Hi, everyone. Welcome back. In today’s video, we’re going to talk about ventilation support and how it pertains to CPR and BLS maneuvers.
Let’s start at the beginning, the basics, the head-tilt-chin lift. Remember, when a victim is unconscious, lying on their back, the most common airway obstruction is the tongue. We’re going to perform the head-tilt-chin lift to get that tongue off the back of the airway and open up the airway. What’s important is how you perform the head-tilt-chin lift. Always grab from the bony part of the jaw. Take your fingers, come underneath the bony part of the jaw and lift straight up. Your tongue is attached here at the base of the jaw. By lifting the jaw, this actually pulls the tongue off the back of the airway and opens up the airway. Avoid putting your hands anywhere in here, the fleshy part of the neck, as that can actually close the airway. If you’re at Walmart and the guy drops, you’re probably not going to have an Ambu bag or your airway kit. You’re going to have to do mouth-to-mouth ventilations. You’re going to get down next to the victim, do a good head-tilt-chin lift, place your mouth over their mouth. Remember, air will take the path of least resistance. You have to pinch off that nose to make sure that air goes into the lungs. If you don’t pinch off the nose, air will come right out through the nose and you’ll probably have snot all over the side of your face, which we want to avoid. Make sure good head-tilt-chin lift. Make sure you pinch the nose before providing that breath into the mouth.
Next, mouth-to-mouth on an infant. The preferred method is to do mouth to nose and mouth, which means you’re going to place your mouth over the nose and the mouth of the infant and ventilate that way. If the infant is so big that you cannot maintain a seal with your mouth over the nose and the mouth, in that case you’re going to just pinch the nose and ventilate the infant through the mouth, just like a child or an adult. Really, it’s the size of the child. The age doesn’t matter. Can you effectively seal your mouth over the nose and the mouth? Then that’s preferred. That’s what you do. If the kid’s so big that you can’t do that, you pinch the nose and ventilate right through the mouth.
Next, let’s talk about gastric insufflation for a moment. This is actually putting air into the stomach, which we want to avoid. One way we can do this is paying attention to our tidal volume. Tidal volume is expressed like this: Vt. Tidal volume is the amount of air, the volume of air we’re going to administer to the patient with each breath. We can calculate this out. If I just intubated a guy and I’m figuring out what his tidal volume is to put him on a ventilator, I’m going to calculate this at 6 to 8 cc/kg. That’s how much tidal volume I’m going to administer to this patient. The average guy on the average day, the average adult, about 500 cc of air. We’re doing BLS today, and I have this Ambu bag. The average volume in this bag is anywhere from 1400 to 2000 cc, but I only need to administer 500 cc to my patient. How do I know how much air I’m giving with each breath? I don’t. We’re completely guessing. We have no idea. How do we gauge it in the field? Chest rise, that’s what we’re looking for. We’re just looking for chest rise. When you’re providing ventilations with the Ambu bag and you’re using one hand, you’re going to provide a certain volume of air. Any time you’re providing ventilations with two hands, know that you’re probably going to be delivering more tidal volume. We have to be conscious of this. We have to watch how much tidal volume we’re actually giving that patient.
Next, still talking about gastric insufflation, another factor is I-time (inspiratory time), which is the amount of time it takes to administer 1 breath of air to a patient, how long it takes us to put that tidal volume into the patient. In the average adult, we’re shooting for about 1 second. That’s our I-time. It should take us 1 second to put 1 breath of air into a patient. If we have an advanced airway, all that pressure is just going into the lungs, which is fine. Without an advanced airway, that air can go into the lungs or it can go into the stomach and cause gastric insufflation. Here’s what’s important to know about I-time: time equals pressure. This is a big deal because the sphincter in the esophagus opens up at about 20 to 25 cm of water. The faster you give that I-time, the more pressure you’re generating within the airway. Let me show you a demonstration of that. I just happen to have a ventilator here. Looking at this ventilator, I have their tidal volume set to 400 cc. That’s the tidal volume I’m administering to the patient. I have the breath rate set to 12, and I have the I-time set to 1 second. We’re going to be looking at the PIP (peak inspiratory pressure). This is one of the pressures that we monitor during transport, to look at how much pressure we’re putting into the patient’s lungs. You can see right now, with this 1-second I-time, I’m generating about 19 cm of water of pressure within the lungs, right? Watch what happens when I cut that I-time down, when I shorten the I-time just down to half a second. I’ve only shortened it by half a second, but look what happens to the pressure it generates. You can see that the pressure now goes up substantially. How does that impact us in the field when we’re bagging a patient? You have to be conscious of how fast you’re putting that breath in. The literature now is emphasizing slower ventilation rates, but we need to be thinking about our I-time. It’s not just slowing the rate of ventilations, the number of breaths per minute, but we need to be conscious of our I-time because the faster you give the breath, the more pressure you’re generating in the patient, which means more air is likely to go into the belly, cause gastric insufflation. It can cause vomiting, aspiration. We just went from the frying pan into the fire, so we need to be conscious of our tidal volume, how much volume we’re delivering, and how quickly we’re administering that volume.
In a pediatric patient, this has additional risks. If we develop gastric insufflation in an infant from bagging them, this pressure in the belly can actually push up on the diaphragm and limit the amount of tidal volume we can now put into the child. It actually lifts the diaphragm and reduces the amount of air that we can get into the lungs. In fact, in PALS, after we intubate a patient, the next tube that goes in is an OG or an NG tube for the purpose of decompressing that belly just so we can get more tidal volume into that infant.
Now we’ve learned that time is pressure. Regardless of the tidal volume, the faster we give the breath, the more pressure we’re going to generate within the airway, higher risk of developing gastric insufflation and vomiting and aspiration. What can we do in the field to minimize this? They’re always coming out with new toys. This particular Ambu bag has a limiter on it. As soon as it hits 20 cc of water, it stops the ventilation. It prevents you from bagging too fast and generating too much pressure. When I’m giving that breath over 1 second, I always remember ‘1 hippopotamus.’ That’s my rule. I give a breath over 1 hippopotamus. When I squeeze this bag (1 hippopotamus), the breath goes in. If I start to ventilate too fast, generate too much pressure, the valve actually stops me. It prevents me from giving the breath too fast, exerting too much pressure on the airway, and increasing my risk of developing gastric insufflation. New toys are coming out all the time. I use this for training my paramedics. This is a great tool.
This has been a quick review of the ventilatory support for CPR and BLS. I’m Mark. Thanks for watching. I’ll see you in the next video.