Airway and intubation
  1. Afferent limb

    The part of the breathing system which delivers fresh gas to the patient. If the reservoir is placed in this limb, as in Mapleson A, B, C and Lack systems, it is an afferent reservoir system. A, B, and C circuits do not have efferent limbs.

    Afferent reservoir systems eliminate CO2 efficiently but, for controlled ventilation, high gas flows are needed. B and C are junctional afferent systems, so need high gas flows for both spontaneous and controlled ventilation.
  2. Aintree Intubation Catheter

    An adaption of the Cooks Airway Exchange Catheter, 56cm long, and with a larger internal diameter of 4.8mm, allowing it to be pre-loaded onto a 4mm fibreoptic intubating bronchoscope, with the directable distal 3cm left exposed. The external diameter of 6.5mm allows ET (endotracheal) tubes, with minimum internal diameter of 7mm, to be loaded onto the catheter. The Aintree system allows intubation via an LMA (or Proseal).
    Aintree intubation
  3. Ambu bag (bag valve mask)

    Hand-held self-inflating reservoir bag, to provide ventilation to a patient who is not breathing adequately. Sizes range from 250 ml to 2 litres, and the bag can deliver about half of it's volume. A one-way valve prevents re-breathing.
  4. Anaesthetic machines

    The general guidance for pre-use checking of anaesthetic machines is mandated by the  AAGBI, with specific procedures set by the particular manufacturer:   Aestiva  |  Fabius  |  Perseus
  5. Anti-hypoxia device

    An interlinking system between the oxygen and nitrous oxide flow controls, which ensures that the patient does not receive any nitrous oxide, without also receiving at least 25% oxygen.
  6. Apnoea

    Suspension of breathing.
    Caused by...
    • Residual effects of a narcotic premedication.
    • Residual effects of induction, or maintenance agent.
    • Hypocapnia - no stimulus for breathing.
    • Hypercapnia - usually caused by fault in anaesthetic circuit.
    • Severe hypotension.
    • Suxamethonium apnoea.
    • Pseudo cholinesterase - caused by liver disease.
  7. Armoured Endo-Tracheal tube 

    ET tube, embedded with metallic helix strip, to prevent kinking and crushing, commonly used in head and neck surgery, where acute flexion of the neck may occur.
  8. Aspiration

    (1) Inhalation,     (2) Drawing off fluid from a cavity.
  9. Awake Intubation 

    A technique to anaesthetise the upper airway, using local anaesthetic, to allow tracheal intubation without the need for general anaesthesia and muscle relaxants. Nasal or oral intubation may be performed. The oral route is more stimulating, and may be more difficult. This technique requires a co-operative patient.
  10. Ayre's T-piece

    A Mapleson E valveless circuit, with corrugated reservoir tubing, typically used for infants. It has minimal dead space and minimal resistance. Exhaled CO2 flows through the efferent limb, and is flushed out of the circuit by an adequate gas flow. For safety, there should be a minimum flow rate of 6 litres/minute, but 10 litres is probably better, as low flow rates can result in dangerous levels of CO2. Reservoir bag sizes are 500 ml and 1 litre.
    Reference to a T-piece is usually made to a  Mapleson F circuit.
  11. Backward Upward Right Pressure (BURP)

    Pressure exerted on the thyroid cartilage, to help visualisation of the vocal cords when intubating. The assistant who performs BURP will move the larynx to the right, whilst the tongue is displaced to the left by the laryngoscope blade.
  12. Bain circuit

    Functionally, a coaxial Mapleson D efferent reservoir circuit, typically used in anaesthetic rooms. Fresh gas flows down the inner tube, and exhaust gases flow through the outer tube to the exhaust valve. Needs high FGF to prevent rebreathing of CO2. If the circuit is attached to a block assembly, connected to the gas outlet of the anaesthetic machine, and incorporates an expiratory valve, gas scavenging and intermittent positive pressure ventilation may be facilitated. Bain circuits are better for assisted than spontaneous ventilation.
  13. Berman Intubating Airway

    Similar to the Guedel pattern Airway, but with a plastic hinge down the left side, a lateral opening down the right side, and used as an aid to blind or fibreoptic intubation.
  14. Bougie

