Chapter 6. Basic management of the airway and ventilation
• Airway management is the cornerstone of emergency care
• Airway obstruction producing hypoxia will lead to circulatory arrest and irreversible central nervous system damage within 3–4 minutes
• Often the application of basic skills is all that is required.
Simple airway management
Upper airway patency can generally be re-established by correctly positioning the head and by use of the head tilt, the chin lift or if the cervical spine may be damaged, the jaw thrust. Simple adjuncts may further improve the situation.
Foreign body airway obstruction
• The algorithm for the management of choking in the adult is on p. 37. In patients who are (or become) unconscious due to airway destruction, tilt the head back and remove any visible foreign object. Perform a chin lift and check for breathing: if this is absent, begin CPR with chest compressions and continue until ALS equipment (laryngoscope, Magill’s forceps, and cricothyroidotomy kit) is available. Ideally the suction end should be manipulated under direct vision using a laryngoscope
• A flexible catheter can be used to clear the lumen of an airway adjunct, such as a nasopharyngeal airway, tracheal tube or laryngeal mask.
Liquid in the airway
• The best way of removing liquid from the oropharynx is by direct suction using a wide-bore or Yankauer suction catheter
• Suction should only be performed under direct vision. ‘Blind’ suctioning may lead to airway injuries or oedema
• Adult suction devices must not be used on neonates. Specialist suction devices (soft tipped, dual chamber) should be used.
Respiratory control
Central control
The brainstem controls respiration. Sleep, sedatives, alcohol, many analgesic drugs and injury to the respiratory centres result in hypoventilation. This reduction in ventilation may result from a fall in respiratory rate or tidal volume or both. Ventilation is stimulated by a rise in arterial carbon dioxide or a fall in arterial oxygen and is also stimulated by a fall in blood pH which may occur, e.g. in a hyperglycaemic diabetic coma.
Chronic obstructive pulmonary disease
Patients with chronic obstructive pulmonary disease tend to have high levels of carbon dioxide in their blood. Some of these patients will have adapted to these high levels and their stimulus to breathing will be provided only by low oxygen levels rather than by increases in carbon dioxide.
Thus, if high inspired concentrations of oxygen are given to these patients they may lose their respiratory drive leading to carbon dioxide retention and decreasing consciousness. It is important to remember that a high carbon dioxide content kills slowly, but a low oxygen content kills quickly. Thus the need to provide immediate adequate oxygenation takes precedence. Hence cyanotic patients should always be treated with high oxygen concentrations.
Peripheral control
• Adequate ventilation also requires an intact chest wall and intrapulmonary mechanics
• Peripheral causes of impaired ventilation include obstruction of the upper airway, most commonly due to the tongue
• The phrenic nerves originate from cervical spinal roots C3–5; therefore diaphragmatic function will be maintained with cord lesions below this level.
Airway and ventilation assessment
• Establish the circumstances of the immediate event and any pre-existing conditions of relevance, such as asthma
• Airway and ventilation problems may be delayed in onset. The effects of smoke or chemical inhalation may not develop until hours after the event
• Physical assessment of the airway and ventilation involves looking, listening and feeling for chest movement and air flow
• Check the respiratory rate, the presence of cyanosis and/or agitation and the use of the accessory muscles of respiration and abnormal movement of the abdominal muscles
• Noisy breathing during inspiration generally indicates obstruction above the level of the larynx, whereas an expiratory wheeze usually indicates that the problem lies at or below the larynx
• Auscultation will give added information about air flow into the lungs.
Simple airway adjuncts
The use of these devices makes the task of keeping an airway open considerably easier.
Oropharyngeal airway
• The oropharyngeal airway stops the tongue falling backwards and may reduce the need for a jaw thrust
• The airway is introduced through the mouth in an inverted position and rotated through 180° as it passes the edge of the palate
• The distal end locates in the oropharynx
• The airway may also be introduced directly using a tongue spatula or laryngoscope. This method is recommended in infants and small children
• The oropharyngeal airway comes in a range of six sizes suitable for an infant (size 000) to a large adult (size 4)
• The correct size for any individual equates to the distance from the mid-point of the incisors to the angle of the mandible
• The airway must be removed if it induces vomiting or coughing in the patient.
