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LMA vs the ET Tube

Free essay example:

 Anthony Quinn

Module 3

The ET tube

&

The LMA

04/10/D001

Student number: 099028691

2704 words

Contents

Introduction                                                3

The Endotracheal tube                                   4                

The Laryngeal mask airway                        4                        

Which device is less traumatic to the patient?    4

Variable factors                                                         5

Difficult airways                                         7

Further indications and contra-indications           9

Freedom of choice and continued education      10

Conclusion                                                          11

References                                                         12                                                  

Introduction

When dealing with a patient’s airway in theatre, the primary concern is ensuring it’s maintained at all times without obstruction. Basically, this is achieved by providing a passage from the mouth to the lungs to achieve positive pressure ventilation of the lungs. There are two popular methods currently in use, both of which have unique features and indications and also contra-indications to consider. These are the laryngeal mask airway (LMA) and the endotracheal tube (ET tube). Both devices are recommended by the Difficult Airway Society (2005) for routine airway management.

In this assignment, the author will be investigating whether practitioners are currently carrying out airway management inline with current manufacturer’s guidelines and whether they understand what is required of them by the Health Professions Council? Furthermore, is this printed information up to date and consistent with the modern workings of an operating theatre. In attempting to answer this, other factors will be considered, such as the degree of continued education available relating to airway management. Also, to what degree is the practitioner influenced by local policy within their particular specialty. Furthermore, does personal experience create a more autonomous approach to selecting an airway device or is there a more generic pattern to treating the individual?

The Endotracheal Tube

ET tubes are measured by their internal diameter, ranging in 0.5 increments from size 2.5 up to 10mm. They are disposable and made of Polyvinylchloridetube (PVC) which moulds to the airway when in-situ and at body temperature. They are transparent which enables the practitioner to monitor breathing via the fogging that occurs and they also possess a dark line along the tubes length which is x-ray detectable. There’s a balloon towards the distal end that seals the airway and a connector at the proximal end, which helps connect the tube to the breathing system. The tube is guided past the patient's epiglottis and past the vocal chords using a laryngoscope. The laryngoscope is an "L" shaped instrument with a light at the end which is used to lift and open the patient's epiglottis so that the practitioner can visualize the ET tube passing through the vocal chords into the trachea. Once the tube is in place, the balloon is inflated to the required pressure to prevent aspiration of gastric contents.

The Laryngeal mask airway

The second device is a Laryngeal-Mask Airway (LMA). It is also made from PVC but has an elliptical mask at the distal end which is inserted into the laryngeal airway. The distal end of the tube is protected by two ‘mask aperture’ bars which prevent the epiglottis from obstructing breathing. A dark line runs along the length of the tube to aid the practitioner in orientating the mask. The mask adjusts to the shape of the hypo pharynx with its mask facing the opening of the laryngeal inlet forming a low pressure seal which permits positive pressure ventilation.

Which device is less traumatic to the patient?

Tenaka et al (2003) describe the placement of an ET tube as a significant development in modern medicine. The same can be said for the LMA with both devices assuring positive pressure ventilation in a variety of clinical situations. Inevitably, however, there are risks involved. The Health Professions Council (HPC 2008) section 2c.1 states that practitioners should “be able to monitor and review the ongoing effectiveness of planned activity and modify it accordingly.” Operating department Practitioner’s (ODP’s) face these challenges when setting up for theatre lists and should ensure that the difficult intubation trolley is close at hand to prepare for any possible eventuality. After extubation, the ET tube can cause respiratory problems, often originating from trauma to the larynx. Laryngeal edema is a common result of this trauma which manifests itself in the form of excessive secretions of mucus and blood due to swelling of the capillary wall structure. This is particularly prevalent in lengthy operations with this swelling seeming to be more common in procedures making use of the ET tube. This was the conclusion drawn in a study by Tenaka et al (2003) where fourteen patients with a physical status of one and two (American Society of Anesthesiologists ‘ASA’ grading) were compared for laryngeal resistance post surgery, with half the group fitted with ET tubes and the other half with LMA’s. Sevoflurane levels were maintained at the minimum alveolar concentration throughout whilst the authors measured laryngeal resistance before and after surgery, with results gathered during both mechanical and spontaneous breathing. Measurements of the angle of the vocal chords were taken, all whilst under paralysis. The results showed a marked decrease in the angle of the vocal chords of the seven patients intubated with an ET tube compared to little or no trace of a change with the LMA. This would certainly indicate that use of the LMA has an advantage over ET tube placement in order to avoid postoperative laryngeal swelling.

