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Level 2 of 6Must-remember

Airway management, oxygen therapy and ventilation

Assess, manage and stay safe — enough on its own

The card — assess, manage, caution

Assessment— look, ask, measure

  • Listen before you touch — the noise names the level of obstruction: snoring means the tongue against the pharynx in an obtunded patient; gurgling means fluid requiring suction; stridor means narrowing at or above the larynx and warns of an airway that may close without warning; wheeze means narrowing below the larynx; and silence with visible respiratory effort means either complete obstruction or a chest so tight that no gas moves.
  • History to ask for: speed of onset, choking or foreign body, allergen exposure, fever and drooling, burns or inhalation injury, trauma to face or neck, opioids or sedatives taken, known COPD, asthma, neuromuscular disease or previous non-invasive ventilation, and whether the patient has ever been intubated before.
  • Conscious level: assume any patient with a reduced conscious level cannot protect the airway until proved otherwise, and remember that a Glasgow Coma Scale of 8 or less mandates a definitive airway whatever the blood gas shows.
  • Signs of respiratory distress to record: use of accessory muscles, intercostal recession, tachypnoea, tachycardia, sweating, pulsus paradoxus (rarely present), inability to speak, unwillingness to lie flat, agitation or diminished conscious level, asynchronous respiration (thoracic and abdominal movement out of time), paradoxical respiration (the compartments moving in opposite directions) and respiratory alternans (breath-to-breath alternation between accessory muscles and diaphragm) — the last three signal impending decompensation.
  • Count the respiratory rate for a full sixty seconds — it is the most sensitive clinical indicator of deterioration; a rate below 8 or above 40 breaths/min demands immediate intervention rather than investigation.
  • Define respiratory failure numerically: PaO₂ below 8 kPa (60 mmHg), or PaCO₂ above 7 kPa (55 mmHg). Type I (hypoxaemic) is a low PaO₂ with a normal or low PaCO₂ — failure of the gas exchanger. Type II (ventilatory) is a low PaO₂ with a high PaCO₂ — failure of the pump, in which more inspired oxygen corrects the hypoxaemia but does nothing for the hypercapnia.Not available at your setup — Arterial blood gas.
  • Read the pH to date the hypercapnia: a low pH with a normal bicarbonate is acute (an emergency); a near-normal pH with a high bicarbonate is chronic; an acidotic pH with an already elevated bicarbonate is acute-on-chronic — the pattern of the decompensating COPD patient and the classic indication for non-invasive ventilation. PaCO₂ above 6 kPa (45 mmHg) with acidosis is evolving type II failure.Not available at your setup — Arterial blood gas.
  • Record the inspired oxygen concentration with every gas — a gas without an FiO₂ cannot be interpreted, and a PaO₂ of 9 kPa on 60% oxygen is far graver than the same value on air. Eject air bubbles at once, since gas in the bubble lowers the PCO₂ and raises the PO₂.Not available at your setup — Arterial blood gas.
  • Signs of hypoxaemia and hypercapnia: hypoxaemia produces restlessness, confusion and eventually depressed consciousness, and central cyanosis requires roughly 50 g/L of desaturated haemoglobin so is insensitive; hypercapnia produces a bounding pulse, warm peripheries, headache, a coarse flapping tremor and drowsiness. Neither set of signs replaces measurement.
  • Identify who needs the lower saturation target of 88–92%: known COPD, previous type II failure or non-invasive ventilation, chest wall disease, obesity hypoventilation, neuromuscular disease, cystic fibrosis and bronchiectasis.
  • Predictors of a difficult airway: obesity, a short thick neck, receding mandible, limited mouth opening or neck movement, high Mallampati class, and pharyngeal soiling.
  • Children compensate efficiently and then fail abruptly — tachypnoea, then recession, grunting and nasal flaring, then exhaustion, bradycardia and arrest. Grunting is expiration against a partly closed glottis, self-administered CPAP, and is a severe sign; the child who goes quiet is not settling; bradycardia in a hypoxic child is a pre-arrest rhythm; and saturation below 92% in air is a red flag.
  • The elderly often lack the expected tachypnoea or distress, and confusion, falls or immobility may be the only manifestation of hypoxaemia.
  • Neuromuscular weakness is the great trap: the lungs are normal, so saturation stays normal until ventilation fails, and bulbar signs such as ptosis and difficulty swallowing saliva precede airway compromise. Serial vital capacity is a better guide than blood gases: ventilate when the vital capacity falls to ≤10 mL/kg, and intubate when the maximal inspiratory force is less negative than −25 cmH₂O or the vital capacity is below 1 L.
  • Acute severe asthma may look deceptively comfortable as the patient tires: a falling respiratory rate, a quietening chest and a rising PaCO₂ indicate exhaustion, not improvement. Grade it — moderate is PEF 40–69% predicted; severe is PEF below 40%, PaO₂ below 60 mmHg, PCO₂ 42 mmHg or above, SaO₂ below 90%; impending arrest is PEF below 25%, paradoxical thoracoabdominal movement, absent wheeze, bradycardia and loss of pulsus paradoxus.
  • Red flags demanding immediate intervention rather than investigation: stridor; a soiled airway; agonal breathing; a silent chest with visible effort; respiratory rate below 8 or above 40 breaths/min; inability to speak a single word; exhaustion with a falling respiratory rate; cyanosis; GCS 8 or less or absent airway reflexes; hypotension with respiratory distress; and, in a child, apnoea, grunting, bradycardia or saturation below 92% in air.

