Chapter 12 – Face Mask Ventilation

Abstract

Face mask ventilation is a basic skill taught to and practised by a large array of medical practitioners. It is usually the first technique applied to an unconscious patient or victim that is unable to generate effective oxygenation and ventilation. Although it is considered a simple technique its outcome is often suboptimal. This chapter describes face mask ventilation devices, techniques and the concept of difficult face mask ventilation. The one- and two-hand face mask ventilation are reviewed in the context of the airway manoeuvres used to address the upper airway obstruction of the supine unconscious patient: head extension, jaw thrust and the triple airway manoeuvre. The concept of measuring the adequacy of face mask ventilation using known objective ventilation outcome markers (tidal volume, airway pressure and the capnogram) is introduced to contrast with the routine unreliable subjective markers (cyclical condensation of the mask dome and bag compliance). Reassessment of face mask ventilation technique using objective ventilation markers is encouraged to further optimisation of the outcome. The predictors and the management of face mask difficulty is examined from a practical point of view.

Chapter 12 Face Mask Ventilation

Adrian Matioc

Basic Face Mask Ventilation Technique

Adult face mask ventilation (FMV) is an airway management technique used by healthcare providers with variable levels of training, inside and outside the operating room for the oxygenation and ventilation of the unconscious patient.

FMV devices are the face mask, the oropharyngeal and nasopharyngeal airway, a suction device and a positive pressure gas-delivery system. The latter may be driven by the rescuer’s expiratory effort (mouth-to-mask ventilation), hand (the bag of an anaesthesia circuit or a self-inflating resuscitator bag) or a machine (any mechanical ventilator). The face mask is the oldest airway management device specifically designed for inhalational anaesthesia. John Snow’s (1847) had all the characteristics of a modern face mask: a symmetrical dome, a soft edge to provide a tight gas seal and increase the patient’s comfort and a connector to the breathing circuit. (Figure 12.1)

Figure 12.1 Face masks (from left to right): early transparent mask (circa 1960), face mask with anatomical shape for soft seal, generic modern face mask, ergonomic asymmetrical face mask, specialty endoscopy face mask.

(Picture taken by the author, at the Wood Library-Museum of Anesthesiology, Schaumburg, Illinois, with their kind support.)

Proper handling of the face mask is critical, as the grip generates both the airtight seal and an optimal airway manoeuvre. The generic left-hand ‘E-C’ technique is performed with the thumb and index finger resting on the dome (the ‘C’), the third and fourth on the mandible and the fifth at the mandibular angle (the ‘E’). It has never been validated for positive pressure ventilation (Figure 12.2) and has been carried over from an era when anaesthesia was a single-agent inhalational technique administered to a spontaneously breathing patient.

Figure 12.2 The one-hand ‘E-C’ grip face mask technique.

Airway Manoeuvres

Airway manoeuvres are blind techniques used to provide upper airway patency by manipulating solid anatomical structures – the mandible, cervical spine and hyoid bone – to stretch soft pharyngeal tissues connected to them – the soft palate, tongue, epiglottis and lateral pharyngeal wall. The stronger the solid–soft tissue connection, the more effective a correct airway manoeuvre (e.g. base-of-tongue and epiglottis obstruction). The weaker the connection, the less effective the manoeuvre (e.g. soft palate obstruction during inspiration and expiration in obstructive sleep apnoea patients). Nasal cavity obstruction is not affected by airway manoeuvres and requires an oropharyngeal or a nasopharyngeal airway for correction.

Airway manoeuvres have been validated only as two-hand techniques for mouth-to-mouth ventilation. With hands on the chin and forehead/occiput the torque generated in the sagittal plane corresponds to and maximises craniocervical extension. Jaw thrust is applied in the transverse plane with hands on the mandibular angles for maximal subluxation of the temporomandibular joints. Both techniques generate chin elevation, positioning the mandibular teeth in front of the maxillary, and increase the distance between chin and sternum, resulting in upper airway stretching. Additionally, it increases the distance between chin and cervical spine, resulting in upper airway enlargement (Figure 12.3). Combining both techniques with an open mouth (with or without an oropharyngeal airway) generates the most effective technique: the triple airway manoeuvre. Turning the extended head to the side may also prove effective. Airway manoeuvres are used in both partial and complete upper airway obstruction.

Figure 12.3 Airway manoeuvres generate chin elevation positioning the mandibular teeth in front of the maxillary and increase the chin–sternum and chin–cervical spine distance (a – head extension, b – jaw thrust, c – mouth opening added to the two previous mentioned manoeuvres: = ‘triple airway manoeuvre’).

A maximal airway manoeuvre is limited by anatomy (maximal mobility permitted by normal tissues) or pathology (e.g. trauma or degenerative changes of bony structures and joints). Maximal head extension in patients with normal cervical spines is approximately 45°. This can be estimated by the angle between a horizontal (longitudinal axis of the operating table) and the longitudinal axis of the face mask at the cushion level. Maximal mandibular advancement measured on normal anaesthetised volunteers at the mandibular-maxillary incisors level is 16.2 ± 3.2 mm. These measurements can be used as technical objective markers for an FMV attempt. Inability to generate a measurable airway manoeuvre may signal the need for an airway adjunct before the ventilation attempt.

Only gold members can continue reading. Log In or Register to continue