Continuous Flow vs Pulse Dose - Know the difference for your personal needs

Two oxygen concentrators can both say "3" on the screen and deliver very different amounts of oxygen. Mistaking one for the other is a documented and common misunderstanding — and it is the reason people end up with a machine that does not do what their prescription intended.

This page explains the difference between continuous flow and pulse dose delivery in plain terms. It is written for people using oxygen and the clinicians advising them, and it is deliberately short enough to work through in a phone call.

Two ways a machine can give you oxygen

Continuous flow

The machine puts out a steady, uninterrupted stream of oxygen, measured in litres per minute (LPM). It runs at that rate whether you are breathing in, breathing out, talking, or holding your breath. Set it to 2 LPM and it delivers 2 litres every minute, all the time.

This is how stationary home concentrators work, and it is the delivery method most prescriptions are written against.

Pulse dose

The machine waits, senses the very start of each breath in, and releases a measured burst of oxygen at that moment. Then it stops until your next breath. Nothing is released while you breathe out.

The reason pulse dose exists is efficiency. On continuous flow, the oxygen produced while you are breathing out is simply lost to the room — and at rest, breathing out takes up roughly two-thirds of each breathing cycle. Pulse delivery puts oxygen only where it can actually be used. That saving is what makes it possible to build a concentrator that weighs around two kilograms and runs on a battery, rather than one that weighs twenty-five and has to stay plugged in.

The mistake behind most of the confusion

Pulse dose machines have settings numbered 1 to 5, or 1 to 6, or 1 to 7. Those numbers sit on a screen and look exactly like a flow rate. They are not one.

A pulse setting describes the size of the dose delivered with each breath, usually measured in millilitres. A continuous flow rate describes litres delivered every minute. They are different units measuring different things, and there is no fixed conversion between them.

It is worth saying plainly: setting 2 does not mean 2 litres per minute. You will sometimes see pulse devices advertised with an "LPM" figure against the settings. That figure is at best a rough equivalence under one manufacturer's test conditions, and it should not be read as a flow rate.

This is not a fringe misunderstanding. A 2026 editorial in the Journal of the COPD Foundation names it directly as "a common misconception in clinical practice", and concludes that the relationship between the two is "neither linear nor fixed" — it depends on both the person's breathing and the particular device. Their recommendation is that pulse settings be treated as "relative, device-specific indices rather than direct equivalents to continuous flow rates".1

Why the same number means different things on different machines

There is no industry standard setting the dose for setting 3. Each manufacturer decides their own scale, and the same editorial describes "the absence of standardization across manufacturers", noting that the same numeric setting "may deliver significantly different amounts of oxygen depending on the specific device".1

This matters the moment someone changes machines. "She is on 3" carries no reliable information from one device to another, even though it sounds like it should. A patient moved from one pulse concentrator to another at the same number may be receiving materially more or less oxygen than before, without anyone having made a decision to change anything.

What happens when you walk up a hill

This is the part that is most often missed, and it is the one with real consequences.

Most pulse devices work to a fixed total output per minute and divide it across however many breaths you take. Breathe twenty times a minute and the total is split twenty ways. Breathe thirty times, and the same total is split thirty ways — so each individual dose gets smaller.

The practical effect: on most machines the oxygen delivered per breath falls as your breathing rate rises — which is precisely when you are working hardest and need it most. Independent bench testing published in 2025 measured this across seven portable concentrators. On typical devices the dose per breath fell by roughly 60% between a resting breathing rate of 15 breaths a minute and an exertional rate of 40.2 Continuous flow does not behave this way. It delivers the same litres per minute however fast you are breathing.

Some newer devices include rate-responsive technology that holds the dose steady as breathing speeds up, and these perform better under exertion.2 It is worth asking whether a particular machine has it.

Where the gap usually opens up

The most common way someone ends up on the wrong setting is not a mistake by any one person. It is a handover problem.