Management— do this, in order

  • Order of priority: a patent airway takes precedence over oxygen, oxygen over ventilation, and ventilation over any drug.
  • Open the airway mechanically first: head tilt and chin lift, or a jaw thrust where cervical spine injury is possible; suction the visible pharynx under direct vision and never pass a catheter blindly beyond the pharynx, which provokes gagging, vomiting and laryngospasm.
  • Add an adjunct: an oropharyngeal (Guedel) airway sized from the incisors to the angle of the jaw — if the patient gags on it or expels it, they are protecting their own airway and it should be removed; a nasopharyngeal airway suits the patient with an intact gag but a noisy airway and is contraindicated where base-of-skull fracture is possible.
  • Position: recovery position for any unconscious, breathing patient; sit the breathless patient upright unless hypotensive or obtunded; in children insert the oropharyngeal airway the right way up under direct vision rather than rotating it, and position infants under one year with the head neutral on a folded towel under the shoulders, since hyperextension closes the infant airway.
  • Bag-valve-mask ventilation with high-flow oxygen and an adjunct maintains oxygenation until an experienced operator arrives; two-person technique is superior — one operator holds the mask with both hands using a jaw thrust while the second squeezes slowly over one second, just until the chest rises, at 10 breaths/min in adults and 12–20 in infants and young children.
  • Oxygen is a drug with a device, a flow rate and a target range: in the critically ill start high and titrate down with 15 L/min via a reservoir (non-rebreathing) mask for arrest, shock, sepsis, major haemorrhage, anaphylaxis and carbon monoxide poisoning. Targets are 94–98% for the great majority of acutely unwell adults and 88–92% for those at risk of hypercapnic respiratory failure; in children 94% or above (92% or above is accepted in acute asthma and bronchiolitis). Reassess five minutes after every change, and obtain a blood gas within 30 minutes in any patient managed in the lower band.Not available at your setup — Arterial blood gas.
  • Know the devices: nasal cannulae 1–4 L/min giving 24–40%; simple face mask 6–10 L/min giving 35–55% and needing at least 5 L/min to avoid rebreathing; Venturi valves at 2, 4, 6, 8, 10 and 15 L/min giving 24, 28, 31, 35, 40 and 60%; reservoir mask 15 L/min giving 60–90%; high-flow nasal oxygen 30–60 L/min giving 21–100% humidified and generating modest CPAP.
  • Stridor is managed differently from all other breathlessness: do not lie the patient flat, do not force a mask onto a frightened patient, and do not inspect the throat with a tongue depressor — laryngoscopy may provoke laryngospasm and complete obstruction, particularly in children, and should be performed only where intubation can follow immediately.
  • Nebulised adrenaline 1:1000 (1 mg/mL) reduces mucosal oedema of any cause — 5 mL (5 mg) in adults, or 0.5 mL/kg (0.5 mg/kg) to a maximum of 5 mL in children, driven by oxygen; the effect wears off within 1–2 hours, so the patient must be observed afterwards.
  • In croup give dexamethasone 0.15 mg/kg orally or intravenously as a single dose, or prednisolone 1 mg/kg orally, or nebulised budesonide 2 mg.
  • Where anaphylaxis is possible give intramuscular adrenaline into the anterolateral thigh — 500 micrograms (0.5 mL of 1:1000) for adults and children over 12 years, 300 micrograms aged 6–12 years, 150 micrograms under 6 years — repeated after 5 minutes if there is no improvement.
  • A life-threatening obstruction that cannot be bypassed with a tracheal tube is relieved by cricothyroidotomy, which is safer, quicker and easier than a formal tracheostomy — hesitation is fatal.Doctor
