Airway and ventilatory management

Inadequate delivery of oxygen to vital sturctures is the quickest killer of the injured patient. Prevention of hypoxaemia requires a protected, unobstructed airway and adequate ventilation. Supplemental oxygen MUST be given to all trauma patients.

Airway

Problem recognition.

• Compromise may be sudden and complete, insidious and partial or progressive and/or recurrent.
• Assessment and reassessment is important.
• Patients with altered levels of consciousness are at particular risk of airway compromise, needs definitive airway.
• ETT intubation is intended to provide an airway, deliver supplemental oxygen, support ventilation and prevent aspiration.
• Vomiting should be anticipated. The presence of gastric contents in the oropharynx confirms a significant risk of aspiration. IMMEDIATE SUCTIONING AND ROTATION OF ENTIRE PATIENT TO LATERAL POSITION MUST BE CARRIED OUT.

1. Maxillofacial trauma:
   • trauma to face demands aggressive airway management.
   • Trauma to midface may produce #/disloc with compromise to the nasopharynx and oropharynx.
   • Facial # may be associated with haemorrhage, increased secretions and dislodged teeth.
   • Mandibular # may cause loss of normal support and airway obstruction may occur if patient is in supine position.
   • Patients who refuse to lie down may be indicating difficulty in maintaining their airway, or handling secretions.
2. Neck trauma:
   • Penetrating injury to neck may result in significant haemorrhage which may result in displacement and obstruction of the airway. Operative control may be required if no definitive airway can be established.
   • Blunt or penetrating injury may cause disruption of the larynx or trachea resulting in airway obstruction or severe bleeding into the tracheobronchial tree. A definitive airway is urgently required.
   • Injuries here may cause partial obstruction, in which the patient may initially be able to maintain airway patency and ventilation. If airway compromise suspected a definitive airway must be established.
   • To prevent extending an existing injury, an endotracheal tube must be inserted cautiously.
3. Laryngeal trauma:
   • Indicated by triad of hoarseness, subcutaneous emphysema and a palpable #.
   • If in respiratory distress an attempt at intubation is warranted, but if unsuccessful an emergency tracheostomy is indicated, followed by operative repair. Surgical cricothroidotomy is a fall back option.
   • Penetrating trauma to larynx or trachea is overt and requires immediate attention. Often associated with oesophageal, carotid artery or jugular vein trauma, as well as extensive soft tissue trauma due to blast effect.
   • Noisy breathing indicates partial airway obstruction that suddenly may become complete. Labored respiratory effort may be only clue in patient with depressed level of consciousness.
   • CT may help to identify this injury.
   • A positive verbal response from trauma patient indicates the airway is patent, ventilation is intact and brain perfusion is adequate. Failure to respond or inappropriate response suggests an altered level of consciousness or airway/ventilatory compromise.

Objective signs - airway obstruction:

1. look: agitation suggests hypoxia, obtunded patient suggests hypercarbia. Cyanosis indicates hypoxaemia (inspect nail beds). Check for retractions and use of accessory muscles.
2. Listen: noisy breathing is obstructed breathing. Stridor is associated with partial obstruction of pharynx or larynx. Hoarseness implies functional, laryngeal obstruction. THE ABUSIVE PATIENT SHOULD NOT BE PRESUMED TO BE INTOXICATED AS MAY BE JUST HYPOXIC.
3. Feel: determine that trachea is in the midline.

