Oxygen delivery: pulse vs continuous flow differences and suitable environments

I didn’t plan to go deep on oxygen delivery this week, but a small moment nudged me there. I was walking behind a neighbor who uses a portable oxygen concentrator, and I noticed the quiet “click” it made only when she inhaled. That tiny sound sent me down a rabbit hole: why do some devices push oxygen nonstop while others wait for the breath to arrive? And more importantly for real life—when does each method make sense? I decided to jot down what I learned, in plain language, the way I’d explain it to a friend who’s weighing equipment choices with their clinician.

The core idea that helped everything else make sense

Once I pictured oxygen delivery in terms of timing and dose, the puzzle pieces settled. Continuous flow is like a faucet left running at a set rate, measured in liters per minute (L/min). Pulse (also called “demand” or “conserving”) flow is like a smart water bottle that gives a sip only when you swallow—in this case, a small bolus of oxygen delivered when the device senses the start of an inhalation. That’s it. Everything else—battery life, portability, sleep compatibility, and how well it keeps your oxygen saturation in target ranges—follows from those two ideas.

• High-value takeaway: continuous flow is predictable and compatible with more setups (like humidifiers and CPAP/BiPAP), while pulse flow is lighter and more efficient but depends on how you breathe.
• Pulse settings don’t map 1:1 to L/min. A “setting 2” on a portable device can deliver very different amounts depending on design and your breathing pattern; the only way to know is testing with a pulse oximeter and clinical guidance.
• Both methods can be appropriate; the “right” choice is situational and should be personalized with your healthcare team’s help (for example, see the NHLBI overview or the ATS patient fact sheet).

How the devices actually deliver oxygen in the moment

Here’s the practical anatomy of a breath with each method:

• Continuous flow: oxygen flows steadily through the tubing at, say, 1–4 L/min in home use, regardless of where you are in the breathing cycle. If you pause or exhale, oxygen still flows. This predictability is why continuous flow remains a mainstay at night and with certain interfaces.
• Pulse flow: a sensor detects the pressure drop at the start of inhalation and triggers a bolus—measured in milliliters per breath—not in L/min. That bolus can be front-loaded (delivered early in the breath) so it preferentially lands in parts of the lung where gas exchange is efficient.

One subtlety that surprised me: if your breathing is very shallow, irregular, or you mostly breathe through your mouth, some pulse systems may miss triggers or deliver less than expected. That’s why clinicians often recommend supervised walk tests or nocturnal oximetry to confirm a given setup actually maintains your saturation targets in the real world (patient-friendly guides from the American Association for Respiratory Care explain this logic nicely).

Where each method shines in everyday environments

When I started listing situations from my own day—working at a desk, walking the dog, riding in a car, napping on the couch—it became clear that the “best” oxygen delivery changes with context. Here’s the cheat sheet I wish I had sooner:

• At rest (daytime, sitting or light puttering): many people do well on pulse flow if their device triggers reliably and keeps SpO₂ in range. It’s quieter, lighter, and batteries last longer. That said, if you notice frequent desaturations with screen-time breath holds (it’s a thing!) or mouth breathing, continuous flow can be more forgiving.
• During activity (walks, errands, household chores): pulse flow can be great because you’re inhaling regularly and the conserved oxygen extends battery/tank time. Try different cannula positions and check saturations during hills or stairs. If you see dips you can’t fix with adjustments, talk with your clinician about a higher pulse setting or switching that activity to continuous flow.
• Sleep and naps: continuous flow is usually the default because breathing can be shallow and variable at night. Some pulse devices have “sleep modes,” but not all are reliable for everyone. Overnight oximetry (with your usual pillow, sleeping position, and mask/cannula) is the only way to know if a pulse setup holds steady for you.
• With CPAP/BiPAP or other ventilatory support: continuous flow integrates more predictably (oxygen “bleed-in”). Pulse flow generally doesn’t sync with positive-pressure cycles unless a device is specifically designed and tested for that interface.
• Car travel and errands: pulse flow wins for packability and fewer tank swaps. Keep a backup (charged battery or small cylinder) and beware heat in parked cars—batteries and electronics don’t love it.
• Commercial air travel: FAA-approved portable concentrators typically operate in pulse mode during flight, and airlines require advance forms for use on board. Even if you do fine at home on continuous flow, you may use pulse in the cabin; ask your clinician for a pre-flight plan and bring extra batteries (see the FAA’s page on portable oxygen concentrators).
• High altitude or colder, drier climates: both altitude and dry air can challenge oxygenation and comfort. Continuous flow with humidification may feel better for some; others do well with pulse plus saline nasal spray. Test and log what happens to your saturations when you arrive at altitude.

What the numbers really mean and how to sanity-check them

It’s easy to get tripped up by dials and settings. Here’s the mental model I use.

• Continuous L/min is literal: 2 L/min means that rate continuously. If a clinician titrates you to 2 L/min at rest and 3–4 L/min during exertion, they’re usually picturing a continuous source or an equivalent delivered dose.
• Pulse “settings” are not L/min: a pulse setting is a manufacturer’s scale that maps to a bolus volume per breath. Two brands set to “2” can deliver very different total oxygen per minute depending on your breathing rate and how the device modulates the bolus at higher rates. Translation: always test your own response.
• Watch the outcome, not just the hardware: the outcome is your oxygen saturation staying in a target range determined with your clinician. A simple finger pulse oximeter (used correctly, warm hands, minimal motion) plus a symptom log tells you whether a given setup is working for you. Patient pages at MedlinePlus give helpful “how to” basics.

