How to Adjust PEEP & Tidal Volume on a Small Animal Bellows Ventilator

1. Set a baseline. Bellows at 300 ml (top), tidal volume rod fully up, flow meter 5 L/min → PEEP typically ~5–7 cmH₂O.
2. Lower flow to drop PEEP. Turn flow meter to 1 L/min → PEEP typically ~5 cmH₂O.
3. Start lower on the bellows for small animals. Set the bellows start to 200 ml → PEEP drops further.
4. Go smaller as needed. Set start to 150 ml → PEEP typically ~3 cmH₂O.
5. Very small models. Set start to 100 ml → PEEP typically ~2–3 cmH₂O.
6. Ventilate and verify. Run the ventilator at the chosen start volume; expect slight PEEP “toggle” within a small range.
7. Fine-tune one control at a time. Use flow (1–5 L/min) and bellows start volume (100–300 ml) to hit your target PEEP; record the combo that works.

Rule of thumb: Smaller animal → lower bellows start volume; Lower flow → lower PEEP.