Oxygen is often titrated in a clinic using continuous flow. The person then goes home and uses a pulse dose portable for much of their day — frequently without being reassessed on that device. The prescription and the equipment were both reasonable; they were just never checked against each other. The COPD Foundation editorial describes exactly this, noting that device-specific evaluation "frequently occurs only after equipment has already been dispensed, if it occurs at all".1

It also notes that the equipment supplier often decides which specific device a patient actually receives. We take that seriously, which is part of why this page exists: if you tell us the prescription, we would rather have the conversation about whether a machine matches it before you buy than after.

How your setting is actually decided

This is the question we get asked most, and the honest answer is that it is not decided by you, and it is not decided by us. It is measured.

The process is called titration. A clinician puts an oximeter on you, starts at a setting, and checks what your oxygen saturation actually does — sitting still, then walking, and overnight if you need oxygen while asleep. The setting is adjusted until your saturation stays in the range they have set for you across those activities. The number that comes out the other end is your setting.

Because pulse settings are device-specific, that measurement only tells you about the machine it was taken on. This is the single most practical consequence of everything above: a titration done on continuous flow in a clinic does not automatically tell you the right setting on a pulse dose portable. The clinical guidance is to titrate using the specific device you will be using, under the conditions you will really be in.1

Ask for the number in millilitres, not just the setting

This is the single most useful thing you can take away from a titration appointment, and most people do not know to ask for it.

A pulse setting of "2" is a label on a dial. What your body actually receives is a volume of oxygen per breath, measured in millilitres, and that volume differs between machines even at the same setting number. If you leave your appointment with only the setting number, you are carrying a figure that may not mean the same thing on the next machine you use.

So ask your clinician what your requirement is in millilitres per dose, or in millilitres per minute. That figure travels. Once you have it, you can compare it against what a machine actually delivers, and the comparison is a real one rather than a matching of dial numbers.

Manufacturers publish this. A typical pulse portable delivers something in the order of 210, 420, 630, 840 and 1050 mL per minute across its five settings — but the scale varies by model, and on most devices the volume per breath falls as your breathing rate rises. Both of those matter when you are choosing.

If you tell us your figure, we can tell you what each machine in our range delivers and where it sits against your requirement. Call 1300 881 824 or send it through and we will go through it with you. That is a far more reliable way to choose than comparing setting numbers between brochures.

Being assessed on the device itself

Where it is practical, the best version of this is to be assessed on the actual machine you will be using, under the conditions you will really be in — walking, not just sitting. If you already own a concentrator and have never been assessed on it, bring it to your next appointment and raise it.

If you do not yet have one, hiring is one way to be assessed before you commit to a purchase, and some of our hire portables switch between pulse and continuous flow on the same unit, which lets a clinician compare both in one appointment. Our hire range is not the same as our sales range, so call us on 1300 881 824 and we will tell you what is possible. See hire oxygen concentrators.

Where pulse dose is usually not the right tool

These are clinical judgements rather than rules, and your prescriber decides. The clinical literature identifies three physiological states in particular where pulse delivery may underperform — rapid shallow breathing during activity, low inspiratory effort during sleep or with neuromuscular weakness, and frequent mouth breathing.1 In practice that means:

• Sleep. Breathing becomes shallower and more irregular overnight, and a pulse device may not reliably detect the breath it needs to trigger on. Manufacturers generally state their pulse devices are not intended for use while sleeping, and low inspiratory effort during sleep is one of the states in which pulse delivery is known to underperform.1
• Mouth breathing. Pulse delivery senses the breath through a nasal cannula. If someone breathes mainly through their mouth, particularly when unwell or exerting themselves, the trigger becomes unreliable.
• Higher flow requirements. Above a certain requirement, pulse delivery cannot practically supply enough, and continuous flow is the only option.
• Anyone who cannot generate a consistent breath trigger. If the machine cannot sense the breath, it cannot deliver on it.

A pulse dose concentrator is also not a life-supporting device, and the manufacturers say so in their manuals. It is worth having a backup oxygen supply for power failures or faults, whichever delivery method is used.

