What Happened to Ventilation?

Today’s
EMS Providers still
use the Bag-Valve Mask device, despite the many years of research which
have conclusively demonstrated that it is a poor performing and
difficult to use resuscitator. We keep using it even though it
delivers low volumes at high flow
rates and high pressures. Every day somebody dies of hypoxia while
being bagged. I often wonder if we use it because
we want to ventilate, or because we have a primal need to
squeeze something. Tidal Volumes with the BVM are typically very low. I
guess nobody was actually meeting the standard of care (10-15cc/kg),
so they lowered it. Completely forgotten is that the volume you deliver
should vary with the patient
size.
Remember that oxygen is a drug. It should be administered in doses
tailored to the size, age, weight of the patient coupled with their
clinical condition. Does the same dose make sense for all adults? No.
How can a BVM address this? It can’t. Most of
our ventilation patients are either in Cardic Arrest or Respiratory
Arrest. They are not hemodynamically stable patients in an ICU bed.
Because they are critically compromised, they need more and not less
oxygen.

A
recent article in a leading EMS Journal stated that “the lowest
possible pressures and tidal volumes should be used” and that “using
one hand instead of two will help avoid over-ventilation.” By the way,
this was otherwise one of the better pieces written about ventilation
lately. You really cannot "over-ventilate" (meaning deliver excessive
tidal volumes) with any commercially
available device. The maximum volume setting on any EMS Ventilator is
1.2-1.5 liters. The maximum one can deliver with any BVM is less than 1
liter, even two-handed on an ET Tube. A Demand Valve at 40LPM can only
deliver 1.3 liters over a two second inspiratory time. The average
adult lung Vital Capacity is 3 to 5 liters, so how can you
over-ventilate with volumes that are always less? Obviously you can’t.
What
you can do is use too much pressure. This is directly caused by too
high a flow rate, which is quite common with a BVM. Without any control
over flow rate, pressures can get as high as 60-80cm, well above
esophageal opening pressures of about 20-25cm (or less). This means if
you put the air in too fast, the limited opening of the trachea will
turn these high flow rates into high airway pressures. It’s the high
pressures that cause complications like aspiration, not tidal volume.
 

That
is why it is so important to control flow rates, because it is the key
to delivering good tidal volumes safely. We live in a world where
hyperventilation only means “Bag Fast”, when it really means to
“Increase Alveolar Minute Volumes”. Hyperventilation can be done with
either Rate or Volume, or a combination of increasing both. It is not
just rate alone. Going real fast gets you to squeeze faster, resulting
in shorter inspiratory times and higher pressures, which forces air
into the stomach. Then they vomit, aspirate, and die. You can easily
and safely deliver a liter or more of tidal volume IF, you extend the
inspiratory times and control the flow rate to keep the pressures
low. A basic Pocket Mask or Pulmonary Resuscitator can do it, and
better than a BVM. This too has been well documented.
 

If
you really must squeeze something rhythmically, please do it in the
privacy of your own home and not on a viable patient. Maybe buy a nice
roll of Charmin to squeeze, and then go buy a decent time cycled,
volume constant ventilator for your patients. Or even just use a Pocket
Mask; hold the seal firmly with two hands, and blow real slow until you
see a nice chest rise. I recently ventilated a patient for over 30
minutes on just room air with a pocket mask type device, to see them
stand up and walk away. NOBODY bagged on an unprotected airway 30
minutes with a BVM ever stands up and walks away. 
 

I
still like the words of a UK Medic who once said to me (when I commented on the nice ventilator they carried) “Back in the
States, aren’t you guys still zipping them up?” It took a few minutes
before I realized he meant, “bagging them” but on reflection I decided
he did not to be need corrected, I did. Yes, we are still “zipping them up”,
-into body bags. We have stuck our heads in the sands of blissful
ignorance, and steadfastly refused to either learn basic ventilation
mechanics, or any of the many technological advances in ventilation
over the last 25 years.

Now
the AHA also seems ready to abandon emphasis on proper ventilation.
Sure, shock fast is great when the down time is under two minutes, but
when it is longer you better oxygenate the myocardium or you are not
going to get anywhere. To simply abandon efforts to improve emergency
ventilation is only going to get us one thing, more dead people. It’s
time to learn the most important job an EMT or Medic will ever do. It’s
time to say, “We will no longer accept ineffective ventilation technologies and
improper techniques that don’t work”. I’m convinced that a continued
lack of emphasis on ventilation science in EMS is leading us down a
wrong road. I’m not following because I like my clinical saves
way too much.

A
wise man once said to me, "Keep doing what you have been doing and you will keep
getting what you have been getting."
I don’t use BVM’s and I keep getting
saves.

What have you been getting?

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About Dan White

I'm a retired Paramedic and EMS Instructor with 35 years EMS and emergency medical product experience. I love canoes, cars and EMS. I have written a lot about EMS Technology on the Paramedic Blog, the Insights on Innovation column for EMS1.com, on AmbulanceWorld.com and Multibriefs.com. I can be reached directly at 573-240-0002.
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6 Responses to What Happened to Ventilation?

