Lesson Outline

BVM

"Masking" or BVM involves squeezing air manually into the lungs by a tight-fitting mask held over the face, using a self-inflating resuscitation bag (versus flow-inflated bags such as used in the OR).
The benefit is that it is non-invasive and purportedly requires little skill. It is therefore the starting point, rescue, and fallback for all other airway techniques - ie bag until you can do something else, bag in between if it didn't work, and as long as you can bag, you are not in an emergency (you can at least oxygenate, the #1 priority).
The downsides are many:

It is actually not easy, for reasons to be discussed.
It requires continuous effort and attention, unlike invasive airways that more or less manage themselves.
It does not isolate the airway, which means:

No protection from aspiration
Air insufflated into the pharynx can go into the trachea, OR into the stomach. The only protection from the latter is the lower esophageal sphincter, which has a finite amount of tone and will open with enough pressure (and once opened may not close; it tends to be somewhat plastic). This pressure is >30-40 cmH2O in healthier patients but may be <20-25 in sick/sedated patients.

Manual bagging is inconsistent and difficult, with a tendency to give large, high pressure breaths. On its own, it also offers no PEEP.

So: bag-mask ventilation should be consider a universal skill even in those who will not intubate, because it's what you do until somebody can. However, it should be treated with respect and MUST be directly trained, and thoughtful approaches used to optimize success for "occasional baggers."
Barrier #1: mask seal
- Very difficult to seal the mask to the face using one hand, ie. the standard technique. Hands just aren't big enough.
- Leak most common contralateral to the sealing hand
- The very best answer: two-hand technique
- Other stuff
- Optimizing the mask
Barrier #2: soft tissue obstruction.

Obstruction to airflow can occur at many points.
- Mouth: closed during standard mask technique
- Nose: nares may or may not be patent
- Pharynx: tongue and other soft tissue may obstruct air entry
- Basically, anterior structures in the airway tend to relax and fall back to the posterior structures in sick/obtunded/sedated patients.
- Any of these may obstruct both spontaneous breathing and mask ventilation.
Solution:

Basic technique

Head-tilt chin-lift/jaw thrust. Gently extending head and protracting the jaw opens the lumen of the posterior airway. (Pull jaw up into mask, don't push down. Much easier with two hands!)

Modest extension
Extend jaw

The most open airway: sniffing position.

Discussed mostly in intubation, but probably relevant to other situations - creates the most open, aligned axes for patency of the airway
Combines atlanto-axial extension with cervical flexion
"Sniffing the flowers," "drinking a beer," "leading with your chin" - basically translating the face anteriorly without substantially angling the face either up or down (slight extension)
Usually requires padding behind the head; pillows may be okay, towels much more reliable/manipulable. Padding behind the shoulders is occasionally useful, particularly "ramping" the obese, but not what you're doing here. Elevating the head of the bed is also different.

Consider airway adjuncts.

NPA: maintains patency of at least one nare.

Okay in patients with a gag reflex
Lubricate well
Avoid in significant mid-face or basilar skull trauma
Some risk of epistaxis
Size from tip of nose to tragus of ear, or edge of nose to tip of ear (but many centers only carry one or two sizes)

OPA: maintains open mouth and patency of oral passage

Only in patients with a gag (ie who will eventually need intubation)
Insert with tip toward palate, then rotate down
Size from center of mouth to angle of mandible

Still need good mask technique with adjuncts, but makes it easier when it's hard (eg may not need as aggressive a jaw thrust), and possible when it was impossible.

In extremis, multiple adjuncts can be used together.

Barrier #3: Overbagging

Most adult bags are >1L in volume, while normal tidal volume is ~500 ml
In stress, most providers squeeze hard and frequently, which tends to overinflate the lungs, and redirect volume into the stomach.

Risk of vomiting/aspiration
Risk of lung injury
High lung volume increases intrathoracic pressure, decreasing venous return (e.g. in cardiac arrest)

Solution: bag judiciously

JUST enough to see chest rise
Gently over 1-2 seconds - don't fire the breaths in

Some BVMs may have an airway pressure manometer to help remind you of reasonable pressure

<20 is a good goal in anyone

Appropriate rate

Normal-ish in most patients (12-20)
Slower end of normal in cardiac arrest (every 6 seconds if asynchronous)
Faster in an acidotic patient to make up minute ventilation - but hard to be aggressive with this without a protected airway

Two-person BVM technique may actually encourage overbagging, as one person is now free to put both hands on the bag
Some have trialed using pediatric bags to discourage overbagging - with mixed results

The reason for the extra volume is mostly to make up for a mask leak. With good seal, very little squeeze is needed.

