How to Adjust BiPAP Pressure? Understanding IPAP, EPAP and BiPAP ST

If a BiPAP machine has just been prescribed for you or for someone you care for, you have probably already met a wall of new words — IPAP, EPAP, pressure support, backup rate, ST mode.

And the question we are asked more than any other is this one: “How do I adjust the BiPAP pressure?”

The honest answer is the one nobody likes at first: you don’t. Not because the machine is fragile or the information is secret, but because the pressures are part of a prescription, the same way a drug dose is. And turning them up or down on your own does not work, for a reason worth understanding: the number that helps you is not the number you feel.

Far more often than not, what feels like too much pressure is a mask that is leaking. That is why our respiratory therapist checks the mask seal before touching a single setting — and usually never has to touch one.

Important: BiPAP is a medical therapy. IPAP, EPAP, mode and backup rate should only be prescribed or changed under medical guidance. Nothing here replaces your doctor’s instructions or the instructions for use supplied with your device.

What is BiPAP?

BiPAP stands for Bilevel Positive Airway Pressure. A CPAP machine delivers one steady pressure all night, whether you are breathing in or out. BiPAP delivers two:

• IPAP — Inspiratory Positive Airway Pressure — the pressure while you breathe in
• EPAP — Expiratory Positive Airway Pressure — the pressure held while you breathe out

The gap between those two numbers is what does work for you. That gap has a name: pressure support.

What is IPAP?

IPAP is the push you get on the way in. It is the number that does the lifting — it helps inflate the lungs and, in conditions where carbon dioxide builds up, helps clear it.

A higher IPAP is not automatically better. Push it too high and you get air swallowing, a leaking mask, and a patient who stops wearing the machine altogether — which helps nobody.

What is EPAP?

EPAP is the pressure that stays behind when you breathe out. Its job is to keep the airway from collapsing between breaths — in obstructive sleep apnea it is doing more or less what a CPAP does. It is normally the smaller of the two numbers.

Pressure support: the number that actually matters

Here is the part most explanations skip.

Two patients can both be “on 16” and be receiving completely different therapy, because their EPAP differs. When your doctor changes therapy, this difference is very often what they are actually changing — not the headline IPAP number.

If you take one thing from this page: BiPAP pressure is not a single number.

What is BiPAP ST mode?

ST stands for Spontaneous / Timed.

• S (Spontaneous) — the machine follows you. Every breath you take, it supports.
• T (Timed) — the machine delivers breaths on a fixed schedule.
• S/T — both. It follows your breathing, and if you stop, or your rate falls below the prescribed minimum, it delivers a backup breath on its own.

That backup breath is the entire point of an ST machine, and it is why ST is prescribed for COPD with CO₂ retention, neuromuscular disease, central and complex apnea, and for patients coming home after ICU. A plain CPAP has no backup rate at all.

There is more detail in our BiPAP ST ventilator guide and on the BiPAP rental page under “what ST mode means”.

BiPAP S vs BiPAP ST — the short version

Which one you need is a clinical decision, not a shopping decision.

So how is BiPAP pressure adjusted?

By the prescribing doctor, using four inputs:

1. The prescription

Mode, IPAP, EPAP, backup rate. This is the starting point. On the machines we deliver, our respiratory therapist enters these values and they then sit behind a clinician code.

2. How you are actually doing on it

Your doctor will want to know about mask tolerance, air leak, whether you can exhale comfortably, how you slept, morning headaches and daytime sleepiness.

3. The therapy data

The machine records what happened each night — leak, residual events, usage hours. That data, not a guess, is what a good review is built on. We can pull it off the device for you to take to your appointment.

4. Your underlying condition

The right settings for a COPD patient with CO₂ retention are not the right settings for someone with obstructive apnea. This is why there is no “best BiPAP pressure” to look up.

Should you change it yourself?

No. And the practical reason matters more than the legal one: the thing that is bothering you is usually not the pressure.

When therapy feels wrong, this is the order to check things in — and you can do the first five yourself tonight:

1. Mask fit. Loosen the headgear slightly, then re-seat the cushion. Over-tightening deforms the cushion and makes leak worse, not better — this single adjustment fixes more complaints than anything else.
2. Leak. Air hissing onto your eye, or a whistle when you exhale. Leak makes therapy feel both too strong and not strong enough at the same time. Use the mask test pressure function to find it while you are still awake.
3. Cushion age. A cushion older than about six months has usually stretched, and will leak whatever you do about the pressure.
4. Humidification. A dry throat and a blocked nose make any pressure feel like too much.
5. Tubing. Kinked, or not seated properly at either end.
6. The prescription itself — and that is your doctor’s call, informed by the four inputs above.

Call us or call your doctor. Do not go looking for the clinical menu.

What you can change yourself

Plenty, actually — and this is the part that decides whether therapy is tolerable at all. On the Löwenstein prismaLINE machines these live in the Comfort menu:

• autoSTART / STOP — the machine starts when you breathe into the mask and stops when you take it off, so you are not reaching for a button in the dark
• Mask test pressure — runs a test pressure so you can check the seal before you lie down. Use this. It prevents most bad nights.
• softSTART — starts you lower and ramps up over a set number of minutes while you fall asleep
• softPAP — softens the switch between breathing in and breathing out, which is what most people are actually feeling when they say the pressure is too high

Plus the time, the time zone, the wake-up alarm and the display dimmer.

None of these change your prescribed therapy. All of them change whether you can stick with it.