Tidal Volumes in Pediatrics: What to Use and When

It had been a while. That’s usually how it goes in a small hospital. You can go months without seeing a pediatric patient who needs a ventilator. Most of the time we stabilize and ship. So when one finally shows up, there’s always that moment where you have to stop and think it through. That’s really the point of this post. Not to make it complicated, just to review the basics so when it happens you’re not guessing.

One of the first questions that comes up is the circuit. Can you use an adult circuit on a pediatric patient with a Hamilton? Technically, yes. But it’s not ideal. Adult circuits have more volume and more compliance, and with a small patient that can throw things off. If you have a pediatric circuit, use it. It’s more accurate and just makes things easier. If you don’t, then you use what you have and pay closer attention to what you’re seeing.

The next thing is setup, and this is where everything comes back to weight. Pediatrics is all weight-based. If you don’t have a weight, get one, even if it’s just an estimate. That one number drives everything you do on the ventilator.

Mode is where people start overthinking things. Pressure versus volume always comes up. A lot of people lean toward pressure control, especially with uncuffed tubes, because you’re going to have some leak and pressure handles that better. That’s generally a safe way to go if you don’t do this often. Modern ventilators like the Hamilton can handle volume modes pretty well too, but if you’re unsure, pressure control keeps things simple and predictable.

When it comes to volumes, you’re usually thinking in the range of about 6 to 8 mL per kilogram. If the lungs are stiff or you’re worried about lung protection, you can go lower, more like 4 to 6. The big mistake is trying to fix problems by giving bigger breaths. Kids don’t need big tidal volumes. That tends to cause more harm than good. If you’re using a pressure mode, including pressure support, you’re not setting a tidal volume directly, so you adjust the pressure until you’re seeing those target volumes. Watch what the patient is actually getting and make your changes based on that, not just the number you dial in.

Rate is where pediatrics really separates from adults. Kids need higher rates. If you use adult settings, you’re going to under-ventilate them. Infants are often in the 25 to 40 range, younger kids somewhere around 20 to 30, and older kids still higher than adults. If your CO₂ is off, you usually fix that with rate before you start pushing pressures or volumes too high.

PEEP is simple. Start around 5 and adjust based on oxygenation. Same thinking as adults. FiO₂, start high if you need to, then bring it down as soon as you can. That part doesn’t change.

Inspiratory time is something people forget, but it matters more in kids. Their lungs are faster, so inspiratory time is usually shorter, somewhere around half a second up to maybe 0.8. If the waveforms don’t look right, this is one of the first things to adjust.

The biggest thing, especially if you haven’t done this in a while, is to watch the patient. Not just the ventilator. Look at chest rise, how they’re interacting with the vent, whether they look comfortable, whether the numbers actually match what you’re seeing. The ventilator can look perfect and still be wrong.

Working in a small hospital also changes your mindset. You’re not trying to manage this patient long term. You’re stabilizing, avoiding harm, and buying time until transport gets there. That takes a lot of pressure off if you think about it that way. You don’t need perfect settings, you just need safe and effective ones.

So if you keep it simple, get a weight, choose a mode you’re comfortable with, stay in a reasonable range for volumes or pressures, set a higher rate than you would for an adult, and watch the patient, you’ll be fine. It might feel uncomfortable if it’s been a while, but the basics don’t change. And in pediatrics, doing the basics well goes a long way.