◆ Endotracheal intubation may sometimes be problematic in ICU (unprepared patients, emergency situations) and non-invasive alternative airway management may be necessary.
◆ In case of difficult mask ventilation (inability to maintain pulse oximetry oxygen saturation > 50% at FiO2 = 100%) proper action must be planned.
◆ The oesophageal tracheal Combitube® and EasyTubeTM may be valid alternatives.
◆ Laryngeal mask has proved of value in cardiopulmonary resuscitation.
◆ Modification of a laryngeal mask such as Fastrach® has been recommended as a rescue device for emergency airway management.
Airway management in the ICU differs from conventional controlled setting, such as general anaesthesia in the operating room (OR). Due to adequate patient preparation and positioning in the OR, endotracheal intubation is mostly easy to perform. However, in the intensive care setting, endotracheal intubation is often difficult or impossible because patients are not prepared and intubation is immediately necessary without sufficient time for putting together technical and pharmaceutical equipment.
In the following, non-invasive alternate airway management with special respect on the recommendations of the ‘Task Force on Managing the Difficult Airway’ of the American Society of Anesthesiologists (i.e. ASA algorithm) is described .
Non-invasive airway management
Non-invasive ventilation (NIV) allows patients to speak and cough  and may reduce complications related to intubation. Indications for use of NIV are patients with diagnosis of chronic obstructive lung disease or cardiac failure, since weaning from respirator and cannula in these patients is often very difficult.
NIV can be performed via face mask covering mouth and nose, where a mask is pressed against the patient’s face with the help of an elastic band. Ventilation is provided by either continuous positive airway pressure (CPAP, i.e. continuous flow), pressure support ventilation (PSV) or volume—or pressure-cycled systems (e.g. bi-level positive airway pressure (BiPAP). New devices include eyes into the mask and are better tolerated since pressure on the root of the nose can be circumvented.
NIV can also be performed via a helmet consisting of a cylindrical transparent part surrounding the patient’s head sealed by an elastic ring around the patient’s neck. The advantages of the helmet are that the patient enjoys a free view through the transparent helmet and may use glasses. Furthermore, additional openings allow nursing of the patient’s face. Special designs of the helmet provide field of view and minimum level of noise.
In the intensive care unit (ICU), patients with hypoxia and deteriorated cardiopulmonary function may experience adverse events after shorter periods of lack of response to ventilation or intubation. Therefore, emergency tracheal intubation in critically-ill patients may be associated with a significant frequency of major complications. Opposite to routine intubation in the operating room, airway management in intensive care patients may be extremely difficult. Immediate need for intubation and ventilation in situations, such as acute respiratory failure, shock, or cardiopulmonary arrest could make securing of airways and adequate ventilation difficult.
In this situation, the intensivist should consider mask ventilation, when general anaesthesia is induced before securing the airway and whether there are any inadvertent obstacles making awake conventional endotracheal or fibre optic intubation difficult. Furthermore, to prevent adverse effects of unsuccessful intubation, a plan B should be ready.
Difficult mask ventilation (DMV) is defined as the inability of a trained anaesthetist to maintain the arterial oxygen saturation beyond 90% by help of a face mask and use of 100% inspired oxygen, when the preventilation oxygen saturation level was within the normal range .
Opposite to previous assumptions, difficulties in laryngoscopy and/or intubation may occur in routine patients in the OR. While minor complications making a second intubation attempt necessary occur in up to 8% of patients, grade 3 laryngoscopy requiring multiple attempts at conventional intubation occurs in 1–4% among all patients. In 0.05–0.35% of routine anaesthesia cases intubate may fail due to grade 3 or 4 laryngoscopic views. A cannot ventilate–cannot intubate situation may occur in approximately 2 out of 10,000 cases.
