BATRA, MATHEW : AIRWAY MANAGEMENT WITH ETI 263Indian J. Anaesth. 2005; 49 (4) : 263 - 268

1. M.D., Prof.2. M.D., Asst Prof.

Department of Anaesthesiology,Postgraduate Institute of Medical Education and Research,Chandigarh - 160 012.Correspond to :Dr. Yatindra Kumar BatraE-mail : ykbatra@glide.net.in

AIRWAY MANAGEMENT WITH ENDOTRACHEALINTUBATION (INCLUDING AWAKE INTUBATION

AND BLIND INTUBATION)Dr. Yatindra Kumar Batra1 Dr. Preethy Mathew J.2

IntroductionEndotracheal intubation for the purpose of providing

anaesthesia was first described by William MacEwan in1878 when he passed a tube from the mouth into the trachea,using fingers as a guide in the conscious patient.1 EdgarRowbotham and Ivan Magill gained wide experience ofendotracheal intubation during the first world war andpopularized it subsequently.1 Endotracheal intubationprovides an artificial conduit between the atmosphereand the patient’s trachea for the purpose of alveolar gasexchange or protection of the lungs from extraneoussubstances. The clinical situations where endotrachealintubation is indicated are listed in table 1.

Table - 1 : Indications of endotracheal intubation.

RoutineTo provide anaesthesia

EmergencyAirway obstruction Respiratory distressOxygenation failure (hypoxia) Ventilation failure (hypercarbia)Mental status alteration (GCS<8/15) Flail chest/Pulmonary contusionCardio pulmonary resuscitation

I. Options

a) Nasal versus oral tracheal intubationOral tracheal intubation is the usual method of

intubation. Nasal intubation is performed when the surgeryis in the oral cavity or on the mandible and when the oralroute is difficult or impossible e.g. temporomandibularjoint ankylosis, trismus. In situations where visualization oflarynx by direct laryngoscopy is poor, blind or fibreopticintubation through the nasal route can be used.

The contraindications to nasal intubation arecoagulopathy, severe intranasal pathology, basilar skullfracture and the presence of cerebrospinal fluid (CSF) leak.There are certain practical disadvantages of nasotracheal

intubation. The inner diameter of tubes used for nasotrachealintubation is usually smaller than those for orotrachealintubation and this may increase the resistance and work ofbreathing.2 The tube tends to soften and kink in thenasopharynx, which could further increase airway resistanceand make passage of suction catheters more difficult. Hence,clearance of secretions could be problematic with anasotracheal tube. There is increased risk of sinusitis andbecause of these concerns nasotracheal intubation is rarelyused for long-term intubation. Nasal intubation may producea bacteremia and appropriate endocarditic prophylaxis shouldtherefore precede it.3

b) Awake intubation versus intubation duringanaesthesia

In the operating room, endotracheal intubation isusually performed after induction of general anaesthesia.The anaesthesiologist must determine whether maskventilation and intubation will be possible after the patientis anaesthetized and paralyzed. If there is sufficient doubtregarding the patient’s airway, awake (conscious) intubationwith sedation and topicalization is indicated.

The indications for awake intubation include a historyof difficult intubation, findings on history or physicalexamination that can make intubation difficult, and severerisk of aspiration or haemodynamic instability. The reasonsfor conscious intubation should be explained to the patientand documented in the chart. Primary consideration of safetyshould be emphasized.

c) Direct versus blindEndotracheal intubation is usually performed using

direct laryngoscopy to visualize the laryngeal inlet. Inconditions where mouth opening is restricted and where thelarynx cannot be seen on direct laryngoscopy, the intubationmay be done blindly. Blind intubation requires experiencefor success.

II. TechniqueThe key to success in intubation is a calm, collected

approach with efficient but complete preparation. Duringthe learning process, mental rehearsals of the steps oflaryngoscopy and intubation help in acquiring the skillfaster.

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Preparationi) Equipment : All the necessary equipments for intubation

including drugs should be readily available at hand.A list of suggested items are given in table 2. Theequipments should be in good working condition. Thelight of the direct laryngoscope should be bright. Theintegrity of the endotracheal tube cuff and pilot balloonshould be tested by attaching a 10 ml syringe to theone-way valve of the pilot balloon and then brieflyinflating the cuff with approximately 10 ml of air.

Table - 2 : Suggested items to be ready for intubation.

