Airway Management Tracheal Intubation Tracheal intubation is required for airway maintenance and ventilation when the use of a face mask or laryngeal mask is difficult, unsatisfactory, or unsafe. INDICATIONS l. Prevent aspiration e.g. full stomach 2. Provide surgical access e.g. oral surgery 3. Maintain a difficult airway e.g. obesity 4. Provide IPPV 5. Facilitate removal of secretions EQUIPMENT • Two laryngoscopes with 3 sizes of blades (check batteries, contact, bulb, light) • Endotracheal tubes (ETT) estimated size, and smaller and larger sizes • Magill's forceps • Stylet, bougie, LMA • Suction apparatus within easy reach • Pillows for the head and shoulders • Wee's detector I ETC02 for confirmation of tracheal placement Endotracheal Tube Tracheal tube sizes are marked according to the internal diameter (ID) in mm. Children : (age/ 4) + 4 mm, a size less if small for age. Adult size at > 14 years. Adult female: oral 7.0-7.Smm, nasal 7.0mm. Male: oral 8.0-9.Smm, nasal 7.5-8.0 Tracheal tube length is marked in cm. starting at the distal end. The length of tube inserted (from the lips or incisors) should be noted. When correctly inserted, the tip of the tube should lie in the mid-trachea. Length from incisors to mid-trachea= (height in cm I 10) + 2 cm. From incisors to carina 24-29cm and vocal cords to carina 12cm (adults). Oral tube lyngth to incisors for adults is 18-20cm (females), 21-23 cm (males), and age/2 + l 2cm in children. Oral tube : Length from tragus to angle of mouth x 1.5 (adults) Nasal tube: Length from tragus to angle of mouth x 2 or tragus to tip of nose x 1.5 Cut the nasal tube to the correct size to prevent kinking just near the nose. 

Tracheal tube cuffs should be inflated with minimal air (2-Sml), just enough to have a light airtight seal to facilitate IPPV and minimize aspiration. Inflation to >25mmHg may cause mucosa) ischaemia, laryngeal oedema, and later polyps and fibrosis. With cuffed tubes use a smaller size to allow for the bulk of the cuff (high pressure low volume cuffs are preferable for GA). Sizes< 6.Smm should be un-cuffed. When extubating, deflate cuff fully, (especially with high volume low pressure cuffs). Choice of ETT for head and neck surgery • Armoured tubes which do not kink • Preformed (RAE) tubes which do not kink and provide better surgical access. To minimize endobronchial intubation, choose the RAE tube according to the length, and not the diameter (as the distance between the mouth and tip is fixed). TECHNIQUE OF INTUBATION Suppression of laryngeal reflexes with a relaxant, deep anaesthesia or LA is essential. 1. OXYGENATION, INDUCTION AND INTUBATION Pre oxygenation, which is the routine administration of 100% oxygen before induction is an integral part of the safe conduct of GA. The aim is to de-nitrogenate the lungs completely and increase 02 stores in the FRC from O.SL to 2L. This will increase the safe period of apnoea from I min to > Smin, so that desaturation is delayed (less if BMR is high or FRC is low). (see page 3.8) Note that one minute of apnoea after breathing room air reduces Sp02 to 80%. Intubation with Rapid Sequence Induction (RSI) for "full stomach" 1. Pre-oxygenate with 100% oxygen via a mask with no leaks till ET02 is >90%. Traditional: Encourage tidal volume breathing for 3 min via Magill's circuit. Fast track : Encourage 4/8 vital capacity breaths for 30/60sec. via circle circuit (see page 2.18) 2. Give i.v. thiopental and suxamethonium and continue holding the mask tightly with 100% 02 to allow mass movement (convective flow) of oxygen caused by the vacuum created due to 250ml/min 02 extracted, with minimal C02 wash out. Intubate after 45 sec when fasciculations subside and the jaw is fully relaxed. Intubation with non-depolarising muscle relaxants for a predicted easy airway 1. Pre-oxygenate with 100% oxygen as for RSI 2. After i.v. induction and non-depolarising muscle relaxant, mask ventilate with only oxygen and volatile agent for 2-3 min before attempting intubation. Never use N20 at this stage as it reduces 02 stores and safe period of apnoea. Awareness will not occur with adequate doses of i.v. induction and volatile agents. Atelectasis is minimized with mild PEEP. 3. To optimize the airway and prevent gas entering the stomach use both hands to hold the mask. while an assistant squeezes the reservoir bag ( 4 hand technique).  

Intubation with deep inhalational anaesthesia (when i.v. induction agents and relaxants are contraindicated) 1. Halothane or sevoflurane (with 02, with or without N20) is administered in gradually increasing concentrations till anaesthesia is achieved. (lsoflurane and desflurane cannot be used as they are pungent and irritant). Spray the cords with 10% lignocaine. 2. Ensure jaw relaxation and unresponsiveness and tolerance for an oro-pharyngeal airway before attempting intubation. Insert the tube gently while the cords are abducted. 2. POSITIONING FOR LINE OF VISION (LOV) a) shows the normal axes of the mouth, pharynx and larynx. These axes need to be brought in one line of vision. for which the following manoeuvres should be performed before intubation. b) Bring the larynx, and pharynx in line by placing a pillow under the head to flex the neck (Fig 4.5b). Obese or pregnant patients need many pillows (see Fig 4.4). c) Bring the mouth in line with the other two axes by extending the head at the atlanto-occipital joint (Fig 4.5c) a b ORALAXIS!O'} "" Figure 4.5 Position for intubation 3. MANOEUVRES TO ESTABLISH LINE OF VISION 1. Insert the laryngoscope blade gently into the right side of the mouth, displacing the tongue to the left and into the sub-mandibular space. This is difficult if the tongue is large or the sub-mandibular space is small. 2. Slide the laryngoscope blade down in the midline till the tip of the Macintosh blade lies in the vallecula i.e. anterior to the epiglottis. Do not pick up the epiglottis except when using a straight blade or in neonates. 3. To see the laryngeal opening lift the laryngoscope upwards towards the roof. Do not lever the blade using the incisors as the fulcrum. 4. External laryngeal pressure (ELP) on the thyroid cartilage may be required to push the larynx more posteriorly and cephalad to obtain a better view. i.e. BURP maneuver (backward, upward, rightward pressure). 

