The bag-valve-mask, or BVM, is possibly one of the devices that is likely to be one of the most effective pieces of equipment in saving the patient’s life. However, unfortunately it is very often used with little to no training and as a consequence not very effectively (R. Levitan, 2004).
There is nothing more likely to induce a degree of panic in a stressful situation than if the person managing the airway is not able to ventilate the patient. Ventilation of the patient is the most important part of the process of intubation. If you can ventilate then an inability to intubation becomes less of a problem. You can continue to ventilate, thereby supplying the patient with the much-needed oxygen, whilst you either seek further options or further help.
Commonly the bag valve mask is used incorrectly in a number of ways. The bag may be inflated too much and/or too often. The mask itself may not be applied to the patient’s face correctly, perhaps using an incorrect number of people or a grip which is not optimal. It may be that the patient’s head has not been positioned correctly, something which is vital to ensure that ventilation can occur.
Let’s first begin by talking about the bag valve mask itself and its components.
The main component is the self-inflating bag. This bag then does not actually require an oxygen supply to fill. Something to be borne in mind when transferring a patient with potentially limited oxygen. If a disaster were to happen and the oxygen were to run out, then the patient could at least be bagged with room air. This is often a consideration when transporting patients from one place to another.
So these bags are made of a plastic material which will re-expand after being manually collapsed and will come in various sizes ranging from 240 ml up to 1600 ml.
The masks themselves can come in a range of sizes and designs depending on whether the patient is an adult or a child, a large or a small person. The cuff around the mask is commonly inflated with air or made of a firm sponge-like material which is designed to mould firmly around the patient’s face. They are independent of the bag and can be easily separated from it and replaced if necessary. This is a feature which we will come back to later on.
There is an oxygen inlet at one end with tubing attached. This can then supply the bag with oxygen thereby ensuring that the desired amount can be delivered to the patient. It is important when bagging the patient, especially if one has taken over the airway from someone who initiated it, that you are sure the tubing is attached to an oxygen supply and that you are not just delivering air.
There is an air intake valve at one end which is what allows the self-inflating bag to self-inflate.
There is an oxygen reservoir bag which has two one-way valves. This reservoir helps to ensure that the patient is breathing the maximum amount of oxygen available and if necessary rebreathing the minimum amount of their own gases. The inlet valve will ensure that room air can enter if the oxygen gas flow is too low, and the outlet valve will allow oxygen to escape if the pressure in the bag is excessive.
There is a standard 15 mm adapter for attaching to masks or the various tubes which may be in the patient’s mouth.
Difficult bagging…there may be trouble ahead….
When approaching the patient with the bag valve mask be aware that the following may make the process more difficult:
- BMI of 30 or greater
- Presence of a beard
- Mallampati score of 3-4
- Severely limited jaw protrusion
- (Kheterpal et al., 2006)
The Mallampati score is a way of looking at the patient’s airway pre intubation to judge how well they can open their mouth. The score ranges from 1-4 with one being the easiest airway and four being the most difficult. This is a visual scoring system and relies on some subjectivity (Mallampati et al., 1985).
The key to being able to bag the patient effectively relies on some important preparation.
Firstly, we need to consider the position of the patient. Hyperextension of the neck. The ‘head tilt chin lift’ may help open the airway in the first instance, but it might not be the best position for the patient to be in if they are about to be intubated.
The ear of the patient should be level with the sternal notch in order to ensure that the plane of the mouth and the larynx are in alignment. This will help ensure that, when the laryngoscope is used, it will be easier for the operator to visualise the structures. They will have less of a ‘corner’ to look around. This will help achieve the ‘sniffing the morning air’ position that you may hear mentioned (Adnet et al., 2001; R. M. Levitan, 2010; Takenaka, Aoyama, Iwagaki, Ishimura, & Kadoya, 2007).
It may be, with the overweight or obese patient, that many pillows are required in order to achieve this important position (R. M. Levitan, Mechem, Ochroch, Shofer, & Hollander, 2003). It is important that the facial plane should be parallel with the ceiling as hyperextending the neck may make the view more difficult and ventilation harder (Collins, Lemmens, Brodsky, Brock-Utne, & Levitan, 2004).
