Oxygen devices used on the go by lung disease patients may not provide users with adequate oxygen, a new study has found.

The devices, known as oxygen conservers and attached to portable oxygen cylinders, are mainly used by those with chronic obstructive pulmonary disease (COPD) to perform daily activities, according to researchers at Case Western Reserve University in Cleveland.

In the study, the researchers tested four of most widely used oxygen conservers to measure performance, then had 13 COPD patients use each device in a random order.

The study found that the conservers’ performance varied from product to product and none of the devices consistently performed to technical expectations.

The devices were unable to keep up with a person’s breathing, matching each breath with a consistent dose of oxygen, and all of the devices in this study showed suboptimal activation with breathing, the researchers said.

The challenge associated with standardising all technical specifications related to oxygen conservers is objectively and scientifically determining what standards are ideal for all devices and patients, according to Reuters.

The study was partly funded by Invacare and was published in the American Journal of Respiratory and Critical Care Medicine.