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A critical review of endotracheal intubation: the ‘gold
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standard’ of airway management in out-of-hospital’
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cardiac arrest?
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ABSTRACT
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For a patient in out-of-hospital cardiac arrest, the unobstructed supply of oxygen to
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their lungs is of paramount importance. The clear flow of oxygen is achieved by airway
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management. Tracheal intubation has long been perceived to be the gold standard of
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airway management however evidence now suggests that this may no longer be the
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case. The following project aimed to assess whether tracheal intubation remains the
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gold standard. The project has reviewed a wide range of literature from varying
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international sources and has discussed the major issues that they raised. The
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discussion came to the conclusion that endotracheal intubation remains the gold
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standard for quality of airway management once placed into the airway. However, this
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is only the case when intubation is performed by a doctor and paramedic team.
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Significant changes to training and pre-hospital practice are required, to ensure
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endotracheal intubation remains the gold standard when performed by paramedics in
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isolation.
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INTRODUCTION
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Emergency medicine is concerned with the treatment of acute illnesses and providing
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immediate care to patients to stabilise them. The Emergency Medical Services (EMS)
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provide this care in the pre-hospital setting. Emergency medical care in the United
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Kingdom has reached a point of great change. In response to the Keogh review 2013,
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aspects of emergency care will be centralised to large major trauma centres. Alongside
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this, growing awareness of the importance of pre-hospital care will raise questions
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about established methods of working.
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The initial treatment of cardiac arrest is one such medical emergency the EMS will be
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involved with. As part of the treatment of cardiac arrest the emergency medical
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personnel aim to ensure a consistent flow of oxygen to the lungs. This is achieved by
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the process of airway management.
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In medicine, constant review and development is required to ensure optimal patient
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care. This is the case with airway management as two main alternative methods are
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used. The original method of endotracheal intubation and the more recently
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introduced supraglottic airways.
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In recent years the long presumed gold standard of airway management, endotracheal
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intubation, has been questioned. The debate continues on an international scale and
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in the following discussion evidence has been drawn on from across the global
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resuscitation community. Ultimately a successful outcome for the patient is survival.
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Therefore the objectives for this discussion became firstly to investigate the main
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methods of airway management; discussing their advantages and disadvantages. The
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secondary aim is to investigate the effect of the medical personnel involved on the
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outcome of cardiac arrest treatment. It will be seen that other questions arise during
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the project, concerning medical training. The discussion can be summarised by asking
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the research question: “Is endotracheal intubation still the gold standard of airway
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management for patients in out-of-hospital cardiac arrest?”
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REVIEW & DISCUSSION
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The biological and physical issues with ETI
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To investigate the methods of airway management available, it is necessary to explore
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the potential flaws which they may have. When any procedure is performed, one must
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consider the possibility of problems that may occur both during and after the
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procedure. For the purposes of this discussion it is necessary to classify the problems
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of ETI under various sections to include: iatrogenic harm, oesophageal intubation and
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time taken to place the endotracheal tube. Endotracheal intubation is a highly invasive
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procedure and as such, this leads to the potential for complications. When combined
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with the high-risk nature of treating out-of-hospital cardiac arrest, these problems can
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be exacerbated.
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Firstly one must acknowledge the potential for airway trauma when placing a hard
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plastic tube into the trachea. Iatrogenic harm can occur to a number of places during
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ETI including the vocal cords and the nasal passages. The most serious cases of airway
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damage, those concerned with lacerations of the trachea, have been documented in
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studies (Minambres et al., 2009). Despite being rare, they occur more regularly in the
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performance of emergency intubation and must be included as a potential worst-case
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outcome (Minambres et al., 2009). E. Minambres et al. in their meta-analysis state:
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“Emergency intubation is the principal risk factor, increasing the risk of death
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threefold compared to elective intubation (Minambres et al., 2009).” This quote refers
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to the risk of post-intubation tracheal rupture.