Variable factors

Since its launch in 1988, the LMA has been estimated to have been used in over 200 million anaesthetics and is the most frequently used airway device in operating theatres throughout the United Kingdom. One of it’s attributes are its ease of use and flexibility in varied disciplines and as described by Chethan et al (2008), it fills a niche between face mask and endotracheal tube both in terms of anatomical positioning and invasiveness. There is room for ‘Practitioner choice’ in healthcare which is backed by the HPC (2008) in section 1a.6 which endorses an autonomous approach using professional judgement. However, this is a double edged sword as the LMA’s flexibility also allows room for varied success of intubation. For example, John Henderson (2006) describes how “a suboptimal airway occurs in a significant proportion of patients in whom the LMA is used.” He goes on to analyse some published results which reveal that in only 40% of insertions was an ideal view of the vocal chords seen. This can be attributed to the practitioner entering the airway ‘blind’ but is a worrying statistic considering that any incorrect positioning of the LMA can result in regurgitation and potential pulmonary aspiration.

The assumption is that the LMA has many advantages over the ET tube but it is important to consider whether these advantages are favouring the patient or the practitioner? The HPC (2008) section 1a.1 stipulates that practitioners; “should understand the need to act in the best interests of service users at all times”. Chethan et al (2008) highlighted some of the Indications of the LMA for the patient including:Lower recurrence of coughing during emergence, enhanced oxygen saturation during emergence, Improved haemodynamic stability during induction and emergence and a minor increase in intraocular pressure after insertion. Ultimately, the LMA is considered to be less painful to the patient post surgery and has a lower incidence of sore throat in adults.Another indication is an increased ease and speed of insertion by inexperienced personnel and anaesthetists. Hartmann et al (2003) anlalysed the time difference between induction and emergence from anesthesia, using an LMA and an ET tube. The LMA proved to speed up induction times but there was no difference in the time taken for emergence from anaesthesia.  Hartmann et al (2003) conclude that “the clinical relevance of reduced anesthesia induction time using an LMA is questionable.” The HPC (2008) section 1a.1 recommends that clinicians should practise in accordance with relevant medicines legislation, so as long as these guidelines are being met, by-products of this care including quicker operating lists can only help in the efficient running of a theatre and must surely give the ODP more scope to give a high level of care. The HPC (2008) section 2b.3 makes reference to this, stipulating the need to formulate specific and appropriate management plans including the setting of timescales.

Difficult airways

On raising this argument, there does appear to be an area for debate on what actually is considered a difficult intubation. Bale and Berrecloth (2003) highlight the usual five variables used to clarify this matter i.e. Modified Mallampati, range of head and neck motion, width of mouth opening, the presence of overbite and the presence of mandibular recession.

Paix et al (2005) conducted a study into the unexpected problems that may arise when intubating and the difficulties this leads to in ventilating the patient. He goes on to say that If not well managed, there can be serious consequences for the patient. A simple structured approach was created to this problem which was developed to assist the anaesthetist in this difficult situation. Of the findings, obesity, limited neck mobility and mouth opening were the most common anatomical contributing factors. They concluded that existing preoperative clinical tests in predicting difficult intubation were not satisfactory and suggested an ongoing need to educate practitioners on pre-intubation strategy’s to deal with potential problems and any associated issues with ventilation. This includes a recommendation that skilled assistance be obtained when problems are expected. Also, patients should be assessed post operatively and informed of any issues encountered and this should all be recorded and referred to if necessary for continued learning. This approach is referred to in the HPC (2008) Section 1a.8 which requires practitioners to, “understand both the need to keep skills and knowledge up to date and the importance of career-long learning.” The need to be technically proficient is obviously something well documented across the discipline of healthcare and can be viewed in the’ Association of Anaesthetists in Great Britain and Ireland’s’ (AAGBI 2009) safety guidlines, ‘safe management of anaesthetic related equipment’, section 3. This stipulates that “All anaesthetists must be adequately trained in the use of, and familiar with, all equipment which they use routinely.” This is very specific to the anaesthetist but the HPC (2008) section 1b, ‘Professional relationships’, calls for the ability to demonstrate effective and appropriate skills in communicating information, advice, instruction and professional opinion to colleagues.