    A semi-rigid device, to introduce an endotracheal tube, when tube placement proves difficult. During laryngoscopy, the Bougie is carefully advanced into the larynx, and through the vocal cords, until the bent tip enters a mainstem broncus. Whilst the Anaesthetist maintains the laryngoscope and Bougie in position, the ODP (or Nurse) threads the tube over the end of the Bougie, and into the larynx. Once the tube is in place, the Bougie is removed.
  15. Bronchoscopy

     Basics   ||   Youtube   ||   Awake Intubation   ||   Bonfils setup   ||   Bonfils Intubation
  16. Can't intubate, can't ventilate

    See Emergencies:  Can't intubate, can't ventilate.
  17. Continuous Positive Airway Pressure (CPAP)

    In spontaneous ventilation, positive airway pressure is maintained until the end of expiration. The closing pressure holds open the alveoli so that partial pressure of arterial oxygen (PO2) is improved, making breathing easier.
  18. Cook Airway Exchange Catheter 

    A long, flexible, hollow tube, designed to facilitate the exchange of an in situ endotracheal tube. This technique can be used in the management of patients with significant tracheal deviation, such as a result of an enlarged thyroid gland. Additionally, The Cooks Catheter may be used for jet ventilation, or for end-tidal carbon dioxide measurement.
  19. Cricoid pressure (Sellick's Manoeuvre)

    Application of pressure to the anterior arch of the Cricoid cartilage, to temporarily occlude the lumen of the oesophagus (upper end), preventing aspiration of stomach contents into the lungs. Typically used during Rapid Sequence Induction, or during normal intubation when the lower oesophageal sphincter is expected to be incompetent. A light force is required when the patient is drowsy, and 30-40 Newtons (3-4 kgs) when unconscious.

    Note: The airway and breathing are higher priorities than the application of cricoid pressure.

    Contra-indications are...
    • Cricotracheal injury
    • Active vomiting
    • Unstable
    • Cervical Spine injury

    Note: Obstetric patients are especially susceptible to aspiration during anaesthetic induction.
  20. Cricothyroidotomy

    See  Details
  21. Dead space

    The volume of the breathing system from the patient end to the point at which to and fro movement of expired gas takes place.
  22. Difficult intubation

    Indications for a potentially difficult airway include:

    • Less than 3″ (7 cm) between mandible and hyoid bone.
    • Less than 5″ (12.5 cm) sternomandibular distance, (head fully extended)
    • Less than 35 º neck extension
    • Poorly visualized uvula
    • Short, thick neck
    • Receding mandible
    • Protruding teeth
    • Emergencies: Difficult Intubation
  23. Double lumen endobronchial tubes

     Position checking
  24. Efferent limb

    The part of the breathing system which carries expired gas from the patient. Efferent reservoir systems (D, E with Jackson Rees modification of Ayre's T piece) work well with controlled ventilation, but need high gas flows with spontaneous ventilation.
  25. Failed Rapid Sequence Induction

    See Emergencies:  Failed RSI
  26. Fibreoptic Intubation

    Camera assisted placement of an ET tube, using a flexible of rigid (Bonfils) bronchoscope, such as when the patient has limited movement of the jaw, or the mouth/pharynx are within the operating site.
    Youtube   ||   Procedure
  27. Fresh gas flow

    Supply of breathing gas delivered to the patient.
  28. Glidescope

    A video laryngoscope which provides a consistently clear, real-time view of the airway and tube placement.
    Anaesthesia UK   ||   Youtube   ||   Verathon   ||   Small children   ||   Manual
  29. Humphrey ADE circuit

    A new circuit which can be switched between the Mapleson A, D and E systems.
  30. Hypoxic guard

    An interlink between oxygen and nitrous oxide flow controls, which prevents the patient from receiving pure nitrous oxide, and maintains a ratio of, for example, 1:3 between oxygen and the nitrous oxide. If the oxygen flow falls below 200 ml/minute, the nitrous oxide flow shuts off.
  31. Induction