Equipment Drugs

Intravenous catheters (16-22 gauge) Atropine

Direct laryngoscope with blades Glycopyrrolate

Macintosh 2, 3, 4. Lignocaine 1%, 4%

Miller 0, 1, 2, 3. Lignocaine jelly, aerosol, viscous

Endotracheal tubes (3-8 mm ID) Midazolam

Syringes (5 ml, 10 ml) Propofol

Magill forceps Saline

End tidal CO2 detector Suxamethonium

Nasal/ oral airways Thiopentone

Suction catheters Non depolarizing muscle relaxant

Tube changer Morphine/ Fentanyl.

Guide wire

Nasogastric tubes

Tape

ii) Patient’s history and airway assessment: Apart fromthe airway, the patient’s cardiac and respiratory statusshould be assessed. History of prior difficulty inintubation needs to be enquired. Also the potential foraspiration of gastric contents into the lung is to beassessed.

iii) Suction : A functioning suction is a must prior to theattempt at laryngoscopy. Suction catheters of variousdiameters should be available.

iv) Oxygen source : In the operating room, anaesthesiamachine and breathing circuits must be checked forleaks. In a peripheral setting, adequate oxygen sourcehas to be confirmed before attempting intubation.100%oxygen is to be administered via a tight fitting maskand reservoir bag prior to any attempt at intubation.

v) Position of the patient : In the supine position, thepharyngeal and laryngeal axes of the patient are offset,making a good view of the glottis extremely difficultduring direct laryngoscopy. Flexion at the lowercervical joints aligns the pharyngeal and laryngeal

axes. In adults, a small foam pillow or several foldedsheets are often employed to achieve this. Theextension of the head at atlanto-occipital joint bringsthe oral axis more in alignment to the laryngeal axis.The alignment of the oral, pharyngeal and laryngealaxes makes the pathway from the lips to the glottisnearly a straight line. This position of head and neckto facilitate intubation is classically described as“sniffing the morning air” position.

In suspected cervical spine injuries, an assistantshould stabilize the head and neck in a neutral position bymaintaining in-line cervical traction during airwaymanipulations. The greatest cervical displacement appearsto occur during bag and mask ventilation.

The height of the bed/trolley should be adjusted sothat the patient’s head is at the operator’s midchest level.

Procedure

Direct laryngoscopyThe Macintosh and Miller blades are commonly used.

The tip of the macintosh blade is inserted into the vallecula(the space between the base of the tongue and the pharyngealsurface of the epiglottis). Pressure against the hyoepiglotticligament elevates the epiglottis to expose the larynx. Themacintosh blade provides good room for passage of theendotracheal tube with minimum epiglottic trauma. Sizeranges vary from 0 to 4 with most adults requiring amacintosh # 3 blade. The miller blade is passed to includethe epiglottis and the tip lies beneath the laryngeal surfaceof the epiglottis; the epiglottis is then lifted to expose thevocal cords. The miller blade provides a better exposure ofthe glottic opening but provides a smaller room through theoro and hypo pharynx. Size ranges vary from 0 to 4, withmost adults requiring a miller no. 2 or 3 blade.

Visualization of airway structures is easier if asufficient distance is maintained between the operator’seyes and the patient’s airway. Crouching too close to themouth results in a narrowed visual depth of field.4

After positioning the patient, the laryngoscope isheld in the left hand and the fingers of the right hand areused to open the mouth gently. A scissoring motion of theright thumb and index finger is described to open the mouth.The clinician should wear gloves because of the likelihoodof entry of fingers into the patient’s mouth. The laryngoscopeblade is introduced along the right corner of the patient’smouth avoiding the teeth and to enable the flange of theblade to keep the tongue to the left. The laryngoscope bladeis advanced to expose the right tonsillar pillar and thenadvanced in the midline until the epiglottis comes in view.

BATRA, MATHEW : AIRWAY MANAGEMENT WITH ETI 265

The tongue and pharyngeal soft tissues are lifted to exposethe glottic opening (fig. 1). The direction of force is alongthe axis of the laryngoscope handle to pull it forward andupward. The blade should never be used as a lever, usingthe upper teeth or maxilla as the fulcrum. External pressureon the cricoid and/or thyroid cartilages may aid invisualization of the glottis.5

adequate mask ventilation and the administration of aneuromuscular blocking agent followed by directlaryngoscopy and intubation. Suxamethonium is a widelyused relaxant for intubation because it produces rapid andexcellent intubating conditions. The intermediate acting non-depolarizing muscle relaxants-rocuronium, atracurium andvecuronium when used in large doses produce rapid onsetof acceptable intubating conditions. Hence, these agentsare also used to facilitate intubation. Adequate maskventilation is a must before administering any musclerelaxant. Pre-oxygenation is recommended as it provides anadded margin of safety.