  • Non-invasive ventilation: CPAP delivers one constant pressure and does not clear carbon dioxide; bi-level (BiPAP) delivers separate inspiratory and expiratory pressures and the difference between them is what moves gas and clears CO₂. For type II failure start IPAP 12–15 cmH₂O and EPAP 4–5 cmH₂O, increasing IPAP by 2–5 cmH₂O every few minutes towards 20–25 cmH₂O; for pulmonary oedema or type I failure start CPAP 5 cmH₂O and increase to 10–12 cmH₂O as tolerated, watching the blood pressure. Entrain oxygen to 88–92% in acidotic COPD and 94–98% otherwise.Doctor / NurseNot available at your setup — Mechanical ventilator.
  • If the blood pressure falls on positive pressure, reduce the pressure and give a 250–500 mL crystalloid bolus (10–20 mL/kg in children) unless the problem is pulmonary oedema. Reassess at 15 and 30 minutes and, decisively, at one hour with a repeat arterial gas; success is a falling respiratory rate, a rising pH, a falling PaCO₂ and a patient who is more comfortable and more alert.Doctor / NurseNot available at your setup — Arterial blood gas.
  • Intubate on clinical assessment, not on waiting for a number: severe distress despite maximal therapy with a respiratory rate above 40 breaths/min, inability to speak or exhaustion; confusion, restlessness, agitation or a decreased conscious level; a rising PaCO₂ above 8 kPa (60 mmHg); extreme hypoxaemia below 8 kPa (60 mmHg) despite oxygen; severe hypercarbia or acidosis despite non-invasive ventilation; markedly impaired mental status, respiratory arrest or haemodynamic instability; GCS 8 or less; and in neuromuscular disease a vital capacity of ≤10 mL/kg, an MIF less negative than −25 cmH₂O, or a VC below 1 L.DoctorNot available at your setup — Endotracheal intubation kit.
  • Prepare properly: tracheal intubation should be performed under anaesthesia only by experienced staff. Pre-oxygenate with 100% oxygen — a tight reservoir mask at 15 L/min for at least three minutes, or eight vital-capacity breaths if time is short, with nasal cannulae at 15 L/min beneath the mask for apnoeic oxygenation. Anticipate hypotension: optimise the circulating volume and, if necessary, start inotropes before intubation is attempted. Have suction, two laryngoscopes, tubes either side of the expected size, a bougie, a self-inflating bag, a supraglottic airway as rescue, capnography and a cricothyroidotomy set; wear personal protective equipment, since intubation is an aerosol-generating procedure; and prefer the orotracheal to the nasotracheal route in urgent situations.DoctorNot available at your setup — Endotracheal intubation kit.
  • Induction and paralysis doses: ketamine 1–2 mg/kg IV (adult and child) preserves blood pressure and bronchodilates; etomidate 0.3 mg/kg; propofol 1–2 mg/kg (children 2–3 mg/kg) halved or quartered in shock, hypovolaemia or old age; midazolam 0.1–0.2 mg/kg; suxamethonium 1–1.5 mg/kg (children 1–2 mg/kg); rocuronium 1 mg/kg or vecuronium 0.1 mg/kg; atropine 500 micrograms to 1 mg in adults and 20 micrograms/kg in children (minimum 100, maximum 600 micrograms) for peri-laryngoscopy bradycardia. Paediatric tube sizing: uncuffed internal diameter (mm) = (age in years ÷ 4) + 4; cuffed = (age ÷ 4) + 3.5; oral length at the lips (cm) = (age ÷ 2) + 12, with weight for ages 1–10 years estimated as (age + 4) × 2 kg.DoctorNot available at your setup — Endotracheal intubation kit.
  • Confirm and then ventilate protectively: capnography must confirm tracheal intubation — a persistent waveform over six breaths — and the tip should lie 2–4 cm above the carina. Use tidal volumes of 4–8 mL/kg ideal body weight (ideally 6 mL/kg), plateau pressure not exceeding 30 cmH₂O, PEEP 5–8 cmH₂O in the majority, and permissive hypercapnia provided the pH remains above 7.2; in severe airflow obstruction invert the strategy to low rates, low volumes and a prolonged expiratory time.DoctorNot available at your setup — Mechanical ventilator.