    Inducing a patient into a state of anaesthesia. Once asleep, the patient can be administered a volaile agent, which might otherwise produce laryngospasm, if the patient were sill awake.
    Verification of anaesthesia can be achieved by ensuring an adequate level of end-tidal carbon dioxide, ET tube condensation (synchronised with respiration), symmetrical chest movement, auscultation, and oxygen saturation. Basics
  32. Induction agents

    Examples...
    • Barbiturates (Thiopentone, Methohexitone)
    • Imidazoles (Etomidate)
    • Phenols (Propofol)
    • Phencyclidines (Ketamine)
  33. Intermittent Positive Pressure Ventilation (IPPV)

    Intermittent inflation of the lungs with a positive pressure delivered by a ventilator, and applied via an endotracheal tube.
    Used in...
    • Anaesthetised patients - with muscle paralysis (Atracurium etc)
    • Acute respiratory or ventilatory failure.
    • To prevent hypoxia.
    • Chest injury and lung contusion (bruising).
    • Coma with breathing difficulties, such as with drug overdose.
  34. Intubating LMA

    A laryngeal mask airway, which allows single-handed blind insertion of an endotracheal tube, without the need to move the patient's head, or place fingers inside the patient's mouth. Typically used in emergency or difficult airway situations, or when the patient may have cervical spinal injury. The LMA section serves as a guide for a reinforced ET tube to be placed, without having to displace the anatomy.
    If the patient suffers from an oesophageal or pharyngeal abnormality, then intubation via the ILMA is contraindicated, unless used in an airway rescue situation. Youtube
  35. Intubation

    Insertion of an endotracheal tube into the trachea: 23cm (men) and 21cm (women) at incissors. An intubation attempt should not last longer than 30 seconds, and should be stopped if patient oxygen saturation drops below 95%. After intubation, patency may be confirmed by:

    • End tidal carbon dioxide
    • Depth of tube (eg 21/women, 23/men)
    • Water vapour within lumen of tube during exhalation
    • Equal bilateral chest rise and fall
    • Auscultation for equal bilateral breath sounds
    • No breathing sounds over the stomach
    • No gastric contents in tube
    • Tube cuff pressure: 20-25 cm/H2O.
  36. Jet ventilation

    Jet, or high frequency ventilation, is a type of mechanical ventilation which employs high respiratory rates (150+ breaths per minute), and very small tidal volumes. High frequency ventilation is thought to reduce ventilator-associated lung injury, especially in the context acute lung injury. This is commonly referred to as lung protective ventilation. There are different flavors of High frequency ventilation, and each type has its own advantages and disadvantages. The types of HFV are characterized by the delivery system and the type of exhalation phase.
  37. Lack circuit

    Functionally coaxial Mapleson A afferent reservoir circuit, similar to the Magill system, but with the expiratory valve at the machine end. Fresh gas flows up the outer sleeve, expired gas flows down the inner tube to the exhaust valve.
  38. Laryngeal Mask Airway

    An LMA is a device which sits over the top of the larynx (supraglottic), for spontaneous or artificial ventilation. The tip of the LMA sits against the valve at the top of the oesophagus, thereby providing a partial seal against regurgitation and aspiration (inhaling fluid or foreign body into the bronchi lungs) of gastic contents. One advantage over bag/valve/mask insufflation, is the reduced possibility of insufflating the oesophagus, which might otherwise cause gastric distention. Additionally, an LMA does not irritate the throat as much as an endotracheal tube. Youtube
  39. Laryngoscope

    Endoscopic instrument to aid visualisation of the airway/larynx during intubation. There are several types of laryngoscope blade available, with the curved Macintosh blade being used for standard intubation. Sizes range from 0 (neonate) to 4 (large adult).
    Blade types...
    • Macintosh (curved) - standard use
    • McCoy - (curved) hinged tip
    • Polio (120°) - obese and large breasted patients
    • Magill (straight) - for infants
    • Miller (straight) - for infants

    The Macintosh blade is positioned in the vallecula, anterior to the epiglottis, lifting it out of the visual pathway, while the Miller blade is positioned posterior to the epiglottis, trapping it while exposing the glottis and vocal folds.

