A Portable Oxygen Concentrator (POC) is a lightweight, battery-operated device that extracts and concentrates oxygen from the surrounding air. Determining the maximum output is complex because capacity varies widely and POCs use two fundamentally different delivery methods. This makes a direct comparison to a simple “liters per minute” (LPM) prescription challenging. Consulting a physician is necessary to ensure the device meets your precise medical requirements.
Continuous Flow Versus Pulse Dose Delivery
Portable oxygen concentrators utilize one of two primary methods for delivering oxygen: continuous flow or pulse dose delivery. Continuous flow provides a steady, uninterrupted stream of oxygen measured in true liters per minute (LPM). This mechanism is identical to stationary home concentrators, delivering the same volume regardless of the user’s breathing pattern.
Pulse dose delivery is designed to conserve oxygen and battery life, making it common in smaller units. This system delivers a precise burst, or “bolus,” of oxygen only when the machine detects the user is inhaling. The oxygen is released on demand, meaning none is wasted during exhalation, which allows for a smaller device size.
The difference makes their outputs inherently incomparable using a single metric. Continuous flow is a fixed rate of volume over time, while pulse dose is a fixed volume per breath.
Maximum Output Capabilities
For the largest portable units offering both modes, the maximum continuous flow rate is 3 LPM. This is the peak sustained output while maintaining high oxygen purity (around 90 percent). A few specialized, heavier models may advertise up to 5 LPM, but this often results in a significant drop in oxygen concentration, sometimes down to 40 percent.
The majority of smaller, mobile POCs only offer the pulse dose mode to prioritize portability and battery life. Their output is represented by a numbered setting, typically ranging from 1 to 10 depending on the brand, rather than LPM. The highest setting signifies the largest possible oxygen bolus the unit can deliver per breath.
These numbered pulse dose settings are proprietary to each manufacturer and model. A setting of 5 on one brand will not deliver the same amount of oxygen as a setting of 5 on a competing unit, as these settings are internal calibrations determining the bolus size.
Translating Pulse Dose Settings to Actual Flow
Translating a pulse dose setting into a usable flow rate is the most complex aspect of POC technology. Pulse dose settings deliver a specific volume of oxygen, measured in milliliters (mL), with each detected breath. The total oxygen delivered per minute (minute volume) is a function of the machine’s setting multiplied by the user’s respiratory rate.
A slower respiratory rate means the machine delivers a larger volume of oxygen per breath. Conversely, a rapidly breathing user receives a smaller bolus with each inhale at the same setting. This dependence on breathing frequency is why pulse dose is not a direct LPM equivalent.
Manufacturers provide conversion charts that estimate LPM equivalency at a standard respiratory rate (e.g., 20 breaths per minute). These charts are only a guide, as the patient’s breathing rate changes with activity. Effective oxygen delivery depends heavily on the user’s physiology and activity level.
The maximum pulse dose setting on a high-end unit is sometimes estimated to be clinically equivalent to a continuous flow of up to 6 LPM under ideal conditions. The true therapeutic effect must be verified by a physician using a pulse oximeter during rest and exertion.
When High-Flow Needs Demand a Stationary Unit
The practical limitations of portable oxygen concentrators become clear when a patient requires a high, sustained flow rate. Because POCs rely on a battery and must remain lightweight, they cannot produce the volume of oxygen that some prescriptions demand. The common cut-off point is a continuous flow requirement above 3 LPM, the maximum output for most high-capacity portable models.
Patients with severe respiratory conditions requiring 24/7 high-volume oxygen (e.g., 8 to 10 LPM) must use a stationary home concentrator. These units are large, plug directly into a wall socket, and are built with powerful compressors capable of producing substantially higher and more consistent flow rates.
Stationary units are designed for continuous, high-volume use, particularly for nighttime sleep when continuous flow is often medically necessary. If a patient’s oxygen saturation drops significantly during exertion or sleep, and the maximum POC setting is insufficient, a stationary unit is required.
A physician may also prescribe liquid oxygen for high-flow needs away from home, as it offers higher flow rates than most POCs without needing an electrical outlet.