Understanding Your Oxygen Prescription: Do You Need a POC, and What Setting?
Your prescription tells you what your body needs. This guide helps you understand what it actually says, and how to translate it into the right device and setting.
Chief Sales Officer, Main Clinic Supply
14+ years helping patients transition from tanks to portable concentrators
Version 1.0 | Published May 2, 2026 | Last verified: May 2, 2026 | Next review: May 16, 2026
Most oxygen prescriptions are written in a clinical shorthand that makes perfect sense to your physician and almost none to you when you are standing in front of a shelf of portable concentrators trying to figure out which device you need and at what setting. A number in liters per minute, sometimes a range, sometimes a note about exertion or sleep, occasionally a reference to pulse dose or continuous flow. What does all of it actually mean, and how do you get from what is written on that prescription form to the right portable oxygen concentrator running at the right setting for the life you actually live? That is what this guide covers.
Key Points: Understanding Your Oxygen Prescription
- LPM means liters per minute: Your prescription number describes the continuous flow rate your physician determined you need based on your blood oxygen measurements.
- Pulse dose settings are not identical to LPM: Setting 2 on a pulse dose POC approximates 2 LPM continuous for most patients at rest, but the relationship varies by device and breathing pattern.
- Activity changes your needs: Most patients need a higher setting during exertion than at rest. If your prescription is a single number, ask your physician whether it applies to activity as well.
- Continuous flow may be required: Some prescriptions specify continuous flow only, which means a pulse dose portable concentrator is not appropriate without physician approval.
- Sleep has its own requirements: Nocturnal oxygen prescriptions almost always specify continuous flow. Pulse dose portable units are not recommended for sleep.
- Prescription on file is required: A valid prescription is required to purchase any oxygen concentrator. Your supplier will need it before the device ships.
What LPM Means and Why It Matters
LPM stands for liters per minute. It describes how much oxygen your device should deliver every minute to meet your clinical needs. Your physician arrived at this number based on blood oxygen testing, typically measuring your SpO2 (blood oxygen saturation) at rest, during exertion, and sometimes during sleep, until they found the flow rate that keeps your oxygen saturation above the threshold they have determined is appropriate for your condition.
A typical prescription looks like: "2 LPM continuous flow" or "2 to 3 LPM at rest and exertion" or "2 LPM at rest, 3 LPM with exercise." The number matters because it is the foundation for every device choice that follows. A device that cannot deliver your prescribed flow rate at your highest activity level is the wrong device, regardless of price, weight, or brand.
Pulse Dose vs Continuous Flow: Which Does Your Prescription Require?
This is the most important question to answer before you buy anything. Oxygen prescriptions can be written for continuous flow, pulse dose, or either. Understanding which category you fall into determines the entire device category.
Continuous flow prescriptions specify a liter per minute rate delivered as a constant stream. This is how tanks work and how most stationary concentrators work. The oxygen flows whether you are inhaling or not. If your prescription reads "2 LPM" without further specification, it is most likely a continuous flow prescription, because that is the clinical standard oxygen therapy has been built on for decades.
Pulse dose delivery is a technology approach, not a clinical prescription type. A pulse dose portable concentrator fires a precisely metered bolus of oxygen the moment it detects the start of your inhalation. For patients whose lungs can effectively use oxygen delivered this way, pulse dose provides adequate therapy. For many patients, pulse dose is clinically equivalent to continuous flow at equivalent settings.
The catch is that pulse dose is not appropriate for all patients. If you breathe primarily through your mouth, if you use a CPAP or BiPAP, or if your physician has specifically indicated that continuous flow is required, a pulse dose portable concentrator is not the right choice for primary therapy. Your physician should sign off on pulse dose use before you buy a pulse dose device.
For a thorough explanation of the clinical and mechanical differences, see our guide to pulse dose vs continuous flow oxygen.
Translating Your Prescription to a Concentrator Setting
Here is where the confusion lives for most patients. Portable pulse dose concentrators use numbered settings, typically 1 through 5 or 1 through 6. Prescriptions are written in LPM. The two scales are related but not identical, and the relationship varies by device model.