  40. Laryngospasm

     Details
  41. Magill circuit

    This is the original Mapleson A system, comprising a three way T shaped tube, which is connected to the fresh gas outlet (FGF), a reservoir bag (90° to FGF), a corrugated reservoir tube and, at the other end, an expiratory valve, then the patient connection.
  42. Magill forceps

    An aid to nasal intubation, and placement of throat packs.
  43. Mallampati classification

    A scheme for grading the visibility of an airway, with respect to endotracheal intubation.

    GradeVisibility
    ISoft palate, faucial pillars, uvula
    IISoft palate, uvula
    IIISoft palate, base of uvula
    IVSoft palate not visible
  44. Mapleson A circuit (Magill and Lack)

    An afferent reservoir circuit, which eliminates CO2 efficiently, but needs high Fresh Gas Flow (FGF) in controlled ventilation. In spontaneous ventilation, requires FGF matching patient minute volume, to avoid functional rebreathing. Mapleson A does not have an efferent limb.
  45. Mapleson B circuit

    A junctional afferent reservoir circuit, suitable for resuscitation and patient transfers, because the bag and valve are close to the patient. Requires FGF of 1.5 - 2 times minute volume to avoid functional rebreathing. Does not have an efferent limb.
  46. Mapleson C circuit

    A junctional afferent reservoir circuit; best for short term use, such as resuscitation and patient transfers, because bag and valve are close to the patient. Also found in Recovery areas. Requires FGF of 1.5 - 2 times minute volume to avoid functional rebreathing. Does not have an efferent limb.
  47. Mapleson D circuit

    An efferent reservoir circuit, which needs high gas flows in spontaneous ventilation, so performs best with controlled ventilation. Requires FGF of 2 - 4 times minute volume to avoid functional rebreathing.
  48. Mapleson E circuit

    The original Ayre's T-piece; a valveless and bagless circuit, with low breathing resistance; for spontaneous or assisted ventilation. See T-piece
  49. Mapleson F circuit

    Not strictly a Mapleson classification, but refers to the Jackson-Rees modification of the  Ayres's T-piece system, which connects a two-ended bag to the expiratory limb of the circuit. Gas escapes via the open end of the bag. A minimal resistance circuit, which allows intermittent positive pressure ventilation by occluding the tail of the bag between a finger and thumb, and squeezing the bag. There is also a version with a closed end bag and an APL valve.
  50. Minute Volume (VT)

    The total volume of gas (litres) exhaled from the lungs in one minute; which is the product of respiratory rate and tidal volume.
  51. Nasal cannula flow rates

    FLow (L/min)O2 delivered (%)
    124
    228
    332
    436
    540
    644

    With an added 4% for every increase of 1 Litre of flow, to a maximum of 60%.
  52. Nasopharyngeal Airway

    The nasopharyngeal airway is less likely to induce gagging than an oropharyngeal airway, and can be used in a conscious patient when the airway is at risk of compromise. It can be life-saving in a patient with a clenched jaw, trismus, or maxillofacial injuries.
  53. Nebulizer

    A device which converts a liquid to a fine mist, which is then inhaled. Typically used to treat respiratory disorders.
  54. Non-rebreather mask

    Provides a patient with an oxygen concentration of 90-100%, whilst exhausting expired carbon dioxide.
  55. Non-rebreathing circuit

    Circuits where the elimination of carbon dioxide is accomplished by removing all expired gases from the circuit, and venting them to the atmosphere. This is normally achieved by allowing the fresh gas flow from the anaesthetic machine to direct the expired gases out of the circuit, via a valve or other arrangement.

