study compared success rates for NTI and fiberoptic bronchoscope in patients with an immobilized cervical spine with ASA I and II status airways while undergoing elective surgery. The authors reported that there was no significant difference in success rates between the groups. The study concluded that ETT cuff inflation could be used as an alternative to fiberoptic bronchoscopy in patients with an immobilized cervical spine (8), but this conclusion is not warranted by this small study, and both techniques are highly operator dependant. Other studies have demonstrated increased success with NTI using a neutral head position (9) and ETTs with directional tip control (10). However, in the immobilized trauma patient without other identified difficult airway attributes (see Chapter 7), RSI will still be considered the primary method of airway management. In the context of specific difficult airway attributes that argue against administering a paralytic agent, either fiberoptic intubation or NTI, performed with the patient spontaneously breathing, may be appropriate (see Chapters 2 and 7).
References
1. Sakles JC, Lauren EG, Rantapaa AA, et al. Airway management in the emergency department: a one year study of 610 tracheal intubations. Ann Emerg Med 1998;31(3):325–332.
2. Bair AE, Filbin MR, Kulkarni RG, et al. The failed intubation attempt in the emergency department: analysis of prevalence, rescue techniques, and personnel. J Emerg Med 2002;23(2):131–140.
3. Horellou MF, Mathe D, Feiss P. A hazard of naso-tracheal intubation. Anaesthesia 1978;33:78.
4. Marlow FJ, Goltra DQ Jr, Schabel SI. Intracranial placement of a nasotracheal tube after facial fracture: a rare complication. J Emerg Med 1997;15:187–191.
5. Walls RM. Blind nasotracheal intubation in the presence of facial trauma—is it safe? J Emerg Med 1997;15:243–244.
6. Rosen CL, Wolfe RE, Chew SE, et al. Blind nasotracheal intubation in the presence of facial trauma. J Emerg Med 1997;15:141–145.
7. Van Elstraete AC, Pennant JH, Gajraj NM, et al. Tracheal tube inflation as anaid to blind nasotracheal intubation. Br J Anaesth 1993;70:691–693.
8. Van Elstraete AC, Mamie JC, Mehdaoui H. Nasotracheal intubation in patients with immobilized cervical spine: a comparison of tracheal tube cuff inflation and fiberoptic bronchoscopy. Anesth Analg 1998;87(2):400–402.
9. Chung Y, Sun M, Wu H. Blind nasotracheal intubation is facilitated by neutral head position and endotracheal tube cuff inflation in spontaneously breathing patients. Can J Anesth 2003;50(5):511–513.
10. O'Conner RE, Megargel RE, Schnyder ME, et al. Paramedic success rate for blind nasotracheal intubation is improved with the use of an endotracheal tube with directional tip control. Ann Emerg Med 2000;36:328–332.