At laryngoscopy, the LOV from the mouth to the larynx must be clear. Difficulty in visualizing the glottis occurs in 1-3 % of patients. Figure 4.6 shows how this line of vision may be blocked by : 1. anterior larynx 2. prominent upper incisors 3. large or posteriorly located tongue. Figure 4.6 Factors leading to a difficult intubation (Lehane & Cormack) Grade I Grade][ Grade ]]I Grade nz:: ....._ ~ ' / -~ "-------" ~ ~~ ~ ~ Complete glottis Anterior glottis Only epiglottis Epiglottis visible not visible visible not visible Figure. 4.7 The four grades of laryngoscopic view (Cormack and Lehane) Cormack and Lehane defined 4 grades of laryngoscopic view (Fig 4. 7). Grades I and II are usually easy to intubate. Grade III: Subdivisions Grade Illa (epiglottis can be lifted) and Grade Illb (epiglottis cannot be lifted) requires the use of the McCoy blade, introduction of bougie and fibre optic techniques. Grade IV requires alternative advanced techniques, as direct intubation is impossible. 4. INTUBATION Intubate under direct vision, gently, to avoid damage to the lips, teeth, mucous membranes, tonsillar pillars and arytenoids. Inflate the cuff by introducing air till the leak around the ETI is just inaudible.  

Nasal intubation Check which nostril is more patent by compressing each nostril in tum, and asking the patient which nostril is easier to breathe through. 1. Choose the EIT size 0.5mm smaller than for an oral tube in the adult. In children the same size can be used, as the nostril is relatively larger. 2. Measure the tube length required, and cut the tube accordingly. (see page 4.6). 3. Instill vasoconstrictor nasal drops to minimize bleeding. 4. Keep the head in neutral position and insert a lubricated tube gently into the nostril, directing the tube vertically downwards to negotiate the naso pharynx. Insert the laryngoscope as for oral intubation, and if necessary hold the tip of the tube with the Magill's forceps to manoeuvre the tube into the larynx. 5. If after passing the vocal cords the nasal tube cannot be pushed further, the tip of the tube is probably impinging on the anterior wall of the trachea. Tum the tube through 180° and gently push it down. 6. After intubation immediately check pulse, tracheal placement and ventilation. 7. Pack the throat with a moist gauze pack to prevent aspiration of blood and debris. Leave the end outside the mouth, but do not obstruct surgery. Do not forget to remove the pack at the end of surgery. Use a label on the forehead or tape or plaster as a reminder. 8. After extubation suction the nasal passages and nasopharynx 9. Watch out for bleeding, dislodgement of polyps from the nasal passage, and damage to adenoids (avoid nasal tubes in children) . CONFIRM TRACHEAL PLACEMENT EXCLUDE OESOPHAGEAL INTUBATION Before ventilation : l. See the tube pass into the larynx. 2. Compress the chest and feel for a puff of air through the EIT. 3. If ETC02 is not available connect the Wee' s detector ( 50 ml bladder syringe attached to a catheter mount) to the ETT, inject air and aspirate fast (slower in children and asthmatics). If the tube is in the trachea, air can be aspirated easily. If it is in the oesophagus, air cannot be aspirated as its walls will collapse. 4. Insert a naso-gastric tube. If the tube is in the oesophagus it will pass to over 40cm, fluid may be aspirated, and withdrawal during suction is more difficult. 

During ventilation: 5. Inspect the chest wall and abdomen for rise and fall as air enters and leaves. 6. If the tube is in the oesophagus the abdomen will not fall in expiration and gurgling sounds may be heard. 7. Three point auscultation of both axillae for bilateral and equal breath sounds, and the epigastrium for no air flow is essential, but not always confirmatory. 8. Capnography is the gold standard. Confirm only after 3 normal wave forms to eliminate gastric C02 (due to antacids, fizzy drinks or mask IPPV). Suspect oesophageal intubation if : • High airway pressures are required to ventilate (>30cm Hp) • Desaturation <90% occurs (maybe delayed for 5-10 min. after pre oxygenation) EXCLUDE ENDO-BRONCHIAL INTUBATION Auscultate for bilateral and equal breath sounds in the axillary region. Fix the tube securely after proper placement is ensured. Check the placement again after fixing the tube, and again after positioning for surgery or changing position. Suspect endobronchial intubation if : • Desaturation occurs which may be delayed (5-10 minutes) after pre oxygenation or 2-3 minutes after changing the patient's position. • High airway pressures are required for ventilation. CONFIRM ABILITY TO VENTILATE If there is difficulty in ventilating with high airway pressures look for a likely cause and correct the problem. Difficulty in ventilation with high Paw could be due to : • Obstruction of ETT due to kinking, herniation of cuff, obstruction of lumen • Misplacement into oesophagus or bronchus • Bronchospasm • Pneumothorax • Aspiration and pulmonary oedema Check the ETT and "if in doubt take it out".