Airway management remains one of the leading priorities when dealing with the unconscious victim of a cardiorespiratory arrest. The majority of first responders are non-physicians and whilst the airway may not be ‘difficult’ to manage in the hands of an anaesthetist, the effective delivery of oxygen to vital organs may be seriously compromised if inexperienced personnel attempt to perform airway maneuvers they are unfamiliar with.

The golden criteria for effective ventilation during cardiopulmonary resuscitation (CPR) remains orotracheal intubation. This skill requires considerable training and a mechanism to ensure it is effectively maintained. The failure rate for performing orotracheal intubation is greatest amongst non-physicians and there are a number of reports highlighting the problems of skill retention and failure with this technique. Training programs for those non-anesthetists performing orotracheal intubation during CPR should include regular updates and specific teaching on manikins, cadavers and anesthetized patients. If such training is not maintained, then one has to seriously question the role of orotracheal intubation during CPR if the airway is managed by non-physicians or indeed non-anesthetists.

If we accept the need to provide rapid delivery of oxygen to vital structures during CPR and that this is largely performed by non-anesthetists initially, then how can we ensure it occurs? To begin with we have to teach good basic life support. The use of simple airway opening maneuvers (chin lift, head tilt and jaw thrust) together with additional airway adjuncts such as Guedel and nasal airways, remains part of our standard teaching practice. Ventilation can occur by mouth to mouth, mouth to mask or by the use of a self inflating bag-valve device. Unfortunately it is well documented that such maneuvers are often performed badly and inefficiently. Gastric inflation remains a problem together with aspiration of stomach contents as well as ineffective ventilation. Oxygen delivery may be improved by the use of oxygen reservoir systems and by teaching a two person technique when using the bag-valve- mask i.e. one person holding the mask and one squeezing the bag. The ability to effectively perform this simple skill however, remains depressingly poor. Recent work has also suggested that tidal volumes may need to be considerably higher when mouth to mouth ventilation or bag-valve-mask ventilation with air is used in order to maintain a satisfactory oxygen saturation. Tidal volumes may be reduced if supplemental oxygen is provided.

More recently a number of new airway devices have found favor amongst those dealing with airway management during CPR. The laryngeal mask airway (LMA) (Figure 1) has been available for some years now and provides an effective means of ventilation in most patients provided airway pressures are not excessively high (<20cm H2O). Trials of its use in adult CPR have shown great success and a remarkably low incidence of regurgitation and aspiration. The LMA is easy to insert and non-anaesthetic staff can be taught to do so during half day courses. Manikin teaching appears as efficient as using anesthetized subjects. More recent work has suggested that if the LMA is used as the first line airway during CPR i.e. before use of bag and mask ventilation, then the incidence of aspiration appears to be significantly reduced. This may be due in part to a reduction in the amount of gastric distension and partly to an ‘oesophageal barrier effect’ the tip of the LMA appears to impart when positioned in the upper oesophageal lumen. The recently introduced ‘Unique’, single use LMA may further encourage use of this device in the CPR arena.

Figure 1: Laryngeal Mask Airway (LMA)

Recent developments with the LMA include the intubating laryngeal mask airway (ILMA) (Figure 2) and the eagerly awaited "Proseal" LMA (Figure 3) which has both an oesophageal cuff and lumen for venting of stomach contents. Use of either of these new devices is limited within the CPR context and we await with interest developments in this area. Recent work has suggested that the ILMA allows ventilation at higher airway pressures than the conventional LMA and this may prove useful in the CPR situation. Both the ILMA and LMA can easily be inserted with the neck in a neutral position, but cricoid pressure appears to significantly impair their function. Medical students have successfully demonstrated the ease of insertion of the ILMA in cadavers and their preference for this device over the conventional LMA. Early work has also suggested that the Proseal LMA allows ventilation at much higher airway pressures than the standard LMA.

Figure 2: Intubating Laryngeal Mask Airway (ILMA)

Figure 3:"Proseal" Laryngeal Mask Airway

The Combitube (Figure 4) is another recent innovation to find favor in CPR. The device, developed over 10 years ago, has 2 lumens and both a pharyngeal and oesophageal cuff. It is inserted blindly and nearly always enters the oesophagus. Successful placement allows ventilation via pharyngeal apertures and oesophageal contents are vented via the other lumen. The device, like the LMA, can be inserted from front or back and with the head in a neutral position. It appears to allow ventilation at slightly higher airway pressures than the currently available standard LMA and may afford a greater degree of airway protection as a result of the oesophageal lumen. Early work using the Combitube suggested that arterial oxygen tensions were higher than those achieved when patients were intubated. This is probably a small positive end expiratory pressure (PEEP) effect from exhalation occurring through the small proximal apertures. The device has been used with great success by paramedics in the USA, Canada and Japan for prehospital CPR and is slowly finding favor in the UK. A number of British hospitals have now reported its successful use in CPR and it is well liked by the nursing staff. The Combitube does have some limitations however. It remains a single use device that is reasonably expensive and it does have a degree of minor pharyngeal trauma associated with its insertion. There have also been occasional reports of oesophageal damage. Limiting the amount of air inserted into the proximal or pharyngeal balloon to that sufficient to obtain a seal, may in part, reduce some of the pharyngeal trauma. Nevertheless, the Combitube remains an easily taught, additional tool for airway management during resuscitation.