As a general working reference that the industry broadly uses: a pulse dose setting on most modern concentrators is designed so that setting 2 approximates 2 LPM continuous flow for a patient at normal breathing rate and depth. Setting 3 approximates 3 LPM, and so on. This works reasonably well as a starting point, but it is a general approximation, not a guaranteed equivalence.
| Continuous Flow Prescription | Approximate Pulse Setting (General Reference) | Notes |
|---|---|---|
| 1 LPM | Setting 1 or 2 | Confirm with physician; some devices start at a higher base output |
| 2 LPM | Setting 2 | Most common starting reference for pulse dose equivalence |
| 3 LPM | Setting 3 | Requires a unit with at least 5 settings for activity headroom |
| 4 LPM | Setting 4 to 5 | Many lightweight units top out at setting 5; verify output matches needs |
| 5 LPM | Setting 5 to 6 | Not all portables have setting 6; may require high-output or continuous flow portable |
The table above is a general reference. The only reliable way to confirm the right setting for your prescription is a conversation between your physician and a knowledgeable equipment supplier. Your oxygen specialist at Main Clinic Supply can help translate your prescription into the right setting for a specific device before you buy.
Why Your Setting May Need to Be Higher During Activity
Oxygen demand is not static. When you walk, climb stairs, carry groceries, or exercise, your muscles demand more oxygen and your breathing rate increases. For most patients, the setting that adequately maintains SpO2 at rest is not enough during moderate activity.
This mismatch causes a problem that shows up frequently in device selection. Patients choose a unit that comfortably handles setting 2 at rest, and then discover during the first week that they feel short of breath walking to the mailbox. The device is not failing. The setting is not adequate for the activity level.
Some physicians write prescriptions that address this directly: "2 LPM at rest, 3 LPM with exertion." Others write a single figure and expect the patient to ask. If your prescription is a single number and you are an active person, it is worth one phone call to your prescribing physician to confirm whether that figure applies equally to rest and moderate walking, or whether a higher setting is clinically appropriate during activity.
Nocturnal Oxygen: Its Own Set of Rules
Many patients are prescribed oxygen for both daytime and nighttime use. The most practical solution is typically a lightweight pulse dose portable for daytime and travel, and a stationary concentrator for overnight use at home. A stationary concentrator typically provides continuous flow oxygen at settings up to 5 or 10 LPM and is designed for continuous overnight operation. Portable continuous flow concentrators exist but are heavier and generally better suited for situations where a stationary unit is impractical.
For a complete explanation of why pulse dose delivery is problematic for sleep and what the clinical alternatives are, see our guide to portable oxygen concentrators and sleep use.
Do You Actually Need a Portable Concentrator?
Not every supplemental oxygen patient needs a portable concentrator. The decision depends on how active you are and how much mobility you want to maintain.
If you spend most of your time at home and leave infrequently, a stationary concentrator for home use and occasional tank use for short outings may be adequate. If you travel, walk regularly outside, or find the logistics of tank management limiting, a portable concentrator addresses all of those constraints in one device. The trade-off is cost: a portable concentrator is a larger upfront investment than a tank subscription, and it requires battery management and periodic service.
For patients who want both: many use a stationary concentrator as their primary home device and a portable as their travel and outing unit. The stationary covers sleep and high-flow home use. The portable covers everything else. For a full look at how portable concentrators and tanks compare across all the dimensions that matter for daily life, see our comparison of portable oxygen concentrators vs oxygen tanks.
Questions to Ask Your Physician Before You Buy
Before contacting any equipment supplier, a short conversation with your prescribing physician can save you from buying the wrong device. These are the five questions worth asking:
- "Is pulse dose delivery appropriate for my prescription, or do I specifically require continuous flow?" This is the gateway question. If your physician says continuous flow only, you have a narrower device category to shop.
- "What setting should I use during walking and moderate activity, not just at rest?" If the answer is different from your resting setting, your device needs enough headroom to cover both.
- "Have you prescribed nocturnal oxygen for me, and if so, does that require continuous flow?" Many patients have separate daytime and nighttime needs and do not know it.
- "Is my current SpO2 level expected to be stable, or should I buy a device with capacity to go higher in the next two years?" Buying headroom into a device costs less than replacing the device when needs increase.