Laryngoscopy and intubation being powerfulnoxious stimuli require deep levels of anaesthesia to bluntthe deleterious patient response. In high-risk population(coronary artery disease, cerebral aneurysm etc.), additionalpharmacological agents like i.v lignocaine, esmolol, fentanyletc. may be used to blunt the haemodynamic perturbations.

In “full stomach” situation or when there ispropensity for aspiration, and there is reasonable certaintythat intubation should not be difficult, a “rapid sequence”intubation is chosen. If there is sufficient doubt about theability to intubate the patient, awake intubation with topicalanaesthesia of the airway should be considered. Beforerapid sequence induction, the patient is pre oxygenated.After pre oxygenation, an intravenous anaesthetic andmuscle relaxant are administered together and maskventilation is not provided until intubation. Proper cricoidpressure is not applied until after the patient is unconscious.Gentle downward pressure is given by the thumb and firstfinger on the cricoid cartilage to occlude the oesophagealarea behind the cricoid. This will prevent regurgitation andshould greatly decrease the risk aspiration.8 Suxamethoniumis the relaxant of choice during rapid sequence inductiondue to rapid onset. Rocuronium 1-1.2 mgkg-1 also providesintubating conditions in 60-90 seconds.

When the initial attempt at intubation fails, maskventilation should be resumed while the situation isreassessed. As long as mask ventilation is maintained, theproblem is not emergent. Cricoid pressure should bemaintained in full stomach situations. Head position andlaryngoscopy technique may be re-examined during the nextattempt.

Verification of endotracheal tube placementOesophageal intubation remains one of the most

common mistakes in airway management associated with afatal outcome9 and no verification technique is entirelyfoolproof.10 The usual standard of care for verification ofproper endotracheal position includes the persistent detection

Endotracheal intubationA 7.0 mm ID endotracheal tube is a reasonable

choice for most women and an 8.0 mm ID endotrachealtube is reasonable for most men. During insertion, theendotracheal tube is held in the operator’s right hand andadvanced through the oral cavity from the right corner ofthe mouth and then through the vocal cords.

When the visualization of the glottis is poor, thetube can be directed anteriorly with the help of a malleablestylet. The end of the stylet should lie at least 1 cm proximalto the end of the endotracheal tube to reduce the chance ofairway injury. The tip of the assembled stylet andendotracheal tube can be bent anteriorly into “hockey stick”curve.

The proximal end of the endotracheal tube cuff isplaced just below the vocal cords. The markings on thetube in relation to the patient’s incisors are noted. In adultmales, the tube is generally inserted to about 23 cm at theincisors to position the tube tip an appropriate 4 cm abovethe carina. For females, the distance is about 21 cm.6 Tubeinserted too far will cause endobronchial intubation, whiletubes that are not in far enough may be more at risk ofaccidental extubation. The endotracheal tube cuff is inflatedto the point of obtaining a seal in the presence of 20-30 cmof H2O positive airway pressure. The tube should be securelyfastened with tape, preferably to taut skin overlying bonystructures. The entire attempt at endotracheal intubationshould take no longer than 30 seconds.7

Anaesthetic managementThe routine intubation sequence includes the

administration of a rapid acting induction agent (thiopentalsodium, propofol, sevoflurane etc.), the demonstration of

Epiglottis

VocalCord

Arytenoidcartilage

Piriformsinus

Fig. 1 : View of the larnyx during laryngoscopy

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of carbon dioxide (CO2) in the end tidal samples of exhaledgas and auscultation over the stomach and both the lungfields. Small concentrations of CO2 may be detected afteran oesophageal intubation, especially if bag and maskventilation has insufflated previously exhaled air into thestomach.11 However, the end tidal value decreasesprogressively with ventilation and should raise the suspicionof oesophageal tube placement.

Listening for breath sounds high in each axilla maydecrease the chances of being misled by transmitted breathsounds from the opposite lung. If the breath sounds areheard over only one side of the thorax, and endobronchialintubation should be suspected, and the endotracheal tubeshould be withdrawn until breath sounds are heard bilaterally.If the breath sounds are not heard over the thorax or areheard over the epigastrium, an oesophageal intubation shouldbe suspected.

