Proper airway management is the core of any emergency medical service (EMS). The purpose of airway management is to allow perfect control of breathing and respiration of the casualty. What procedures should be used to gain control of airway and breathing in a prehospital emergency setting is a much debated topic. Prehospital airway management has been practiced by many systems of EMS all over the world for several years. Both physicians and paramedics have been performing these procedures. The most commonly used basic procedure for gaining airway control is bag and mask ventilation.
However, many EMS personnel resort to intubation and ventilation as a means of airway control and this has raised many doubts because of increasing evidence from various research reports about the increased risks involved in prehospital intubation. The aim of this assignment is the compare the basic and advanced airway control procedures and explore the risks involved in advanced airway procedures in a prehospital setting. Methods of airway control in a prehospital setting Airway control is very important for advanced life support.
Hypoxemia and asphyxia can cause damage to the cardiovascular and central nervous systems and also to other organs (Helm et al, 2006). Hence adequate respiration is critical in any casualty. Also, most of the emergency cases are trauma patients who are at risk for pulmonary aspiration of blood or stomach contents and hence airway must be controlled in these patients as soon as possible to prevent disastrous effects of aspiration (Helm et al, 2006). The easiest method of airway control is bag-mask ventilation or BMV.
In this method, oxygen is delivered into the lungs by bagging air into the airways by a mask. With some practice, this technique can effectively deliver oxygen into the lungs and cause respiration. Bagging may not be effective when the lungs have collapsed a lot and it is difficult to bag a bleeding trauma patient. Bagging allows escape of air into the stomach and distends it increasing the risk of regurgitation and pulmonary aspiration. In such situations, invasive airway control by endotracheal intubation allows perfect control of breathing and respiration.
Endotracheal intubation (ETI) is a method by which a flexible plastic tube is placed into the trachea to protect the airway of the patient and to provide a means of mechanical ventilation. The trachea can be gained access though two methods namely oropharyngeal and nasopharyngeal methods. Oropharyngeal intubation is the most common method of ETI. In this procedure, the ET tube is passed through the mouth, larynx and vocal cords into the trachea. It is done with the assistance of a laryngoscope. The ET tube is secured in position by inflating the bulb.
In nasopharyngeal intubation, the ET tube is passed though the nose, larynx and vocal cords into the trachea. ETI permits air to pass freely in and out of the lungs, thus ventilating them. Air can be pushed through ET either by bagging or by connecting to a ventilator. This technique is not without risks especially in a prehospital setting. Other than BMV, other non-invasive methods of airway control include supraglottic devices. Supraglottic devices are non-invasive, in the sense they are not inserted beyond the vocal cords. There are many such devices.
The commonly used ones are laryngeal tube, laryngeal masks and esophageo-tracheal bitube. Of these, laryngeal mask airway or LMA is the commonest. Other supraglottic devices are pharyngeal airway xpress, airway management device, streamlined liner of the pharyngeal airway, cobra perilaryngeal airway and iGel (Erlac et al, 2008). The platform for all airway procedures is bag and mask ventilation. It is a basic skill and involves usage of a self-inflating bag and a non-return valve attached to a mask. Risks involved in endotracheal intubation When ETI is performed, it should be done with expertise and in a perfect manner.
Inadvertent placement of the ET tube into the esophagus which is right behind the trachea can lead to inadequate respirations contributing to hypoxic brain damage, cardiac arrest and death. Stomach contents may be aspirated which can result in pneumonia, aspiration pneumonitis and acute respiratory distress syndrome. During the procedure, damage can occur to the vocal cords, cervical spine, soft tissues of the throat and even teeth. Invasive control of airway demands expertise, availability of salvage devices and appropriate monitoring. Intubation also prolongs the time spent before reaching the hospital.
According to Bocchicchio et al (2003), prehospital endotracheal intubation in trauma patients without acute lethal injury only prolongs the prehospital duration and does not improve the long term outcome. Difficulties encountered in managing airway in a prehospital setting Prehospital airway management is difficult because of many factors. Unlike in a hospital set up, there is limited equipment, inadequate monitoring, lack of skilled help, inadequate lightening or too much bright lightening making laryngoscopy difficult, impaired patient access due to entrapment, anatomical reasons, hypersalivation and excessive noise.
In addition to these, access to airway may be difficult because of debris, blood and vomitus (Dean, 2000). Due to these factors, prehospital intubation is difficult even for anesthetists (Dean, 2000). Also, many a times unskilled physicians and paramedics perform this procedure increasing the risk of endotracheal intubation. Many errors can occur while performing ETI. Common errors which can occur in endotracheal intubation are multiple attempts (4 and more than 4), ET tube misplacement or dislodgment and failed intubation on hospital arrival (Wang et al, 2005).
These errors are affected by many clinical factors like age and sex of the patient, cardiac status of the patient, medical condition and also the extent of trauma in the patient. The estimated per service error rates are anywhere between 0% to 40% (Wang et al, 2005). The error rates are higher in children less than 6 years of age, in those who do not have cardiac arrest, in those who have suffered extensive trauma and in those receiving sedation-facilitated or conventional intubation (Wang et al, 2005). Is advance airway support superior to basic airway control in a prehospital setting?
Recent evidence has shown the futility of ETI especially when performed in the difficult environment of a prehospital setting. Helm et al (2006) reported that about 85% of deaths in major trauma cases are as a result of airway obstruction caused by endotracheal intubation. Wang et al (2004) reported that outcomes of prehospital intubated cases are worse than those intubated in a hospital. In one retrospective study conducted in the US (Stockinger and McSwain, 2004), there was evidence that mortality in those with ETI was much higher than compared to mortality in those who received bag and mask ventilation.
Similar reports were produced by a study by Davis et al (2003) according to which the mortality rate in those who were intubated in a prehospital setting was 33% but in those who received BMV until they reached the hospital was only 24. 2%. This study also showed evidence that the good outcomes in ETI were much lower when compared to the outcomes in bag and mask ventilation cases. Another important disadvantage with ETI is the increased dispatch time. Retrospective studies by Bochicchio et al (2003) and Eckstein et al (2000) revealed that the dispatch time in prehospital ETI was much higher than those who just received BMV.
Also, poor outcomes and other complications like respiratory complications and longer stay in ICU were seen in the field ETI group. Sloane et al (2000) also reported similar outcomes with ETI in prehospital setting. Murray et al (2000) and Davis et al (2005) reported increased mortality in those who underwent prehospital ETI when compared to those who were not intubated. In about one fouth of the patients intubation failure is most likely due to combative patients or gagging (Karch et al, 2001). Rapid sequence intubation or RSI There is not much clinical data on the uses of RSI in a prehospital setting.
This procedure can be performed only by trained anesthetists and these personnel are available as emergency personnel only in severely traumatic patients. RSI has many theoretical benefits. It improves oxygenation and ventilation; it protects the airway from aspiration and decompensation and also protects the spine through sedation and paralysis (Wang et al, 2005). It decreases the number of failed intubations (Wang et al, 2005). RSI is useful to overcome the trismus and gag reflex associated with intubation. The sedation and paralysis produced during RSI make it easy to intubate in difficult situations.
Inability to intubate and ventilate after paralyzing kills the patient and hence this procedure should be done only by experts. RSI also increases the transit time (Bernard et al, 2006). Conclusion From the above literature review it is obvious that prehospital intubation is associated with increased mortality, longer transit times, increased respiratory complications and probably less good outcome when compared with BMV and hence it can be said that BMV must be the first choice of airway management as and when possible. ETI is an advanced procedure demanding skilled personnel to perform it.
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