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A second consideration regarding intubation for out-of- hospital cardiac arrest should
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be the unrecognised misplacement of the endotracheal tube. Tube misplacement can
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result in the tracheal tube being placed too far into the lungs and entering one of the
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bronchi. This would lead to aeration of one lung whilst the other receives little oxygen.
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Although any form of tube misplacement is not a desired scenario, the risk of harm to
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the patient is greatest when oesophageal intubation occurs. The unrecognised
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misplacement of a tube in the oesophagus will cause the patient to return to the state
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of hypoxia that airway management attempts to alleviate. Due to the fact that oxygen
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from the endotracheal tube is now being supplied to the stomach instead of the lungs.
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With the near total lack of oxygen to the brain and muscles, cell death is accelerated
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and the patient’s already critical condition could potentially become irreversible and
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fatal. This however is not the only risk; the likelihood of gastric aspiration also
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increases. This is because oxygen is now inflating the stomach which distends it and
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risks gastric fluid running back up the oesophagus and into the trachea.
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protection that the tube did offer when placed correctly is also negated.
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If gastric fluid enters the lungs, the patient is at risk of developing aspiration
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pneumonia because of lung damage caused by the stomach acid and the pathogens
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present in the fluid.
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To summarise the threat of an oesophageal intubation to a patient, it is necessary to
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turn to the study of M. Jemmett et al. This study clearly demonstrates the extent to
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which an oesophageal intubation threatens the patient’s survival and impedes the
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advanced life support process.
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“Even inefficient bag-valve-mask ventilation is still superior to unrecognized
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oesophageal placement of an endotracheal tube.” (M.Jemmett et al., 2003)
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The third ETI problem is of a physical nature. Any invasive procedure needs to be
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performed with suitable accuracy to prevent harm, whilst also paying regard to the fact
Any
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that the faster ventilation can be achieved, the better the outcome of the patient. This
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was shown by the study of K.Kajino et al. that indicated; increased time from cardiac
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arrest to placement of airway device led to decreased survival (K.Kajino et al., 2011).
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This study however did not investigate a crucial factor in the use of ETI, the quality of
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cardiopulmonary resuscitation (CPR) during OOHCA.
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CPR chest compressions act as a replacement to the regular heartbeat of a patient
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during cardiac arrest and thus should be maintained to a sufficient standard
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throughout treatment. In the words of the ERC guidelines on basic life support “the
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perfect solution is to deliver continuous compressions…” (J.P.Nolan et al., 2010) and
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the latest ERC guidelines emphasise the fact that any intervention should minimise
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the interruption of chest compressions to no more than ten seconds (C.Deakin et al.,
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2010). ETI has a large disadvantage in this respect when compared to SGA, ETI
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requires longer to achieve successfully. As seen in the study of 2005, by C.Deakin et
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al., which shows the mean time of insertion for the LMA to be 47 seconds compared to
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an average of 52.0 seconds for the insertion of ETI (C.Deakin et al., 2005). Analysis of
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the highest time taken for each individual method is perhaps more useful to
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demonstrate a potential worst-case scenario. The time taken for insertion of SGA was
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126 seconds however for ETI the longest time was substantially higher at 148 seconds
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(C.Deakin et al., 2005) . When you recognise that the study was carried out on patients
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undergoing elective surgery the figures present more reason for concern. Deakin et al.
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go on to state, “It is probable that performance in the field is less successful” (C.Deakin
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et al., 2005). In the pre-hospital setting many factors such as: situation, lack of access
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to the airway or bystander pressure, could combine to further increase the time taken
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for ETI to be successful, thus leaving a patient not only without oxygen but also
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without a substitute for their heart. The interruption to CPR is one factor that
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confronts the idea that ETI is the gold standard of airway management. It could be
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argued that the time taken to insert an endotracheal tube could be more worthwhile to
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a patient if used for CPR and the use of a SGA would allow this to occur.