- "Do I need a new prescription, or is my current one still valid for equipment purchase?" Prescription validity requirements vary by supplier and by state. Confirm before you start shopping.
Not Sure What Your Prescription Means for Device Selection?
Main Clinic Supply's certified oxygen specialists translate prescriptions into equipment every day. Call us with your prescription details and we can tell you exactly which device category fits your needs and which settings correspond to your clinical requirements.
Call 1-800-775-0942 or browse our portable oxygen concentrator collection.
Main Clinic Supply ships throughout the United States and Canada.
Frequently Asked Questions
What does my oxygen prescription number mean?
Oxygen prescriptions are written in liters per minute (LPM), which describes the flow rate of oxygen delivered continuously. A prescription of 2 LPM continuous means the device should deliver two liters of oxygen per minute at all times. On a pulse dose portable concentrator, settings 1 through 6 correspond approximately to those continuous flow rates, but the relationship is not exact and varies by device model. Your physician or a certified oxygen specialist can translate your prescription into the appropriate concentrator setting.
How do I know if I need a portable oxygen concentrator or a stationary one?
If your prescription allows pulse dose delivery and your oxygen needs during activity can be met by a portable pulse dose unit, a portable concentrator gives you the most freedom. If you require continuous flow oxygen, you may need a heavier continuous flow portable concentrator for travel and a stationary concentrator for home use. Your physician's prescription and a conversation with an oxygen specialist are the right starting points.
Can I use a lower setting than my prescription to save battery life?
No. Your prescription specifies the minimum oxygen delivery your physician has determined you need. Using a lower setting than prescribed means receiving less oxygen than your clinical requirement. Battery planning should never compromise your oxygen delivery. If battery life is a concern, a second battery or external charger is the right solution.
Should my oxygen setting be different during exercise and at rest?
Often yes. Oxygen demand increases with physical activity. Many physicians write prescriptions with different settings for rest and exertion, or specify a range. If your prescription is written as a single figure, ask your physician whether that applies equally to rest and moderate activity, or whether a higher setting is appropriate when you are walking or exercising.
My prescription says 2 LPM. What pulse setting does that correspond to on a concentrator?
As a general reference, pulse dose setting 2 on most modern portable concentrators is designed to approximate 2 LPM continuous flow for a patient breathing at a normal resting rate. However, this equivalence is approximate and varies by manufacturer, device model, and individual breathing pattern. Do not assume a setting number equals a liter per minute number without confirming with your prescribing physician or an oxygen specialist.
What is the difference between a pulse dose and a continuous flow prescription?
A continuous flow prescription specifies a liter per minute rate delivered steadily, the same way an oxygen tank works. A pulse dose prescription allows delivery by a device that fires a measured bolus of oxygen on each inhalation. Not all patients can use pulse dose delivery effectively. Patients who breathe through their mouths, use BiPAP or CPAP, or require nocturnal oxygen typically need continuous flow.
Do I need a new prescription every time I buy a new concentrator?
You need a valid current prescription on file to purchase an oxygen concentrator. Whether you need a new prescription when replacing a device depends on how long ago your existing prescription was written and whether your clinical status has changed. Many suppliers, including Main Clinic Supply, can advise on prescription validity requirements. When in doubt, a quick call to your physician's office can confirm whether a renewal is needed.
Authoritative Resources
- Pulse Dose vs Continuous Flow: What Your Doctor Didn't Fully Explain
- Portable Oxygen Concentrators vs Oxygen Tanks: What Actually Matters for Daily Life
- Do Portable Oxygen Concentrators Work While Sleeping?
- How to Choose a Portable Oxygen Concentrator: Complete Buyer's Guide
- What It Feels Like to Switch From Oxygen Tanks to a Portable Concentrator
- Browse All Portable Oxygen Concentrators
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Disclaimer: This guide is provided for educational purposes and does not constitute medical advice. Portable oxygen concentrators are Class II medical devices that require a prescription. The LPM-to-setting equivalence table above is a general industry reference and is not a substitute for physician guidance on your individual prescription. Always consult with your prescribing physician before changing oxygen equipment, settings, or delivery method. Medicare and insurance coverage rules change; confirm current requirements with a licensed Medicare advisor or your private plan.