Most non-coding patients will have some spontaneous breathing, so you will need to synchronize breaths with their efforts (supporting volume and FiO2); can usually feel the compliance change as they inhale and support. Make sure to completely release bag when done, or they will not be able to exhale. Even if their breaths are adequate, squeeze at least slightly during inspiration to ensure opening of valve and insufflation of O2.

Other stuff: hardware

Basic BVM offers no PEEP, and most of our hypoxemic patients need some. No real solution except to add a device.

Add-on PEEP valves are widely available, attach to the exhalation port and provide "drag" to expiration. Usually a simple spring valve that can be dialed to rough amounts of PEEP.

Would always have one available during airway management, and would generally/always use it if hypoxic at all.
Side benefits as well - creates a one-way valve on the expiration port (usually open), to ensure spontaneous breathing draws air purely from the O2 supply.
Generally avoid in cardiac arrest, where positive intrathoracic pressure should be minimized.
Note that PEEP will still drop to zero with most devices once expiration stops, so if dealing with serious hypoxemia, maybe bag before full expiration has occurred. Also, no PEEP will be retained if mask seal is not perfect (two hands!).

Capnography

Usually thought of in context of intubation to confirm airway
Continuous wave-form capnography is also an excellent adjunct to mask ventilation, as it provides constant confirmation breaths are actually going in (not just theoretically). Can be applied between bag and mask. Will be needed anyway for intubation.
Can be applied to supraglottic airways as well - usually not to NIPPV masks as these tend to be open circuits.

Mask straps/BiPAP

Rubber straps are available to attach some masks to the face, reducing the need for a tight hand seal
May make you wonder why we don't just use BiPap machines/masks to ventilate - in many cases you can

Very good tool for pre-oxygenation and temporization before intubation
In a deeply obtunded/sedated patient, even if mask seal is reliable, will still need to maintain a patent airway (positioning, jaw thrust, adjuncts), and have caution with airway pressures (risk of gastric insufflation, as the machine will not be gentle unless you tell it to)

Similar mask straps can be attached to some masks and used to help secure during manual bagging as well

Masks with attachment points and mask straps usually more available in the anesthesia setting, less often in the ICU.

How do you get good at masking?

Go to the OR and practice

LMA placement

There is an entire category of airway devices called:

"Blind" - ie insertable without visualizing the airway
"Supraglottic" - ie they do not (necessarily) enter the actual glottic opening and trachea, but sit above it
"Rescue" - sometimes used as a backup when patients cannot be intubated, although they have plenty of other applications.

Some examples include the King airway and Combitube, which are more often seen in EMS
Most common in hospital setting is the laryngeal mask airway or LMA
Pros:

Relatively low skill technique, high success rate, no visualization needed
Provides fairly reliable semi-isolation of the airway without holding a mask, less concern for gastric insufflation

Can manually bag through it, or even place on vent

Totally different technique than masking and intubation, so may work when something else fails you
Can be transitioned to an endotracheal tube via various methods when an expert is available, from simple moves (remove LMA and intubate) to fancy ones (putting a bronch through the LMA and intubating over that, etc)

Downsides:

Need a certain amount of mouth opening
Distorted airway anatomy (epiglottis, etc) may limit seal, although it may still work adequately
Doesn't really seal airway, so doesn't offer much protection from aspiration, and will not hold substantial amounts of PEEP in the lungs
Can be a little finicky to place perfectly, and most non-anesthesia providers don't get a ton of practice - this tempers its "low skill" benefit. Fortunately, it usually works at least somewhat even if not ideally placed.
Generally, should view this as an alternative to mask ventilation, not to intubation

Placement

Candidates are generally the same people we would intubate - LMAs are not well tolerated with an intact gag reflex
May need to induce and/or paralyze to place, much like intubation, outside of the severely obtunded or cardiac arrest
Sizing (for classic LMA): #4 for 50-70 kg, #5 for 70-100 kg
Lubricate posterior surface (dome)
Insert along palate (depress tongue or extend jaw if needed) until stopped or depth markers
Inflate to recommended volume (usually 30-50 - a 10cc syringe will not be enough), or when elevates
Secure and confirm with ETCO2 (always)

Key points

BVM is the universal, baseline skill, but is not very easy

Mask seal is difficult; the best tool is two-handed grip
Optimize positioning with a jaw thrust and perhaps a sniffing position, and consider airway adjuncts
Don't overbag (just until chest rise)
Consider PEEP valve for any hypoxic patient

LMAs are an excellent, relatively approachable fallback skill, a good alternative if you don't intubate, and a first or second line backup for anyone who does

Consider it an alternative to bagging

Use capnography on any invasive airway to confirm adequate placement and ventilation, and strongly consider it during mask ventilation as well for the same reason.

Problem #1: Mask seal

Lesson Outline