If you're working with small patients, getting a non rebreathing system ready is normally one of the first items on your own to-do list. It's one of those pieces of equipment that appears relatively simple—just the few tubes and a bag—but the physics happening inside individuals tubes is actually pretty clever. Unlike the bulkier circle systems you may see on larger animals or human beings, these little setups are designed intended for speed and reduced resistance, which is a lifesaver whenever you're coping with the patient that doesn't have a great deal of lung capacity.
The majority of us just call them "non-rebreathers" and proceed, but understanding why they work the way they do makes a huge difference whenever you're troubleshooting the patient who isn't staying deep plenty of or, conversely, is definitely waking up too fast.
The reason why we even use these things
The primary reason a non rebreathing system exists is to get rid of resistance. Think about a tiny kitten or a toy poodle under anesthesia. Their particular lungs are small, and their chest muscles aren't specifically powerhouses. If you attempted to make them breathe via a regular circle system, they'd have to drive air through weighty one-way valves plus a big canister associated with soda lime. It's like trying to breathe through a long garden hose while wearing a tight corset—it's exhausting.
In a non rebreathing circuit, those large valves are long gone. The patient just breathes in clean gas and breathes out waste gas. Because there's no soda lime container to scrub the carbon dioxide out of the exhaled air, we have to find another way to create sure the patient isn't breathing their own CO2 back within. That's where the particular high fresh gas flow is needed. You're essentially using a high-pressure "wind" of new oxygen and anesthetic to sweep the old breath out of the tube before the patient takes their next one.
The Mapleson mystery
If you've ever looked in to the history of these systems, you've possibly run into the particular "Mapleson" classifications. It sounds like some thing out of a boring textbook, but it's just a method of categorizing exactly where the fresh gas enters and in which the waste gas results in.
In the veterinary world, we all usually use the Mapleson F , which a lot of people know as the Jackson-Rees routine. It's about mainly because simple as it gets: fresh gas is available in right simply by the patient's nasal area, and the waste gas exits by way of a bag at the other end. It's incredibly efficient regarding tiny patients because there's almost zero "dead space. " Dead space is definitely basically the environment that just sits in the tubes and not actually makes this towards the lungs. In a tiny individual, too much deceased space means they're just moving the same stale air back and forth without getting any new oxygen.
The trade-off with gas flow
Here is the particular catch, and it's a big 1: a non rebreathing system is a bit of a gas hog. Since you aren't recycling one of the exhaled air, you have to operate your oxygen stream much higher compared to you would on a circle system.
Usually, we're discussing a flow rate that's roughly two to three occasions the patient's minute volume. In case you turn the flow as well low, the individual starts rebreathing that exhaled CO2, which can lead to some scary numbers on your capnograph. If you turn it as well high, you're simply wasting expensive anesthetic gas and drying out the patient's airways. It's a bit of a balancing act. You want enough flow to clear the "trash" out of the tube, but not really so much that you're blowing a gale-force wind down their trachea.
Altering depth on the particular fly
One of the coolest things regarding using a non rebreathing system is usually how fast it reacts. If you've ever worked along with a large canine on a circle system, you know that when a person turn the vaporizer dial up, it takes a while intended for that change in order to actually reach the dog. The gas needs to mix with just about all the air currently in the huge tubes and the CO2 canister.
With a non-rebreather, the particular change is almost instant. Since the quantity of the routine is so small and the flow rate is really high, whichever you set on the vaporizer is exactly what the patient gets within seconds. This is a double-edged sword, though. It's great if the patient is waking up and you need to get them back under quickly, it also means points can be south quick if you aren't having to pay attention. You are able to unintentionally get a small patient very heavy very quickly in the event that you're heavy-handed along with the dial.
Keeping things comfortable and moist
One downside that people often forget is that these types of systems are frosty. In the circle system, the chemical response in the soda lime canister in fact creates a bit of heat plus moisture, which assists keep the patient's internal temperature upward.
In a non rebreathing system , you're blowing cool, dry medical grade oxygen directly into the lungs from a high rate. Since small individuals already find it difficult to keep onto body temperature, this can prospect to hypothermia fairly quickly. This is the reason you'll almost always observe us using temperature lamps, warm drinking water blankets, or even those little "baby socks" for the paws of cats under anesthesia. We need to make up for the reality that the respiration circuit isn't performing any of the heavy lifting intended for temperature control.
Setup and typical hiccups
Establishing these up will be usually straightforward, but there are a few places where people trip upward. The first is the pop-off valve (or typically the APL valve). Upon some non-rebreathers, this particular is a moving shroud or a little thumb-screw. In the event that you leave this closed and maintain the oxygen running, the particular pressure will build up in the lungs and may cause some serious damage.
Another thing in order to watch for is usually the connection in the endotracheal tube. Because the system is so light, it's easy for the pipes to get kinked or pulled. I've seen more when compared to the way one case exactly where a patient began waking up just because the circuit was slightly turned, cutting from the flow of anesthetic. It's always worth doing a quick "tug test" to make sure everything is definitely seated properly plus the lines are usually clear.
Is it worth the waste?
Some people argue that we need to use circle systems for everything to save money on gas and be more environmentally pleasant. And sure, non-rebreathers do dump more gas in to the scavenging system. But when you're looking at a 2kg kitten, the particular safety benefit of that low resistance far outweighs the particular cost of some extra milliliters of isoflurane.
It's really about choosing the correct tool for the job. You wouldn't use a sledgehammer to hold a picture framework, and you shouldn't use a heavy group system to get a patient the size associated with some bread. The non rebreathing system fills a specific niche that will makes anesthesia for our smallest patients a lot safer.
Final thoughts on maintenance
Taking care associated with these sets is definitely pretty easy given that there aren't several moving parts. Make absolutely certain the breathing bag hasn't developed any kind of tiny pinprick holes—those will drive you crazy trying to figure out why your patient won't stay under. Provide the tubes a good squeeze every right now and then to check for leaks.
In the end of the day, the particular non rebreathing system is a staple in the medical center for a reason. It's simple, it's fast, and this lets those small lungs breathe simple without fighting towards the machine. Simply keep an vision on your flow rates as well as your patient's temperature, and you're golden. It's 1 of those things that, as soon as you obtain the hang from the flow math, becomes second nature.