Another simple way to improve the patient’s airway is to use some airway adjuncts. These would be the guedal airway and the nasopharyngeal airways. It is recommended that, where possible, the patient should have a guedal and a nasopharyngeal down each nostril (Weingart & Levitan, 2012).
Because of the differences in oxygen and carbon dioxide across the alveolar membrane there is a mass flow of gas from the pharynx to the alveoli. This is known as apnoeic oxygenation and permits the maintenance of oxygenation without spontaneous or administered oxygen (Weingart & Levitan, 2012).
It is beneficial then to apply nasal cannula, running at 15L/min to the patient as well as the facemask. Whilst this flow rate does seem high it has been shown that patients can tolerate this for a time (Brainard, Chuang, Zeng, & Larkin, 2015). This will serve two functions. Firstly, it will wash out the expired gases that accumulate in the nasopharynx prior to intubation and, secondly, then provide some apnoeic oxygenation once the patient is sedated and no longer breathing for themselves (Christodoulou et al., 2013; Miguel-Montanes et al., 2014).
Some recent studies have questioned the benefits of apnoeic oxygenation (Patel & Nouraei, 2015), but it is felt, certainly with the non-intensive care patient, i.e. the patient in the accident and emergency department or out on the wards, that it does provide some benefit at little expense or delay in procedure time. That benefit is increased time before the patient begins to desaturate during the procedure, thereby allowing the practitioner more time to pass the tube (Weingart & Levitan, 2012).
Proper grip….proper fit!
There are two ways for the novice user to apply the facemask to the patient’s face….the wrong way and the right way.
The wrong way:
Those who hold a patient’s airway regularly, anaesthetists mainly, tend to hold the patients mask to the face using one hand only. They will then bag the patient using the other hand. In their set up, in the anaesthetic room the bag is attached to the gas machine so they need to be able to reach it. They become expert at this one handed technique as they perform it many times a day.
This is NOT the way the novice should hold the mask to the patients face. It is most likely that a good seal will not be created and, consequently, the patient will not be ventilated properly (Gerstein et al., 2013). The other problem with this technique, in the hands of the novice is that they will become very quickly tired and their ventilation will become even less effective than it already was!
One method taught for holding the mask to the face was the E-C clamp. This is a grip in which the thumb and index finger hold the mask down over the nose and mouth of the patient, forming a C while the other three fingers of the hand grasp the patient’s mandible, forming an E.
This could be done using one or two hands, but once again, in a novice’s hands, a two handed grip is more appropriate (Otten et al., 2014).
The right way:
The better grip, however, would be the thenar eminence grip. With this method, the facemask is first placed over the bridge of the nose and mouth and then held in place using a jaw thrust manoeuvre with the index and second finger of each hand and maintaining mask contact using the thumbs. This has been shown to be a better technique (Gerstein et al., 2013; Hart, Reardon, Ward, & Miner, 2013; Otten et al., 2014; Wheatley, Thomas, Taylor, & Brown, 1997)
Note here, that you are not pushing the mask into the face, but rather lifting the face into the mask. This will lift the soft structures of the oropharynx away from the posterior wall and give you a better airway to work with.
This is, therefore, a two-person technique. One person will hold the mask in place and the other will then squeeze the bag valve mask. This approach is superior to the one handed technique (Joffe, Hetzel, & Liew, 2010).
Once you are sure that the mask is fitting correctly then the bag should be inflated slowly and gently. Over inflation can risk pushing air into the stomach, making vomiting and aspiration more likely and a high rate of ventilation, particularly in cardiac arrest has been shown to be detrimental.
Be aware of the components of the bag valve mask.
Use of adjuncts.
Thenar eminence grip.
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Brainard, A., Chuang, D., Zeng, I., & Larkin, G. L. (2015). A Randomized Trial on Subject Tolerance and the Adverse Effects Associated With Higher- versus Lower-Flow Oxygen Through a Standard Nasal Cannula. Annals of Emergency Medicine, 65(4), 356–61. doi:10.1016/j.annemergmed.2014.10.023
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Originally posted 2016-04-15 18:09:48. Republished by Blog Post Promoter