When you think of weapons of mass destruction, a bag-valve mask probably doesn’t come to mind. But according to Timothy Redding, NRP, I/C and founder of Emergency Education Consultants, they certainly fall under this category when used improperly. “We’re killing people," Redding said at his Virginia EMS Symposium session “Ventilation Basics: This Session Will Change Your World,” on Nov. 8 in Norfolk, Va. Redding reviewed the main problems associated with improperly ventilating patients.
Volume and Rate
If the volume of an adult BVM is approximately 1500 milliliters (mL) and an adult’s normal tidal volume is around 500 mL, or 350 if you account for dead space, why are we ventilating three to four times that amount with a full squeeze of the bag? On average, what we really need to give is 6mL/kg. Use a patient’s estimated height (not weight) to calculate the ideal amount for their body—for reference, the NIH has a chart listing the appropriate tidal volume according to a patient’s predicted body weight.
For example, Grandma Betty who is five-feet tall and weighs around 45.5 kg only requires about 270 mL while the six-foot tall, 78kg high school football player needs 470 mL. Hyperventilation increases the risk of gastric distension, hypotension and poor perfusion (especially during compressions). Redding offers four solutions to ensuring proper volume:
If ALS is on scene, put the patient on a ventilator and dial to 450 mL to stabilize them.
If no ALS is present, use the BVM the right way—when assessing ventilations by chest rise, it should be barely visible. You don’t need to see a huge expansion of the lungs to indicate sufficient ventilation.
“Sleeve” the bag. Keep the end part of it squished in to lower the volume to 500-600 mLs.
Use an adult mask on a pediatric BVM, which will provide about 500 mLs (Redding cited this study concluding that pediatric BVMs are consistent with lung-protective volume).
Redding noted that if you’re afraid of the ED nurses or doctors yelling at you for sleeving the bag, just expand it when arriving at the hospital and squeeze less. “Do what’s right for the patient,” he said.
As far as rate goes, 10 breaths per minute is ideal the majority of the time. Redding cited that CARES data shows we’re doing 160 compressions per minute on average. It takes discipline to wait 5-6 seconds to administer a breath under the stress of working a code, so using a metronome on your smart phone or counting “one one-thousand, two one-thousand,” and so on helps you slow down to the proper pace.
Redding also recommended products designed to help providers maintain proper pacing, like ventilation timing light stickers, manometer timers (which help correct volume, rate, and speed), and the SMART BAG®, which responds to the rescuer’s ventilations by mechanically resisting excessive squeezes.
Redding advised the following steps for achieving and maintaining a proper seal:
Spread the mask first.
Using both hands, pull the mask apart.
Apply the mask without the bag.
Contrary to what we learn in EMT and paramedic school, the head-tilt/chin-lift technique is not effective in opening the airway. One rescuer should be holding both sides of the mask while the other ventilates so air doesn’t leak on the side you’re not holding. Make sure you don’t push the mask onto the face—rather lift the jaw to the mask using the jaw-thrust maneuver (or thumbs-up technique).
Opening the Airway
Proper positioning of the patient is crucial during airway management. The airway opens significantly more from a jaw-lift than a head-tilt/chin-lift. This is done by first putting the patient into a ramped position: place padding such as towels under the patient’s upper back and neck at a 45-degree angle. Make sure you line the ear to the sternal notch if there is no suspected c-spine injury. Don’t use pillows, as the face must be flat and parallel to the ceiling (Redding referred to the acronym COFFIN: Cannot Oxygenate Face Flat In Neutral, coined by airway management expert Rich Levitan, MD). Then, move the jaw by translating the mandible anteriorly and begin airway management.