Figure 4: Combitube Airway

Figure 5: Cuffed Oropharyngeal Mask Airway (COPA)

Both the LMA and Combitube suffer from limitations regarding cost and training. The use of more simple, recognizable airway adjuncts may overcome some of these problems. The recently introduced cuffed oropharyngeal airway (COPA) (Figure 5) is a simple modification of a Guedel airway and goes a long way to fulfilling these goals. The device is inserted like a standard oral airway with the addition of an inflatable pharyngeal cuff and universal connector. Whilst originally developed for use during spontaneously breathing subjects under general anaesthesia, the COPA does allow positive pressure ventilation to occur provided lung compliance is good and airway pressures are not high. Initial work has suggested the device is easily inserted by nursing staff and ventilation is possible in nearly every case. There appears to be a leak in a number of patients but this rarely impairs the ability to effectively ventilate the lungs. A larger size COPA than standard Guedel airway also appears to be more effective. Further work has suggested that the COPA, whilst conferring no advantage to patients if bag and mask ventilation is being done well, does allow good ventilation if the bag and mask system is proving ineffective. Thus whilst the device confers no protection of the airway against regurgitation and aspiration, it does appear to have some advantages over simple bag and mask ventilation if this is not being performed well. If we accept that training all nursing staff in the use of the LMA and Combitube is a practical impossibility then the COPA may represent an important intermediary between bag and mask and more sophisticated airway devices.

Figure 6: Airway Management Device (AMD)

New airway devices such as the Airway Management Device (AMD) (Figure 6) and Laryngeal Tube have recently been described. Their role in the CPR setting remains poorly evaluated although in principal, like the devices described above, they may have a role as a substitute to conventional laryngoscopy and orotracheal intubation.

The use of cricoid pressure during resuscitation has recently been addressed with its incorporation into the European Resuscitation Council guidelines for Airway Management during Resuscitation. Cricoid pressure has for many years been the mainstay of avoiding aspiration during induction of anaesthesia for patients with a full stomach or at risk of aspiration from other causes. Its use during resuscitation remains controversial however. There is no doubt that if it is correctly applied at the precise moment a patient has a cardiorespiratory arrest then the incidence of aspiration may well be reduced. However, most patients collapse and aspirate prior to receiving any form of medical intervention. This, together with the fact that cricoid pressure makes insertion of the Combitube impossible and correct functioning of the LMA difficult or impossible, suggests that its role is limited to the witnessed arrest in whom intubation of the trachea is performed early. Furthermore, there is evidence that cricoid pressure causes a degree of airway obstruction if applied incorrectly or with too much force and causes complete airway closure in up to 10% of patients. Recent research however, has shown this to be much less of a problem if the force applied is reduced to the now acceptable level of 30 N. Cricoid pressure may also induce relaxation of the lower oesophageal sphincter thus potentially encouraging regurgitation. Its use during conventional laryngoscopy however, may be beneficial both to improve the view at laryngoscopy and prevent inadvertent oesophageal intubation.

To finish a discussion on airway management during resuscitation one cannot ignore the increasing weight of evidence suggesting that ventilation ‘per se’ during the initial few minutes of a cardiorespiratory arrest may not actually make any difference to outcome. This concept has come about from observations that during these first minutes after the heart has stopped, ‘gasping’ occurs which may provide a degree of ventilation. Furthermore, chest compressions actually cause a reasonable degree of airflow in and out of the lungs by virtue of the pressure changes they institute. It has been suggested (and subsequently hotly debated) that the initial sequence of events after diagnosing cardiac arrest should be ‘open airway, perform chest compression and consider ventilation after a few minutes’. This may have its most appropriate audience in the pre-hospital environment where ‘lay’ people may be involved in the initial stages of CPR treatment. Opponents of this view are quick to point out that this practice ignores all the respiratory causes of cardiac arrest and in particular most paediatric cardiac arrests. The argument has been further complicated by research suggesting that the efficiency of chest compressions i.e. cardiac output, during CPR is significantly improved when the airway is totally obstructed. Indeed, an impedance valve has recently been described that allows the airway to become obstructed during chest compressions but opens when ventilation is performed. There is little evidence in human models to suggest that this ‘no ventilation CPR’ is effective at present. However, a recent study where patients were intubated after a cardiac arrest and had oxygen insufflated down the endotracheal tube without ventilation, has shown no difference in outcome with those patients who were ventilated.

In conclusion, airway management during resuscitation remains largely in the hands of non-physicians during the crucial first few minutes. Orotracheal intubation remains the gold standard if it can be achieved quickly and safely by experienced personnel. Until control of the airway has been achieved in this manner then a variety of simple airway adjuncts are available that may, with varying degrees of success, allow ventilation and some degree of airway protection. Such devices differ in the degree of difficulty of insertion and cost. Whether such devices are even necessary during the first few minutes of any adult cardiac arrest remains unanswered.