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Other factors such as operator technique and the personnel performing intubation also
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affect the time taken to place an endotracheal tube. These will be reviewed later in the
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discussion.
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Problems associated with supraglottic airways
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So far the focus has been on endotracheal intubation, the perceived gold standard of
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airway management and the problems it can cause. However, of equal importance are
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any problems with the alternative methods of airway management. As mentioned in
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the literature review, the SGA sits above the tracheal entrance as opposed to the
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endotracheal tube, which sits in the trachea above the bronchi. This means that the
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oxygen delivery is less direct using an SGA and therefore less efficient. The inefficient
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oxygen delivery of the SGA is compounded by its lower sealing pressure when
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compared to a cuffed endotracheal tube (JRCALC, 2008). Leakage from the SGA can
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occur, potentially leading to gastric inflation due to oxygen entering the oesophagus.
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The lower sealing pressure also means dislodgement is more likely and with
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dislodgement comes a risk of trauma. In the hospital setting this problem can be
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avoided somewhat as patient transportation can be kept to a minimum. In the case of
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OOHCA the problem can be more severe as the patient must be moved as quickly as
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possible to more advanced medical care. The LMA has been shown to cause airway
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trauma whilst being placed and in rare cases has been associated with oesophageal
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rupture. The risk of airway trauma can be reduced, with certain SGA giving a better
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performance when investigated in trials (JRCALC, 2008) .
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Advantages of ETI
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The discussion thus far has focussed on the negative aspects of both methods of airway
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management. The next stage of the discussion aims to investigate the benefits to the
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patient of both ETI and SGA.
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It is essential to remember that the primary role of airway management is to provide
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a clear route for ventilation to the lungs. Delivery of oxygen to the lungs should be of
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the highest priority. ETI is widely regarded to achieve the strongest ventilation and the
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most efficient oxygen delivery to the lungs compared to other methods (J.P.Nolan et
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al., 2010). This is due to the fact that the tube is placed inside the trachea thus
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delivering oxygen into the airway at a greater depth. A second advantage is that correct
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placement of the endotracheal tube allows CPR chest compressions to continue
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without interruption. It enables a medical professional to solely focus on chest
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compressions without the need to stop and manually ventilate a patient.
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Improved protection from gastric aspiration is another advantage of ETI. The
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endotracheal tube sits deeper inside the airway than an SGA and therefore it offers a
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better seal against regurgitated gastric fluid. This will lower the risk of developing
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aspiration pneumonia, if resuscitation is successful or damage to the airway caused by
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gastric fluid.
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ETI also gives the ability to insert a suctioning tube into the lungs of a patient. This
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can be exceptionally useful in cardiac arrest as fluid may build up in the lungs of a
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patient due to congestive cardiac failure. If it were not possible to suction fluid away
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from the lungs then the patient would have limited gaseous exchange and ventilation
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would be less effective in delivering oxygen to the blood.
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The overall advantage of ETI has been indicated in the trial of H. E. Wang et al.
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“Compared with successful SGA insertion, successful ETI was associated with
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increased survival to hospital discharge with satisfactory functional status” (H.E.Wang
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et al., 2012). This has been echoed in the study conducted by S.Tanabe et al. in Japan,
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which indicates that ETI is significantly better than SGA devices (S.Tanabe et al.,
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2013). Arguably the most compelling evidence the study provides indicating that ETI
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is a stronger option, is the data regarding return of spontaneous circulation (ROSC).
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The study showed that the rate of ROSC was 7.24% in ETI cases compared to a greatly
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reduced rate of 4.90% for cases using LMA (S.Tanabe et al., 2013). It could be argued
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that this data is more useful as the measured ROSC was always accounted for before
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hospitalisation (S.Tanabe et al., 2013). ROSC allows oxygen to be transported around
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the body and metabolic waste to be removed. If ETI can achieve this rate of pre-
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hospital ROSC, it could be clearly argued to be the gold standard.