It is clear to see for anyone involved in intubating a patient that the LMA is an easier device to master. Reinhart and Simmons (1994) compared the Placement of the LMA with the ET tube during a study of nineteen practitioners. Ten of these failed on their first attempt with the ET tube but all succeeded with the LMA. Their conclusion was that the LMA is an acceptable alternative to failed endotracheal intubation. However the indications in the The ‘Laryngeal Mask Company Limited’ (2005) instruction manual are that the LMA airway is not a replacement for the ET tube, and is best suited for use in elective surgical procedures where tracheal intubation is not necessary. The author has never witnessed any occurrence of the LMA being used as a substitute for an ET tube and A large proportion of difficult intubations have simply called upon the use of a bougie. The ODP will also assist with a jaw thrust when necessary and also apply cricoid pressure if need be.

The LMA is considered to be less painfull with less coughing post surgery. However, if manufacturer’s guidelines are not followed, post operative complications can occur. For example, Chan and Grillone (2005) describe a case of vocal chord paralysis after the use of an LMA. This was diagnosed as an immobile left chord after the patient had been in Orthapaedic surgery and suggested this problem may have been due to either an inflated cuff before insertion, the LMA being held down during inflation (it may rise slightly as it fits into place) or simply over-inflation of the cuff. The ODP can listen for leaks and also monitor chest movement and the capnograth reading on the monitor to determine whether sufficient inflation has been achieved.

Asai et al (1998) discuss how an over inflated cuff can cause hypoglossal nerve paralysis and a precautionary step should be to inflate as little as necessary to prevent any leaks, i.e. the guidline on the instruction manual is a maximum volume but ODP’s should aim to establish the minimum volume by listening for leaks and securing the LMA accordingly, with the aim being to reduce the pressure (and potential damage) on the pharynx.

It becomes apparent, therefore, that manufacturer’s guidelines should also be dealt with sensibly with an experience of intubation and extubation technique being important in translating the information. This is backed up by Middleton (2009) who highlights the variations of LMA insertion to the original Brain technique and also by Yodfat (1999) who indicates that these variations exist because patients have different needs.

Further Indications and contra-indications

LMA’s don’t protect from aspiration or allow for suction of fluids but Brimacombe (1999) explains that suctioning is not necessary as secretions won’t enter the larynx and suction may cause laryngospasm. He continues, highlighting that if the patient doesn’t have sufficient reflexes, however, secretions could enter the larynx and cause laryngospasm. A possible solution is to leave the cuff inflated on extubation but this carries its own possible side effects, namely, post surgery pain of the pharynx with Brimacombe (1999) telling us that the aim is to stop any contact with the epiglottis or larynx that could cause trauma or nerve stimulus.  Patient’s at risk from aspiration i.e. those who are likely to regurgitate like the morbidly obese, pregnant women or those with acid reflux. These are all considerations that need to be taken into account and on collection of a patient, any history of acid reflux, asthma etc are checked once again. With obese patients, Bale et al (2010) describes the intubation restrictions that may exist i.e. a large tongue, high anterior larynx and excessive palatal and pharyngeal tissue. These factors create problems for both insertion of an LMA and an ET tube. Furthermore, the decreased jaw mobility of an obese patient only adds to the problems encountered.

A tracheal tube is most likely used during longer operations, where muscle relaxation is required and also where access to the airway is restricted. In the authors experience, ET tubes have been used in ear, nose and throat (ENT) and Maxillofacial operations where there is a need to protect the airway from aspiration and secretions of blood or gastric contents.

Freedom of choice and continued education

The AAGBI (2009) safety guidlines, section 6 outlines the ‘choosing and trialing’ of equipment and refers to the consequences for the practitioner of local and national policy. For example, the reduction of costs may motivate a hospital to restrict purchase to one type of LMA or ET tube. This takes away freedom of choice from the practitioner which shunts the autonomous approach somewhat. In the AAGBI (2009) safety guidlines, section 13 states, “There is little or no national framework for the standardization of training in use of devices in anaesthesia…” The result is that it is left up to the individual to ensure they receive the appropriate training and that this is continually updated.