  1. Unknown says:

    good points there. correct me if i am wrong, but in my area, demand valves were pulled because people were popping blebs? it is so hard to train somebody how to use a BVM, and i have almost never seen anybody use them correctly. so what are these ventilators running these days anyhow?

  2. Dan says:

    All the demand valves were changed many years ago from high flow rates of 120 to 160 LPM, down to 40 LPM flow. This reduced flow (since about 1994-95) and pressure relief valves have made Demand Valves actually safer than the BVM in my opinion. With the Demand Valve you have controlled flow rates and a pre-set maximum inspiratory pressure (+- 60cm). With the BVM you can have very high flow rates, and uncontrolled maximum pressures – which can reach 80cm or more. Congratulations, you are thinking smart and asking the right questions.

  3. Unknown says:

    I never hear of anyone using an FROPVD — just putzing along with the one-person BVM. At the BLS level, it\’s especially problematic I think. Using a pocket mask just doesn\’t Look Cool. A pocket mask with supplemental O2 will do what, about 50%, pure oxygen? It is the Proven best method to deliver o2 to the apnic patient, but also the most underutilized. People talk about hating the demand valves because they can\’t check for lung compliance, but these people never use a pocket mask. The BVM just adds one more complication to check lung compliance. With the pocket mask, you can assure a good mask seal, see and feel directly for lung compliance, deliver a good volume, and a nice even flow. The National Registry exams reinforce this false lust for the BMV. The skill station for the apnic patient is single person, then two person BVM. Never is there any consideration for the Science and Data behind proper oxygenation methods. Because so many medics spend their time trying to get a mask seal, they never really give their patients a chance. Most medics around here scoff at the FROPVD, despite it having a better effectiveness than the one person BVM. I don\’t get it.

  4. Dan says:

    Don\’t let go of your most excellent common sense – it will keep your patients alive !

  5. Dom says:

    Gday guys, im training to be a paramedic at uni down here in Aus (2nd year) and I\’ve still got a lot to learn, but this post intrigues me. We have been rigorously trained in the use of BVM at high flow rates, 100% O2 for patients in respiratory or cardiac arrest, we have no pocket mask that i know of and we are discouraged in using the demand valve thingy because of the risk of over ventilation. Are we being mislead here or is it just a difference in protocol and equipment? Also, if you have set up an effective airway with good head tilt, jaw thrust etc, and evn have an ET tube or LMA lpaced in properly, aren\’t you pretty safe in not blowing air into the stomach?
    Cheers guys  

  6. Dan says:

    There are two different kinds of flow rates being discussed. When I talk about ventilatory flow rates, I mean the volume of gas per second delivered to a victim who is being artificially ventilated. You are talking about the flow rate of oxygen being provided to the ventilatory adjunct. They are two different things. BVM\’s must be able to deliver over 85% oxygen from a wall flowmeter at 15LPM. We always say 100%, but they rarely can do that. What folks are really saying is that they gave 100% oxygen set at 15 or 25 LPM, which results in a final inspired (or delivered) FIO2 of about 90%. But of course unless you have an oxygen blender, you always use just 100% oxygen.
     
    The faster or more gas you force through the airways into the lung each second, the higher the inspiratory pressure and tidal volume. For example, 1 liter per second flow over a one second inspiratory time = a tidal volume of 1000cc.
     
    You really cannot "over ventilate" with any commercially available device less than 10 years old. An adult can hold 3-5 liters of gas in the lung, and nothing can deliver more than half of that. The most common problem in ventilation is delivering low tidal volumes at high inspiratory pressures over short inspiratory times. Bottom line is slow down, quality not quantity.
     
    While there were serious issues with demand valve devices back when they flowed at 160LPM, for a long time most have been flow limited to 40LPM, with a pre-set "pop-off” or safety relief vale set at 60cm H2O pressure. In other words, they don\’t flow so fast that the inspiratory pressure spikes quickly, causing air to be delivered into the stomach with resulting aspiration. They are pretty safe now. Yours may well have a small marking or sticker on it indicating the flow rate.
     
    As to different airways and methods of protecting from aspiration, only an ET tube, Combitube or EasyTube protects the airway. Manual methods, head tilt, jaw thrust, LMA, facemask, do not block the esophagus. They only facilitate the movement of gas freely into the trachea. While I like the intubating LMA\’s and the similar Cookgas ILA – I\’m really not a big LMA fan. You are better off and have more options with a duel lumen rescue airway. Even the old PTL airway does a better job keeping aspirate out of the trachea. LMA\’s most appropriate application is the OR on patients who have not eaten for more than 12 hours. In that venue, they rock.
     
    If it’s your Father, Mother, Kids or loved one, please just grab your pocket mask. Deliver nice, slow, full breaths over about 1.5-2.0 seconds until you see chest rise. Deliver each big breath slowly with a good head tilt/jaw thrust about 10-12 times a minute, and they could easily survive. I did just that for over 40 minutes on a narcotic OD and he got up and walked away.
     Hope this helps clarify a few things :>)
     
     

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