The other methods for verifying the placement of theendotracheal tube include visual observation of theendotracheal tube passing through the vocal cords,observation of chest and abdominal movement with ventilationand palpation of trachea as the tube is passed.12,13 Gurglingsounds over the stomach and absence of noticeable chestwall expansion are signs of oesophageal intubation. Theexhaled tidal volume may be measured and is reduced withoesophageal intubation.14 Water vapour may be observed tocoat the endotracheal tube upon expiration and disappearupon inspiration after proper placement. Fibreopticendoscopy can be used to confirm endotracheal tubeplacement.15

Nasotracheal intubationMost of the basic techniques for nasotracheal

intubation are similar to those used for orotrachealintubation. Assessment of patency and preparation of thenasal passage is an additional step during preparation.Vasoconstriction of nasal mucosa is critical to reducemucosal oedema and the chance of epistaxis duringintubation. Vasoconstriction is usually accomplished with atopical solution such as oxymetazoline. Both nostrils shouldbe treated. If both nares are equally patent, the right nostrilmay be preferable because the bevel of endotracheal tubewill face the flat nasal septum when introduced through theright nostril, reducing damage to the turbinates. The inferiorturbinates limit the size of the endotracheal tube. A 6.0 to6.5 mm ID endotracheal tube for women and 7.0 to 7.5 mmID endotracheal tube for men are suitable for nasotrachealroute. Insertion to a depth of 26 cm, measured at the narisin women and 28 cm in men has been reported to result inproper position within the trachea.16 The tube should beadvanced in a direction that is perpendicular to the face

and parallel to the hard palate. As the tube is passed intothe nasopharynx, it may impact against the posteriornasopharyngeal wall. The tube should then be retractedslightly, the patient’s neck extended, and the tube readvanced.Forcible advancement of the tube risks tearing the mucosaand creating a false passage. After the tip reaches thepharynx, the tube is advanced through the glottic opening.This may be accomplished with direct laryngoscopy andMagill forceps to guide the tip of the tube anteriorly throughthe glottis. The forceps should grasp the tube proximal tothe endotracheal tube cuff. This reduces the chance ofdamaging the endotracheal tube cuff during insertion. Anassistant must then advance the tube as it is directed withthe forceps.

Blind nasal intubationBlind intubation is easier to describe than to

perform. Patient may be intubated either awake or asleep,without visualizing the larynx. Once the endotracheal tubehas passed into the nasopharynx, the monitoring of breathsounds becomes the key for successful intubation. At eachinspiratory effort, the tube should be advanced whileconstantly monitoring breath sounds. If advancing the tuberesults in loss of or reduction in breath sounds, then thetube should be withdrawn to the point at which the breathsounds are maximally heard. The endotracheal tube thencan be turned slightly and readvanced with each inspiratoryeffort. Successful tracheal intubation will be detected bycontinued auscultation of distant breath sounds, someresistance as the tube passes through the vocal cords, thepatient coughing, and the capnography reading and waveform.If repeated insertions of the endotracheal tube fail to enterthe trachea, then the tube should be withdrawn to the pointwhen the breath sounds are heard loudest. At this point,10 ml of air can be introduced into the tube cuff (thisdirecting the tube tip anteriorly away from the posteriorpharyngeal wall) and the endotracheal tube can be advanceda further 2 cm without loss of breath sounds. The cuff isthen deflated and the tube advanced further into the trachea.Most commonly, the tube tends to enter the oesophagus.Extending the patient’s neck or providing cricoid pressuretends to align the tube with the glottis and may increase thechances the success.

Blind nasal intubation is an important skill for theanaesthesiologist, as it remains an important adjunct in themanagement of difficult airway. Indications for this techniqueinclude potentially difficult orotracheal intubation andpatients in whom muscle relaxants or a surgical airway areundesirable or contraindicated. The former situation mayinclude patients with dental fractures, arthritis or dislocationsof the temporomandibular joints, a small mouth, a short

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neck, a large tongue, a history of previous head and necksurgery, or cervical spine immobility. This technique isoften performed with the patient sitting upright in bedand so is useful when the patient cannot or should not beplaced supine. Contraindications include acute epiglottitis,apnoea, basilar skull fractures with or without cerebrospinalfluid rhinorrhoea, bleeding diathesis, upper airway foreignbody, large bilateral nasal polyps, abscesses and severelaryngeal trauma. Complications are rarely serious, butcan include nasopharyngeal haemorrhage, laryngeal trauma,retropharyngeal perforation, and paranasal sinusitis.

Blind oral intubationDuring direct laryngoscopy, if the laryngeal inlet is

not visualized, a bougie can be passed blindly below theepiglottis followed by threading the endotracheal tube overthe bougie. The placement of the endotracheal tube isconfirmed as described in the previous section.

Blind intubation with the aid of light wand is anotheroption. It has a malleable stylet with a light source at thetip. The handle containing the battery for the light sourceis attached to the proximal end of the stylet. The endotrachealtube is threaded over the lighted stylet in the conventionalfashion and introduced into the oropharynx blindly followingthe curve of the tongue. It is helpful to bend the styletanteriorly close to the tip. The glow visible over the anteriorneck–bright glow in the midline- guides tracheal intubation.Darkening the surroundings enhances appreciation of theglow. The endotracheal tube can be slid off the light wandas if it were a standard malleable stylet.