Ventilation

1. Problem recognition:
   • ventilation may be compromised by airway obstruction but also by altered ventilatory mechanics or CNS depression. If breathing is not improved by clearing the airway other aetiologies should be sought.
   • Direct trauma to the chest leads to rapid, shallow ventilation and hypoxaemia. Those with pre-existing lung disease and the elderly are particularly prone.
   • Intracranial injury may cause abnormal patterns of breathing and compromise adequacy of ventilation.
   • C-spine cord injury may result in diaphragmatic breathing and interfere with ability to cope with increased oxygen demands. Complete cervical cord transection which spares the phrenic nerves (C3,4) results in abdominal breathing and paralysis of the intercostal muscles.
2. Objective signs - inadequate ventilation.
   1. look: symmetrical rise and fall of the chest and adequate chest wall excursion. Asymmetry suggests splinting or a flail chest. Any labored breathing should be regarded as an imminent threat to patient’s oxygenation.
   2. Listen: search for air movement on both sides of the chest. Beware of rapid respiratory rate which may indicate air hunger.
   3. Use a pulse oximeter: gives advice on oxygen saturation and peripheral perfusion but not assure adequate ventilation.
3. Management
   • Pulse oximetry is essential.
   • If problems found OR SUSPECTED start measures to improve oxygenation and reduce risk of ventilatory compromise. These include airway maintenance techniques, definitive airway measures and methods to provide supplemental ventilation.
   • PROTECTION FO THE C-SPINE MUST BE PRESENT IN ALL PATIENTS AS ALL ABOVE MAY REQUIRE NECK MOVEMENTS.
   • Patients wearing a helmet who require an airway should have head and neck held in neutral position while the helmet is removed. This is a 2 person procedure. One person provides in line manual immobilisation from below while the 2^nd expands the helmet laterally and removes it from above. In line manual immobilisation is reestablished from above and patients head and neck are secured during airway management. Removal of helmet with cast cutter while stabilising head and neck minimises C-spine motion.
   • Supplemental oxygen should be administered before and immediately after airway management measures are instituted.
   • A rigid suction device is essential and should be readily available.
   1. Airway maintenance techniques.
      Tongue may fall backwards and obstruct the hypopharynx if patient has decreased level of consciousness. Can be readily corrected by the chin-lift or jay thrust maneuver and airway maintained by oropharyngeal or nasopharyngeal airway.
      • chin lift: fingers of 1 hand are placed under the mandible, which is gently lifted upward to bring the chin anterior, the thumb of same hand lightly depresses lower lip to open the mouth. Should not hyperextend the neck.
      • Jaw thrust: Grasp angles of jaw, one hand on each side and displacing the mandible forward.
      • Oropharyngeal airway: Inserted into mouth behind tongue, preferably by depressing tongue with tongue depressor. Alternatively insert upside down until soft palate encountered, then rotate 180 degrees, SHOULD NOT BE USED FOR CHILDREN.
        The airway must not push the tongue backwards.
        Must not be used in conscious patient due risk gagging and aspiration.
      • Nasopharyngeal airway: Inserted in 1 nostril and passed gently into the oropharynx. Should be well lubricated and inserted into an unobstructed nostril. If obstruction is encountered stop and try other nostril.
        Preferred in conscious patient as less likely to induce vomiting.
        If tip visible in posterior nasopharynx it may provide safe passage of NGT in facial # patient.
   2. The Definitive Airway
      
      • requires tube present in the trachea with the cuff inflated, the tube connected to some sort of oxygen enriched assisted ventilation, and the airway secured in place with tape.
      • 3 varieties: orotracheal tube, nasotracheal tube and surgical airway (cricothroidotomy, tracheostomy).
      • Factors influencing decision to provide a definitive airway:
        • Apnoea.
        • Inability to maintain a patent airway by other means.
        • The need to protect the lower airway from aspiration.
        • Impending or potential compromise of the airway.
        • Presence of closed head injury requiring assisted ventilation (GCS < or = 8).
        • Inability to maintain adequate oxygenation by face mask oxygen supplementation.
        • Continued assisted ventilation is aided by supplemental sedation, analgesics, or muscle relaxants.
        • Orotracheal and nasotracheal intubation are the methods used most frequently.

      Indications for a definitive airway

      NEED FOR AIRWAY PROTECTION	NEED FOR VENTILATION
      Unconscious	Apnoea: Neuromuscular paralysis. Unconscious.
      Severe maxillofacial fractures	Inadequate respiratory effort: Tachypnoea. Hypoxia. Hypercarbia. Cyanosis.
      Risk for aspiration	Severe closed head injury with need for hyperventilation.
      Risk for obstruction: Neck haematoma. Laryngeal, tracheal injury. Stridor.

   3. Definitive airway - endotracheal intubation:
      
      • Important to establish the presence or absence of a C-spine #, but establishment of definitive airway shouldn’t be delayed when one is indicated by a trip to the x-ray department.  Remember a normal lateral c-spine film doesn’t exclude an injury.
      • GCS of 8 or below requires prompt intubation.
      • Oesophageal occlusion by cricoid pressure is useful in preventing aspiration and providing better visualisation.
      • Two person technique with in line immobilisation should be used.
      • Following insertion cuff should be inflated and assisted ventilation started.
      • Proper placement is suggested but not confirmed by hearing equal breath sounds bilaterally and detecting no borborygmi in the epigastrium.
      • The presence of gurgling noises in the epigastrium suggests oesophageal placement.
      • A carbon dioxide detector (colorimetric CO2 monitoring device) is indicated to help with correct positioning as the presence of CO2 in expired air is an indication that the tube is somewhere in the airway, but not correct position.
      • Proper position of the tube is best determined by CXR.
      • Once proper position is determined it should be secured in place.
      • If patient is moved the position of the tube should be rechecked by auscultation and assessment of exhaled CO2.
      
      

      Nasotracheal intubation:

