Introduction
In paramedic practice, the success of resuscitation depends on the maintenance of a patent airway and oxygenation. The return of a patient to the pre-morbid condition is therefore dependent on the efficiency of ventilation and oxygenation than any of the interventions that a paramedic may provide. The achievement of this is also dependent on the technique used, the qualification of the paramedic, and most importantly, the instrumentation used. Various methods of maintaining airway patency and delivering oxygen in pre-hospital settings have been explored in previous studies. Some studies, however, have concluded that the success rates are still low with patent survival following a cardiac arrest still being a challenge. Some have even quoted the survival rates at less than 10% (Bobrow et al, 2009, p.660). The various methods of providing ventilation and overall airway management in cardiopulmonary resuscitation (CPR) include; Nasopharyngeal Airway (NPA), Oropharyngeal Airway (OPA), Endo-tracheal intubation (ETI) Cuffed Oropharyngeal Airway (COPA), Laryngeal mask airway (LMA), and Bag-Valve-Mask (BVM). Endotracheal intubation (ETI) is the preferred method of intubation in most areas of the world and has long been accepted as the ‘gold standard’ due to its ability to protect the airway when correctly used. It, therefore, offers minimal risk of pulmonary aspiration of gastric contents after regurgitation. This is supported by various scientific literature, which prefers ETI to the other methods of airway support for pre-hospital and in-hospital use (Grein, & Weiner, 2005, p.36). There are challenges, however, with the use of ETI in CPR in both hospital and pre-hospital backgrounds. The use of ETI requires training that is not always available and is, therefore, a preserve for highly trained paramedics and healthcare professionals such as anesthetists. Where ETI is not available or use is not feasible, the use of LMA and BVM applies. The efficiency of LMA and BVM in ventilation during CPR is important to establish, as both have been said to be interchangeable. This research paper looks at the efficiency of ventilation with Bag-Valve-Mask and Laryngeal Mask Airway in paramedic CPR, the limitations to their use in both adult and pediatric patients according to the literature regarding their use.
Methods and Techniques
A literature review on the effectiveness and limitation to the use of BVM and LMA was conducted on materials both comparing and contrasting the methods of airway management. The literature review involved articles on the effectiveness of BVM and LMA in Cardiopulmonary Resuscitation. A search on the limitations to the use of these methods in resuscitation in adult and pediatric population was also done with materials on the same being analysed. Various medical electronic databases were utilised ranging from those of 1980s to late 2010 and 2011. Various medical databases were used in the literature review with some of the key words being the efficiency of Bag-Valve-Mask and Laryngeal Mask Airway. The findings were analysed according to the requirements of the study with those meeting the inclusion criteria being selected.
Research in the field of airway support is important in the medicine field. This is because most of the information available shows that intervention in the pre-hospital setting is important in the general survival of the sick people who undergo a cardiopulmonary arrest outside a hospital setting. There is an increased loss of life during the time when a patient is picked up from the site of an emergency to the specialised centre. The airway, being the most critical in the survival of patients, has however received a little attention in the previous studies. More focus is needed on the techniques used in airway support. Therefore, in most of the research materials, the LMA was quoted to have better results in intubation and airway management in paramedic practice. Articles included those comparing the efficiency of BVM against LMA irrespective of the study design used. Most of the research methods involved human patients who were undergoing airway maintenance procedures in paramedic practice where the choice of the technique was according to the competence of the medical practitioner. However, some studies included simulated emergencies where mannequins or humans were utilised. Most of the researches that relate to the field of interest were deficient of information: the methods used were mainly in hospital settings. This means that there was limited material looking into the utilisation of either BVM or LMA in resuscitation and airway management. A further limitation to the review is that the literature was mainly inclined to adult patients with significantly little in the pediatric generation. The exclusion criteria included articles written in any other tongue apart from English and those whose focus was on other techniques other than BVM or LMA. Other sources that were not in the preliminary search lists appeared in the acknowledgments of the available articles. They were fully utilised. A comparison resulted with evidence based on the research findings from these previous studies. Knowledge gaps were extracted along the way with a critical analysis of the methods.
Discussion
Significant results showed that the LMA technique had a better chance of maintaining a patent airway as compared to BVM both in paramedic pre-hospital and in-hospital ventilations. Most people agree that a BVM or LMA may be used as a replacement for Endotracheal Intubation (ETI) in a setting where the ETI is not available, or its use is not possible due to untrained personnel. In most cases, a BVM is the only option that an emergency team has to provide ventilation to a patient in the case of an emergency.
