Chapter 7. Advanced management of the airway and ventilation
The gold standard for airway control in prehospital care is endotracheal intubation using a cuffed tracheal tube, however basic airway management must be mastered before learning advanced techniques.
Accidental and unrecognised oesophageal intubation is likely to be fatal. Excessive movement of the head and neck during laryngoscopy and intubation may aggravate a cervical spine injury.
Tracheal intubation
The trachea can be intubated via the oropharynx or via the nasopharynx. Oropharyngeal endotracheal intubation requires a laryngoscope for successful placement.
Indications
• Airway obstruction or potential airway obstruction in the profoundly unconscious patient with no gag reflex
• Patient at risk of aspiration of foreign material (e.g. gastric contents, blood from maxillofacial trauma)
• Patient requiring positive pressure ventilation, e.g. in cardiorespiratory arrest
• To gain access to the lower respiratory tract to aspirate secretions or foreign material.
Contraindications
• Insufficient operator skill or experience
• Conscious or semiconscious patient
• Immobility of the head and neck (relative)
• Distorted anatomy (relative)
• In children:
• Croup
• Epiglottitis
• Gag reflex present.
On NO ACCOUNT should attempts be made to intubate children with croup or infections such as acute epiglottitis.
However, if the child loses their airway anyway, then cautious intubation or surgical airway may be life-saving.
Equipment for conventional endotracheal intubation
The following equipment is required:
• Appropriate sized laryngoscope in working order, different size blades
• Appropriate range of tubes cut to correct length with connections (15 mm) to fit the bag valve device
• Suction apparatus
• Lubricant on a gauze swab (only occasionally required in the prehospital setting)
• 20 mL syringe for cuff inflation
• Flexible bougie and stylet
• Magill’s forceps
• Tape or tie to secure tube in place
• Apparatus to inflate the lungs (bag valve device or ventilator)
• Pulse oximeter to monitor patient during and after intubation attempt
• End-tidal CO 2 apparatus to detect correct tube placement
• Rescue equipment including laryngeal mask airway and surgical airway.
Size of endotracheal tube
ET tubes of size 7–9 mm will fit most adults. ET tubes are made longer than is generally needed and should be cut to a length of 21–25 cm in order to reduce dead space. The length required in any individual will be twice the distance from the corner of the mouth to the angle of the jaw.
For children, the correct size can be calculated using the following formulae:
Once the correct diameter has been calculated, have the next biggest and the next smallest tube available to ensure a good fit.
In children it is important that the full range of ET tube sizes (including half sizes) are available. ET tubes <6.5 mm are not supplied with an inflatable cuff, in order to avoid pressure damage to the trachea.
Technique for endotracheal intubation using laryngoscopy
1. Ensure that all equipment functions correctly and that tubes and bougies are well lubricated if necessary
2. The patient should be supine with the head and neck aligned in the clear airway position (preferably with the head on a small pillow or rolled-up blanket). Apply cricoid pressure if possible
3. Holding the laryngoscope in the left hand, insert the curved blade into the right-hand corner of the patient’s mouth, ensuring that the lip is not caught between the blade and lower teeth
4. Advance the blade, aiming for the larynx in the midline, and displacing the tongue towards the left-hand side of the mouth to leave a clear view
5. When the tip of the blade reaches laryngeal level, lift the handle forwards and upwards. Slide the tip of the blade into the recess between the epiglottis and the base of the tongue
6. Maintain the backwards tilt of the head by pressing on the occiput with your other hand and against the tip of the blade to get the best view of the glottic opening. Cricoid pressure will generally improve the view and should be used in all patients in the field
7. Pass the tracheal tube from the right-hand side of the mouth through the glottic opening, rotating it 90° counter-clockwise if necessary, to ease entry between the vocal cords
8. If a full view of the glottis is not possible a bougie may be passed under direct vision through the cords and the tube introduced over the bougie into the trachea. The bougie is then withdrawn. Alternatively, a malleable stylet may be placed inside the lumen of the tube and bent to a curve suitable for introduction of the tube through the glottis
9. Once the tube has passed between the vocal cords it should be advanced so that the cuff lies below the larynx
10. The cuff should be inflated with air (or sterile water if the patient is to be transported at altitude or in a decompression chamber). Sufficient air should be introduced to eliminate any leak at the peak of positive pressure ventilation. Cuff inflation volumes requiring more than 15 mL should lead to a suspicion that the tube is misplaced in the oesophagus or that the cuff itself has developed a leak
11. Check that the tube is in the trachea by observing bilateral chest movement and listening for air entry over both upper lobes. Unilateral chest movement (generally on the right) may indicate that the tube has gone down too far and has entered the main bronchus. A check should also be made that air entry is not heard in the epigastric area. However end tidal CO 2 monitoring is the gold standard