Comfort add-ons, safety must-knows, and the small tweaks that matter

Comfort and safety shape whether you’ll actually use the equipment the way it was prescribed. A few small tweaks made a big difference for me and people I’ve talked with:

• Humidification: generally paired with continuous flow (especially above ~3 L/min) via a bubble humidifier bottle. It’s usually not used with pulse conserving devices because the bolus delivery bypasses continuous bubbling. If dryness persists, ask about alternatives like nasal gels or saline sprays.
• Cannula fit and rotation: skin grooves and irritation often come from pressure points more than from the oxygen itself. Rotating cannula types, using soft foam ear cushions, and adjusting tubing routing can help.
• Battery and backup planning: for pulse concentrators, think in segments (errands, appointments, the unexpected detour). A rule of thumb I like is to leave home with the charge you think you need plus one extra segment.
• Fire safety: oxygen itself doesn’t burn, but it does feed combustion. Keep it away from open flames, lit cigarettes, and heat sources. Post a small reminder near your favorite chair; it helps visitors too. Many patient guides (e.g., AARC) summarize these precautions clearly.
• When to ask for re-titration: changes in health, medications, altitude, weight, or activity level can shift your oxygen needs. If your oximeter is consistently showing lower readings during routines that used to be fine, that’s a prompt to check in.

Choosing gear without getting overwhelmed

I tried to boil down device shopping into a few questions that cut through the noise. I find it grounding to answer these on paper before visiting a DME (durable medical equipment) provider:

• Which environments matter most to me this month—sleep, desk work, dog walks, travel? Rank them.
• What are my clinician-set targets for SpO₂ at rest and with exertion, and how will we verify them at home and at night?
• Do I need compatibility with CPAP/BiPAP or specific masks? If yes, lean toward continuous flow capability.
• What is my realistic carry weight and battery budget? Pulse devices are lighter for most on-the-go time, but some scenarios still call for continuous.
• What’s the backup plan—spare battery, small cylinder, or stationary concentrator—and how will I practice switching?

If you want authoritative primers to share with family or caregivers, I’d start with the NHLBI Oxygen Therapy page and the ATS patient fact sheet. For practical equipment do’s and don’ts, the AARC patient education hub is concise and actionable. And if air travel is on your horizon, bookmark the FAA POC guidance well before you pack.

Red and amber flags that tell me to slow down

I keep a tiny note on my phone titled “Oxygen check.” It lists things that mean stop and reassess rather than “push through.”

• Red: sudden shortness of breath at rest, chest pain, bluish lips, confusion, or SpO₂ readings far below your usual target that don’t rebound with your rescue plan—seek urgent care.
• Amber: desaturations during usual activities that were fine last month; new morning headaches (especially with sleep-disordered breathing); frequent device alarms; nasal bleeding or severe dryness despite humidification and care.
• What I do next: switch to a known-reliable setup (often continuous flow), rest, recheck readings after a few minutes of quiet breathing, and contact my care team with a simple report (what I was doing, readings, what changed, and what helped).

What I’m keeping and what I’m letting go

I’m keeping the principle that measurement beats myth: it doesn’t matter whether a device is “cool” or “old school” if it keeps you in range in your actual life. I’m keeping a bias for simple, reliable setups for sleep and for any time I add CPAP/BiPAP into the mix. And I’m letting go of the idea that a pulse setting number means the same thing across brands—it doesn’t. My last note to myself: check trusted sources first, then ask the DME to help you test, not guess. For quick refreshers, I lean on NHLBI, ATS, and AARC—short, clear, and updated often enough to stay useful.

FAQ

1) Does a pulse setting of “2” equal 2 L/min?
Answer: No. Pulse settings are device-specific and refer to a bolus per breath, not a continuous L/min rate. Two devices at “2” can deliver different amounts. The only way to confirm adequacy is monitoring your saturation and working with your clinician on titration.

2) Is pulse flow safe for sleep?
Answer: It can be for some people, but many do better on continuous flow at night because breathing patterns change during sleep. If considering pulse at night, request supervised overnight oximetry to make sure it maintains your target range.

3) Why can’t I use a humidifier bottle with my pulse device?
Answer: Because pulse systems deliver intermittent boluses rather than a steady stream, standard bubble humidifiers won’t function as intended. If dryness is an issue, ask about nasal gels or saline and consider continuous flow with humidification when appropriate.

4) Will my portable concentrator work on airplanes?
Answer: Many FAA-approved units are allowed, typically used in pulse mode during flight. Airlines may require forms and advance notice, and battery requirements are strict. Check the airline policy and the FAA guidance before you fly.

5) How do I decide between pulse and continuous for daily life?
Answer: Start with your most important environments (sleep, errands, exercise). Use continuous for scenarios needing predictability or interface compatibility, and pulse for portability and battery life—as long as your measured saturations stay in range. Your clinician can help you test and mix modes as needed.

Sources & References

• NHLBI — Oxygen Therapy
• American Thoracic Society — Oxygen Therapy (Patient Guide)
• American Association for Respiratory Care — Oxygen Therapy
• MedlinePlus — Oxygen Therapy
• FAA — Portable Oxygen Concentrators

This blog is a personal journal and for general information only. It is not a substitute for professional medical advice, diagnosis, or treatment, and it does not create a doctor–patient relationship. Always seek the advice of a licensed clinician for questions about your health. If you may be experiencing an emergency, call your local emergency number immediately (e.g., 911 [US], 119).