What size oxygen concentrator do you need? Matching the machine to your LPM prescription

Oxygen prescriptions are written in liters per minute of continuous flow — 2 LPM, 4 LPM, and so on, often with different values for rest, exertion, and sleep. Pulse-dose machines don't deliver liters per minute; they deliver a fixed bolus per detected breath, and their numbered settings are just index positions. Setting 2 on a pulse machine is not 2 LPM, and two different manufacturers' setting 2 aren't even the same as each other.

This is the mistake that produces most sizing regret: buying a portable whose top setting 'matches the number' on a continuous-flow prescription. The honest translation between a continuous LPM value and a pulse setting depends on your breathing rate and depth, which is why it's a titration question — your prescriber or respiratory therapist confirms which setting keeps your saturation in range, ideally tested while walking, not just seated.

Machine classes map to prescription ranges roughly like this: up to 2–3 LPM continuous, compact stationary units (like the 0.5–2 LPM Philips SimplyFlo) and continuous-capable portables can both work; 3–5 LPM, you're in standard stationary territory (0.5–5 LPM units like the Caire Companion 5) with pulse portables as a daytime complement if titration supports it; above 5 LPM, high-flow stationary machines (2–10 LPM class) are the tool, and portability comes from cylinders rather than concentrators.

Practical rule: size for your worst regular case, not your best. If your exertion flow is 4 LPM, a machine that covers 4 is the machine — with headroom, since needs can drift over time. This is exactly what our concierge team checks your order against during prescription verification, and it's why that step occasionally means recommending a cheaper machine than the one in your cart.