INTRODUCTION
Since the inception of anaesthesia, the facemask has been an indispensable and adaptable piece of equipment. It is a simple, non-invasive way of administering oxygen as well as anaesthetic gases and vapours to the patient, and is frequently used for both induction and maintenance of general anaesthesia. It is an efficient method of ventilating the unconscious patient and so plays a critical role during resuscitation. Each anesthesiologist should have confidence in their ability to use this piece of equipment.
FACEMASK TYPES
The phrase ‘facemask’ is a broad term that encompasses a variety of various styles, however there are two primary varieties.
The first kind is a ‘open’ mask, such as the Hudson mask, which is often used for supplementary oxygen delivery (Figure 1). It does not need a tight seal against the patient’s face, and often includes extra openings to allow for the escape of expired gases.
As a result, it cannot be used safely to ventilate a patient or deliver volatile drugs. This sort of mask is often used in recovery rooms in the theatre setting to supply oxygen to a spontaneously ventilating patient during intravenous anaesthesia or sedation.
‘Closed’ facemasks are meant to completely seal the mouth and nose of the patient. This function enables the safe administration of volatile agents and, if necessary, positive pressure ventilation of the patient. This mask is often used during cardiopulmonary resuscitation and general anaesthesia. Numerous variations have been documented, all of which have a rim, a body, and a connection (Figure 2). The rim is flexible and air-filled, providing for an excellent seal against the patient’s face. Certain types have a filling valve that allows for precise control of the degree of pressure in the rim (Figure 2). The body is more rigid and is often constructed of plastic, neoprene, or rubber. A wire stiffener may be inserted in certain circumstances to enable the mask to be moulded to the patient’s face. The connection should be made of strong plastic or metal and have an inner diameter (ID) of 22mm to accommodate connector hosing or a self-inflating bag.
Numerous facemasks are now composed of a transparent plastic that allows for visualisation of skin color, fogging, and regurgitation indications.
Additionally, many facemasks have a plastic or metal ring with hooks for attaching a harness (Figure 2, label D). In many areas of the globe, the facemask with harness has been mostly phased out in favor of the laryngeal mask airway.
The interior volume of the mask is considered to be dead space in the device. While this is negligible in adults, it may account for up to 30% of a neonate’s tidal volume. 3
As a result, masks for paediatric usage have been designed to minimize this dead space, and a variety of designs are now in use.
APPLICATIONS OF THE FACEMASK
The facemask’s primary applications are outlined in Table 1. Along with carefully positioning a facemask for a spontaneously breathing patient, an anaesthetist’s ability to do efficient bag-mask ventilation (BMV) is critical. It’s noteworthy that significant emphasis in airway education is paid to tracheal intubation, especially for difficult-to-intubate patients. However, the extreme unfavorable outcomes that might occur are not attributable to an inability to implant an endotracheal tube, but rather to a patient who does not get enough oxygenation. Numerous standards exist for addressing these cases, and important to all of them is appropriate oxygenation rather than recurrent intubation attempts.
Facemask ventilation continues to be critical in doing this.
HOW TO USE A FACEMASK
The purpose of an anesthetic facemask is to establish a full seal between the mask and the patient’s face while applying the least amount of pressure possible without causing soft tissue injury. To begin, it is critical to choose the appropriate size for your patient.
It should be positioned over the patient’s bridge of the nose, with the top border aligned with the pupils. The sides of the face mask should seal just lateral to the nasolabial folds, with the bottom resting between the lower lip and chin. The mask is kept in this position in the awake patient either by hand or by connecting a strap behind the patient’s head. Adults are available in standard sizes; a size 3 or 4 fits the majority of ladies, while a size 4 or 5 fits the majority of guys.
When the patient is unconscious, the airway must be maintained open while this seal is maintained. It is critical to maintain a patent airway because gases given under positive pressure may insufflate the stomach, increasing the risk of aspiration. In this situation, the most effective approach to open the airway is via a jaw push technique. This may be accomplished with either one or two hands.
Plunge of the jaw
Technique using just one hand
• Cover the nose and mouth with the appropriate sized mask.
• Position the facemask using your non-dominant hand, holding the mask’s body between your thumb and index finger.
• Support the jaw with your remaining three fingers, with your little finger hooked behind the angle of the mandible. Avoid applying pressure to the sub-mandibular soft tissues, since this may obstruct the airway, particularly in young patients.
• Raise the mandible upward, toward, and into the mask, forming an airtight seal.
• Slight head extension may help maintain the patency of the airway.
• Squeeze the bag or use bellows to ventilate the patient with your dominant hand.
• Evaluate the technique’s efficacy on a continuous basis by examining bilateral chest movement, hearing for air leaks, and analyzing for indicators of insufficient facemask ventilation.
The primary advantage of using a one-handed approach is that it allows one person to make an airtight seal with the facemask while freeing the other hand to ventilate the patient. However, even for the most skilled anaesthetist, obtaining a good seal while maintaining an open airway is not always attainable. Additionally, it is exhausting for one person to keep this hand posture for an extended period of time, and reaching beyond the angle of the jaw may be especially challenging for persons with tiny hands. Therefore, a two-handed approach should be explored early on and should not be seen as a sign of failure.