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Advantages of supraglottic airways
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A major advantage of supraglottic airways is the speed at which they can be placed, as
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described above. This speed could be argued to outweigh the benefit that ETI gives
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when protecting the airway. In the words of C.Deakin et al., “Hypoxia is likely to be a
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far larger contributor to morbidity than aspiration of gastric contents” (C.Deakin et
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al., 2005) . Essentially saying survival depends on efficient oxygen delivery.
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This means the speed at which the SGA can be placed could outweigh the lack of
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protection from aspiration it provides. Therefore achieving ventilation as quickly as
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possible could lead to a decrease in patient morbidity. C.Deakin et al. proceed to
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discuss that hypoxia itself increases the chance of gastric aspiration (C.Deakin et al.,
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2005) . If one could prevent hypoxia then the threat of gastric aspiration could be
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significantly reduced. However it must be remembered that ETI offers improved
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protection and ventilation thus reducing hypoxia alongside risk of gastric inflation.
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THE PERFORMANCE OF AIRWAY MANAGEMENBT TECHNIQUES
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The biological importance of the actual airway management technique has been
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thoroughly discussed above. Both points of view have been looked at with regard to
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the actual biological performance of both of the suggested methods. However the
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discussion has only briefly mentioned the medical personnel that are performing
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airway management. It is equally important when investigating which method is the
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gold standard to systematically review the training, the success and the failures of the
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personnel performing ALS. The method of airway management relies on the technique
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of the person who performs it. The literature review showed that the personnel
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involved in ALS would vary dependent on the situation. To begin with it would be
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worthwhile discussing the most common occurrence; intubation by paramedics.
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Paramedic intubation
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The first clear area of discussion is with regard to the training that paramedics receive
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for airway management. During IHCD training 25 intubations are required of which
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only 5 have to be unassisted. The critical reassessment of ambulance service airway
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management in pre-hospital care, suggests that the number 25 is entirely arbitrary and
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has no clinical reasoning (JRCALC., 2008) . This number becomes increasingly
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worrying as the learning curve for intubation is investigated.
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The learning curve for any skill aims to show the number of repeat performances
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required in order to become competent in that given skill. Again it is necessary to turn
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to Japan to investigate the most recent research in the field. The work of Toda et al.
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indicated that after 30 intubations on patients undergoing elective surgery the success
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rate was at 87% (S.Toda et al., 2013).
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However, figure 1 shows that the learning curve is clearly flattening at this point. A
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success rate of around 90% whilst being high is unacceptable in such a procedure,
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which can have such serious complications (M.Jemmett et al., 2003).
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Figure 1- A graph showing the learning curve for paramedic intubation by 32
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paramedics in Japan (S.Toda et al.,2013)
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The study can then be quoted as saying “The frequency of complications remains at a
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high level even after training. It is desirable to conduct a more detailed and rigorous
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assessment of the benefit of pre-hospital intubation that controls for the skill level of
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paramedics” (S.Toda et al., 2013) . This quote shows the dangers of intubation when
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performed by paramedics. The view of the study is clear, we cannot accurately
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understand the precise number of intubations required to become “competent”. At
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current, medical personnel may be undertaking a procedure of which the training
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required is not truly understood. This argument becomes ever more apparent when
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compared to the research of Konrad et al., which aimed to create a learning curve for
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the skills learnt by anaesthesia trainees. At the 25 intubations required in IHCD
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regulation, the trainees had only reached a success rate of 70% (C.Konrad et al., 1998)
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. To achieve the same level of success as the above study the trainees required an
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average of 57 attempts at intubation (C.Konrad et al., 1998). It is worth considering
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that these anaesthetics trainees were intubating patients on a more regular basis than
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the paramedics above.