Caution— what harms

  • Never withhold oxygen from a hypoxaemic patient for fear of worsening respiratory acidaemia — severe hypoxaemia is more dangerous than hypercapnia, and the hazards of reducing hypoxic drive are frequently overemphasised.
  • Pulse oximetry says nothing about carbon dioxide: a normal saturation on supplemental oxygen does not exclude hypoventilation with CO₂ retention. It is unreliable in poor perfusion, hypothermia, shivering and severe anaemia, is falsely high in carbon monoxide poisoning (carboxyhaemoglobin is read as oxyhaemoglobin), and overestimates saturation in patients with darker skin.
  • Never pass a suction catheter blindly beyond the pharynx, and never inspect the throat of a stridulous patient with a tongue depressor or lie them flat — laryngoscopy may provoke laryngospasm and complete obstruction, particularly in children.
  • Hyperextension closes the infant airway — position infants under one year with the head neutral on a folded towel under the shoulders, and never rotate an oropharyngeal airway into place in a child.
  • Avoid suxamethonium where hyperkalaemia is likely — renal failure, crush injury, rhabdomyolysis, burns beyond 24 hours, chronic neuromuscular disease and cord injury beyond 72 hours.Doctor
  • Halve or quarter the propofol dose in shock, hypovolaemia or old age, and anticipate hypotension during and following intubation, because sedatives and positive pressure both reduce venous return and these patients are frequently dehydrated.Doctor
  • Do not ventilate a metabolic acidosis to a normal PaCO₂: low bicarbonate with a low PaCO₂ means the tachypnoea is compensatory, and normalising it is harmful. Equally, in severe airflow obstruction hypercapnia and acidosis are expected, averaging PaCO₂ 65 mmHg and pH 7.20 after initial intubation, and should not prompt hyperventilation.Doctor
  • Absence of a capnography waveform in a perfusing patient means oesophageal intubation requiring immediate removal and re-oxygenation; auscultation supports but does not replace capnography. A tube advanced too far enters the right main bronchus and collapses the left lung — the tip must lie 2–4 cm above the carina.Doctor
  • Non-invasive ventilation is contraindicated in respiratory or cardiac arrest; inability to protect the airway or GCS 8 or less (unless drowsiness is hypercapnic and a closely supervised trial is undertaken); vomiting or high aspiration risk; undrained pneumothorax; facial trauma, burns or surgery preventing a seal; upper airway obstruction; copious secretions; haemodynamic instability; and agitation. Patients with acute lung injury or ARDS, or severely impaired oxygenation, are less likely to benefit and should be intubated if they require mechanical ventilation.Doctor / Nurse
  • The most important complication of NIV is delayed intubation in the patient who was never going to respond — a failure to respond, or further deterioration, must trigger a decision regarding intubation, since delayed invasive ventilation in this context is associated with worse outcome.
  • Any pneumothorax under positive-pressure ventilation requires a chest drain, and a tension pneumothorax is needled before any film is taken.DoctorNot available at your setup — Chest drain / tube thoracostomy.
  • Falsely reassuring pictures: normal saturations in neuromuscular weakness until ventilation fails; a comfortable-looking asthmatic who is in fact tiring, with a falling respiratory rate, a quietening chest and a rising PaCO₂; a child who has gone quiet; and central cyanosis, which needs roughly 50 g/L of desaturated haemoglobin before it appears.
  • Naloxone (400 micrograms IV, titrated in 100–200 microgram increments; 10 micrograms/kg in children) should not delay intubation and mechanical ventilation if that is required, and support must never mask the diagnosis — treat the cause throughout.Doctor / Nurse
  • Do not wean slowly: approaching removal of support as a gradual wean extends unnecessary ventilation time by up to 40%. Liberation should be active, guided by resolution of the underlying process, wakefulness, FiO₂ below 0.5 with PEEP below 8 cmH₂O, stability and a good cough, and confirmed by a spontaneous breathing trial.Doctor

Refer / escalate

Call for anaesthetic or critical care help immediately for stridor, a soiled or unprotectable airway, GCS 8 or less, a respiratory rate below 8 or above 40 breaths/min, exhaustion with a falling rate, failure of non-invasive ventilation at one hour, or any child with apnoea, grunting or bradycardia — and prepare for cricothyroidotomy if the airway cannot be bypassed with a tracheal tube.

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