12. Secure the tube in place with a tie or tape. Remove cricoid pressure.
The entire process of intubation should be accomplished in 30 seconds or less. If the attempt is taking longer, then it should be temporarily abandoned and the patient ventilated with oxygen via a face mask for 1–2 minutes before trying again. Note that ventilation via a mask between intubation attempts is pointless if the airway remains obstructed. No more than two attempts should be made before moving to other measures.
Complications of endotracheal intubation
• Trauma to lips, teeth, tongue and structures in the pharynx and larynx (a common problem is using the teeth as a fulcrum, causing damage to crowns particularly)
• Oesophageal intubation likely to guarantee patient death
• Intubation of a single bronchus will lead to hypoxia and collapse of the opposite lung
• Aspiration of foreign material such as stomach contents or blood during the intubation attempt
• Kinking of the tracheal tube
• Overinflation of the cuff leading to pressure damage of the tracheal mucous membrane or ballooning of the cuff over the lumen of the tube
• Exacerbation of cervical spine injury
• Beginning positive pressure ventilation may convert an open pneumothorax to a tension pneumothorax in the trauma patient.
Aids to orotracheal intubation
The intubating laryngeal mask
The intubating laryngeal mask (ILM) is a variant of the conventional laryngeal mask airway which is specifically designed to facilitate blind tracheal intubation. The midline position of the bevel of this tube is designed to increase the chances of successful blind intubation by passing a conventional endotracheal tube down the lumen of the ILM. A handle is fitted at the proximal end to introduce the device and manipulate it to the correct position.
• Size 3 (child age 10–14)
• Size 4 (adult female or small male)
• Size 5 (normal to large adult male).
The device is introduced in the head and neck neutral position, which is of value in patients with suspected cervical spine injury.
Indications
The device should be used, by trained personnel, in unconscious patients with suspected cervical spine injury when an airway is required. It may also be used in patients with known or anticipated difficult intubation or if access to above the patient’s head is difficult or impossible.
Technique
1. Test the cuff for leaks and lubricate the back and sides, but not the aperture, of the laryngeal mask airway (LMA) at the distal end
2. Test the tracheal tube cuff for leaks
3. Lubricate the tracheal tube and slide it in and out of the ILM until it moves easily
4. Deflate the cuff of the ILM completely
5. With the head and neck in the neutral position, grasp the handle of the ILM and position it over the patient’s lower neck and upper chest
6. Introduce the top of the mask behind the upper incisors and, using a rotating movement, roll the mask along the surface of the palate and down into the hypopharynx
7. Inflate the cuff of the ILM (20 mL for size 3; 30 mL for size 4; and 35–40 mL for size 5)
8. Connect a ventilating device to the ILM and check for chest movement and leaks around the cuffs
9. Make final adjustments to the position with the handle to achieve inflation with least resistance. Usually a slight elevation of the mask will achieve the best position
10. Holding the handle firmly in this position, introduce the tracheal tube into the ILM and attempt to pass it through into the trachea. Passage without resistance will occur in the majority of cases
11. If resistance occurs, partially remove the ILM by rotation of the handle and then reintroduce it. This may dislodge a down-folded epiglottis
12. When it is thought that the tracheal tube is in position, inflate the cuff and check for bilateral lung inflation and the absence of gastric inflation
13. The ILM can now be removed. Deflate the cuff of the ILM
14. Remove the connector from the tracheal tube and, using a pusher, hold the tracheal tube in place while removing the ILM with a rotation action
15. Once removal of the ILM is nearly complete, grasp the tracheal tube in the mouth to prevent its dislocation and complete removal of the ILM, ensuring the tracheal tube pilot balloon passes easily through the ILM
16. Replace the tracheal tube connector and check again for correct tracheal tube placement.
The lighted stylet
Another intubation aid uses a malleable lighted stylet passed through the lumen of the tracheal tube so that the light at the end does not quite emerge from the distal end of the tube. Bent to a ‘J’ shape, the tube is introduced directly through the glottis into the trachea. Correct positioning just above the glottic opening is confirmed by maximal transillumination in the midline. Once the tube is correctly placed, the lighted stylet should be unclipped from the proximal end and withdrawn from the tube.