Oesophageal-tracheal double lumen airways: combitube® and easytubetm
The oesophageal tracheal combitube (ETC) has designed as a double-lumen airway with a ‘pharyngeal’ and an ‘endotracheal’ lumen where the lumens are separated by a partition. At the proximal end, the ETC is surrounded by a large oropharyngeal balloon, at the distal end by a conventional cuff (Covidien, Mansfield, MA, USA). As an advantage, the ETC can be inserted blindly without help of a laryngoscope and works equally well in oesophageal or tracheal position. The ETC is inserted as deeply until the printed ring marks are positioned at the level of the upper teeth. Then, the oropharyngeal balloon is inflated with 85 (37F) or 100 mL (41F) of air sealing the oral and nasal cavities, while the distal cuff is inflated with 5 to 12 (37F) or 15 mL of air (41F) sealing either oesophagus or trachea. In about 97% the ETC enters the oesophagus after blind insertion. Therefore, test ventilation is recommended via the longer ‘pharyngeal’ blue lumen No. 1 (i.e. supraglottic ventilation). Confirmation of the tube’s position may be done by auscultation of breath sounds in the absence of gastric inflation, and by capnography and/or oesophageal detection method. If the ETC has blindly entered the trachea (3% of blind insertions), ventilation is performed via the shorter transparent lumen No. 2, and ventilation is done like via a conventional endotracheal tube (ETT). Two different sizes of the ETC are available: a small adult model (37 Fr, Combitube® SA) for use in patients with a height ranging from 120 to 200 cm and a 41 Fr model for use in taller patients.
The ETC has been studied and used under emergency conditions, as well as during routine anaesthesia. To become familiar with the ETC, it is recommended to train during elective surgery before using the airway in emergency situations. When used routinely, the ETC could be inserted using a (video-) laryngoscope to minimize the risk of pharyngeal injury. Contraindications for use of the ETC are oesophageal pathologies, ingestion of caustic substances and central airway pathologies.
A major advantage of the Combitube® is its unequalled safety to prevent aspiration of gastric contents and the applicability of high airway pressures. The ETC can be left in place for up to 8 hours; replacement by an ETT can be performed either by tracheostomy or by cricothyrotomy with the ETC in place (since the trachea is not occupied in most cases), by direct laryngoscopy after deflation of the oropharyngeal balloon, or by fibre optics.
Recently, the EasyTubeTM has been designed (Well Lead, Guangzhou, China). Its appearance is similar to the Combitube®, however, provides several advantages.
The ‘pharyngeal’ lumen of the EasyTubeTM ends just below the oropharyngeal balloon. Therefore, the ‘tracheo-oesophageal’ lumen is thinner than that of the Combitube®, which carries the two lumens down to the end. Since the distal single lumen of the EasyTubeTM is significantly thinner, the potential danger of mucosal damage is minimized. Another advantage is that the oropharyngeal balloon is latex free. The device comes in two sizes: the 28 F EasyTubeTM (‘paediatric size’) is available for patients with a height ranging from 90 to 130 cm; the 41 F EasyTubeTM is designed for patients taller than 130 cm. A small fibrescope may be passed via the so-called ‘pharyngeal’ lumen, since it is open at the distal end. This feature allows inspection of the trachea and possible replacement of the EasyTubeTM using a guide wire. Furthermore, a larger suction catheter can be passed via both lumens (14 F suction catheter in the 41 F EasyTubeTM).
Laryngeal mask airway
The laryngeal mask airway (LMA) (LMA North America, San Diego, CA, USA) has been developed in parallel to the Combitube®. It was accepted rapidly and is used extensively during general anaesthesia. The LMA is used for different reasons—as a routine ventilatory airway as an alternative to conventional endotracheal airway or as help for tracheal intubation. The initial intention for use of the LMA was to replace the conventional face mask in the operating room in Great Britain. Tidal volumes were higher and problems associated with airway management (difficulties in maintaining the airway or maintaining SpO2 > 95%) less frequently encountered during LMA use when compared with conventional regular face mask.
