Self-inflating bag vs T-piece vs flow-inflating bag: what NRP expects you to know
NRP uses three devices for ventilation, and the exam loves asking which one can do what. All three connect to a face mask, a laryngeal mask or an endotracheal tube, and all three should be used with a manometer so you know the pressure you're giving. The differences come down to how each one fills with gas.
The three devices side by side
| Self-inflating bag | Flow-inflating bag | T-piece resuscitator | |
|---|---|---|---|
| Needs compressed gas | No | Yes | Yes |
| How it fills | Refills on its own after each squeeze | Only with gas flowing in and a sealed outlet | Gas flows continuously; a breath is given by covering the cap opening |
| PIP set by | How hard you squeeze | Squeeze plus the flow-control valve | A preset dial |
| PEEP | Only with an added PEEP valve | Yes | Yes (dial on the cap) |
| CPAP | No, even with a PEEP valve | Yes | Yes |
| Free-flow O₂ | Not through the mask (some bags: via an open reservoir "tail") | Yes | Yes |
| Tells you about a leak | Poorly: it reinflates even without a seal | Immediately: the bag deflates | Stable PEEP on the manometer means a good seal |
Self-inflating bag
It springs back after each squeeze and pulls gas in on its own, so it works without a compressed gas source or a tight seal. That makes it the device you can always fall back on. NRP wants everyone to know how to use one, even if their unit uses T-pieces, and to keep one ready wherever a baby might need resuscitation.
The trade-offs: pressure depends on how hard you squeeze, inflation time is hard to control, and because the bag reinflates even without a seal, a big mask leak can go unnoticed. Without oxygen tubing connected to a compressed gas source it delivers room air (21%). The oxygen reservoir keeps blended gas from being diluted with room air at low flow rates.
Most self-inflating bags have a pop-off valve that usually releases at 30 to 40 cm H₂O, but it isn't reliable and may let higher pressures through. Watch the manometer, not the valve.
Flow-inflating bag
Also called an anesthesia bag. It only inflates when compressed gas is flowing in and the outlet is sealed, so with no seal it collapses like a deflated balloon. It's the hardest of the three to set up and takes practice to balance gas inflow against the flow-control valve (a flowmeter at 8 to 10 L/min usually works with a good seal).
That same behavior is its advantage: you know right away if you've lost pressure or have a leak. It can deliver PEEP, CPAP and free-flow oxygen, and you can lengthen the inflation time by squeezing longer.
T-piece resuscitator
A mechanical device that directs compressed gas toward the baby. You set the inflation pressure and PEEP with dials, and give a breath by covering the opening on the T-piece cap with a finger. It usually runs at 10 L/min.
Its main advantage is more consistent pressure with every breath than either bag, and the operator doesn't tire from squeezing. It also has a maximum pressure-relief control: NRP recommends a maximum of 40 cm H₂O for term infants and 30 cm H₂O for preterm infants. One thing to watch: don't let your finger rest on the cap opening, or the baby gets a prolonged inflation.
For the starting numbers on any of these devices, see NRP PPV settings: rate, PIP, PEEP and FiO₂.
What the 2025 guidelines recommend
The 2025 AHA/AAP guidelines say it can be beneficial to use a T-piece resuscitator instead of a self-inflating bag, with or without a PEEP valve, particularly for preterm infants. In a meta-analysis of 4 randomized trials (1,247 infants), the T-piece shortened the duration of assisted ventilation and lowered the risk of bronchopulmonary dysplasia, with no difference in mortality.
The guidelines also note that the right device depends on the setting: number of births, case mix, access to compressed gas, staff familiarity, training and cost. And because the T-piece and the flow-inflating bag both depend on compressed gas, a self-inflating bag serves as the backup if the gas supply fails.
- Free-flow oxygen through a self-inflating bag's mask: no.
- CPAP with a self-inflating bag: no, even with a PEEP valve.
- Needs compressed gas: flow-inflating bag and T-piece. Works without it: self-inflating bag.
- More than 21% oxygen from a self-inflating bag requires oxygen tubing connected to a compressed gas source.
Frequently asked questions
Can you give free-flow oxygen with a self-inflating bag?
Not through the mask. Gas only flows toward the baby while the bag is squeezed. Some self-inflating bags can give free-flow oxygen through an open reservoir ("tail"). The flow-inflating bag and the T-piece resuscitator can both deliver free-flow oxygen.
Can you give CPAP with a self-inflating bag?
No, not even with a PEEP valve attached. Use a T-piece resuscitator or a flow-inflating bag for CPAP.
Which neonatal resuscitation devices need a compressed gas source?
The flow-inflating bag and the T-piece resuscitator. The self-inflating bag works without compressed gas, which is why it should always be available as a backup.
Can a self-inflating bag give PEEP?
Only if a PEEP valve is attached. Even then, keeping PEEP steady during face mask ventilation is difficult with most self-inflating bags.
How does a self-inflating bag deliver more than 21% oxygen?
The bag has to be connected to a compressed gas source through oxygen tubing. Without it, the bag fills with room air (21%). The oxygen reservoir keeps the blended gas from being diluted with room air at low flow rates.
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References
- American Academy of Pediatrics, American Heart Association. Textbook of Neonatal Resuscitation. 9th ed. Itasca, IL: American Academy of Pediatrics; 2025. Lesson 4: Ventilation (Devices used for ventilation; Appendix); Lesson 8: Resuscitation and Stabilization of Preterm Infants.
- Lee HC, Strand ML, Finan E, et al. Part 5: Neonatal Resuscitation: 2025 American Heart Association and American Academy of Pediatrics Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2025;152(16 Suppl 2):S385–S423. doi:10.1161/CIR.0000000000001367