What is the difference between pulse and continuous flow?

If you want to buy or rent a POC you should be informed about the differences between Pulse and Continuous Flow.

Continuous Flow

Continuous flow machines supply the patient with a continuous supply of oxygen, preferred by some patients who have very poor respiratory effort and a low oxygen level although some oxygen is wasted while the patient is exhaling and the supply can be used up quickly but do offer the patient mobility and freedom.

With continuous-flow, oxygen delivery is measured in LPM (liters per minute). 

The continuous flow machine emits oxygen constantly irrespective of whether the user is inhaling or exhaling.

Air compressor compress normal air and deliver high pressure air into oxygen system.
Oxygen system ( PSA system ) is made by two cylinders filled in molecular sieves.
It separates N2 and deliver O2. The bigger two cylinders, the more molecular sieves.

More molecular sieves need more compressed air. The more compressed air, the bigger compressor and more oxygen coming out per minute. That is why big home unit could produce 5 liters 93% oxygen per minute. Because big machine has big compressor and big Oxygen system.

The concentrator draws in room air and passes it through a series
of filters that remove dust, bacteria, and other particulates. In
the first step of the concentration process, a compressor force
air into one of the two cylinders containing sieve material, where
nitrogen is adsorbed, leaving concentrated oxygen and a small
percentage of other gases found in room air. Simultaneously, in
the other cylinder, nitrogen is desorbed and exhausted into the
atmosphere. In the second step, the function of the cylinders is
reversed in a timed cycle, providing a continuous flow of oxygen
to the patient.

Some cheap small potable units will mix normal air with oxygen when you turn up its flow above 1 liter.

Pulse Flow

The pulse flow POC provides a ‘pulse’ of oxygen each time you inhale. Oxygen concentration processing won’t stop no matter continuous flow or pulse flow.
Pulse flow machine take full advantage of people exhale time.

With pulse-flow delivery is measured by the size (in milliliters) of the ‘boluses’of oxygen per breath, referring to the burst of oxygen released when you inhale.

Pulse flow has a storage system inside of machine. When people exhale, storage system will stock oxygen and stop delivering oxygen out. There is a sensor to detect people inhale action. When people inhale, sensor will activate and deliver storage oxygen out.

Pulse flow top capacity equal to triple of continuous oxygen capacity, no matter how many settings this machine has. If oxygen concentrator biggest capacity is 1 liters continuous oxygen per minute with 90% purity, its pulse flow top capacity equal to 3LPM.

Usually pulse-flow oxygen concentrators are not used by patients while they sleep, as sometimes the machine is not able to detect when the patient is inhaling, as night-time breathing is low and shallow. Sleep apnea patients are specifically not advised to use Pulse-flow units as they usually require a CPAP (Continuous Positive Airway Pressure) mask.

Pulse flow or pulse-dose portable oxygen concentrators are the smallest, often the size of a briefcase and weigh about 2kg. Pulse flow portable oxygen concentrators can deliver oxygen only when patients inhale which avoids any waste of oxygen when the patient exhales. Their ability to conserve oxygen and not waste it is key to keeping the units so compact as the oxygen supply will last longer.

Pulse vs Continuous Flow

Portable Oxygen Concentrators – Continuous  or pulse flow?

What is the better solution for me?

The best solution is the one that keeps you healthy and covers your demands. This is depanding from your prescription and your budget.

There are some machines on the market that offer both continuous and pulse flow. These machines offer flexibility as they are great for nocturnal use, use with sleep apnea equipment and during the day on pulse dose.

There are different brands with slightly different characteristics, but the most important thing for the patient to consider when choosing which type of POC to have is their medical needs around the supply of oxygen they need.