Battery life, and one thing you should never do to extend it

On a portable, the setting and the battery life are directly connected. A higher setting means more oxygen produced, which means more power drawn, which means less time before it goes flat. The drop is steeper than most people expect.

Two examples from machines in our own range, using the manufacturers' published figures:

On both, setting 5 gives you somewhere between a third and a quarter of the time you would get on setting 1. Runtimes also vary with breathing rate, battery age and temperature, so treat published figures as a guide rather than a promise.

If your battery is not lasting the outings you need, the answer is more battery rather than less oxygen. A spare battery you can swap, an external charger, or a car adaptor for longer trips will all extend your day without touching the dose — see concentrator accessories, or call us and we will work out what fits your machine.

Starting on pulse does not mean staying on pulse

A pulse dose portable suiting you now does not mean it will suit you forever, and that is not a failure of the machine or of the original assessment. Oxygen requirements change. They can change gradually as a condition progresses, they can change temporarily during a chest infection or a flare-up, and they can change with the seasons or with how active you are.

The delivery method that suits you can change with them. Plenty of people start on a pulse portable and later need continuous flow for part of the day, or overnight, or for longer outings. Some need a second machine rather than a different one.

Things worth mentioning to your clinician rather than adjusting yourself:

• You are more breathless doing the things you used to manage on the same setting.
• Your oximeter readings are lower than they used to be on the same activities.
• You find yourself stopping to recover more often than you did.
• You are waking unrested, or someone has noticed your breathing overnight.
• The machine feels like it is not keeping up, even though nothing about it has changed.

Any of these is a reason to ask for a review, not a reason to change the setting. The useful question to put to your clinician is not just "should my setting change?" but "is a pulse device still the right delivery method for me?" — because the answer to the second one may be what has moved.

Side by side

Five questions worth asking before you choose a machine

Take these to your appointment, or work through them with your patient.

1. Continuous flow or pulse dose? Not which machine — which delivery method the prescription calls for. Everything else follows from this.
2. What is the number, and in what unit? Litres per minute for continuous. For pulse, the setting number and the make and model it was set on.
3. What is the target saturation? The machine is a means to an end. The number that matters is the one on the oximeter.
4. Measured doing what? Resting, walking, on stairs. If the person needs oxygen while moving, a resting measurement is not enough on its own.
5. Is oxygen needed overnight? If yes, that usually decides the delivery method on its own, and may mean two machines rather than one.

What this means for the machine you end up with

Most people needing oxygen at home and out of the house end up with two devices rather than one: a stationary continuous flow concentrator for home and overnight, and a portable pulse dose unit for getting out.

If your prescription is continuous flow, you are looking at a stationary machine. Our range runs from 5 LPM units through to 10 LPM for higher requirements — see the stationary concentrators.

If a pulse dose portable is suitable, the things that then matter are the setting range, the weight and the battery life for the outings you actually do. Those are on the portable concentrators page.

If you need continuous flow away from home, that is a much smaller group of machines — most portables are pulse only. It is worth a phone call rather than an online order, because the trade-offs in weight and battery life are significant. Call us on 1300 881 824 and we will go through what is available.

Whichever way it goes, check the specification on the product page against the prescription before ordering, and if anything does not line up, ring us before you buy rather than after.

Common questions

References

1. Giannini HM, Labaki WW. Not all oxygen is delivered equally: pulse-dose versus continuous flow in practice and physiology. Chronic Obstructive Pulmonary Diseases. 2026;13(5):340–342. doi:10.15326/jcopdf.2026.0871
2. Gardenhire DS, Murray RB, Gardenhire RE, Brandenberger KJ, Zavorsky GS. Comparison of portable oxygen concentrators and inspired oxygen levels in a model of respiratory failure. Pulmonary Therapy. 2025;11(4):741–752. doi:10.1007/s41030-025-00314-1 (Bench study; funded by a device manufacturer, with data collection and analysis conducted independently.)