Nasopharyngeal airway
• The nasopharyngeal airway consists of a bevelled tube with a flange at the proximal end
• The airway is introduced, well lubricated, into either nostril (generally the right is attempted first because of the direction of the distal bevel)
• It should be directed backwards (not upwards) along the roof of the palate so that the tip lies in the hypopharynx, just above the larynx
• If resistance to the passage of the airway is encountered, it should be withdrawn and an attempt made through the other nostril
• Suction should be on hand to control any bleeding
• The correct size of airway equates approximately with the diameter of the patient’s nostril – an airway of 6.0 or 6.5 mm internal diameter will be suitable for the majority of adults
• The nasopharyngeal airway is particularly valuable in patients with maxillofacial injuries or a clenched jaw. Once in place, it is better tolerated than an oropharyngeal airway
• If a basal skull fracture is suspected then extra care should be taken when inserting the device.
Simple ventilation aids
The simple foil
• Foil devices provide a barrier between patient and rescuer during expired air ventilation
• A plastic film with a central orifice and a textile filter or one-way valve which is aligned with the patient’s mouth is applied to the oronasal region
• Expired air ventilation is applied in the usual way with the patient’s nostrils occluded with the fingers of one hand, while the other hand applies chin lift and seals the foil to the face.
The face mask device
• A moulded face mask, made from transparent material, is fitted with an inflation port incorporating a one-way valve which directs the patient’s exhaled air away from the rescuer and traps macroscopic particles
• Some models incorporate an additional port for supplemental oxygen. The oxygen flow rate should be set at the maximum available
• The mask is applied over the mouth and nose with both hands, applying jaw thrust and head tilt to draw the face into the mask and sealed to the face with the index fingers and thumb of each hand.
The self-inflating bag valve device
• Use of a self-inflating bag with valve allows the rescuer to ventilate the patient by hand instead of using expired air
• Inflation of the lungs is provided through a valve which directs the air/oxygen to the patient and vents exhaled air to the atmosphere
• Oxygen enrichment (only achieving an inspired concentration of up to 50% – FiO2 0.5) can be provided through a port adjacent to the unidirectional air inlet valve
• Much better inspired concentrations can be achieved (FiO2 0.9, an inspired oxygen concentration of 90%) when an oxygen reservoir bag is attached to the air inlet valve and the flow rate adjusted to 10–15 L/min
• The aim is to adjust the flow rate to ensure that the reservoir bag remains at least partially inflated at all times. If this is achievable with a flow rate of 10 L/min then oxygen can be conserved
• The self-inflating bag may be used with a face mask or may be attached to a tracheal tube or laryngeal mask airway
• A two-person technique is advocated, one person using two hands to hold the mask with the airway aligned and the other inflating the patient’s lungs by squeezing the bag
• A modified patient valve can permit positive end-expiratory pressure (PEEP) to be applied when the bag is used with a tracheal tube
• The use of PEEP may be particularly valuable in patients with pulmonary oedema by reversing the leakage of fluid into the alveoli
• A filter can be fitted on the intake valve to permit operation in contaminated atmospheres.
Ventilation volumes
Inflation volumes of 10 mL/kg (600–900 mL in an adult) should be used if ventilating on air. If supplemental oxygen is available, the volume of each inflation should be limited to 400–600 mL (7 mL/kg). Overinflation will lead to gastric inflation and increased risk of regurgitation, as well as the possibility of barotrauma (lung damage).
Cricoid pressure
The unconscious patient with an insecure airway is continually at risk of regurgitation of gastric contents and pulmonary aspiration. True security of the airway can only be provided by placing a cuffed tube within the trachea but cricoid pressure (Sellick’s manoeuvre) during artificial ventilation in the patient with the unsecured airway substantially reduces the risk of gastric regurgitation. The technique should always be used when endotracheal intubation is to be attempted. Cricoid pressure is applied to either side of the cricoid cartilage using the thumb and forefinger of one hand at a pressure of 30 Newtons (which feels equivalent to the weight of three 1 kg bags of sugar).
Oxygen therapy in the spontaneously breathing patient
Patients with airway or ventilatory compromise, major trauma or chest disease should be given oxygen. High inspired concentrations can only be achieved with an oxygen mask that incorporates a reservoir bag. The oxygen flow rate should be set at 10–15 L/min, to ensure the reservoir bag remains inflated.
If a pulse-oximeter is available then patient saturations should be kept above 94%. However, in patients with COPD, oxygen should be administered at a concentration of 24–28% using a Venturi mask. Lower saturations of 88–92% are acceptable.
Some COPD patients may be on long-term home oxygen, which means high flow oxygen can be used safely as they will not have developed a hypoxic ventilation drive.
For further information, see Ch. 6 in Emergency Care: A Textbook for Paramedics.
