What Is Pulse Flow Oxygen?

Pulse flow oxygen is an oxygen-conserving delivery method. The concentrator monitors the user’s breathing through the nasal cannula and delivers a measured burst of oxygen when it detects the beginning of an inhalation.

Because oxygen is delivered primarily during inhalation rather than flowing continuously throughout the entire breathing cycle, pulse-dose equipment can often be made smaller, lighter and more energy efficient than continuous-flow equipment.

Pulse flow may also be called:

• Pulse dose
• Demand flow
• On-demand oxygen
• Intermittent flow
• Oxygen-conserving delivery

The terms are often used to describe similar concepts, although the exact delivery technology and performance vary between manufacturers and models.

What Is Continuous Flow Oxygen?

Continuous flow oxygen is delivered steadily through the cannula regardless of whether the user is inhaling, exhaling or briefly pausing between breaths. The prescribed output is measured in liters per minute.

For example, a continuous-flow prescription may state 2 LPM. That means the oxygen system is intended to provide oxygen at a continuous rate of 2 liters per minute while operating under the prescribed conditions.

Continuous flow generally requires more oxygen production and electrical power than pulse flow. Portable concentrators capable of continuous flow are therefore commonly larger and heavier than pulse-only models.

Continuous flow may be considered when:

• The prescription specifically requires continuous flow
• The patient does not reliably trigger a pulse-dose device
• Continuous flow is required during sleep
• A respiratory device must be used with the oxygen source
• The prescribed oxygen needs exceed the capabilities of a pulse-only unit

Pulse Flow vs Continuous Flow: Main Differences

Does a Pulse Setting Equal Liters Per Minute?

No. A pulse setting number should not automatically be interpreted as the same number of liters per minute.

Continuous flow describes oxygen delivered at a rate measured over time. Pulse flow describes a discrete amount of oxygen delivered with individual breaths. These are different methods of measurement and delivery.

A portable concentrator may use settings such as 1 through 5 or 1 through 6, but those numbers are not a universal conversion chart. A setting of 3 on one model can differ from a setting of 3 on another model.

Pulse delivery may vary according to:

• The amount of oxygen delivered in each pulse
• The manufacturer’s delivery algorithm
• The user’s breathing rate
• The timing of inhalation detection
• The device’s triggering sensitivity
• The maximum oxygen-production capacity
• Whether the device reduces pulse size as breathing rate increases

How Does a Pulse Oxygen Concentrator Detect a Breath?

A pulse-dose portable oxygen concentrator monitors pressure changes through the nasal cannula. When the patient begins to inhale through the nose, the device detects a small change in pressure and releases an oxygen pulse.

Reliable triggering depends on the device, cannula position, tubing, breathing pattern and operating conditions. Some people produce a stronger inspiratory signal than others.

Factors that can affect pulse triggering include:

• Shallow breathing
• Breathing primarily through the mouth
• Improper cannula placement
• Kinked, damaged or excessively long tubing
• Very rapid breathing
• Sleeping position
• A loose cannula connection
• Device-specific triggering sensitivity

Many medical-grade devices include an alarm or safety response when a breath is not detected. The exact behavior varies by model and should be reviewed in the manufacturer’s instructions.

Can Pulse Flow Oxygen Be Used During Sleep?

Some patients use pulse-dose oxygen during sleep, while others require continuous flow or a different nighttime setup. The correct approach depends on the prescription, breathing pattern, device performance and clinical evaluation.

Breathing can become slower and shallower during sleep. Some people may also breathe through their mouth or fail to create a strong enough nasal inhalation signal for reliable pulse triggering.

A portable concentrator should not be assumed suitable for sleep merely because the manufacturer describes it as capable of around-the-clock use. The individual patient must still be able to trigger the machine and maintain the oxygen level prescribed by the healthcare provider.

Pulse Flow and Continuous Flow During Activity

Oxygen needs and breathing rates can change during walking, exercise, bathing, shopping and other activity. A setting that appears adequate while sitting may not provide the same support during exertion.

As breathing becomes faster, a pulse-dose concentrator must detect more breaths and provide more pulses each minute. Depending on the device’s maximum oxygen-production capacity, the amount delivered with each pulse may change at higher breathing rates.

Evaluation should reflect real-life activities

When appropriate, testing should include the activities the patient expects to perform while using the concentrator, such as:

• Walking at a normal pace
• Climbing a small number of steps
• Moving through an airport
• Shopping or attending appointments
• Participating in pulmonary rehabilitation
• Performing ordinary household tasks

Never change prescribed oxygen settings solely because a device feels inconvenient, produces an alarm or uses the battery faster during activity. Contact the appropriate healthcare provider or equipment professional.

How Flow Type Affects Weight and Battery Life

Pulse-dose concentrators are generally the smallest and lightest portable oxygen systems because they do not produce a continuous stream throughout the complete breathing cycle.

Continuous-flow equipment must produce oxygen continuously, which generally requires larger components, greater power consumption and larger batteries. Portable continuous-flow concentrators are therefore commonly heavier and may have shorter battery duration than pulse-only systems.

Battery claims should always be reviewed at the prescribed setting. Runtime at a low pulse setting does not indicate how long the system will operate at a high setting or in continuous-flow mode.

Why Testing the Specific Concentrator Matters

A prescription establishes the required oxygen therapy, but portable concentrators do not all perform identically. The same person may respond differently to two machines even when both devices display the same pulse setting.

When directed by a healthcare professional, evaluation may include checking oxygen saturation while the patient uses the actual concentrator during rest, walking or sleep.

Questions to discuss during evaluation

How to Choose Between Pulse Flow and Continuous Flow

The correct oxygen-delivery method begins with the prescription and medical need. Portability, weight and battery life should be considered only after confirming that the machine can deliver appropriate oxygen therapy.

Before comparing concentrators, know:

• Your prescribed oxygen flow or setting
• Whether your prescription specifies pulse or continuous flow
• Your oxygen needs at rest
• Your oxygen needs during activity
• Your oxygen requirements during sleep
• Whether you use CPAP, BiPAP or another respiratory device
• How long you need to operate away from electrical power
• How much weight you can safely carry or pull

Pulse flow may offer practical advantages when appropriate

For patients who can use pulse delivery effectively, pulse-only portable oxygen concentrators may offer lower weight, longer battery life and easier transportation for appointments, errands and travel.

Continuous flow may be necessary for some oxygen users

Some prescriptions and breathing patterns require continuous delivery. In those cases, selecting a lighter pulse-only machine simply because it is more convenient can result in choosing equipment that does not meet the prescribed need.

Common Mistakes to Avoid

• Assuming a pulse setting equals the same number of liters per minute
• Assuming every machine delivers the same pulse at the same setting
• Choosing equipment based only on weight
• Comparing battery duration at different oxygen settings
• Ignoring oxygen requirements during sleep
• Failing to consider breath-triggering ability
• Testing a concentrator only while sitting still
• Changing a prescribed setting to extend battery duration
• Assuming pulse flow works with every respiratory device
• Purchasing a non-prescription product marketed as a medical concentrator

Frequently Asked Questions About Pulse and Continuous Flow Oxygen