    In general, non-rebreathing systems provide good control of inspired gas concentrations, since fresh gas delivered from the anaesthetic machine is inspired in each breath. They are, however, less economical in use than rebreathing systems, because the minute volume of ventilation (or more) must be supplied to the patient to prevent rebreathing, and they contribute more to atmospheric pollution with anaesthetic agents. They are also less forgiving of operator error, since an inadequate fresh gas supply will result in rebreathing. See  Mapleson A, D, E
  56. Oropharyngeal airway

    In an unconscious patient, the muscles in the jaw relax, allowing the tongue to obstruct the airway. An oropharyngeal (or Guedel pattern) airway is a device which maintains a patent (open) airway, by preventing the tongue from covering the epiglottis, which could prevent the patient from breathing. The correct size is chosen by measuring from the corner of the patient's mouth to the tip of the earlobe. The oropharyngeal airway is then inserted into the patient's mouth upside down. Once contact is made with the back of the throat, the oropharyngeal airway is rotated 180 degrees. These airways are often used in conjunction with head tilt and jaw thrust techniques.
  57. Oxygen toxicity

    A condition resulting from the harmful effects of breathing molecular oxygen at elevated partial pressures (hyperoxia). Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lungs and eyes. Oxygen toxicity is a concern for those on high concentrations of oxygen - particularly premature babies - and those undergoing hyperbaric oxygen therapy.
    Symptoms...
    • Anxiety
    • Burning sensation with deep breathing
    • Other breathing problems
    • Vision changes
    • Vomiting
  58. Pin index system

    Mechanical system of ensuring correct fitting of gas cylinders to their respective housings, according to ISO standard 407 for Small medical gas cylinders. The positions of the holes on the cylinder valve correspond with the pins fitted to the yoke attachment, such as on an anaesthetic machine.

    GasPins
    Air1,5 
    Carbon dioxide1,6
    Heliox2,4
    Nitrous Oxide3,5
    Oxygen2,5
  59. Positive End Expiratory Pressure

    At the end of expiration, PEEP exerts pressure to oppose passive emptying of the lungs, and to keep airway pressure above atmospheric. The presence of PEEP opens up collapsed or unstable alveoli, and increases functional residual capacity. The closing pressure holds open the alveoli so that partial pressure of arterial oxygen (PO2) is improved, making breathing easier.
  60. Proseal

    A laryngeal mask airway, with a reinfoced airway tube, bite block, and a drain tube which opens at the upper oesophageal sphincter, allowing drainage of gastric secretions, and access to the alimentary tract.
    Youtube
  61. Pulmonary Ventilation

    The total amount of air/gas exchanged between the lungs and the ambient air.
  62. RAE tube

    Preformed endotracheal tube, cuffed and uncuffed types, named after their creators - Ring, Adair, Edwin. South and North facing RAE tubes are available, designed to facilitate Ear, Nose, & Throat surgery.
  63. Rapid Sequence Induction (crash induction)

    Rapid induction for patients at risk of gastric aspiration, such as non-fasted and obstetric patients.  Details
  64. Schrader valve

    Push-fit connector for low pressure gas supplies. A "tug" test confirms connection.
  65. See-saw breathing

    Breathing pattern, seen in airway obstruction, where the chest and abdomen move in opposite directions.
  66. Specialist laryngoscopes and endoscopes

    Rigid endoscopes...
    • Arthroscope
    • Laparascope
    • Laryngoscope
    • Oesoophagoscope
    • Sigmoidoscope

    Flexible endoscopes:
    Transmit images, so bending possible.

    Laryngoscopes...
    • Retractor type eg, Macintosh and McCoy.
    • Rigid fibeoptic.
    • Flexible fibreoptic.
  67. Stylet

    Used for pre-forming a tracheal tube to a required shape, prior to insertion.
  68. Suction catheters

    Sizes
  69. T-piece circuit

    See Ayre's T-piece.
  70. Tension pneumothorax

     Details
  71. Tidal volume (VT)

    Total air moved with each normal breath. Typically 6-8 ml/kg in adults.
  72. Valsalva manouvre

    Taking a deep breath and, keeping the mouth closed and nostrils pinched, attempt exhalation. The result is a rise in stroke volume.
  73. Ventilation

    The process of inhalation and exhalation - taking in oxygen, and expelling carbon dioxide by exhalation. During anaesthesia, the paralyzed patient will need assistance to ventilate, by hand or machine.
    FRCA  ||   Tutorial
  74. Venturi (air-entrainment) mask

    A medical device to deliver inspired air mixed with a known oxygen concentration to patients on controlled oxygen therapy.
    Colour coding