Awake intubationInstrumentation of the airway is uncomfortable and

distressing to a conscious patient. An informed and reassuredpatient adds to the success of awake intubation. A strugglingpatient markedly reduces the chances of successful intubation,increases morbidity from cervical or cranial fractures, andaccentuates the degree of oral, dental, or laryngeal trauma.Laryngoscopic stimulation also precipitates vomiting, breathholding and laryngospasm, which further interfere withairway management. Irritation of the larynx or trachealmucosa during attempted intubation causes significantincreases in airway resistance, especially in patients withreactive airway disease or those recovering from upperrespiratory tract infection. Hypertension, tachycardia, ordysrhythmias secondary to CNS responses may precipitatemyocardial ischaemia, as well as unacceptable increases inintraocular and intracranial pressure. The impact of awakelaryngoscopy and intubation can be minimized with judicioususe of topical anaesthesia and conscious sedation.

Opioid analgesics are used to facilitate awakeintubation as they provide mild sedation, analgesia and

reduction of cough and bronchospasm. Of the narcotics,fentanyl is most suitable and the greatest advantage is theease of reversibility by naloxone. Benzodiazepine group ofdrugs is useful adjuvant to narcotics, midazolam being mostpopular. The principal disadvantage of the combination ofnarcotic and midazolam is the profound decreased level ofconsciousness that results in loss of verbal contact with thepatient, which is vital during awake intubation. In thosepatients at severe risk of aspiration, narcotics and othersedatives must be used sparingly. When awake intubation isplanned, a dose of anticholinergic, such as glycopyrrolate0.2 mg IV is recommended.

Local anaesthetic agents are rapidly absorbed by themucous membrane of the respiratory tract to effectivelyeliminate pharyngeal, laryngeal and tracheobronchialreflexes. These agents are less effective on topicalapplication due to diminished buffering capacity of mucousmembranes, limiting release of anaesthetic base andpresence of cilia and secretions on the mucous membraneacting as barriers to the penetration of drugs. To compensatefor these, a higher concentration of drug must be used. Thecommonly used agents are lignocaine, benzocaine andtetracaine. Lignocaine is available as 2%, 4% solutions,2% viscous solution, 10% aerosol preparation and 5%ointment. Local anaesthetics can be applied to mucousmembranes with cotton-tipped applicators or pledgets orsprayed over the mucosa directly or via aerosol inhalation.

Nares may be anaesthetised by pledgets soaked in4% lignocaine. The nasopharynx may be instilled througha 16 or 18 gauge catheter inserted deeply into the nose. Thetongue and oropharynx can be anaesthetized with 10 %lignocaine spray using the laryngoscope blade or a tonguedepressor. Alternatively, the patient can gargle andexpectorate viscous lignocaine to produce topical anaesthesiaof the pharynx. The larynx can be sprayed with lignocainedirectly onto the visualized glottis. The trachea can beanaesthetized with a translaryngeal application of 2 to 3 mlof 1% lignocaine. A 22-gauge catheter or a 23-gaugeneedle is inserted through the cricothyroid membrane in themidline, air is aspirated to confirm the location of theneedle tip and lignocaine is quickly injected and the needleremoved. The cough induced provides excellent spread ofthe anaesthetic in the larynx below the vocal cords. Thesuperior laryngeal nerve may be blocked by an externalapproach using a 23-gauge needle to inject 2-3 ml of 1%lignocaine between the greater cornu of the hyoid bone andthe thyroid cartilage. This nerve may also be blocked bythe application of lignocaine soaked pledgets with Krauseforceps held in the pyriform fossa. Nebulization of lignocainecan also be employed to anaesthetise the nasal passage,pharynx, larynx and tracheobronchial tree.17

INDIAN JOURNAL OF ANAESTHESIA, AUGUST 2005268 PG ISSUE : AIRWAY MANAGEMENT

Techniques for awake intubation : The choiceof technique depends on the preference for oral versus nasaltube placement, experience and availability of equipment.If one technique fails, another is usually tried. The variousoptions are oral intubation with direct laryngoscopy, blindoral intubation, blind nasal intubation, retrograde intubationand fibreoptic bronchoscopy guided intubation.

ConclusionAirway management is the most important skill

required of an anaesthesiologist and one of the first ones tobe taught during training. Endotracheal intubation is askill based on the knowledge of airway anatomy, equipmentsfor airway manipulation, aided by judicious use ofpharmacological agents and enhanced by experience.

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