Technique using two hands
As with the one-handed approach, the objective is to completely seal the mask to the patient’s face and preserve patency of the airway.
This strategy may be used in two distinct ways (Figure 5). The first method is similar to the one-handed technique mentioned above, except that the extra hand is positioned on the opposite side of the mask and face (Figure 5a). Alternatively, you may support the mask with your thumbs while hooking your index and middle fingers behind the angle of the jaw (Figure 5b). Regardless of whether a one- or two-handed approach is utilized, it is critical to open the airway by elevating the jaw toward the mask rather than pressing downward on the mask.
VENTILATION OF A DIFFICULT FACEMASK
Ventilation via a facemask is not always simple. The general prevalence of problematic facemask breathing is about 5%, as shown by the patient variables listed in Table 3. It is critical to search for these aspects during preoperative evaluation.
Ventilation difficulties or inadequacy must be detected early. Reduced chest movement, considerable air leakage, cyanosis, desaturation, or haemodynamic deterioration are all symptoms (Table 2). It is critical that the anesthesiologist recognizes this early on and has a well-defined strategy in place to rectify the condition. Table 4 lists common difficulties and solutions, and a few are described in further detail below.
The use of an oropharygeal (e.g. Guedel) airway may often greatly increase airway patency, and many anaesthetists advocate for its regular use in unconscious patients requiring facemask ventilation. A nasopharyngeal airway may also be employed, even in conscious individuals who would not tolerate an oropharyngeal airway. Because the use of these supraglottic airway adjuncts decreases the frequency of problematic BMV to less than 0.5 percent, they should be evaluated early anytime facemask ventilation is a concern. Due to the lack of collagen in older individuals’ soft tissues, achieving an appropriate seal around the mask might be challenging. When a one-handed approach is performed, this leak is most noticeable on the contra-lateral cheek. This may be enhanced by having an assistant raise the skin and soft tissue of this cheek toward the mask rim to establish a seal, albeit a two-handed method may be more successful. Additionally, this age group is prone to dentures or a total lack of teeth (edentulous). If dentures are stable, it is often beneficial to keep them in place during face mask ventilation, since this supports the mouth and prevents the cheeks from sunkening. Loose dentures, on the other hand, should be removed since they may shift and obstruct the airway. For patients who are edentulous, a recent research recommended that the bottom pole of the facemask be placed over the lower lip itself, therefore decreasing air leakage at the cheek. 6
Even if there are no additional airway obstructions, the presence of facial hair may make it very difficult to achieve a seal. Numerous ways for improving the seal have been documented. These include placing aqueous gel under the rim of the facial mark or covering the beard with a big occlusive air-tight garment with a hole cut for the mouth. However, it may be worthwhile to investigate a solution that does not need the use of a facemask, such as a laryngeal mask airway or an endotracheal tube.
Finally, if preoperative indications and symptoms of upper airway blockage exist, face mask ventilation will be challenging, if not impossible. Proceed with considerable caution in these circumstances and devise a meticulous anesthetic strategy. Prior to ventilating, a gas induction to sustain spontaneous breathing may be necessary; however, in extreme situations, consider eliminating facemask ventilation entirely by opting for awake fibreoptic intubation or tracheostomy.
VENTILATION OF THE FACEMASK DURING GENERAL ANAESTHESIA
It is customary to use a facemask to maintain general anaesthesia, especially during brief surgeries or when alternative airway equipment is unavailable. While many of the strategies discussed before are applicable in this context, there are a few extra factors to consider.
• Allowing the patient to spontaneously breathe provides a number of benefits, particularly for lengthy treatments. Even with proper technique, stomach insufflation is likely to occur during positive pressure breathing, increasing the risk of gastric reflux, especially at pressures greater than 20cmH2 0. If this happens, the facemask will not protect the airway from aspiration. Additionally, it mitigates the possibility of a considerable increase in the partial pressure of carbon dioxide (PaCO2).
• It’s exhausting to maintain the mask seal and keep the airway open for extended periods of time. To remedy this, a harness may be used to secure the facemask in place, and an oropharyngeal or nasopharyngeal airway can be used to maintain airway patency.
When breathing circuits using high pressure gases are used (such as the Boyle’s machine or circular systems), the Adjustable Pressure Limiting valve enables an easy transition from spontaneous to positive pressure ventilation. Maintaining an open valve during spontaneous breathing will help prevent stomach insufflation.
CONCLUSION
The facemask is a critical component of anaesthetic equipment, and confidence in bag-mask ventilation is a key competency for every anesthesiologist. It is critical to identify patients who may have difficulty ventilating with a face mask, to recognize when ventilation is insufficient and to know how to increase it.
In this circumstance, a facemask may be utilized to maintain general anaesthesia, and spontaneous breathing is preferred. However, it is critical to appreciate the technique’s limits, most notably that prolonged positive pressure breathing might result in stomach insufflation. Additionally, the airway is left vulnerable to tracheal aspiration. However, the facemask continues to be a useful tool for airway control and should be worn throughout all anesthetics. When utilized properly, it may be an efficient and quick technique of ventilating and oxygenating patients.