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If we assume that the learning curve for this study is a potential worst-case scenario
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then paramedics today are receiving insufficient training in the procedure of
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endotracheal intubation. The number of intubations required by paramedic training
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regulation is under half that of the average number required to achieve 90% success
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rate in Konrad’s study. In addition, paramedics are not involved with the more
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advanced anaesthetic procedures, also seen in the study. These advanced procedures
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will undoubtedly improve the skillset of the practitioner. However, if the training for
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supraglottic airways is also insufficient then overall neither process would have an
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advantage. This is not the case; supraglottic airway insertion requires little training in
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comparison with ETI. The procedure is far less invasive and SGA insertion does not
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require the need for laryngoscopy, a technique which takes time to master.
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It must be remembered that training is not solely based on the initial level of success
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of a practitioner. The time it takes for a skill acquired to fade is equally important and
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the opportunities for the skill to be used should be discussed. The Critical
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Reassessment for Ambulance Service airway management makes its views clear by
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stating “Skill fade is faster with more complex tasks” before concluding to say that the
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skill fade is faster with ETI than with SGA (JRCALC, 2008) . The research of Reutzler
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et al. investigated the skill retention after 3 months of paramedics who were newly
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introduced to the techniques of airway management (Reutzler et al.,2011) . Initially
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the success rate of intubation was at 78%, with the SGA insertion rate being 100% for
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5 out of 6 of the supraglottic airway devices available. However after 3 months the
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success rate of ETI dropped to 58% whilst the SGA rate remained constant (Reutzler
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et al., 2011). This clearly indicates that the skill fade for intubation is greatly increased
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compared to that of supraglottic airway insertion. The increased skill fade can be
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argued to undermine the belief in ETI as a gold standard. Arguing that these
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paramedics were very inexperienced and that skill fade may lessen for those who have
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been operating for longer can counteract this view. Undoubtedly this would be true for
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paramedics who are regularly exposed to intubation, perhaps by working as part of the
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HEMS teams.
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However, it has become clear that many paramedics in active operation perform so
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few intubations that they could easily be considered relatively inexperienced in
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endotracheal intubation. Paramedics in certain EMS have been shown to perform an
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average of 1-2 intubations per annum (JRCALC, 2008) . Can something be a gold
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standard if skill fade is such an issue?
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The problem of skill fade could be negated if regular training was facilitated. This
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presents further problems for ETI and advantages for SGA. The use of SGA has become
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commonplace in elective surgery and due to this the use of ETI has diminished
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(JRCALC, 2008) . This means that the opportunities for paramedic intubation practice
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have become reduced whilst the chances to use supraglottic airways have increased
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substantially. Importantly, practising intubation opens up issues of consent when it
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occurs on a patient. Patients having anaesthesia conducted are required to consent to
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the procedure which they are having performed in advance, for cases of non-
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immediate lifesaving care (D.G.Bogod et al., 2006) .
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When a training procedure is being carried out during elective surgery, additional
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specific consent is not always required.
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The consent to anaesthesia report details the text below as guidelines to whether
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specific consent is needed for a training procedure:
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“The risks and benefits of each procedure and its components, both to the
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patient concerned and to society in general, must be considered;
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• The harms should be minimised as much as possible, e.g. by close supervision,
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prior practice on manikins, etc.;
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• The benefits should be maximised as much as possible, e.g. by close
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supervision, and targeting skills to practitioners most likely to use them in the
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future;
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• Alternatives should be considered, e.g. other ways of learning/maintaining
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skills, other techniques.” (D.G.Bogod et al., 2006)
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If we consider the above for the case of training paramedics in SGA and ETI it is clear
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which approach is more favourable and easier to achieve. ETI is a highly invasive
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procedure when compared to SGA and therefore it is far easier to train paramedics in
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SGA insertion.
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The final point highlights this with the statement ‘alternatives should be considered’
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the difficulty of obtaining consent for ETI is limiting the ongoing training that it
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requires. The report goes on to talk about paramedic students in particular and argues
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that as long as the procedure is not dangerous or invasive then specific consent is not
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required (D.G.Bogod et al., 2006). This creates the situation where the regular
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training that is required to prevent ETI skill fade in paramedics cannot be easily
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achieved. Whereas SGA insertion is far easier to obtain consent for and thus far easier
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to practice. A dichotomy is created, where the harder skill is at odds with the
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opportunities to practice it and again this suggests that ETI cannot achieve the gold
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standard it is perceived to be.