An example of a study done was the comparison of ventilation with BVM, Laryngeal Tube S-D and LMA Supreme. The study provided evidence on which method may be the most efficient and safest to improve cardiopulmonary resuscitation. The study was interventional with a single blind design. It looked at the success rate of airway management until the first effective ventilation (90 seconds) and stomach inflation at 60 seconds. The study however did not include pediatric patients and patients with cervical or spinal pathology.
BVM: Its Effectiveness and Limitations
Ventilation using a BVM involves the use of a self-inflating bag and non-return valve that is attached to a mask. The technique is relatively easy to master and use. It is rapid to deploy especially in an emergency. Its use however requires practice and skill (Ocker, Wenzel, Schumacher, & Dorges, 2001, p.9). Verenthusiastic ventilation with high pressures and tidal volume leads to more of the gas entering the esophagus rather than the trachea leading to gastric inflation. Regurgitation may result with attendant pulmonary aspiration. Some research methods have found the risk of gastric content aspiration higher in the use of BVM as compared to LMA. A good BVM technique therefore requires gentle smooth and slow ventilation to a patent airway (Wenzel et al, 2009, p.130).
The use of BVM in pediatric and adult patients in pre-hospital and hospital settings has greatly been studied in previous researches with varying conclusions. The relative ease with which the device can be used has made it popular. It is especially preferred in pediatric resuscitation in various centers. Its success in resuscitation depends on the technique such as the use of clearing maneuvers such as head tilt, chin lift, and jaw thrust. The last two are inappropriate in trauma patients with suspected cervical spine injury. Practice involves routine techniques, training in the use of two or three person techniques for patients with difficult airways. As highlighted earlier, the use of BVM is coupled with the risk of gastric inflation and resultant pulmonary aspirations. The risk is reduced when using the classical LMA (Ho-Tai, Devitt, Noel, & O’Donnell, 1998, p.210). The technique is also associated with leakage of air around the oral cavity and the nasal area when ventilating due to poor cover of the orifices by the mask during inflation. The leakage of ventilating air can be as high as 40% even with experienced hands of professional paramedics or anesthetists (Goodwin, Pandit, Hames, Popat, & Yentis, 2003, p.62).
During sustained ventilation using the BVM, fatigue in the hand used to ventilate is also a limitation to the use of this device in ventilation. This limits the effectiveness of ventilation besides influencing the overall result of the resuscitation attempt. Alexander et al (1993, p.233) found in their study that only about 40% of the patients receiving ventilation via BVM were still receiving adequate ventilation after a period of sustained inflations as compared to about 90% of patients being resuscitated using the classical LMA. This therefore proved that the BVM is a tiring maneuver whose results in resuscitation are user and time-dependent. Upon correct insertion of LMA, there is less skill required to maintain a patent airway. This is therefore more time efficient. A person who responds to an emergency first is therefore at a greater chance of maintaining a patent airway efficiently using an LMA.
LMA: Its Effectiveness and Limitations
The LMA has been in clinical us since the clinical trial of 1983 shortly after Dr Archie Brian developed its prototype in 1981 paving way to its use in the pre-hospital setting thereafter. The classical LMA was introduced in 1988. Anesthesia has since been revolutionised since its inception. It consists of a mask and a tube with the mask sitting over the larynx and an inflatable cuff surrounding the larynx to form a seal that allows ventilation. The tube runs from the mask section to the outside of the oral cavity and allows connection to the ventilator or self- inflating bag. Although its deployment is slower as compared to BVM (Tolley, Watts, & Hickman, 1992, p.320), there is evidence stating that in, anesthetic practice, it establishes an airway in 99% of cases. Existing airway obstruction resolves 95% of cases where BVM ventilation is impossible (Parmet, Colonna-Romano, Horrow, Miller, Gonzales, & Rosenberg, 1998, p.664). The intubation method used is under the influence of various factors among them being the qualification of the personnel, the patient condition, and the setting ion, which it is done (Hirsch-Allen, Ayas, Mountain, Dodek, Peets, & Griesdale, 2010, p.826).
Some research findings have advocated for the use of LMA in resuscitation as opposed to the use of BVM. Some even show no evidence of regurgitation of gastric contents in its use (Stone et al., 1998, p.5). A tube that is correctly positioned lies and partially blocks the top of the esophagus. It can be reused for up to 40 times and is accessible in different sizes for all patients including pediatric patients. Its use is markedly explored with over 2500 publications and reports of over 200 million insertions worldwide. Though insertion takes longer as compared to a BVM, it is more efficient in maintaining a patent airway and ventilation.
