Pulse Volume Setting for 2 Liters per Minute

For a pulse-dose oxygen concentrator, the volume setting for 2 liters per minute (L/min) depends on the device’s bolus size and breaths per minute, but a common starting point is setting 2 or 3 on most machines. This delivers roughly 2 L/min of supplemental oxygen when averaged over a typical adult respiratory rate of 20 breaths per minute. The exact setting varies by brand and model, so always check your device’s manual or consult your healthcare provider.

Formula

The average flow rate from a pulse-dose concentrator is calculated as:

Average flow (L/min) = (Bolus volume in mL / 1000) × Breaths per minute

Where:

• Bolus volume is the amount of oxygen delivered per breath, in milliliters (mL). Most pulse-dose machines deliver between 20 and 60 mL per breath.
• Breaths per minute is the user’s respiratory rate. A typical resting adult breathes 12–20 times per minute.
• The division by 1000 converts mL to liters.

Worked Example

Using the calculator defaults: 60 minutes, 20 breaths per minute, and a bolus volume of 40 mL.

1. Convert bolus to liters: 40 mL ÷ 1000 = 0.04 L
2. Multiply by breaths per minute: 0.04 L × 20 = 0.8 L/min
3. Over 60 minutes: 0.8 L/min × 60 min = 48 L total

The average flow rate is 0.8 L/min, and the total delivered over an hour is 48 liters. Note that this is not 2 L/min—to reach 2 L/min with a 40 mL bolus, you would need 50 breaths per minute, which is unrealistic. Most machines adjust bolus size automatically based on the setting and your breathing pattern.

Understanding Pulse-Dose vs. Continuous Flow

Portable oxygen concentrators come in two delivery modes:

• Continuous flow: Delivers a steady stream of oxygen at a set L/min, regardless of breathing. This is the standard for home concentrators and some portables.
• Pulse dose: Delivers a bolus of oxygen only when it detects a breath. This conserves oxygen and extends battery life, but the effective delivery depends on your respiratory rate.

How Pulse-Dose Settings Relate to L/min

Manufacturers label pulse-dose settings with numbers (1, 2, 3, etc.) or sometimes with L/min equivalents. The relationship is not linear across brands. For example, a setting of “2” on one brand may deliver a 32 mL bolus, while another delivers 40 mL. To know the actual L/min, you need the bolus size and your breaths per minute. Many manuals provide a chart like:

• Setting 1: ~0.5–1 L/min equivalent
• Setting 2: ~1–2 L/min equivalent
• Setting 3: ~2–3 L/min equivalent

But these are rough guides. The only way to be certain is to measure your blood oxygen saturation with a pulse oximeter while using the device, under your doctor’s supervision.

Choosing the Right Setting for 2 L/min

If your prescription says “2 L/min continuous,” your clinician will typically recommend a pulse-dose setting that approximates that flow. Common practice:

• For a typical adult at rest (12–20 breaths/min), a setting of 2 or 3 on most machines delivers around 1.5–2.5 L/min equivalent.
• If you are more active or breathe faster, a higher setting may be needed to maintain the same average flow.
• Always titrate with a pulse oximeter: adjust the setting until your SpO₂ stays in the target range (usually 88–92% for COPD, or as prescribed).

Never change your oxygen setting without medical guidance. Too little oxygen can cause hypoxia; too much can be harmful, especially in certain lung conditions.

Common Problems and Misconceptions

One major misconception is that the number on the dial is the same as L/min. It is not—it is a relative scale. Another issue is that pulse-dose machines may not deliver the full bolus if you breathe too shallowly or too rapidly. Some devices have a minimum inspiratory effort to trigger, which can be a problem for weak breathers. Also, battery life and oxygen conservation are affected by the setting; higher settings consume more oxygen per breath, reducing battery duration.

Comparing Pulse-Dose Settings Across Brands

Because there is no industry standard, a setting of 2 on a Philips Respironics SimplyGo may differ from a setting of 2 on an Inogen One G5. The bolus sizes are not published consistently, and some machines offer multiple sensitivity levels. When switching devices, your provider should re-evaluate your settings. Some machines have a “continuous” mode for nighttime use when breathing is irregular; this is not the same as pulse-dose.

Safety and Accuracy Tips

• Always use the manufacturer’s cannula and filters; they affect trigger sensitivity.
• Check the device’s display for the actual delivered volume if it shows it (some newer models do).
• Do not assume that a higher setting is always better; too much oxygen can cause oxygen toxicity, especially at high flows for long periods.
• If you feel short of breath or your SpO₂ drops, contact your healthcare provider, not just increase the setting.
• Regularly clean the device and replace filters as recommended to maintain accurate delivery.

Frequently Asked Questions

What setting is 2 liters per minute on a portable concentrator?

There is no universal setting. On most machines, setting 2 or 3 approximates 2 L/min, but you must verify with your device’s manual and a pulse oximeter. The actual flow depends on your breathing rate and the bolus size.

Can I use a pulse-dose concentrator at night?

Some models have a continuous flow mode for sleep, because breathing rate and depth change. If your prescription requires continuous flow at night, use a machine that offers it. Pulse-dose may not deliver enough oxygen during sleep.

How do I know if my pulse-dose setting is correct?

Use a pulse oximeter to check your SpO₂ after 5–10 minutes of rest. If it is below the target range, you may need a higher setting. Always consult your doctor before changing settings.

Does breathing faster give me more oxygen?

Yes, up to a point. A higher respiratory rate triggers more boluses per minute, increasing the average flow. However, if you breathe too fast, the machine may not have time to refill between breaths, reducing the bolus size. Also, very rapid shallow breathing may not trigger the device.

Why does my concentrator have a setting “1” but my prescription says 2 L/min?

Setting numbers are not standardized. A setting of 1 on some machines may deliver 1 L/min equivalent, but on others it might be 0.5 L/min. Your provider should set the device based on your oxygen saturation, not just the number.

Can I convert a pulse-dose setting to continuous L/min?

Only approximately. You need to know the bolus volume (from the manual) and your breaths per minute. Use the formula: (bolus mL ÷ 1000) × breaths/min. For example, 40 mL × 20 breaths = 0.8 L/min. This is rarely exactly 2 L/min, which is why clinical titration is essential.

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in t | Time (min) | min | 60 | 0
in bpm | Breaths per minute | breaths/min | 20 | 0
in bolus | Bolus volume (mL) | mL | 40 | 0
out total_vol | Total oxygen delivered (L) | L | (bolus / 1000) * bpm * t | 1
out avg_flow | Average flow rate (L/min) | L/min | (bolus / 1000) * bpm | 2