Alternatives to tracheal intubation
The laryngeal mask airway
The LMA consists of a wide-bore tube with a standard 15 mm connector at the proximal end. At the distal end is an elliptical cuff designed to seal the hypopharynx around the laryngeal opening.
Indications
The LMA is indicated when an airway is required in an unconscious patient and tracheal intubation is precluded by lack of available expertise or equipment or has proved difficult or impossible.
Technique
1. Test the cuff inflation for leaks and then lubricate the back and sides, but not the aperture, of the cuff and the distal part of the tube
2. Deflate the cuff completely
3. The patient should be supine with the head and neck in the clear airway position
4. The mouth should be opened by an assistant depressing the chin
5. The tube is held like a pen in the gloved hand and introduced into the mouth with the aperture facing the tongue. As the LMA is advanced it should be applied to the roof of the palate
6. Once the hand cannot go further inside the mouth, it should be moved to the proximal end of the tube and the mask pressed into position until resistance is felt as it locates in the hypopharynx. The coloured line on the tube should be aligned with the nasal septum
7. The cuff is inflated with the correct amount of air for the size (Table 7.1). As the cuff is inflated, the tube rises out of the mouth by approximately 1 cm
| Patient | Weight (kg) | Size | Cuff volume (mL) |
|---|---|---|---|
| Neonate/infant | <6.5 | 1 | 2–4 |
| Infant/child | 6.5–15 | 2 | 10 |
| Child | 15–30 | 2.5 | 15 |
| Small adult/child | 30–50 | 3 | 20 |
| Adult | 50–75 | 4 | 30 |
| Large adult | >75 | 5 | 40 |
8. Confirm that a clear airway exists by listening for spontaneous breathing or check for chest movement and breath sounds during inflation with a bag attached to the tube
9. Insert the bite block or oropharyngeal airway alongside the tube and secure it in place with a tie or tape.
Normally the operator will be positioned at the head of the patient to introduce the tube, but if access to this position is impossible the operator may stand or kneel in front of the patient and introduce the tube from below.
Detection of correct tube placement
An undetected misplaced tracheal tube is the most serious complication of airway management. A protocol to check correct placement should follow each intubation attempt.
If there is any doubt about the correct placement of a tracheal tube – remove it.
Clinical methods
• Visualising the tube passing between the vocal cords during the intubation attempt
• Palpation of the tube as it passes through the larynx
• During positive pressure inflation applied to the tube – Note:
– Absence of leak around the inflated cuff
– Bilateral chest expansion
– Breath sounds in both axillae
– Absence of sounds in the epigastric area.
Detection of carbon dioxide emerging from the tube generally indicates that it is in the trachea:
• Simple, inexpensive and reliable colorimetric devices such as Easy Cap® can be used
• Easy Cap® will turn from purple to yellow with six breaths/ventilations if CO 2 is passing through it
• Carbon dioxide can emerge from the oesophagus if the patient has recently had a carbonated drink
• Miniaturised electronic devices are also available which provide a capnograph trace and digital readings
• End-tidal CO 2 monitoring represents the gold standard for confirming ET tube placement
• Effective BLS may produce measurable carbon dioxide levels in patients in cardiac arrest.
Airway management in suspected cervical spine injury
Special care must be taken during management of the airway in patients with suspected cervical spine injury. However, securing the airway remains the higher priority.
Flexion and rotation of the head and neck are the most dangerous movements.
Oral intubation using direct laryngoscopy can be safely accomplished by a skilled operator in the vast majority of cases.
Airway management in patients with pharyngeal or laryngeal oedema
Oedema in the pharyngeal or laryngeal region can be related to thermal injury, anaphylaxis or acute infection such as epiglottitis.
In the prehospital setting, the airway should be managed by basic positional methods and a high inspired oxygen concentration, with rapid transfer to a hospital.
Life-threatening airway obstruction should be treated by needle cricothyroidotomy and jet ventilation or surgical cricothyroidotomy.
Patients with inhalational thermal injury should be intubated early before serious oedema develops, however, there is usually time for this to be achieved following arrival in the hospital.
The surgical airway
The surgical airway is indicated in patients with life-threatening airway obstruction where basic positional methods and endotracheal intubation (or alternatives) have failed. Access to the trachea should be made through the cricothyroid membrane. In the first instance, the recommended method is needle cricothyroidotomy, however ventilation provided by this method is marginal and sufficient only to buy a few minutes’ time until an alternative is available.