      • contraindicated in apnoeic patient.
      • Relative contraindications are facial #, frontal sinus #, basilar skull # and cribriform plate #.  These are identified by presence of nasal #, raccoon eyes, battle sign and possible CSF leaks.
      • Precautions regarding c-spine immobilisation should be followed as with orotracheal intubation.
      • Patients who arrive at hospital with an endotracheal tube in place must have proper position of tube confirmed.  A CXR, CO2 monitoring and physical examination are essential to assess the position of the tube.
      • Patients difficult to intubate may require the use of a flexible, fiberoptic endoscope.
      • Technique for rapid-sequence intubation is as follows:
      • Be prepared to perform surgical airway.
      • Preoxygenate the patient with 100% oxygen.
      • Pressure to cricoid cartilage.
      • 1-2 mg/kg succinylcholine iv.  NOT IN PATIENT WITH CHRONIC RENAL FAILURE, CHRONIC PARALYSIS, CHRONIC NEUROMUSCULAR DISEASE DUE POTENTIAL FOR SEVERE HYPERKALAEMIA. Has rapid onset of 1 min and lasts for 5 minutes or less.  If fail patient must be ventilated with bag and mask till paralysis resolves.
      • Intubate post relaxation of patient.
      • Inflate cuff and confirm tube placement.
      • Release cricoid pressure.
      • Ventilate patient.
      • Induction agents, such as thiopental and sedatives, are dangerous to use in hypovolaemic trauma patient.
      • Small doses of medazolam or diazepam are appropriate to reduce anxiety in paralysed patient.  Flumazenil must be available to reverse effects after administration.
      • A DEFINITIVE AIRWAY IS A CUFFED TUBE IN THE TRACHEA, not a mask.
   4. Definitive airway - surgical airway
      Inability to intubate the trachea is a clear indication for creating a surgical airway.
      Surgical cricothyroidotomy is preferable to a tracheostomy for most patients as requires less time, causes less bleeding and is less complex.
      
      Jet insufflation of the airway (see skills – cricothyroidotomy):
      
      
      • insertion of a needle through the cricothyroid membrane to provide oxygen on a short term basis.  Obviously below level of obstruction.
      • Jet insufflation can provide temporary supplemental oxygenation by large bore cannula (12-14, 16-18 in children).
      • Cannula then connected to a Y-connector or a side hole cut in the tubing attached between oxygen source and cannula.
      • Insufflate 4s off, 1s on.
      • Only for 30-45 min and only in patients with good lung function and no chest injury.
      • Is slow accumulation of CO2 due limited exhalation, so technique poor for head injury patients.
      • To avoid pulmonary rupture with tension pneumothorax low flow rates of 5-7 l/min should be used when persistent glottic obstruction is present.
      
      Surgical cricothyroidotomy (see skills cricothyroidotomy):
      
      
      • Make skin incision through cricothyroid membrane.
      • A curved haemostat may be inserted to dilate the opening.
      • Insert small (5-7mm) ETT or tracheostomy tube.  If use ETT cervical collar can be applied.
      • Care must be taken not to damage cricoid cartilage which is only circumferential support to the upper trachea.  NOT RECOMMENDED FOR CHILDREN UNDER 12 YRS OF AGE.
      • Percutaneous tracheostomy is not a safe procedure in emergency situation as neck must be hyperextended.
   5. Airway decision scheme
      
      • the airway decision scheme applies only to the patient who is in acute respiratory distress (or apnoeic) and in need of immediate airway AND in whom c-spine injury is suspected.
      • 1st priority is airway by jaw thrust and oro/nasopharyngeal airway.
      • In patient still showing some respiratory effort a nasotracheal tube may be passed if skilled in this technique, otherwise orotracheal tube while 2nd person provides in line immobilisation.  If neither can be performed and ventilation in jeopardy a cricothyroidotomy should be performed.
      • In apnoeic patient in line immobilisation should be performed by 1 and oropharyngeal intubation by another, if can’t be achieved – cricothyroidotomy.
      • Oxygenation and ventilation must be maintained before, during and immediately after insertion of whatever definitive airway done.
   6. Oxygenation
      
      • Oxygenated inspired air best provided by tight fitting oxygen reservoir face mask with flow rate of 10-12 litres/min.
      • Pulse oximetry should be used continuously.  Measures oxygen saturation not partial pressure, this depends on the oxygen dissociation curve.  However a reading over 95% is strongly corroborating evidence of adequate, peripheral arterial oxygenation.  Use limited in strongly vasoconstricted patient and in patient with carbon monoxide poisoning.  Profound anaemia and hypothermia decrease the reliability of the technique.

      • Approx O2 sats for PaO2

        PaO2 (mmHg)	Approximate O2 saturation
        90	100 %
        60	90%
        30	60%
        27	50%

   7. Ventilation
      
      • Effective ventilation may be achieved by bag-valve-face mask techniques, one person techniques are less effective than 2 person techniques.
      • Patient must be ventilated episodically during long attempts to intubate, doctor should take a deep breath at start and when he needs to breath so does patient.
      • Positive pressure breathing techniques should be used post intubation.  A volume or pressure – regulated respirator can be used, depending on availability of the equipment.
      • Be alert to the complications secondary to changes in intrathoracic pressure, which can convert pneumothorax to tension pneumothorax.  Or even create pneumothorax due barotrauma.
   8. Pitfalls
      
      • Inability to intubate patient results in hypoxia and patient deterioration, remember to buy time with needle cricothyroidotomy.
      • Trauma patients may vomit and aspirate, therefor secure, patent airway must be ensured in all patients and suction equipment should be at hand.
      • Gastric distension may occur during mask ventilation and may cause patient to vomit.  Stomach may distend against vena cava, resulting in hypotension and bradycardia.
      • Equipment failure may occur at any time.