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Intubation by doctors and paramedics
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Whilst intubation by a solely paramedic team is commonplace, a team consisting of a
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doctor and a paramedic also regularly intubate patients. The addition of a doctor to
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the emergency team is normally seen as part of a HEMS team and adds a new level to
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the discussion.
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It is necessary to turn to the HEMS system of Queensland Australia to investigate
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whether a doctor does make a difference. The doctors involved were all consultants or
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registrars in emergency medicine, intensive care or anaesthesia and would therefore
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have had many years of training.
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The study of Gunning et al. showed failure rate of in-hospital intubation was 0.1% to
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0.4% whilst the failure rate of intubation in the pre-hospital setting was 2.4%
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(M.Gunning et al., 2009) . This low figure also concurs with other studies that have
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occurred around the world who have recorded 100% success rates (M.Gunning et al.,
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2009) . This is due to the fact that the doctor adds the experience of regularly
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performing intubations. ETI becomes a more standard procedure when you have this
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paramedic and doctor team.
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Gunning et al. conclude by saying “Well-trained doctor paramedic teams… can safely
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perform RSI and ETI in the pre-hospital and emergency environment” (M.Gunning et
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al., 2009) . It is clear that having a doctor present has a positive effect on the outcome
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of intubation. It can be seen that hospital standards can be brought to the pre-hospital
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setting and that efficient and effective ventilation can be achieved.
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CONCLUSION
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The discussion has clearly shown that the question “Is endotracheal intubation still
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the gold standard of airway management for patients in out-of-hospital cardiac arrest”
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leads to a complex set of problems to address.
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Firstly, one can conclude that from a biological point of view that endotracheal
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intubation remains the gold standard for airway management. It delivers oxygen
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deeper into the lungs than a supraglottic airway, thus ensuring that oxygen will enter
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the circulatory system with greater efficacy. The higher sealing pressure of an
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endotracheal tube compared to that of a supraglottic airway will reduce oxygen leakage
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and give a stronger protection against gastric aspiration. Overall ETI achieves a faster
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return of spontaneous circulation.
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Secondly, with regard to time, supraglottic airways offer a quicker time of placement
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into the airway; both in the pre-hospital setting and during elective surgery. This is
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due to the procedure for endotracheal intubation being more complex and invasive
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than for SGA.
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The final area of discussion focussed on the performance of airway management and
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this leads to the most concerning conclusion. It concluded that paramedics are
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significantly less effective when inserting endotracheal tubes than when performing
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supraglottic airway insertion. This conclusion can be applied with regard to time
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taken, misplacement and damage caused.
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It can also be seen that paramedic training is significantly responsible for this lack of
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skill. The IHCD regulations for training were seen to be unproven and learning curve
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analysis showed that intubation skill levels remained low after the training
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programmes. One can also confirm that the skill fade for intubation is much greater
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than for supraglottic airways. However, the discussion also concludes that if a doctor
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is present whether performing or supervising, the success rate is improved.
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Overall one can summarise that in the current pre-hospital medical situation,
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endotracheal intubation remains the gold standard, when performed by a combined
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doctor and paramedic team. However, currently the paramedic training, both after
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qualification and during it, is insufficient. This needs to be improved so that the
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benefits of endotracheal intubation can be reliably used in all cases of cardiac arrest.
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Endotracheal intubation is the gold standard of airway management for patients in
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out-of-hospital cardiac arrest, however the circumstances surrounding its use must be
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improved. As part of the current changes to emergency medicine thought should be
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given to further reassessment of the long-standing techniques of airway management.
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To ensure optimal pre-hospital medical standards for treating out-of-hospital cardiac
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arrest is maintained.
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