The use of the LMA as the immediate airway in cardiopulmonary resuscitation has been discussed controversially. Murray et al. performed a two-phase observational study of the effect of paramedic training for LMA insertion using a mannequin and the success rate in the prehospital setting. All paramedics successfully completed classroom mannequin training. Two-hundred-and-eight paramedics (100%) successfully completed training. The mean number of attempts was 1, and only four (2.1%) paramedics required a second attempt with a mannequin. The paramedics’ perception of ease of use comparing the LMA with a bag valve mask (BVM) was evenly distributed across the three descriptors: 70 (39%) scored the LMA as easier to use, 57 (31%) as more difficult, and 54 (30%) stated there would be no difference. Of the 291 arrests during the study period, insertion of the LMA was attempted in 283 (97.3%) and was successful in 199 (70%) patients. The LMA became dislodged in 5 (2.5%) cases and was removed in 12 (6%) to clear vomit from the airway. The overall success rate was 182 (64%). The incidence of regurgitation prior to attempted insertion of the LMA was 28% (79 patients). Success rates did not vary significantly with the incidence of vomiting prior to insertion (p = 0.11). The majority of the paramedics evaluated LMA insertion as ‘Very easy’ 49/220 (22.3%) or ‘Easy’ 87/220 (39.6%). Paramedic evaluation of ease of use varied with success (p = 0.001). This study reports a 100% training success rate with a mannequin, and a 64% success with LMA insertion and ventilation in the field by paramedics among adult out-of-hospital non-traumatic cardiac arrest patients.
The potential value of the LMA was assessed in a multicentre study when the LMA inserted by ward nurses during cardiopulmonary resuscitation as a method of airway management before of the advanced life support team with tracheal intubation capability arrived. One-hundred-and-thirty nurses were trained, and 164 cases of cardiac arrest were studied. The LMA was inserted at the first attempt in 71% and at the second attempt in 26% of cases. Satisfactory chest expansion occurred in 86% of cases. The mean interval between cardiac arrest and LMA insertion was 2.4 min. Regurgitation of gastric contents occurred before airway insertion in 20 cases (12%), and during insertion in three cases (2%).
Early LMA insertion should be considered in patients suffering from supraglottic pathologies and unfavourable anatomy for face mask ventilation and/or tracheal intubation. Drawbacks of the LMA include the lack of access to the patient’s central airways, risk of aspiration, limited applicability of positive airway pressures due to the often inadequate seal, and the need for training. Moreover, the LMA is a supraglottic ventilatory device and is thereby unable to establish adequate gas exchange in patients with central airway obstruction.
Several modifications of the LMA have been designed, e.g. the intubating LMA (FastrachTM, the Laryngeal Mask Company, Ltd.). The so-called Fastrach differs from conventional LMAs by having a wider, shorter stainless steel tube, a handle to steady the device, and an epiglottic elevating bar (a moveable flap fixed to the upper rim of the mask). The FastrachTM allows passage of endotracheal tubes up to an inner diameter (ID) of 8.5 mm providing blind or fibre optic intubation using the correctly placed Fastrach as a conduit. Success rates for blind FastrachTM intubation in the 75 to >90% range have been shown by several investigators.
This has been recommended as a rescue device for emergency airway management. Ferson et al. used the FastrachTM in 254 patients with different types of difficult airways. Insertions of the LMA-FastrachTM were accomplished in three attempts or fewer in all patients. The overall success rates for blind and fibre optically-guided intubations through the LMA-FastrachTM were 96.5 and 100.0%, respectively. Oesophageal perforation has occurred after repeated ‘blind’ intubation attempts with the LMA-FastrachTM in an elderly patient. Therefore, the specially designed silicone-tube with rounded bevel should be used for blind FastrachTM intubation, because success rates exceed those encountered with standard reinforced tubes. Muscle relaxation may help to increase success rates for blind FastrachTM intubation.
LMA and LMA-FastrachTM versus Combitube®
Sealing capacities and protection against regurgitation of gastric contents of LMA/FastrachTM are inferior to those of the ETC, e.g. average leak fractions of the LMA are in the range 20–25% during positive pressure ventilation with airway pressures ranging from 20 to 30 cmH2O. The special design of the ETC allows the use of high peak airway pressures and permits PEEP ventilation, thereby enabling higher tidal ventilation and maintenance of adequate gas exchange, even in patients suffering from severe underlying pulmonary pathology (e.g. aspiration of gastric contents). In contrast to the ETC, blind, or fibre optic intubation is possible through the LMA lumen (using conventional ETTs up to an ID of 6.5 mm) and especially through the FastrachTM (up to 8.5 mm). With the currently available ETC model, no blind or fibre optic access to the patient airway is necessary. Krafft et al. modified the standard ETC model and created a larger ventilation hole, which can be used for fibre optic intubation or tracheal toilette. However, the redesigned model is currently not available and it is uncertain whether it will be produced in the near future.
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