Needle cricothyroidotomy
1. A 14-gauge intravenous cannula directed slightly towards the feet (caudally) is introduced through the cricothyroid membrane, while aspirating continually through an attached 20 mL syringe until a free flow of air is obtained
2. The needle is withdrawn, leaving the cannula in situ
3. The cannula is secured, the safest way is to hold it
4. A 14-gauge cannula is of insufficient diameter to allow any significant spontaneous ventilation to occur. Positive pressure ventilation can be provided using a self-inflating bag attached to a 3 mm tracheal tube connector which will fit a Luer intravenous connection
5. Adequate insufflation can be provided using a high-pressure jet injector system. The cannula is connected by non-compliant tubing to an oxygen cylinder fitted with a regulator, which will produce a pressure in the region of 400 kPa. This is the pressure produced by an oxygen cylinder before a flow meter is attached and requires a special fitting. This system can not be relied upon for more than 20 minutes due to build up of carbon dioxide
6. Inflation is produced by a finger intermittently occluding a hole in the tubing or by a specially designed system with a manually operated trigger which produces inflation when depressed. Alternatively, a ‘Y’ connector may be used to connect the tubing to the cannula, with the stem of the ‘Y’ towards the patient and one of the top ends attached via the tubing to the oxygen supply. The open branch can be intermittently occluded to produce insufflation
7. Time must be left for lung deflation (1 second inflation: 4 seconds deflation). For the technique to be safe there must be a clear route through the larynx and mouth for the expired gases, otherwise lung barotrauma will occur.
Surgical cricothyroidotomy
Surgical cricothyroidotomy may occasionally be performed by a medical practitioner before the patient reaches hospital.
1. A 2–3 cm transverse stab incision is made through the cricothyroid membrane
2. The membrane is widened using forceps or by using a tracheal hook
3. The forceps may be left in the wound to maintain the track
4. A 6–7 mm lubricated tracheal tube (tracheal/tracheotomy) is inserted through the incision and directed towards the lower trachea
5. The cuff is inflated and the tube is secured with a tape and connected to the ventilating apparatus.
Blind stab techniques
Devices such as the Portex Mini-Trach® II or expandable trochar systems such as Nu-Trach® use a combination of both techniques allowing wider lumen devices to be inserted giving better ventilation. Even with these devices ventilation is unlikely to be successful for more than 1 hour.
Ventilators
• Oxygen-powered ventilators have been designed to take over from the self-inflating bag
• They are driven from a high-pressure (400 kPa) oxygen source, so are valuable in contaminated atmospheres
• Ventilators may be connected to a tracheal tube or laryngeal mask
• The inspiratory flow rates should be restricted to a maximum of 40 L/min and should incorporate a blow-off valve with automatic warning if the inflation pressure exceeds 60 cmH 2O in adults (this level can be altered in some models)
• Intubated patients with head injury will receive better ventilation from an automatic ventilator than can be achieved even by practised personnel with a hand bag-valve system.
Ventilator settings
Inspiratory flow rates (if available)
Generally 1.5–2 seconds (longer if there is an increased resistance to inspiration).
Expiratory flow rates (if available)
Generally, the expiratory time should be twice as long as the inspiratory time. It may need to be longer in patients with increased expiratory resistance such as asthma.
Ventilation rate
Generally, rates should be similar to natural breathing, i.e. 20 breaths/minute in an infant; 15 in a child and 12 in an adult. Shocked patients may require higher rates and rates may be adjusted in response to end-tidal capnography.
Relief/alarm pressure
This should be set to = 60 cmH 2O. Start at a much lower setting such as 30 cmH 2O so that problems with ventilation are identified immediately.
Tidal volumes
Normally 7–8 mL/kg body weight (approximately 500 mL in a 70 kg patient).
Epiglottitis
Epiglottitis is a bacterial infection of the epiglottis, seen most often in children. It leads to marked swelling of the epiglottis, with a typical ‘cherry red’ appearance.
The patient will often be grey, distressed, drooling at the mouth and leaning forward. There is severe continuous stridor.
Examination of the mouth and pharynx must not be attempted in suspected epiglottitis.
Complete airway obstruction can develop within minutes. Any procedure that can cause crying or gagging, including simple examination of the throat, can precipitate laryngeal spasm and airway obstruction.
If the condition is suspected, the patient should be calmed, given high-concentration oxygen, sat forward and transported quickly to hospital. A paediatric team and senior anaesthetist should be requested to stand by. If airway obstruction occurs before arrival at hospital, intubation or needle cricothyroidotomy may be required.
For further information, see Ch. 7 in Emergency Care: A Textbook for Paramedics.