Conclusion

As the research has shown, the ET tube and the LMA both posess unique features and indications and also contra-indications to consider. The manufacturers guidelines should be studied closely but there must always be room for the practitioner to approach each case independently using their knowledge of the patient and the equiptment to make an informed decision when selecting a device. It is only with a degree of choice that safe practice can be ensured with The HPC (2008) section 1a.6 stating that practitioners should be able to use their initiative in their approach to a medical situation. Middleton (2009) also touches upon this and discusses the importance of being aware of issues raised regarding insertion and to understand why a certain approach is being adapted and the pro’s and con’s attached to it. Also, the ODP should remain vigilant and ask themselves, are these decisions based on evidence or simply routine?

The LMA clearly offers ease of use and is a practical solution to controlling the airway whilst the ET tube is a more reliable option as it offers the greatest management of the airway and is easier to control. From the author’s perspective, practitioners are currently carrying out airway management inline with manufacturer’s guidelines with the general approach to airway management demonstrating a good understanding of what is required by the HPC (2008).

Continued education is largely down to the individual but the environment strongly promotes this approach as each case is an education which can be learned from to advance future practice.

References

Asai et al (1998), cited by Middleton, 2009:p32

The Association of Anaesthetists of Great Britain and Ireland (2009). Safety guidelines. Safe management of anaesthetic related equipment. http://www.aagbi.org/, (23/09/2010).

Bale, E. and Berrecloth, R. (August 2010). The obese patient. Anaesthetic issues: airway and positioning. Clinical feature, 20.http://www.afpp.org.uk/books-journals/journal_archive/search?keywords=the+obese+patient&more=, (16/09/2010).

Brimacombe, 1999, cited by Middleton, 2009:p33

Chan & Grillone, 2005, cited by Middleton, 2009:p32

Dr Chethan, D. and Dr Hughes, R. (March 2008),  Tracheal intubation,tracheal tubes and laryngeal mask airways. (March 2008). Intubation, 18.  http://www.afpp.org.uk/books-journals/journal_archive/search?keywords=Tracheal+intubation%2C&more=&x=14&y=9, (19/09/2010).

Dr Chethan, D. and Dr Hughes, R. (August 2010). The obese patient. anaesthetic issues: airway and positioning. Clinical feature, 20. http://www.afpp.org.uk/books-journals/journal_archive, (30/09/2010).

Difficult Airway Society. (2005). Difficult Airway Society Equipment List.

http://www.das.uk.com/equipmentlistjuly2005.htm, (28/10/2010).

Hartmann, B. et al (May 2004). Laryngeal mask airway versus endotracheal tube for outpatient surgery: analysis of anesthesia-controlled time. Journal of clinical anaesthesia, 16(3), 195-199. http://www.Laryngeal mask airway versus endotracheal tube for outpatient surgery analysis of anesthesia-controlled time.mht, (28/09/2010).

Health Professions Council. Standards of proficiency. (2008). Operating department practitioners. (Policy). Health professions council.

Henderson, J. The laryngeal mask-have we gone too far?

www.eams.eu.com/abstracts/2006/LMA-Henderson.doc, (15/09/2010)

Paix, A. Williamson, J. and  Runciman, W. Crisis management during anaesthesia: difficult intubation. Clinical feature, 20. . http://qshc.bmj.com/content/14/3/e5.full, (22/09/2010)

Reinhart , D. Simmons , G. (August 1994).  Comparison of Placement of the Laryngeal Mask Airway With Endotracheal Tube by Paramedics and Respiratory Therapists. Annals of emergency medicine, 24. http://www. Comparison of Placement of the Laryngeal Mask Airway With Endotracheal Tube by Paramedics and Respiratory Therapists.mht, (15/09/2010).

Tanaka. A. M.D et al. (2003). Laryngeal Resistance before and after Minor Surgery: Endotracheal Tube versus Laryngeal Mask Airway(TM). Anesthesiology, Clinical Investigations, 99(2), 252-258

Middleton, P. (January 2009). Insertion techniques of the laryngeal mask airway:

A literature review. Clinical feature, 19. http://www.afpp.org.uk/books-journals/journal_archive, (27/09/2010).

Yodfat, 1998, cited by Middleton, 2009:p33

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