When compared to other methods of ventilation, LMA has been found to have some added advantages in both experienced and inexperienced hands. A study done on the use of the LMA by untrained naval medics found its use to be faster as compared to other methods of ventilation used. It was faster than the tracheal tube (TT) and twice as successful with 100% first time success versus progressive improvement in intubation technique (Davies, Tighe, Greenslade, & Evans, 1990, p.998). The use of LMA in inpatient procedures has also been described in various literatures.
Most of the studies conducted showed that the initial effectiveness of “the LMA when used for the first time was very high and that when utilised correctly on the first attempt was successful on 94 % of cases” (Nickel et al, 2008, p.216). This means that a first time user of the LMA in resuscitation had a probability of getting it right in 94% of cases. This makes the technique a preferred one among paramedics. This is also supported by many other studies that find a success rate of LMA to be relatively high.
Murray et al (2002, p.340) provides a contradiction of these findings. They challenge these findings stating that there is only 64% success rate with the use of LMA in airway management for first timers. They also state that the risk of regurgitation is relatively low with LMA when used to ventilate (Murray et al, 2002, p.340). This means that there is an added advantage of the protection of patients from gastric content aspiration, which is notorious for aspiration pneumonias. Compared to a BVM, LMA was found to be slower in the establishment and initiation of the first ventilation. The time-lapse ion establishment of first ventilation and spontaneous ventilation may mean life and death for a patient during CPR. It may also provide a risk of permanent neurological damage especially for pediatric patients following recovery to a pre-morbid position.
Knowledge Gaps
Pediatric resuscitation using the LMA has elicited a lot of debate on its efficiency with some literatures quoting efficiency that is two times that of BVM (Rechner et al, 2007, p.792). There is, however, the need for more research in the field of resuscitation of children. Special attention is necessary in the models used for facemasks in the various age groups to prevent leakage during ventilation procedures.
Most of the research literatures provide information on the use of BVM and LMA in adult patients, and comparison is made in only this population of patients with little done for the pediatric population. A gap therefore exists on the use of BVM and especially LMA in children. This provides an opportunity for research in pediatric patients. Children are especially at risk of complications following an attempted resuscitation. They are more likely to need resuscitation following the birth of asphyxia that may cause longtime neurological damage. There is also a need to get research done on the efficiency of both the use of BVM and LMA in the resuscitation of newborns especially in the setting of asphyxia.
An exclusion criterion for patients with preexisting gastric regurgitation was also set. A special research should also be done to determine the efficiency of these methods of airway management in this category of patients to establish the exact risks and the outcomes. The fear about the research is from the complications that may arise following intubation in a patient with a history of regurgitation. This happens in everyday intubation. It should thus be investigated further. Regurgitation of gastric contents into the airway, depending on the amount, may cause aspiration pneumonia and pulmonary blockage leading to death of a patient on the resuscitation table.
A prospective area of study relating to this field is also on the long-term effects and complications of using either BVM or LMA in resuscitation of patients in pre-hospital and in-hospital situations. There are also limited resources on the complications and focused research in this area should improve ventilation outcomes. Only one randomised control trial exists on the use of LMA as compared to BVM, and this means that there is a deficit in high quality research regarding them. The randomised clinical trial by Rechner et al utilised “critical care nurses concluding that LMA ventilation was 77% efficient in the patients” (2007, p.792). This is a significant finding in airway management providing a foundation for further research.
In both methods of oxygen delivery, complications exist. These include hyperventilation and hypoventilations depending on the technique used. For the BVM, efficiency can be increased by the use of low pressure, slow insufflations, and low volume to decrease the complications. The use of BVM is also contraindicated in the presence of complete upper airway obstruction, and there is a relative contraindication after paralysis and induction due to the increased regurgitation of gastric contents and their aspiration into the lungs. This, as noted earlier, could be detrimental to the patients’ health and resuscitation outcome.
Conclusion
The maintenance of a clear airway appears at the top in the hierarchy of life support. It comes before the initiation of breathing and supported breathing. The literature review supports the use of BVM and LMA in the management of an airway in pre-hospital setting. A significant conclusion in most of the researches is that LMA is better at the establishing and maintaining of a patent airway in comparison with BVM. There are still questions to be answered in the research questions. This leaves a room for further research. Some of them include the efficiency of BVM against LMA in pediatric patients and in patients with pre-existing gastric regurgitation. There is also a deficiency of professional randomised clinical trials in the comparison of BVM with LMA. These gaps may provide an opportunity for further research. In many research materials, the setting is in a sanatorium leaving room for more research in the pre-hospital setting.
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